# Changes in Body Mass and Movement Strategy Maintain Jump Height Immediately after Soccer Match
## 1 Introduction  
In professional soccer, half of surveyed strength and conditioning coaches report the regular use of force plates for the assessment of neuromuscular capabilities [1]. The rise in force plate assessments across the football codes is likely to continue as more commercially available and affordable force plate systems are validated against both industry gold-standard force plates [2; 3] and criterion data analysis procedures [4]. One application of force plate testing in professional sports is to monitor acute neuromuscular fatigue (NMF) [5]. Although several definitions of NMF have been proposed, it can be broadly defined as an exercise-induced reduction in (1) maximal voluntary force generation [6] and (2) the control of submaximal force production [7] by a single muscle or several muscle groups. In soccer, acute NMF has been shown to reduce kicking accuracy and increase the time required to perform a kicking task [8], in addition to increasing injury risk, particularly during periods of soccer fixture congestion [9]. Such congestion is characteristic of the modern soccer game, with players regularly, and for a large part of the calendar year, exposed to competitive match-play environments. Therefore, studies concerned with the assessment of acute fatigue are of considerable value. The bilateral countermovement jump (CMJ) is the most common test of lower-body neuromuscular readiness (i.e., recovery from NMF) in peer-reviewed studies involving athletes from the football codes, including soccer [10]. However, the application of force plate assessments of the CMJ in the context of monitoring acute NMF within the soccer literature is limited. Force plate assessments of either the bilateral or unilateral variationin the CMJ have been explored in academy males [11; 12; 13], collegiate females [14], and elite females [15] to explore the acute effects of soccer match play on NMF but with inconsistent methodological designs employed, most notably, distinctions in the CMJ variables presented for analysis, the timing of the post-match CMJ assessment(s), and the sample sizes. Consequently, the collective results from these studies have been largely equivocal, although some similar patterns can be identified. For example, a significant difference in bilateral CMJ height was observed in one study, with higher values before versus immediately after a soccer match [15], but this outcome was not reinforced [11] or evident for the unilateral CMJ height performance [12]. The post-soccer-match bilateral CMJ height was significantly lower than the pre-soccer-match values at two discrete time points (5 and 21 h post-match) in the study by [PERSON] et al. [15]. This was similar to the findings of a more recent study, with a lower post-soccer-match CMJ height reported 12 h post-match [14]. In this study, the post-match testing was not immediate (e.g., 12 h afterwards only). Interestingly, the reduced jump height values within the 24 h post-match period were reported only in the studies involving female soccer players [14; 15]. Despite the similar post-soccer-match unilateral CMJ height values, [PERSON] et al. [12] reported a reduction in the propulsive net impulse immediately after a soccer match (for both legs) and 24 h later (left leg only). A reduced propulsive net impulse should coincide with a reduced jump height when using the impulse-momentum method to calculate the latter [16], which the authors did, unless the players' body mass had reduced to counteract this. Thus, it may be deduced that the mean body mass had acutely reduced as a consequence of soccer match play. Acute reductions in body mass of \(\sim\)2% can be expected in response to soccer match play, and this can be attributed to dehydration and glycogen depletion [17].