By Lawrence W. Judge, Phillip J. Cheetham, Brian Fox
This article’s lead researcher is Larry Judge, professor and senior research fellow at Ball State University in Muncie, Indiana. He has contributed often over the years to the pages of Track
Coach. This study follows the pre-Olympic buildup of shot putter Felisha Johnson in 2016 and was first published in the International Journal of Sports Science and Coaching, Volume 16(3), 2021.
Abstract
During a shot put, there are different finite variables that can be controlled by the thrower, including release angle, release height, release direction, and release velocity. Previous studies have determined thresholds of release velocity necessary for achieving certain distances, and this case study sought to expand upon that concept. Conclusions from key biomechanical data can make a significant difference in the performance of athletes in the shot put if properly understood by coaches. By utilizing this scientific approach to the shot put event, the throws coach will be able to determine more accurate adjustments and devise training stimuli to better accommodate the athlete. In this case study, researchers and the coach attempted to bridge the gap in the approach to teaching and coaching the glide shot put by using a physics- based equation regarding projectile motion in tandem with biomechanical analyses. The use of immediate feedback via video analysis was an essential part the coaching and teaching system. The athlete’s release angles decreased, and her maximum release velocities increased from 12.5m/s in 2015 to 13.1 m/s in 2016. This USATF coaching education shot put project is an example in which the cooperation between sport science and coaching helped to produce an Olympic berth (19.24m/63’1½”) by Felisha Johnson in the women’s shot put in 2016.
Introduction
The elite level shot put as a track & field event is a harmonious combination of strength, power, and proper technique. It is difficult to replicate the exact parameters needed for an ideal throw, but the implementation of biomechanical data can allow coaches to have a better grasp of the ideal parameters for their athlete. Recent research on the shot put has yielded valuable kinematic information for elite athletes.(1) By utilizing this evidence based approach, the coach can determine the velocity of release (e.g. >13 m/s) and angle of release (e.g. 36 degrees) necessary for elite performance.
The conclusions that can be made from a segment of video on a particular throw depend on a number of factors related to the type of video, the way in which the video was recorded, and the skills of the videographer and the researcher. Keep in mind, any individual throw by an athlete could be unique and atypical. Using information gathered in training and competition may allow more accurate technical adjustments to be made, and training stimuli can be devised to better accommodate the athlete’s target performance.
Biomechanical studies have been conducted regarding the shot put event in track & field, serving to quantify and describe the ideal range of conditions necessary for a successful throw.(1,2) However, few studies have observed the progress of an athlete throughout a comprehensive training program, using kinematic analyses in tandem with experienced coaching.(2,3) While coaches typically seek to increase uniform power production in their athletes to improve performance, the concept of utilizing real time kinematic feedback and the inclusion of physics principles can effectively allow coaches and athletes to make minute adjustments during practice. Proof based on the video evidence of the immutable laws of physics is both convincing and motivating to athletes. Kinematic feedback also allows a coach to work backwards and design and later adjust training program variables to achieve a desired kinematic result.
The athlete has control over four variables that directly influence the distance of the throw: release height, release angle, release direction, and release velocity.(4,5) Previous studies have observed that release velocity is highly correlated with superior shot put performance,(5 9) and as the mathematical equation used to calculate throw distance is based on the quadratic equation, modifying the release velocity is theorized to have the greatest effect on the throw distance.(10) Other studies have suggested that neither release velocity nor other release parameters have any effect on throw distance.(11,12) However, as the reported data for these release parameters do not match values observed in elite and sub-elite shot put athletes, there stands reason to believe that the former data may be flawed and possibly incorrect. Similarly, it could be argued that release height is an anthropometric measure, coming as a result of the athlete’s height and arm length, and thus is unchangeable. However, release height may be affected by technical execution. For example, if the athlete utilizes an active reverse and jumps rather than just blocking and using fixed feet, this would slightly increase their release height relative to the ground.(1) Hubbard et al (2001) also suggests that release height can be minutely affected by increasing release angle.(13) Based on these concepts, release height can become a modifiable variable. Release direction also has an effect on distance and is especially important with regard to fouls.
Several studies have been done to understand the ideal ranges of each of these variables. Optimal release height has been shown to fall between 2.0 and 2.2 meters in elite athletes(7) and junior athletes,(6) although some studies have shown optimal performance with release heights in the range of 2.2-2.35 meters.(14) Obviously, athletes with larger statures (i.e., increased height or longer arm length) will be at an advantage in the shot put, as they will be granted a greater release height, increasing the amount of time the shot has in the air to travel horizontally.
