Quantifying Asymmetry and Performance of Lower Limb Mechanical Muscle Function in Varsity Athletes—Using Non–Countermovement Jumps

Abstract

Quantifying asymmetry and performance of lower limb mechanical muscle function in varsity athletes-using non-countermovement jumps. J Strength Cond Res 37(1): 98-106, 2023-The ability to automatically quantify jump performance and lower limb muscle function in athletes would be beneficial for both training and rehabilitation purposes. Countermovement jumps (CMJs) and non-CMJs (NCMJs) are simple, quick, and require relatively inexpensive equipment to effectively and reliably monitor lower limb function. In a previous study, CMJ characteristics were assessed across different varsity sports. This study is a follow-up study to incorporate NCMJs into assessing jump characteristics of the same sports and investigate the additional information provided by the complementary jump type. The main objective of this study was to look at a means of quantifying the lower limb mechanical muscle function automatically to provide information for rehabilitation and performance purposes in athletes of specific sports. Male and female varsity athletes from 4 different sports completed 5 trials of an NCMJ on dual force plates. An analysis program was developed using Wolfram Mathematica to analyze force-time jump data. Various parameters of interest were generated, including peak force, force-time curve shape classification, jump phase lengths, phase-specific kinetic impulse, asymmetry index, takeoff velocity, jump height, phase-specific center of mass displacements, and reactive strength index modified. Results obtained indicate that similar jump characteristics to the CMJ study can be quantified, which can be used for performance enhancement or injury rehabilitation. Additional data found, such as the ability of an athlete to hold a steady squat during an NCMJ, could also be meaningful in aiding trainers to design programs tailored for athletes.

Manuscript Clarification for “Quantifying Asymmetry and Performance of Lower Limb Mechanical Muscle Function in Varsity Athletes—Using Non–countermovement Jumps”

“…The present study describes sampling data at 1,000 Hz through dual force plates, where the raw ground reaction force (GRF) data are later passed through a 10th-order Gaussian filter to reduce noise. What they fail to acknowledge or justify is that in the other study (4) they describe resampling the data to 250 Hz. In previous studies, reducing the sampling frequency to this level led to identification or calculation errors in a range of outcome measures (2,6).…”

“…1. The authors refer throughout the article to another study that used their analysis program to evaluate the countermovement jump (4). The authors direct the reader to this study where they describe their data processing and analysis approach in full detail.…”

“…Request for Clarification: I read the recent paper by Stadnyk et al (5) with great interest as they evaluated the application of the non-countermovement jump (NCMJ) in quantifying asymmetry and performance of lower limb mechanical muscle function. As the NCMJ can provide insight on the concentric forces developed by the lower limb, understanding whether this can illuminate adaptations to typical sporting demands or accommodations because of an injury is valuable to the strength and conditioning coach.…”