Biomechanics Of The Glide Shot Put
This is an original article by Michael Young on the kinematics of the shot put. Coach Young guides us through each element of the glide shot put, from the preparation phase through the completion phase movement criteria.

By Michael Young United States Military Academy & Human Performance Consulting

    Throwing heavy objects is one of the oldest forms of competitive sport. In fact, Homer makes mention of rock throwing between soldiers during the siege of Troy. In the Iliad, Homer documents that throwing stones and rocks were an integral part of Achaean sport. From Homer's use of the term Ķᾳṱṳtwuȋǫȉǫ, meaning "thrown from the shoulder," Gardiner suggests that the Achaeans may have been practicing an early form of shot putting. This may be the earliest documentation of a shot put competition.
    In addition to the Greeks, Quercetani reports shot put-like events being practiced in ancient Scotland and Ireland as tests of strength. The exact technique used during these early feats of strength is somewhat unknown; in more recent history shot put technique of course has evolved greatly.
    This paper is the first in a sixpart series examining the kinematics of shot putting. The kinematics of the glide shot put from the initiation of the throw through the flight phase will be examined.

OPERATIONAL TERMINOLOGY

    Before going into discussion on the kinematics of shot putting, some terminology should be defined. The following terms were chosen to best simplify discussion and will be used wherever possible for the entire article series. The push-off leg will be defined as the leg that is last in contact with the throwing circle prior to the flight phase. For right-handed gliders, this is the right leg; for right-handed throwers using the spin technique this is their left leg. The rear foot will be defined as the foot that is towards the rear of the circle when the athlete touches
down following the flight phase. For right-handed throwers using both the glide and spin technique this would be the right foot. Likewise, the front foot is the one that is clo­sest to the toe board when the athlete is in double support following the flight phase. This is the left foot for a right-handed thrower using both the glide and spin technique.
    In addition to the performer terminology defined above, the following terms will be used to define various events and phases in the throw. The preparatory phase begins with the initiation of the throwing movement and is concluded at the moment of takeoff. Takeoff is defined as the moment at which the push-off leg breaks contact with the surface of the throwing circle and the athlete enters the flight phase. The period of time in which the athlete is moving towards the front of the throwing circle and has no contact with the throwing surface will be called the
- flight phase. Rear-foot touchdown (RFTD) is the point at which the thrower's rear foot makes contact with the throwing circle following the flight phase. Likewise, front­foot touchdown (FFTD) is the point at which the thrower's front foot makes contact with the throwing circle following the flight phase. The time between RFTD and release will be referred to as the delivery phase. The delivery phase will be further subdivided with the time between RFTD and FFTD being referred to as the transition phase and the time between RFTD and release the completion phase. See Figure 1 for a visual breakdown of the events and phases of the throw to be used in this review.