Reviewers: Kevin McGill (Columbia University (retired), USA) Wayne Spratford (University of Canberra, Australia) Meg Stone (East Tennessee State University, USA) ‘Biomechanics Laboratory, Ball State University, Muncie, USA Corresponding author: Lawrence W Judge, School of Kinesiology, Ball State University, Muncie, IN 47304, USA. Email: LWJudge@bsu.edu
Based on physics principles of projectile motion, the optimal release angle for an object landing at the same height at which it is released is 45 degrees.(5) This angle ensures both the greatest amount of air time as well as the greatest horizontal velocity. However, due to the fact that the shot is not landing at the same height of its release (as well as a few other factors), 45 degrees may not be the optimal release angle to increase throw distance. An angle of forty-two degrees may be better for a release height of 2 m, based on the projectile equations. Linthorne (2001) reported from several studies that the range of release angles for world class shot put athletes varied from 27^45 degrees, with an average of 37 degrees.(7) Many studies observing release angles of elite and sub-elite shot put athletes have displayed release angles below 40 degrees, ranging from 32 – 38 degrees for optimal distance.(8) This is potentially due to the fact that athletes can produce more force in the horizontal direction, so having an angle below 45 degrees may be advantageous mechanically. Additionally, a higher release angle has a larger gravity component action on the shot put, making it harder to accelerate.
As previously mentioned, release velocity has been shown to have the greatest effect on throw distance, both in practical application and mathematical simulation. The release velocities required to reach elite performances of 19 meters (women) and 21meters (men) have been established in the literature.(10) New radar and video technology for measuring the release characteristics of shot put throws has been developed for use by potential United States of Ameerica (USA) Olympic and Paralympic athletes. Hundreds of throws have now been captured and analyzed at the Chula Vista Olympic Training Center since 2015. These data have been helpful in tracking athletes’ progress through each season up to and including major competitions, and of course, the Olympics.
The technology uses a combination radar and a video device positioned approximately six meters behind the ring at approximately 1.6 meters high on a tripod. The radar bounces a signal off the shot put and measures the phase shift of the returning signal. Using digital signal processing methods, the system is able to calculate both the distance and landing position of the implement, in addition to several release characteristics, including speed, angle, direction, and height. Video of each throw is also included with the data. It is captured, trimmed, and transmitted to the computer together with the data for each throw. The software allows all the data and video to be tagged to each athlete and exported to a spread sheet for later analysis. All of this information is gathered without any need to interfere with the athlete, allowing a training session to progress at its normal rate totally unencumbered.
Alternatively, if the athlete or coach wishes, they can review the data and video after each throw to make indicated technique changes.
Upon completion of the training session, the data is immediately uploaded to the cloud. Data from past years has been available, allowing for comparisons and statistical analysis. A web-based user interface has been built, allowing the coach and athlete to review their data on a regular basis without the need for the radar unit’s computer. Training issues can be identified and progress tracked from the coach’s own computer at home or in the office.
Previous studies have determined thresholds for obtaining certain throw distances.(10) However, having more tangible, immediate feedback supported by physics and biomechanical principles can be beneficial for coaches and athletes if interpreted properly. To our knowledge, few studies have been performed observing changes in athlete performance as a result of this combined training approach. Thus, the purpose of the present study was to examine the effect of an evidence-based comprehensive training protocol that utilized knowledge of results, integrated physical capacity development, and technical interventions based on a quantitative biomechanical analysis on an athlete’s performance. The United States Track and Field (USATF) shot put project is an example of cooperation between sport science and coaching education, which helped to produce Felisha Johnson’s Olympic Trials (19.24 m) performance in the women’s shot put in 2016. This paper will address how the data was used to track and modify her training program, leading to her accomplishment of of her goal of becoming a USA Olympian at the Rio Olympic Games in 2016 (Figure 1).
Methods
Participant
The participant in the present study was 26 years of age. Anthropmetric characteristcs were as follows: height 185 cm (Seca metric stadiometer, Chino, CA), weight of 127 kg (Seca electronic stadiometer, Chino CA) and body fat of 19.8% (Lange skinfold calipers, Cambridge, MD) and a 3-site method (tricep, thigh, suprailium). Before any data was collected, the participant was informed of the study purpose, along with any associated risks and benefits. In accordance with the university institutional review board and the Declaration of Helsinki, the participant gave her informed consent and completed a health history questionnaire before the first test session. The Institutional Review Board at Ball State University approved the present investigation. The participant was required to keep a detailed weekly online training log and to email the log to the coach. The coach reported, via a datasheet, the throwing volume, resistance training volume, as well as the participant’s season bests in the indoor shot put, outdoor shot put, weight throw event, and weight room IRMs for the bench press, power clean, and squat exercises. In total, the datasheet consisted of eight items. Following the coaches report, the data for the athlete was entered into a spreadsheet program, and the data report sheet was destroyed.
