Countermovement Jump Assessment for Monitoring Prolonged Fatigue in Collegiate
Female Soccer Players
Authors: Wilkins Jeffrey A. 
Published: September 2020

Introduction: Females are 4 to 6 times more likely to sustain an anterior
cruciate ligament (ACL) injury than their male counterparts during running and cutting sports,
such as soccer. This sex disparity is thought to result from altered lower limb neuromuscular
control that females present when fatigued at the end of practice or games. Yet, current
fatigue monitoring techniques typically vary in their reliability, applicability and efficiency.
Purpose: The purpose of this study is to test the feasibility of the countermovement
jump (CMJ) to quickly and reliably monitor fatigue in female soccer athletes. Methods:
Twenty-two (age: 19.3 ± 1.1 yrs, ht: 1.7 ± 7.2 m, and wt: 61.9 ± 7.7 kg) females
from an NCAA Division I soccer team had peak isokinetic strength and power and specific ground
reaction metrics of a CMJ including: peak and rate of force/power development, impulse, and
reactive strength index modified, quantified immediately before off-season training, and
immediately prior to- and following the completion of the competitive season. Results:
Quadriceps and hamstrings peak torque and average power increased following the competitive season for
both limbs compared to pre-season and pre-training time points (all: p < 0.05). During the CMJ,
maximum rate of power production and peak force were greater at the post-season compared to
pre-training (p = 0.023 and p = 0.007, respectively) and pre-season (p = 0.024 and p = 0.044,
respectively) time points, while peak power was greater at post-season compared to the pre-training
(p = 0.018) time point. Changes in relative net impulse, peak power, peak landing force, and jump
height during the CMJ demonstrated moderate to strong relations to changes in isokinetic variables
from pre-training to post-season (all: p < 0.05, r > 0.4). Lastly, the same CMJ measures
accurately identified 96% of starters (Eigenvalue = 2.147, p = 0.038) and 86% of first-year
athletes, although the classification of first-year athletes was not statistically different
than non-first-year athletes (Eigenvalue = 1.279, p = 0.173). Conclusion:
The current research identifies the CMJ task as a promising tool for athletic trainers and sports
performance coaches to reliably monitor female soccer performance in general, and training loads
specifically. Immediately following the competitive season, the current athletes increased
isokinetic strength and power as well as CMJ performance, with changes in CMJ performance
exhibiting a significant relation to changes in isokinetic strength and power. Yet, following
off-season training, where isokinetic strength and power declined, albeit insignificantly, a
similar relation between changes in CMJ performance and isokinetic strength and power was not
observed. The experimental outcomes may indicate that the CMJ task is better suited for identifying
increases in strength and power rather than decrements and fatigue. These same CMJ measures may
serve as an effective tool for identifying improved strength and power, and performance differences
for specific members of a collegiate soccer team, as 96% of starters and 86% of first-year athletes
were accurately identified.