PREPARATORY PHASE

    As described above, the shot put will be broken down into its various phases by events within the throw to better facilitate interpretation of the data. The preparatory phase is
the first phase of the glide shot put and it is important for establishing a good position from which to start the throw. Several authors have sug­gested that the preparatory phase is important because the starting rhythm and balance present in the preparatory phase greatly affect the outcome of the throw.
    In general, preparatory phase movements should be simple yet effective while minimizing movements that do not contribute to the objectives of the phase.
    Two starting strategies have been employed for the glide technique: static and dynamic. The static start strategy is characterized by the athlete beginning the push­off from a stationary position. Using this starting strategy, throwers typically begin in single support with the athlete flexed at the hip, such that his/her trunk is lowered towards the ground.
    Several starting positions have been observed for the static start. The first is the more traditional "T-position." This starting position is characterized by the athlete balanced in single support on the rear leg with the nonsupport leg and trunk held close to parallel with the throwing circle to form a position resembling a "T".
    In the alternative static starting start position, athletes assume a crouched position. This position differs from the traditional "T­position" start in that the chest is lowered closer to the support leg and the non-support leg is tucked under the body, close to the support leg. Regardless of the specific technique, the free arm should be relaxed and used in conjunction with the non-support leg to maintain balance.
    Several authors have stressed the importance of a low starting position with the shoulders facing the rear of the circle. And while the crouch position may permit a lower starting position, Holmes believed that there is no true advantage to either technique. One thing that should be noted, however, is an athlete's individual strength levels may play an important role in determining which starting position is best for a given athlete. Several authors have suggested that lack of strength may make the preparatory phase particularly difficult to execute proficiently and starting in a position that is too low may have detrimental effects on all subsequent phases of the throw.
    The alternative starting tech­nique to the static start is the dynamic start. Athletes using the dynamic start technique initiate movement from an upright position. They then drop aggressively into a low position from which the initial push-off is made. Some have claimed that a dynamic start can increase the range over which the implement may be accelerated as well as increase the momentum of the athlete-plus-shot-system (APSS). The validity of these state­ments has not been verified and both the static and dynamic starts have been observed in elite shot putters.
    As hinted above, the dynamic start concludes with the athlete in a position very similar to the starting position of the static start. That is, following the aggressive drop from the upright position, the athlete's trunk will be lowered close to the flexed support leg. This shared position provides the advantage of both lowering the starting position of the implement and also placing it outside of the ring.
    As discussed previously, this theoretically permits a greater range over which the implement can be accelerated. This position is also thought to place the support leg in a position from which it is better able to accelerate the APSS into the takeoff as well as place the trunk musculature in a position from which it will be able to greatly contribute to the final delivery of the shot.
Just prior to the initial push­off, throwers flex the knee and hip of their non-support leg so that it comes underneath the body. Combined with the aforementioned trunk and support-leg flexion, this puts the athlete into a low and compact position. It is from this position that the athlete begins the drive across the circle. This drive consists of a combination of several well coordinated but separate movements:
       1. A backwards shift of the athlete's center of mass (COM) beyond the limit of his base of support. This shift is brought about by the downward and forward swing of the non-support leg and an accompanying backward falling action of the thrower's hips. This action is referred to as "unseating."
       2. Active extension of the non-support leg toward the front of the circle.
       3. Extension of the support leg.
    Ward suggested that the athlete should unseat (allow his weight to shift backwards) and then push with the support leg without emphasizing the action of the non-support leg. Others have claimed the non-support leg plays a crucial role in the push-off portion of the preparatory phase. Some suggest that both legs should extend simultaneously for optimal effect. Others suggest that it is best to first unseat, actively drive the non-support leg towards the toe board, and then push with the support leg.
    Experimental data from Mileshin confirmed that the latter movement strategy is the most common in elite throwers. This data indicated most elite throwers complete extension of the non-sup­port leg prior to extension of the push-off from the support leg.
    Opinions on the action and function of the action of the non­support leg differ. One use of the non-support leg is indirectly in­creasing propulsive forces at takeoff (13, 59, 60, 80). As attainment of maximum velocity of the APSS at takeoff is likely not beneficial and the push-off is primarily achieved by the support leg, the benefit of this use of the non-support leg is questionable.
    Another role suggested for the non-support leg is to help direct the trajectory of the APSS push-off. In this role, some suggest that the non-support leg should assist in generating both horizontal and vertical velocity of the APSS. These authors claimed that the non-support leg should be both forward and upward rather than directly to the toe board. On the other hand, others have claimed that the non-support leg should be directed towards the toe board to enhance horizontal movement. The coordination of such an action is said to be simpler and also facilitates correct foot contact with the ground. It has also been cautioned that if extension of the non-support leg is directed too high, it becomes difficult for the thrower to keep his upper body in the desired position.
    In addition to the lower body kinematics, several recommenda­tions have also been made for the positions and movement of the upper body during the preparatory phase of the glide technique. Most of these suggestions are related to the orientation of the shoulders. Several authors have suggested that the shoulders should face the rear of the throwing circle throughout the preparatory phase. Other authors have suggested that a relaxed and extended free arm during the preparatory phase may assist in orienting the thrower's shoulders in the appropriate directio.

TAKEOFF

    The final moment of the pre­paratory phase is the takeoff. This is the instant at which the athlete's support foot breaks contact with the ground and the athlete enters a pe­riod of flight. Intuitively it may seem as though athletes should strive for a maximal takeoff velocity. This is not necessarily the case. Several authors have suggested that all movements prior to RFTD are subordinate movements with a primary objective of creating favorable positions for the delivery. As such, a successful takeoff may be more characterized by the effect it has on the positions an athlete is able to attain later in the throw than by the attainment of maximal linear velocity. This is supported by the findings of another study which compared the flight phase durations of skilled and highly skilled shot putters using the glide technique and found no significant difference (0.13s vs. 0.14s).
    In light of this, recommenda­tions for the takeoff position have been focused more on influencing body position for the subsequent delivery rather than on the magnitude of the final push-off. For instance, some authors have suggested that some shoulder-hip separation should be evident by takeoff.
    Shoulder-hip separation refers to the differential angle formed between the plane of the shoulders and the plane of the hips in the transverse axis. Holmes suggested that this separation may be aided by the action of the non­support leg, which should encourage the hips to turn sideways while the shoulders remain facing the rear of the circle.
    Two foot positions have been observed for the final push-off in the glide technique: takeoff made from the heel with a dorsiflexed ankle and takeoff from the toe with a plantarflexed ankle. Grigalka stated that short athletes typically push off from the heel while taller athletes push off from the toe without fully extending the knee. Although Turk and others have suggested that the heel should be the last contact point before takeoff, there is no known research indicating that one technique is superior. In fact, some have suggested that this matter is of little importance with the preferred technique being dependent on the individual athlete.