Data collection
Kinematic data from the video record of athlete Felisha Johnson was collected at the 2015 indoor and outdoor (see figure 2) nationals and 2016 indoor and outdoor (see figure 3) USATF National Championships. Two digital video cameras (Canon Elura 60) were used to record a control object and Felisha Johnson’s performances at a sampling rate of 60 Hz. The cameras were placed near the shot put throwing circle spaced approximately 90° apart. Following collection of the performance data, the calibration frame was placed in the center of the throwing circle and recorded so that the direct linear transformation (DLT) procedure could be performed.(15)
Kinematic variables including release height, release velocity, release angle, release direction, and distance travelled were collected using a Trackman Doppler Radar system (Scottsdale, AZ). The radar system was then used for subsequent practices to offer real time biomechanical feedback to the athlete, coach, and biomechanist. The Trackman system has been validated in providing accurate ball parameters in golf,(16) and has been implemented at the Olympic Training Center in Chula Vista, CA, since 2015 to analyze shotput and hammer throws.
Data reduction
Video data was digitized using MaxTraq (InnoVision Systems, Columbiaville, MI). The video records of each performance were manually digitized at a sampling rate of 60 frames per second from two frames before the initiation of the throw to four frames after the release of the shot. In each digitized field, 23 points were manually digitized to model the athlete-plus-shot system (APSS, see Young(17) for details). The digitized 2D data was time synced based on the release of the shot. A second event, front foot touch down (FFTD), was used to verify the accuracy of the synchronization. All analyzed clips met both synchronization criteria. The DLT procedure was used to determine 3 D coordinates of 22 body landmarks and the center of the shot for each trial. The digitized control object coordinates were used to estimate the DLT parameters for each camera. The 3 D coordinate data were smoothed using a fourth-order zero-lag Butterworth low pass digital filter with a cutoff frequency at 6 Hz.18
Data processing
After data was acquired, the kinematic variables were integrated into a quadratic equation to provide a close estimate of the throw distance based on principles of projectile motion (equation (1)). There does exist a slight discrepancy between the measured distance and the mathematical distance due to the mathematical distance not taking into account the dimensions of the toe board. Once these variables are included, the biomechanist can make small adjustments to these variables to predict the parameters necessary for a desired throw distance.
In which L = throw distance, Vr = release velocity, θr = release angle, g = acceleration due to gravity (a positive value in this instance), and hr = release height.
Parameter selection
A seven variable technical model of elite women’s shot put was used for a technical intervention between 2015 and 2016. This technical model was developed from the findings of previous research.1 The goal of this prior research was to determine the most critical variables for success in elite women’s shot putting.(17,19,20) The seven kinematic variables indicated as being related to elite performance were used as the basis of the athlete’s technical focus and subsequent feedback. The seven variables are presented in Table 1. Although release velocity is clearly a significant indicator for performance, it was excluded from the variables due to the fact that it was measured daily, and the athlete and coach received immediate data on release angle and release velocity. Likewise, because previous research(17) has indicated that release velocity explains so much of the variance of a throw by itself (90+%), it was concluded that it could mask the importance of other variables that may be more applicable to beneficially affecting a technical intervention.
Data analysis
The method employed in this study to break down the throw into phases by predetermined events allowed for comparison of this research with previous research conducted on the shot put. This method has been used previously to examine the shot put.(17,19,20)
Training program
The goal of the athlete’s training program was to expedite the acquisition of the skills and abilities required to duplicate the required speed and angle of release necessary for effective performance (to make the U.S. Rio Olympic Team). The training program components included: hurdle mobility, plyometrics, throwing, throwing drills, bodyweight work, and traditional “weight training” activities. The program included a high percentage of multi-jointed movements with significant tissue under tension and emphasis on power output. Examples included: (1) Olympic lifts and modifications (e.g., cleans, snatch, high pulls, DB cleans, DB jumps) (2) Static lifts (e.g., squat, bench, incline, deadlift, RDL, pullovers, assisted pullups). The athlete’s training program paid attention to ratio of push and pull movements (1 push: 2 pulls). A typical session began with one Olympic lift, progressed to an Olympic lift derivative, and then concluded with one upper body static lift and one lower body static exercise.
When considering the design variables that make up the training program (i.e., training load, training volume, exercise selection, and training frequency), each variable’s threshold necessary to create a quality training plan depended upon the athlete’s training age, strengths and weaknesses, the phase of the training year, and many other factors. For the athlete in the present study, there was a balancing of the training loads with restorative and prophylactic (injury prevention) measures.
A classic Matveyev periodization model was utilized with the athlete(21) and was based on previous research.(1) The mesocycle sequencing of the training program began with hypertrophy methods, progressing into strength building methods, followed by neural activation methods, and finally speed-strength methods. The total cycle was repeated three times annually. For example, the first mesocycle emphasized strength- endurance, basic conditioning, and hypertrophy methods (mid-Aug. – early Sept.) The second mesocycle emphasized basic strength with an emphasis on improving the back squat (late Sept.- early Oct). The third mesocycle emphasized strength/power using 3- 4 weeks of neural activation methods with an emphasis on Olympic lifts, Olympic lifting derivatives, and plyometrics (late Oct- early Nov). The fourth mesocycle emphasized explosive power and speed development using time controlled speed-strength methods (late Nov.-early Dec). The sequence was then repeated following a regeneration period (December holiday).
