Evaluating and Developing Force Plate Practice for Monitoring Lower-Body Neuromuscular Function in Soccer

Badby, Andrew

Abstract

The aim of this thesis was to evaluate and identify a best practice for force plate assessments for monitoring lower body NMF in soccer. It was evident following a literature review and scoping review that there is a variety of options for force plate testing application, but no general consensus on a best practice approach for the purpose of monitoring acute changes in NMF. The scoping review highlighted the CMJ and DJ tests as the most utilised in studies monitoring acute changes in NMF using force plates. From study 1, the HD Inc. wireless dual force plate system can be considered valid for collecting CMJ and DJ force-time data, because no fixed or proportional bias was present for any CMJ variable (N = 17) and was present for only 2 out of 18 DJ variables, where percentage differences were considered small when compared to a laboratory grade “gold standard” system. The mean effective fall height recorded during the DJ test was approximately 5 cm less than the prescribed 40 cm box height, which renders the DJ unsuitable as an assessment in physical profiling (i.e., for objective benchmarking) unless fall height can be established during trials. The utility of the CMRJ test (i.e., alternative RJ test where fall height is determined by a preceding CMJ) was investigated in study 2 following this determination. Acceptable test-retest reliability was demonstrated for 13 CMJ metrics for professional soccer players in the pre-season period in study 2 (a). Acceptable test-retest reliability was demonstrated for a limited number of CMJ (N = 5), DJ (i.e., only body weight and net braking impulse), CMRJ (i.e., only body weight and RJ portion net braking impulse) metrics and no IMTP metrics for youth soccer players in the pre-season period in study 2 (b). Acceptable test-retest reliability was demonstrated for 15 CMJ metrics for youth soccer players in the in-season period in study 2 (c). In study 3, a targeted sampling approach led to 7 professional EFL clubs with a total of 139 professional (age: 24 ± 5 years; height: 184 ± 7 cm; mass: 81 ± 9 kg) and 137 youth (age: 17 ± 1 years; height: 178 ± 17 cm; mass: 72 ± 8 kg) soccer players being recruited, where acceptable within-session reliability was demonstrated for 32 CMJ metrics, and 25 of these metrics discriminated between professional and youth soccer players in the pre-season period. Acceptable within-session reliability was demonstrated for all CMRJ CMJ portion (N = 5) and RJ portion (N = 25) metrics, and CMJ portion body weight and 20 RJ portion metrics discriminated between professional and youth soccer players in the pre-season period. Peak force and relative peak force derived from the IMTP test demonstrated acceptable within-session reliability and discriminated between professional and youth soccer players in the pre-season period. Out of the 15 CMJ metrics which demonstrated acceptable test-retest reliability in study 2 (c), 14 of these metrics demonstrated sensitivity to change and thus utility for monitoring acute changes in NMF following a competitive, in-season, youth soccer match in study 4. Based on the body of work produced within this thesis, the author proposes the use of a combination of 10 (out of an applicable 28) CMJ metrics for different purposes. Specifically, jump momentum, mean propulsive power, and mean propulsive force may be applied concurrently for objective benchmarking and monitoring acute changes in NMF. Additionally, metrics such as mRSI, JH, relative mean propulsive power, and relative mean propulsive force may be utilised as objective benchmarks for professional and youth soccer players in the pre-season period, and metrics such as propulsive phase time, countermovement depth, and body weight may be utilised for monitoring youth soccer players’ acute changes in NMF in the in-season period. From the key findings in study 3, practitioners may also utilise CMRJ RJ portion RSI, JH, jump momentum, mean propulsive force, relative mean propulsive force, mean propulsive power, and relative mean propulsive power, and IMTP peak force and relative peak force, for objective benchmarking for professional and youth soccer players in the pre-season period. A physical practitioner working in soccer can utilise the information presented within this thesis including test and metric selection, appropriate data collection and analysis procedures, statistical processes for determining objective benchmarks and observing meaningful change, and information regarding the practical application of these processes into real-world environments when utilising the wireless dual force plate systems.

• Thesis Type: Thesis
• Deposit Date: Jan 8, 2025
• Publicly Available Date: Feb 24, 2025
• Keywords: Sports Science; Strength and Conditioning; Biomechanics; Four Corner Model; Physical Corner; Preparedness; Profiling; Reporting; Statistical Analyses; Association Football.
• Award Date: Jan 23, 2025