FLIGHT PHASE

    As soon as the push-off has been completed, the athlete enters the flight phase. Following takeoff in the glide technique, the push-off leg should travel close to the ground and land close to the center of the circle . Several authors have recommended that the push-off leg be actively and rapidly brought underneath the COM of the APSS during the flight phase and the free arm used to counter the movement of the legs to keep the shoulders facing the rear of the circle.
    Most of the implement speed present during the flight phase is lost at RFTD. For this reason, several authors have suggested that the primary benefit of the flight phase may be to elicit a stretch-shortening cycle by plyometrically loading the lower extremities for a more powerful delivery of the implement. If this is true, greater vertical displacement of the APSS during flight may be more beneficial than attempting to maximize horizontal velocity of the APSS.
Previous research has reported a wide range of durations for the flight phase. Some researchers have reported durations of 0.4­0.5s while others have reported significantly shorter durations (<0.2s). It is unclear why the difference in results is so large but some of the variance may be explained by different throwing styles.
    Large variation has also been reported for the length of the flight phase (as indicated by the dis­placement of the foot from takeoff to RFTD). According to Hay, the linear displacement of the push-off foot during the flight phase varies greatly from athlete to athlete with the stature of the athlete being the primary determinant.
    For an effective delivery, the RFTD must be made somewhere within reasonable distance of the center of the throwing circle. Hay speculated that taller athletes, who require a slightly wider completion phase stance due to their size, often restrict the length of their glide to less than 1.05 m and thus place the rear foot either on the center line or just behind it in the rear half of the throwing circle.
    Likewise, shorter athletes, who benefit from a narrower completion phase stance, must travel more than 1.05 m during the flight phase and typically make RFTD in the front half of the ring. These claims are supported by a study by Alexander and colleagues which examined the displacement of the push-off foot for subelite male and female throwers during the flight phase and found that it was highly correlated with the athlete's height.
    Despite the findings above, height alone does not fully explain the variances observed in flight phase length and it is likely that other factors may also be responsible. For instance, Stepanek examined male and female shot putters and found that females tend to have shorter glides (0.15 m) than their male counterparts. As females are typically shorter in stature than their male counterparts, this would necessitate that women take off deeper into the circle for Hay's observations to be completely true. Such a starting position has not been previously noted.
    Other research examined elite male and female athletes using the glide technique and found only two athletes with flight phases longer than 1.05 m and many consider­ably lower than Hay stated (with the shortest female flight phase being 0.74 m and the shortest male 0.79 m).
    A final factor, which certainly plays a role in the length of the flight phase, is the specific technique employed by the athlete. Two distinct variations of the glide tech­nique have been observed. The first technique is likely the one that Hay described in which the throwers generally make RFID somewhere close to the center of the circle. This is referred to as the long-short technique because it is characterized by a longer flight phase and a shorter completion phase stance.
    The second variation of the glide technique was first popularized by the East Germans and is characterized by a shorter glide and a wider stance. Predictably, it has been named the short-long technique. Although some have advocated one technique over the other, both the long-short and short­long techniques have been observed among elite athletes of both genders.
    Previous literature has indicated that the optimal technique may be specific to the individual characteristics of a given athlete. According to Alexander and colleagues, the narrower stance observed in the long-short technique may be better for less powerful athletes. In contrast, the wider stance of the short-long technique allows for a longer delivery path, but it likely requires greater strength and power.