Olympic-style lifts (Clean, Jerk, Snatch) and their derivatives (Pulls and Shrugs) were the primary focus of the resistance training program. Numerous studies and review articles have recommended and supported the use of explosive exercises for shot putters.(22-26) In addition to the weight lifting exercises, throws, sprint drills, and jumps, the workout contained sport-specific release movements that force core stabilization in high velocity activities. Sport-specific exercises that mirror sport-specific release parameters are an effective way to develop specific throwing strength. Heavier throwing implements (e.g 7.26 kg shot puts) were used for power development, and lighter implements were used for speed development. These shot put release exercises were designed to emulate key sport-specific (the inside out pushing motion) release positions.
Following the 2015 season, the volume of throws was incrementally increased due to the relatively young training age of the athlete and to make up for the lack of experience with the shot put. With the Rio Olympic Games quickly approaching, increasing the demands of training was determined as the best way to secure a berth on the United States Olympic team for the athlete. The number of total throws increased from 3320 in 2015 to 4900 in 2016 (Table 2). Keep in mind that these numbers included everything that was done with a delivery. This includes full throws and also extraneous drills (i.e. throws on knees, kettlebell throws) with a release. Throws were completed with shot puts ranging from 3.5 kg to 7.26 kg. The athlete also continued training the 20lb weight throw event, which is an indoor event thrown with technique similar to the hammer throw. Throws were completed in the 20lb weight throw event with implements ranging from 9 kg to 14.5 kg. The majority of the weight throws were performed in the Fall and Winter months as a core training exercise. During the pre-competitive phase, three (two throwing and one resistance training) workouts were performed daily. This was reduced to two workouts a day (one throwing and one resistance training) during the competitive phase. Two training days were generally followed by one recovery day. During the lead-up to the Olympic Trials, the emphasis was on improving maximum strength in the lower body (back squat strength).
Kinematic feedback
Following the competition in 2015, the athlete’s coach and the biomechanist responsible for the kinematic analysis at the Olympic and Paralympic Training Center in Chula Vista, CA reviewed the video record of each throw in the competition using the aforementioned technical model for elite women’s shot put performance as the guideline for suggestions. Several weeks following the conclusion of the 2015 season, a detailed biomechanical analysis report was sent to the coach. This report provided quantitative data on the seven kinematic variables previously noted as being important for success in the women’s shot put.(8) Recommendations to improve performance and address technical weaknesses (as based on the seven variable technical model) were also provided.
Statistical analysis
In 2015, the athlete finished seventh in the United States National Championships in Eugene, OR and did not qualify for a berth on the United States World Championships Team. In 2016, the thrower did qualify for the final and thus took six total attempts. After her first three attempts, she was in eighth place. In the fifth round, the athlete recorded her best throw of 19.24 meters and moved into the lead in the competition. The athlete ultimately finished third in the competition to make the United States Olympic team. To maintain relative consistency of trials between years, the best throws from 2015 and 2016 were included in this analysis.
Parameters were examined from the athlete’s best throw from the 2015 USATF National Championships and the best throw from the 2016 USATF National Championships (Olympic Trials). A Shapiro-Wilk test was used to determine the normality of the raw data. The test indicated that the data were normally distributed. Stata software from StataCorp LP (Austin, TX) was used to perform the analysis.
Results
Based on equation one, researchers can modify variables to seek desired throw distances. In order to do this, researchers grouped throws by similar variables (i.e., grouped throws that maintained a certain release velocity) and observed how the other variables affected the resultant throw distance.
Release velocity
Researchers initially chose to isolate the importance of release velocity. By maintaining a release angle of 36 degrees and a release height of 2.3 meters, researchers incrementally increased the release velocity by 0.1 m/s from 12.4 to 13.0m/s and observed an average distance increase of 25 cm (range: 24-26cm) for each 0.1 m/s (from 17.61m to 19.12m).
Release angle
While the importance of release velocity appears to be linear, that is not the case with release angle. By isolating throws which maintained a release velocity of 13 m/s and a release height of 2.3 meters, researchers incrementally increased release angle by 2 degrees. At lower release angles, 2 degree increases led to greater throw distances (37 cm increase from 30 to 32 degrees) but yielded lesser increases as angles increased (9 cm increase from 38 to 40 degrees). Researchers found that when release angles reached 44 degrees, throw distances no longer increased, but decreased by approximately 5 cm.
Release height
While maintaining a release angle of 38 degrees and a release velocity of 13 m/s, researchers increased release height from 2.0 to 2.4 meters by 10 cm increments. Researchers found that for every 10 cm added to release height, there was also a 10 cm increase in throw distance (from 18.99m to 19.38m).
However, increasing both release angle and release height had a more substantial effect. Researchers increased release angle, determined how release height increased as a result, and observed the changes to throw distance while maintaining a constant release velocity. Similar to how release angles caused lesser increases in distance as angles increased, increases in release angle (and release height as a result) caused an increase of 33 cm from 34 to 36 degrees, but only a 10 cm increase in distance from 40 to 42 degrees.
