# Changes in Body Mass and Movement Strategy Maintain Jump Height Immediately after Soccer Match
## 4 Discussion
Additionally, extended soccer match time (i.e., extra time) has been shown to further induce fatigue and the associated muscle glycogen depletion from 266 \(\pm\) 64 mmol\(\cdot\)kg\({}^{-1}\) dry weight after 90 min of match play to 186 \(\pm\) 56 mmol\(\cdot\)kg\({}^{-1}\) dry weight after an additional 30 min of match play [32]. This is noteworthy, given that depletion beyond \(\sim\)250 mmol\(\cdot\)kg \({}^{-1}\) is associated with reduced high-intensity exercise performance [33] and is specifically aligned with impaired exercise tolerance in elite soccer [34]. Although alterations in muscle glycogen stores post-match may be considered more of a metabolic than neuromuscular response, a recent study showed that through a principal component analysis, a force plate assessment of the CMJ can distinguish metabolic fatigue from NMF [35]; however, more research involving this approach is required. The total sweat rate was 2.04 \(\pm\) 0.57 L during first 90 min of soccer match play in the study by [PERSON] et al. (2023), and the lead author's research group previously reported that many professional soccer players are typically hypo-hydrated [36]. The monitoring and coaching of hydration status and strategies, respectively, can improve hydration among professional soccer players [36]. Although the intake of carbohydrate-electrolyte gels improved blood glucose levels and soccer dribbling performance during an extra-time period of a simulated match, it did not attenuate reductions in hydration status or CMJ height [37]. Body mass was not significantly lower 12 h after a soccer match compared to the pre-match values in a study involving NCAA Division 1 female players [14]. However, body mass and CMJ measurements were, unfortunately, not recorded immediately post-match [14], so it is unknown whether the participants experienced a reduction in body mass immediately post-match, similar to the present study, which then returned to pre-match values by the 12 h time point due to the replenishment of water and glycogen stores. Aside from the reduction in body mass, a shallower countermovement may have also contributed to the unchanged jump height post-match (Table 3). Previous studies have reported that a reduced countermovement depth leads to a reduction in CMJ height [38; 39; 40] by limiting the time and distance to generate a propulsive net impulse and work, respectively. Interestingly, the interactive effects of body mass and countermovement depth on the relationship between propulsive power output (propulsive work divided by time) and jump height in non-fatigued conditions were previously documented [41], but to the authors' knowledge, this is the first study to report acute alterations in each of these parameters due to competitive sports participation. In isolation, the countermovement depth was shown to be reduced immediately post-match [11] and on match day minus three [13] for male academy soccer players. Outside of soccer, the countermovement depth was shown to be the most sensitive CMJ variable when monitoring NMF across a full season in professional ice hockey [42]. Thus, the present findings suggest that reporting countermovement depth, along with body mass, jump momentum, or propulsive net impulse, alongside jump height, may be worthwhile when utilizing the CMJ to monitor acute NMF. Although not statistically significant, there was a small effect for the time to take-off (Table 3), which may suggest that a longer time is required to perform the CMJ despite a reduction in countermovement depth. While the current study was not able to prove this conclusively and only moderate pre-test reliability (ICC = 0.67) was noted, a previous cross-sectional study involving professional rugby league players (tested in a non-fatigued state) reported a very large correlation (\(r\) = 0.719, \(p\) < 0.001) between the time to take-off and countermovement depth [24]; thus, taking longer to perform the CMJ when performed with a shallower depth may be a potential subtle indicator of the presence of NMF and warrants further exploration.