REAR-FOOT TOUCHDOWN

    Following the flight phase, in which the push-off foot travels close to the ground, the push-off foot lands near the center of the circle. Much has been written about
the orientation, position, and location of the foot at RFTD (rear-foot touchdown). Hay noted that the orientation of the foot at RFTD varies greatly from athlete to athlete. Despite this, several authors have suggested the foot should be turned 45°-90° from the direction of the throw. Others have suggested the foot be oriented more (80°-135°) towards the rear of the circle.
    No known research has exam­ined whether one orientation is superior to the other. Indeed, the problem may be more complex than simply having a universally superior foot orientation. The optimal foot position may be related to whether an athlete employs a long-short technique or a short-long variation of the glide.
    More specifically, the delivery phase of an athlete using the narrower stance associated with the long-short technique may require a more forward-facing orientation than an athlete using the short-long technique. The reason for this dif­ference is the dissimilar action and function of the rear leg during the delivery phase of each glide technique variant.
    Several authors have suggested that RFTD should be made flat­footed. These suggestions have largely been made on the grounds that extension of the rear ankle could then begin immediately without the necessary delay of first having to flex the ankle and lower the heel.
    An alternative reasoning is that the ankle joint is the weakest joint in the lower extremity and, as a result, complete contact between the foot and the ground may be a more effective technique when athletes are attempting to apply maximum force to the ground.
    While this may be true in theory, many have made suggestions to the contrary. Of these authors, Grigalka and Kristev further suggested that an upward movement should immediately follow ground contact. Hay noted that a forefoot landing at RFTD is far more common among elite throwers than a flat-footed landing. It is obvious that more research is necessary to determine the rela­tionship between foot position and overall technique (short-long vs. long-short) and whether one foot position is superior.
    Location of the foot position at RFTD has also been discussed. Most are in agreement that RFTD should be made directly under the athlete's center of mass. Mechanically, however, there may be an advantage to RFTD being made slightly behind the athlete's center of mass. Such a position would likely provide a mechanical advantage to accelerate the upper body during the delivery phase. There will be some variation depending on whether the athlete is using a short-long or long-short technique, but most authors have recommended that RFTD be made near the center of the circle.
    Several other recommendations have been made regarding the position of the thrower at RFTD. As was the case during the preparatory and flight phases, many have written that the trunk should face the rear of the circle. It has also been widely suggested that the knee of the rear leg be flexed at RFTD. In fact, a study by Young and Li indicated that among elite female shot putters, rear-knee flexion at RFTD has a strong positive relationship with performance.
 

TRANSITION PHASE

    The period of time between RFTD and FFTD is the transition phase. Many authors are in agreement to the importance of this phase of the throw. Moreover, Ariel claimed that this phase is the primary distinguishing factor between good and elite athletes using the glide technique. The importance of this phase is likely due to the effect it can have on the acceleration pattern of the implement.
    A poorly executed transition phase will result in great decelera­tion of the implement. Bosen observed decelerations ranging from 1-2.75 m/s during this phase. Conversely, a well-executed transition phase will produce a significant acceleration of the implement during the transition phase.
    A well executed transition phase has also been noted as the initial condition for a long completion phase trajectory. Furthermore, Ariel stated that the primary objective of this phase should be to minimize deceleration of the center of mass of the athlete-pIus-shot system and allow transfer of energy to the delivery.
    Achieving these objectives appears to be largely a matter of timing. Previously reported transition phase durations for athletes using the glide technique range from near simultaneous rear-foot and front-foot touchdown to 0.37 seconds.
    Many authors have suggested shorter transition times are bet­ter for athletes using the glide technique. Experimental data on elite athletes supports this point. It should be cautioned, however, that a simultaneous rear-and front-foot touchdown (making transition phase duration = 0.0 seconds) is probably not advisable. While some have suggested a simultaneous landing of the rear and front foot, most authors agree that the rear-foot should land prior to the front-foot. While a shorter transition time is beneficial, some authors (61, 63, 70) have suggested a simultaneous rear and FFTD may be detrimental because it may halt the forward momentum of the athlete-pIus-shot system.