Descriptive statistics
The seven variables of the optimization model are presented in Table 3. Additional temporal (Table 4) and release parameter (Table 5) data presented to the coach and athlete are also provided for comparison against previous studies. These data are in agreement with previous literature,17 indicating that the data collected for this study is comparable to those used in previous research on the event.
The athlete’s performance improved more than 1 m, approximately 5.48%, from 2015 to 2016. As would be expected, release velocity increased 4.8% (12.5m/s to 13.1 m/s). The results of the comparative analysis on the seven optimization model variables indicated positive changes in all variables. Changes were considered positive if the pre- to post-technical intervention numbers moved toward the desired value as indicated in Table 1. The results of the pre- and post-intervention comparative analysis are presented in Table 3.
Discussion
Shot-putting is a complex three-dimensional movement in track & field that presents many technical challenges. Felisha Johnson utilized the glide technique throughout her training and competition. Her anthropometries (Table 6) allowed her several advantages over other female shotputters, including an increased release height due to her 185 cm stature, and a stronger frame for greater force production (weight: 127 kg, body fat: 19.3%). As a result of effective, multidimensional training methods and fine-tuned form, Felisha was able to clinch a United States Olympic berth with one of the top throws recorded by an American female (Table 7).
Technical interventions
In the shot put, each stage of movement flows directly into the next; thus, the performance in one stage will directly affect the performance of subsequent stages. Felisha had difficulty maintaining a consistent starting depth in the back of the ring and would lose posture by rounding her back by the end of the preparation phase. An improper starting position in the preparation phase led to increased variability in how force and impulse were produced throughout the rest of the movement. A weak postural position then caused a delay in FFTD due to the tendency of her left leg to hang on the glide. A delayed FFTD then led to a delay in establishing a base, and reduced the effectiveness of shoulder-hip angle separation, which is essential for power production.(1,2,27,28) Researchers determined that this lag in the left leg needed to improve; time to FFTD needed to decrease in order to establish a more effective power position (increased shoulder-hip angle separation about the transverse axis), allowing Felisha to ideally produce more rotational torque and increase core musculature stretch to facilitate an increased influence of the stretch shortening cycle.(10) The coach observed these deficiencies and modified Felisha’s starting position to be more upright, and time was spent modifying the subsequent unseating and glide building momentum phases.
It was determined that the main point of focus for Felisha would be modifying joint power production, especially through the lower extremity joints (hip, knee, and ankle). Deficiencies in her lower extremity control (used to generate linear impulse) suggested that changes to joint power production efficiency were needed. The objective of the coach was to modify Felisha’s current movement pattern in order to optimize her lower extremity joint angles during power production and to properly load the neuromuscular components responsible for the movement.
Felisha’s starting position was changed to improve her posture throughout the rest of the movement; this was accomplished by flattening her back and maintaining a more upright posture, while also establishing a proper starting depth. The coach used posture-specific exercises to reinforce these changes, including multiple glides with a bar (broomstick and cross bar), glides while wearing a weighted vest, and glides with ankle weights.
Felisha’s initial shot put technique consisted of a long-short pattern in her hips, defined as a longer glide and a shorter (narrower) stance following FFTD.(10) One of the most important aspects of this technique is ankle flexibility and hip mobility, requiring the thrower to turn the right foot to 90 degrees in the middle of the ring relative to the direction of the throw. When working through this technique with Felisha, it became apparent that she did not have the ankle flexibility and hip mobility needed to properly execute this manuver. In order to better accommodate her abilities, her technique was changed to a short-long glide instead, defined as a shorter glide phase and a wider (longer) stance at FFTD.(10) This allows for the right foot to be positioned at a more comfortable angle of 135 degrees (versus 90 degrees) in the power position and for the stance in the power position to be slightly wider than shoulder width.
The next modification was to increase rear knee (RK) flexion angles at RFTD, as suggested by prior literature.(1,29,30)
According to Judge and Young (2010), the short-long glide is characterized by a shorter glide phase and a wider stance at FFTD.(10) This technical variation allowed Felisha to employ a lift and rotate movement strategy following FFTD. In the short-long technique, the right foot is positioned closer to 135 degrees, and the base is slightly wider then shoulder width. After finding a comfortable power position, the focus was on increasing RK flexion. Previous research has indicated that it is beneficial to make RFTD with greater RK flexion.(17,29,30) In 2015, Felisha had a tendency to raise her torso prematurely during the momentum building phase of the glide and project forward in the transition phase to the power position. The rounded back and excessive tilt in the torso in the starting position in the back of the ring also contributed to the lack of RK flexion. The center of mass needed to be positioned behind the blocking leg at FFTD to create the blocking impulse and angular impulse needed to initiate rotation. This premature “opening” of the upper body (shoulders) caused her to primarily utilize the musculature in the shoulder and arm to generate force. Controlling the angle of the trunk and keeping the upper body closed was a point of emphasis,(31) and glides with a high jump cross bar helped Felisha feel the desired position. As evidenced by the hip and pelvis angles at the power position in the throws from 2016, the athlete’s hips were in a fairly low position, and the shoulders were in a closed position at FFTD, although the upper body was fairly erect.
