Ground Reaction Forces
Rate of Force Acceptance as an Injury Prevention Strategy in Athletic Populations (Open Access)
Authors: Jeronimo, Luis; Pelot, Tim
Looking at ground reaction forces in previous studies it suggests that injuries are typically correlated with eccentric muscle actions. Making the ability to rapidly absorb force a key part of injury prevention. Having poor deceleration may be a precursor to injuries in the lower half, evidence suggests that most ACL injuries occur during deceleration, pivoting or landing. If certain muscles are not able to absorb the force effectively the ligament may be forced to pick up the slack.
It was suggested that training with light and heavy loads (15-35% and 85-90% of 1RM) in certain exercises may help train athletes in injury prevention. Training with lighter loads leads to faster movements while heavier loads lead to higher force production.
Training to tolerate high eccentric forces in the lower half and arm may play a key role in injury prevention in an athlete’s training.
Authors: McNally, Michael P.; Borstad, John D.; Onate, James A.; Chaudhari, Ajit M.W
18 former competitive baseball players threw off of a mound to measure ground reaction forces under both the drive and stride legs.
Stride leg ground reaction forces during the arm-cocking and arm-acceleration phases were strongly correlated with ball velocity. Drive leg ground reaction forces showed no significant correlations.
More specifically the ground reaction forces of the stride leg in the vertical and posterior directions, as well as resultant ground force, were strongly correlated to peak wrist velocity. Meaning that force against the direction of the throw appears to contribute strongly to velocity as it explained 61% of the variance in wrist velocity.
Not all of the baseball players in the study were pitchers previously and none of the players were currently playing competitively. These findings do suggest that the study should be replicated with pitchers who are playing competitively to compare the results.
It also is suggested that improving eccentric knee flexion control through single-leg exercises and plyometrics would improve stride leg forces and ball velocity.
Authors: Laffaye, Guillaume; Wagner, Phillip; Tombleson, Tom
This study looked at different markers of the vertical jump to see what differences there were with different genders and athletes who play different sports.
The study looked critically at average eccentric rate of force development, total time, eccentric time, ratio between eccentric and total time, and average force. These were taken from force-time curves in a countermovement jump.
Athletes used jumping strategies which reveal specific constraints of the sport that they played. It was found that football and baseball players tended to display more explosive profile. Usually having high values of average eccentric rate of force development, average force as well as higher value in jump height. This suggests that even though football and baseball aren’t focused on vertical jumping they require more maximal rested explosive muscular actions which translates to a higher vertical jump. This could mean that the force component is dependent on the muscle-tendon system regardless of the direction of the ground reaction force.
Authors: Lehman, Graeme; Drinkwater, Eric J; Behm, David
There is a lack of research examining throwing velocity with frontal and unilateral exercises. This study aimed to examine a number of lower-body tests with velocity: medicine ball scoop toss, medicine ball squat throw, bilateral vertical jump, left leg vertical jump, right leg vertical jump, broad jump, triple board jump, hop and stop from left to right, hop and stop from right to left, lateral to medial jump right (LMJR), lateral to medial jump left (LMJL), 10-yd sprint, 60-yd sprint, and both left and right single-leg 10-yd hop for speed.
The lateral to medial jumps were found to have a consistent correlation to high velocity in both right and leg handed throwers. The lateral to medial jump is a unilateral jump in the frontal plane that mimics the stride.
This finding suggests that the ability to push of the trail leg is correlated to velocity. In theory having a powerful leg drive sequenced into the pitching delivery would enable more energy to be transferred up the kinetic chain. This is in agreement with the findings of MacWilliams et al. in “Characteristic ground-reaction forces in baseball pitches”.
Future studies should examine different training in the frontal plane to see if increases throwing velocity occur.
Authors: MacWilliams, Bruce; Choi, Tony; Perezous, Mark; Chao, Edmund; McFarland, Edward
This study found high correlations between push off and landing forces with different sections of the pitching delivery. Specifically push-off forces during with cocking phase and the landing force with ball release.
Within the group of pitchers there was a lot of variance. Some pitchers exhibited increasing ground forces with an increase in wrist velocity and others demonstrated the opposite. The more force they produced the slower wrist velocity. This likely means that the amount of force you can produce shouldn’t be the sole focus of training but the timings of those forces.
The authors also found that pitchers that produced the highest forces (normalized to body weight) threw the fastest. Which would contradict the theory that pitchers should have a ‘controlled fall’.
Authors: Elliott, Bruce; Grove, Robert; Gibson, Barry
This study wanted to examine if ground reaction forces of the back leg changed during the windup versus the stretch position and between throwing a fastball or curveball.
Vertical and Horizontal force of the back leg reached its peak during the arm cocking phase for both the fastball and curveball in both the stretch and windup.
Some interesting difference appeared when splitting the pitchers into high velocity and low velocity groups. The maximum forces were similar with both groups peaking at arm cocking. The slower pitchers seemed to begin their back leg drive earlier. The forces decreased faster between the cocked position and stride-foot landing for the slower pitchers. The faster pitchers had higher force readings on their back let at front-foot landing. The researchers found that the faster pitchers had the ability to drive the body over a stabilized front leg.
This study only included 6 pitchers. Further research should be completed with a larger sample size and with a force plate at front foot landing as well.
The researchers found that pitchers should find a balance between ‘pushing off as hard as they can’ and ‘having a controlled fall.’ Trunk rotation and forward movement of the throwing arm did not occur until after the stride foot had planted.