FRONT-FOOT TOUCHDOWN

    Two different techniques for FFTD have been described in the literature: a forward-downward drive of the foot into the toe board and a downward "raking" movement with the front foot toe turned somewhat in the direction of the throw.
In the first case, the foot initially contacts the ground with the toe and then flatly contacts the ground. In the second method, the landing is flat-footed permitting an earlier active extension of the limb.
    Whatever the case, observations of elite throwers indicate a more active placement of the front leg at FFTD is beneficial. In other words, top athletes using the glide technique appear to actively direct the front foot towards the ground rather than passively waiting for ground contact to occur.
    As with the RFTD, recommendations for FFTD generally focus on the orientation and location of the feet. Tschiene suggested that both feet be oriented approximately 90° from the direction of the throw.
    It is generally recommended that FFTD be made near the toe board and because this is typically the case, considerably less variation is observed in FFTD location when compared to RFTD location. There is still considerable variability in the width of the completion phase stance (distance between RFTD and FFTD) as a result of the variation in RFTD location.
    Several researchers have reported stance widths rang­ing from less than 0.8 to over 1.1 meters. The simple explanation of this variance is it is a result of throw­ers intentionally using a short-long or long-short technique. Athletes using a short-long glide technique shorten their flight phase and make RFTD closer to the rear of the ring with the intention of having a wider stance from which to deliver the shot. Conversely, athletes using the long-short technique cover a greater distance during their flight phase, make RFTD closer to the front of the circle and subsequently have a narrower completion phase stance at FFTD.
    There are pros and cons for both variations of the glide. Authors advocating the narrower stance (<1.0 m) of the long-short technique assume that such a position provides a greater opportunity to apply force from the lower extremity because of a longer period of knee extension.
    However, a narrow stance has the disadvantage of decreased bal­ance during the completion phase and a potentially shorter implement trajectory during the completion phase. A wider completion phase stance (1.0-1.2 m) reduces the amount of force that can be applied by the rear leg but lengthens the path over which the implement travels during the all-important completion phase.
    Analysis has shown that the advantages of increasing the length of the completion phase path outweigh the loss from incomplete use of the strength of the rear leg, provided that the strength of the rear leg is sufficiently high.
    Interestingly, both Stepanek and Knudson reported slightly wider completion phase stances for elite women than elite men. Stepanek speculated this was because of women's shorter flight distances. Among a sub-elite population, Alexander and col­leagues reported opposite results with the average width of stance for women and men being 1.01 m and 1.13 m respectively.
    It appears that elite women either have shorter flight distances than their sub-elite counterparts or sub-elite women begin their preparatory phase motions with their support foot placed closer to the center of the circle. Further research is necessary to fully understand this relationship.
In addition to the width of the completion phase stance, recommendations for the fore-aft positioning of the feet have also been made. It is generally recommended that the toe of the rear-foot and the heel of the front foot should straddle the midline of the throwing circle.
    Research data indicates the front foot contacts the ground 0.15-0.20 m or 0.20-0.35 m behind the rear leg. Lanka suggested the distance of separation is dependent on the variation of glide technique used by the thrower. If emphasis is placed on rotation during the delivery as is typically the case in the long-short technique, the front foot should be placed more posterior to the rear-foot.
    Additional recommendations have also been made on the positions of the shoulders at FFTD. Several authors have claimed that the shoulders should remain facing the rear of the circle at FFTD because of the lengthening affect it will have on the completion phase trajectory path. However, Ward suggested the hips and shoulders should be slightly turned from the initial rear-facing position to enhance continuity of the implement's movement.
    Perhaps more importantly, considerable discussion has been made on shoulder-hip separation at this point of the throw. While some have claimed that the axes of the shoulders and hips should be parallel to each other and facing the rear of the circle at FFTD, it is difficult to achieve this position. In fact, Zatsiorsky and colleagues pointed out that the hips are more likely to be aligned in the direction of the throw due to the fact that the backwards movement of the non­support (front) leg at takeoff tends to turn the hips and because the feet are placed at least 1 m apart.
    Perhaps due to this, some au­thors no longer consider this position to be incorrect, provided the transverse plane of the shoulders is perpendicular to the direction of the throw. This is because the "open" hip position has the advantage of placing the muscles of the trunk on greater stretch and permits an earlier initiation of the put.

COMPLETION PHASE--­MOVEMENT CRITERIA

    The final phase of the throw is the completion phase. The completion phase begins with front-foot touchdown (FFTD) and continues until the moment of release. The outcome of a throw is largely determined by what happens during this phase. In fact, Turk suggested that 80-90% of the distance of the throw for gliders can be explained by what occurs during completion.
    Most authors consider FFTD as the begin­ning of the completion phase and for the purposes of this review, it will be seen as such. It should be noted, however, that others have defined the completion phase as the final coordinated sequence of movements that culminates in the release of the shot.
    Using this less precise definition of the completion phase, some have suggested that the completion begins at rear-foot touchdown (RFTD). Booysen, noting that the shoulders and hips begin to turn prior to RFTD, actually thought that the delivery of the implement began while the athlete was still in flight. This would mean that the completion phase begins prior to RFTD.
    Any debate, however, may be moot with an examination of both implement and athlete-pIus-shot center of mass velocity profiles for the glide technique. These profiles indicate that a rapid acceleration occurs only after FFTD is made.
    Others have refined this defini­tion to suggest that the completion phase begins with the weight shift from the rear to the front leg. As stated above, this review will consider the completion phase to be the time between FFTD and release.