As previously mentioned, the shot put has several stages, each transitioning smoothly into the next, and each stage affecting the next. Another obstacle Felisha was faced with was making the transition phase between the glide and power positions as efficient as possible, namely by reducing the pause during this phase. An ideal transition phase should be seamless, as the relationship between the transitional phase and the lift/rotate phase is generally indicative of the athletic ability and fitness of the thrower. In Felisha’s case, a smoother transition phase was taught by performing throws in smaller 1.828 meter throwing circles (six foot ring); this makes movement across the ring easier, thus making transitions smoother. As Felisha got more comfortable with throws in this smaller ring, the length of the glide was gradually increased and the standard (seven foot) throwing ring was re-introduced.
Following FFTD, three important actions occur: trunk rotation, hip drift, and trunk elevation performed by the legs. Felisha’s hip mobility was developed by implementing specific drills into her specific warmup (such as the hip pop drill), which helped improve her hip mobility, allowing for more aggressive rotation of the trunk (Figure 4). This, coupled with a more aggressive trunk elevation by the legs, helped Felisha minimize her drift. Several studies have discussed the importance of a greater shoulder-hip separation angle in trunk whip speed and amplitude development.(20,31-34) Increasing Felisha’s hip mobility (thus increasing shoulder-hip separation angle at FFTD) allowed for increased rotational torque through increased utilization of the stretch shortening cycle and better recruitment of larger lower extremity muscles, facilitating the necessary acceleration of proximal and distal segments.
In 2015, the athlete had trouble creating the necessary release velocity to finish in the top three at the National Championships due to poor arm strike mechanics and blocking action. This was due in part to a lack of specific strength. Bartonietz suggests that power summation is a primary factor separating elite throwers from inferior throwers.(35) The lack of a blocking force of the left side was a possible limiting factor in achieving release velocity. The stopping force of the front leg was needed to contribute to the transfer of force to the putting arm.
A technical adjustment in this area was needed to foster the necessary increase in release speed necessary for overall improvement. Felisha was taught to sequentially turn and move forward the left arm and upper body with the right arm remaining in position so that the elbow remained in line with the path of the shot. Later, after the upper and lower body is properly positioned, the left arm blocks this rotation by pulling downward and inward close to the rib cage of the non-throwing side of the body. When working on this technical point, the athlete stated that she had difficulty feeling the left arm during the throw.
Achieving additional shoulder and hip separation (S-H) prior to delivery was a technical focus during training sessions. The orientation of the hips relative to the orientation of the shoulders was continually reinforced through drills and was a continual theme (focus) in training. A neutral position, or zero degrees of separation, occurs when the shoulders and hips are aligned with one another, as would be the case in anatomical position. A positive angle occurs when the throwing side shoulder is posterior to the throwing side hip.(10)
In 2015, Felisha performed a larger percentage of her full technique throws in training with the reverse. Although reversing the feet was beneficial for her overall rhythm, it limited her development of S-H separation and development of a solid blocking action. The reverse gave the athlete a false feeling of S-H separation, overall hip mobility, and hip rotation. Some authors argue that a large amount of reversing in training may mask certain technical flaws.(1) In 2016, the athlete performed 75% of her training throws with no reverse to work on the blocking action of the left side. The additional no-reverse training throws allowed the athlete to feel exactly how much S-H separation and hip rotation was being achieved on each training throw. This helped her improve her mobility, overall hip drive, blocking action, and subsequent release velocity.
To increase release velocity, the arm strike was another area that needed improvement from 2015 to 2016. Release velocity was compromised at release when the athlete turned her head prematurely toward the landing area and, as a result, would drop her elbow prematurely and flatten the orbit of the shoulders.(2) A technical intervention was needed to help her keep her shoulder orbit and the elbow behind the shot. The starting position in the back of the ring was adjusted to be a more upright torso position with a flat back (Figure 5). Before Felisha would enter the ring to throw, an object was placed four meters behind the circle as a focal point. The athlete was instructed to keep her eyes on the spot (focal point) until the implement left her hand. This technical cue helped the athlete keep her eyes focused on the spot while she turned her hips and maintained the orbit in the shoulders, which helped her keep her elbow behind the shot put.
As mentioned previously, there are four kinematic variables that can be controlled by the athlete to affect throw distance: release height, release angle, release direction, and release velocity. Regarding principles of projectile motion, an optimal release angle for a projectile (when the desired outcome is the greatest throw distance) is 45 degrees. Past literature has suggested that for the furthest throw distance in shotputters, optimal release angles fall somewhere between 40 and 43 degrees. Felisha’s release angles fell within this range during 2015, which could potentially be explained by her coach’s preferences in high school. More current literature suggests that optimal release angles for the shot put fall between 36 and 38 degrees.(36,37) It is thought that the discrepancy in optimal release angles between principle and the shotput activity is due to the inability to undergo adequate force production at a 45 degree angle, causing the optimal release angle to be slightly more horizontal. This could be related to the body’s ability to produce vertical vs. horizontal force through the recruitment of more horizontal adductors vs the smaller abductors of the shoulder. Note: For a 2m release height, the optimum calculated angle is 42 degrees. Forty-five degrees is only optimal when the release height and landing height are the same.
Felisha’s throws in 2015 were slightly higher than the desired 36-38 degree range, with her best throw having a release angle of 39.1 degrees. This angle was lowered in 2016 to fall within the desired range, with her best throw having a release angle of 36.9 degrees. This reduction in release angle is likely to have played a role in her increased throw distance; her top throw in 2016 was recorded at 19.24 m, whereas her best 2015 throw was recorded at 18.24m. This reinforces the concept that release angle and release velocity are inversely correlated.(4,7,13,38) As Felisha’s release angles decreased, her release velocities increased, from 12.5 m/s in 2015 to 13.1 m/s in 2016. This of course is only the case within a specific range of release angles. Once the throw becomes too flat then the distance decreases.
While resistance training interventions will be discussed in the next section, it is important to note here that an explanation of this modification to release angle can be attributed to Felisha’s training with incline bench press. Increasing strength and power with overhead exercises or exercises that work at oblique angles (such as the incline bench press) could contribute to the athlete’s increase in performance. Regarding technical interventions, Felisha developed further specific strength in the arm strike movement pattern, which was one of the most effective technical interventions employed. Performing throws from modified positions, such as a kneeling position, as well as utilizing overweight implements (i.e., 7.26 kg shot put) and a 10 kg weight vest allowed for the development of arm strike strength and proper release mechanics.
In the present study, it is important to note that the most effective variable to modify for the purpose of increased throw distance was release velocity. While the importance of release angle and release height are not to be ignored, the focus of the athlete was to improve specific arm strike strength and power in order to produce the greatest release velocity. The focus in training was on keeping the important aspects of the technical model consistent from throw to throw. The instantaneous feedback received from the video and radar device allowed for minor adjustments to be made on the fly; if the desired distance was not achieved in a certain throw, the variables that the athlete has control over could be looked at, and the coach could make slight adjustments to form as needed. These minute adjustments, based on video footage and radar values, allow both the coach and the athlete to feel more confident about their training.
Resistance training interventions
The shot put requires large amounts of force production in a short amount of time in order to maximize performance. It is key that performance is improved by taking into account the athlete’s anthropometries, athletic ability, and potential errors throughout their chosen technique. Felisha had a relatively short preparation training phase in 2015 (28 weeks), providing an explanation for her deficiencies in lean body mass, stability and mobility, and strength and power production. Prior observations suggest that elite athletes need anywhere from 32-36 weeks of training in order to achieve their peak performance level.(39) Performance in the weight room, specifically one repetition maximum (1RM), has been shown to be directly related to performance in shot put athletes.(40) Statistically significant linear and quadratic trends exist that relate 1RM measures of the power clean, back squat, and bench press to the personal best of shot put athletes.(41) Similarly, strength in field athletes has been previously described as the basis of high-level performance.(26) Thus, resistance training was another important aspect of Felisha’s training in 2016.
Felisha’s overhead strength had significant room for improvement coming into 2016. In the shot put, force is generated against the ground by the hips and legs, transmitted up through the trunk, and then applied through the shoulders and arms in an overhead position at release. Overhead exercises are important because they neccessitate a high demand on thoracic mobility, optimal scapulohumeral function, and the high coordination of the entire body. As mentioned previously, several overhead press-like exercises were integrated into her training, including overhead press with barbells and dumbbells, barbell push presses, and split jerks. She continued to perform wide and narrow grip bench press and incline bench press. Because of the additional emphasis on overhead movements, Felisha was able to increase her incline bench 1RM by 15 kg in 2016, from 105 kg to 120 kg.