GENERAL OBJECTIVES

    The primary purpose of the completion phase is to maximize implement velocity while releasing at an angle, height and horizontal release distance that are suitable for high-level performance while still permitting a fair throw. Several mechanical and biological principles underlie the attainment of this goal: the length of the completion phase implement acceleration, the speed of the performer's movement during the completion phase, the attainment of positions which allow the athlete to generate the greatest magnitude of force in the direction of the throw, and development of conditions which allow the athlete to remain in the circle once the implement has been released.
 

Criterion 1: Foul prevention
    The first factor affecting the effectiveness of the completion phase is the development of conditions that allow the athlete to remain in the circle once the implement has been released. In fact, all subsequent criteria could be considered subordinate to this factor. If the thrower is unable to remain in the ring following the release of the implement it is of little consequence how well the previous three criteria were executed.
    Several recommendations have been made to set up such a scenario. One recommendation is to ensure maximum transfer of momentum from the athlete-plus-shot-system to the implement during the final moments of the delivery. Such a transfer of momentum would not only be beneficial with regards to the legality of the throw (whether it is fair or foul), but also to projected distance.
    Several recommendations have been made on how best to produce this transfer of momentum. For instance, Ariel suggested that deceleration of the hips greatly contributes to the force applied to the implement and the transfer of momentum. Additionally, blocking the non-throwing side has been indicated as beneficial because it accelerates the throwing side and allows for greater transfer of momentum to the implement.
    Another way in which the athlete can preserve a throw is by stopping his own momentum fol­lowing the release. In fact, several authors have suggested this is one of the primary benefits of the glide technique. The performer's final movements of the delivery as well as those immediately following release may be effectively used to stop the thrower's forward momentum and preserve a fair throw.
    As momentum is the product of mass and velocity, and the mass of the athlete is certainly not going to change, it becomes clear that the horizontal velocity of the athlete needs to be halted. To do so, braking forces in the opposite direction of the throw must be applied. Bartonietz and Bartonietz and Borgstrom claimed that the wide stance observed in the short-long technique can improve conditions for a braking action of the front leg and also helps to stabilize the body. Besides this, there is still considerable debate over what are the most efficient way and time to apply this braking force.
    In general, three movement strategies have been observed to preserve a legal throw. In the first option, the athlete stops their for­ward momentum by applying braking forces in the final moments of the delivery phase and immediately following release. Knudson referred to this method as the non-reverse, because unlike the other two methods, the athlete does not switch the position of his feet following release. Although Ward suggested this method to be optimal, it has rarely been observed among elite level shot putters.
    As indicated above, the two other methods of preserving a throw in­volve an exchange in the position of the front and rear feet. The first such technique is called the step-reverse or delayed reverse. Using this method, the forward momentum of the athlete is adequately stopped so as not to require a full exchange of foot positioning, but the athlete does step forward with the rear foot after a considerable delay from the release. The delayed reverse has been said to allow time for increased range of motion at the hip to take place and when combined with a violent blocking action, it can be very effective in stopping the athlete's forward momentum.
    The final method used to preserve a legal throw is the so-called reverse. This technique is characterized by the athlete exchanging the front and rear foot positions so that the rear foot can be used to stop the forward momentum of the athlete-plus-shot system. Several authors have advocated this method as best for stopping momentum and prevent­ing foul throws without being det­rimental to the projected distance of the throw.
    Whatever the case, some have suggested that the reverse should not begin before release and should only result from an explosive extension of the lower extremity rather than being thought of as an action unto itself. The validity of this statement remains in question as it appears to contradict the overwhelming use of the jumping release observed in elite throwers.
 

Criterion 2: Increase speed of movement
    The second factor that de­termines the effectiveness of the completion phase is the performer's speed of movement. Stepanek noted
that the duration of the completion phase is inversely directly related with performance. Dessureault suggested that the best performers reduce the time of their completion phase . This is supported by data on athletes of varying skill levels.
    The duration of the completion phase for sub-elite athletes has been observed to be as great as 0.4 seconds while the duration for elite throwers typically falls in the range of 0.2-0.3s. This is especially interesting considering the best throwers typically move the implement over a greater distance during the completion phase. This means that the best athletes are moving the implement over a greater distance in a shorter period of time. This speaks strongly to the incredible power needed to compete at the highest levels of shot putting.
 

FROM: TRACK COACH 180