Lower extremity strength was another key component to Felisha’s training in 2016. The coach employed front and back squats, quarter and single leg squats, step ups, and lunges, among other lower body exercises to futher develop lower extremity strength. Prior studies observing electromyographical impulses from core musculature during lower extremity exercises, such as the squat, determined that core muscle activation was equal or greater than activation observed during corespecific exercises.(42) Thus, the importance of lower extremity exercises was twofold; it served not only to improve lower extremity strength and power but also to increase core strength, stability, and mobility, which are essential to proper rotation and force generation during the movement. Felisha was able to improve her squat 1RM by 10 kg coming into 2016, and the researchers believe there to be a direct correlation between the improvement in her squat 1RM and her increased performance in 2016 based on prior literature.(42,43)
Another goal for Felisha was increasing power production through her lifts. Kyriazis et al.(25) found that increased power production in the lower extremities was more strongly correlated with increased shot put performance than muscular strength but also stated that muscular strength development could serve as a foundation for proper muscular power production development.(25) Power development for Felisha consisted of Olympic-style lifts (clean, jerk, and snatch) as well as their derivatives (pulls and shrugs) based on reports from several sources discussing the advantages of the Olympic-style lifts for power production over squat and deadlift exercises.(23,26,44)
Her standing long jump increased from 2.46m in 2015 to 2.65 m in 2016, her vertical jump increased from 61cm in 2015 to 71cm in 2016, and her overhead shot put distance increased from 18.60m to 19.63m. These improvements were attributed to the main Olympic-style lifts, their derivatives, and variations of Olympic-style lifts, including hang snatch, hang cleans, and mid-thigh pulls. The pulling movements exhibited by these exercises and the shot put movement share similar ground reaction forces, musculature recruitment, and force and rate of force development profiles.(35)
Special strength work
A training philosophy called movement pattern specificity, focusing on performance of training exercises that overload the athlete near the specific force velocity requirements for the event performance, was utilized.(1) Following the 2015 season, Felisha started to feel frustrated because she was not able to perform the ideal technique to finish in the top three at the U.S. National Championships. She failed to realize the true cause of her technical difficulties: a lack of special and specific throwing strength. In high school, Felisha Johnson was a basketball player who was a part-time track & field athlete. The movement pattern of shooting a basketball may have been ingrained in her nervous system and interrupted or influenced her throwing mechanics. This shooting movement pattern may have caused her to drop her elbow at the finish.
Felisha became a full-time resident track & field athlete at the Olympic training center in Chula Vista, CA, in 2016. It was there that she was introduced to extreme overweight (e.g., 20% over the competition weight) implement throwing, which had been previously unexplored in her training protocol. By focusing on specific strength in varying positions during the throw, Felisha was able to overcome many of the previously discussed technical challenges. Previous researchers have discussed the benefits of training with overweight implements.(1,45) However, more recent developments have provided a more technical definition among physiologists, called post-activation performance enhancement (PAPE),(46,47) which is defined by utilizing a high force or high power movement in order to increase the magnitude of a subsequent movement (post-activation potentiation).
The concept behind this training protocol was for the athlete to perform the movement at a greater intensity than usual without having to perform high intensity Olympic-style lifts, which could potentially fatigue the athlete more quickly. For Felisha, a ladder system was used in which two implements (10 and 20% greater than competition weight) would be implemented. The objective for this training emphasis was to increase force generation through the movement. Felisha was asked to perform a prescribed number of throws with the 20% implement first while maintaining ideal performance form, and she was then asked to do the same with the 10% implement. By performing the ladder in this way, the competition weight shot would feel easier by comparison, while also reinforcing proper throwing form throughout the movement. Throws were completed twice a day, with 8-10 throws being performed in the morning session, and 20-25 being performed in the afternoon session. This same protocol was followed in competition; Felisha warmed up with the 20% implement, then the 10% implement, and would not perform throws with the competition weight until the competition began. This strategy was implemented into her pre-performance warmups for the 2016 USATF Olympic Trials and was a determining factor for her 2016 Olympic berth.
Recommendations
The movement patterns associated with the glide shot put are directed towards generating the maximum velocity of the shot under the given conditions. The athlete in the present study must continue to develop mobility, strength, and power production in order to make the following technical adjustments
1. Increase the blocking force at the front of the circle.
2. Maintain a loaded position throughout the glide into the push-off phase.
3. Maintain a constant increase in the shot acceleration by starting slowly and constantly raising the speed of the implement.
4. Continue to increase release velocity while maintaining a release angle of approximately 36 degrees as increases in strength and power permit.
5. Explore changing to the more efficient rotational technique (longer path of acceleration).
Conclusion
To achieve a longer application of force, Parry O’Brien and his coach pioneered the glide shot put technique by turning his back to the throwing area. The glide technique was subsequently modified and improved by throwers after him. As each phase of the shot put segues smoothly into the next, proper development of strength and power in each phase is essential for maximal performance. Felisha Johnson utilized a sound technical pattern with an optimal release angle that created the velocity necessary to accelerate the implement past the 19m mark. By using a scientific approach to the shot put that provides immediate visual feedback and release data (angle of release, direction of release, speed of release and height of release), the coach was provided with immediate feedback on several variables which the athlete has control over, allowing them to make minute adjustments as needed to improve the athlete’s performance and to develop a training protocol based on patterns exhibited by the athlete. Tremendous confidence was developed by relating biomechanical data and underlying principles to the presentation of fundamental techniques of shot putting. Evidence based proof provided by advanced modern technology tied to the laws of physics is both convincing and motivating to athletes. By adopting the above procedure in the selection and development of fundamental skills in the shot put, one can have increased confidence in the soundness of the conclusions. The Rio Olympian Felisha Johnson recorded the second best throw (19.24 meters) of her career at the Olympic Trials, no doubt aided by her ability to train for prolonged stretches without sustaining injury.
Acknowledgements
Thank you to USA Track and Field for their support of this study.
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