ECSS Paris 2023: OP-AP10
INTRODUCTION: Many authors reported changes in Total Distance (TD, measured by GPS) and Dynamic Stress Load (DSL, measured by accelerometry) at the end of soccer matches, suggesting the possible influence of fatigue (Bradley PS et al., 2009). Fatigue induces many changes in the pattern of movement, such as increased ground contact time and stride frequency, reduced stride length and a flatter centre of mass trajectory (Small K et al., 2013). Some authors reported reductions in Locomotor Efficiency (LE), calculated as the ratio between DSL and TD (Barrett S et al., 2016), at the end of basketball matches (Vazquez-Guerrero J et al., 2019) and Oliva-Lozano et al. (2020) also reported lower LE in the second half compared to the first half. It was suggested that LE might be able to capture some of the fatigue-induced changes in the biomechanics of movement, due to the higher reductions in accelerometer-derived load compared to TD. Thus, the aims were to investigate: the within-match changes in LE and the differences in LE between starters and substitutes. METHODS: Under 19 male (n=35, 17.8±0.4 yrs, 72.1±4.9 kg, 179.7±6.7 cm) and adult female (n=33, 24.3±5.6 yrs, 61.4±5.8 kg, 168.5±6.0 cm) players from a professional Serie A soccer club participated in this study. Using a GPS that included an accelerometer on board (Apex model, STATSports Technologies, USA), TD, DSL and LE were measured in 60 matches of the 2022–23 season (34 U19 and 26 senior female matches) collecting 639 individual match data. Mixed models were used to analyse differences between the six 15-minute time frames (T1 to T6). Tactical role, match location, opponent’s rank and soccer match result were included in models to control for contextual variables. RESULTS: For males and females, TD and DSL were higher in Q1 than all other time frames (all p<0.015) and were higher in Q2, Q3 and Q4 than Q5 and Q6 (all p<0.004) . For males and females, LE was higher in Q1 than Q3, Q5 and Q6 (all p<0.021) and was higher in Q4 than Q5 and Q6 (all p<0.001). These results indicate that the reduction in DSL was higher compared to the reduction in TD. LE of substitutes in Q6 was higher than starters (p=0.005), suggesting that LE might reduce under fatigue. CONCLUSION: Compared with the beginning, LE was reduced at the end of the soccer match, suggesting a biomechanical running pattern change (Buchheit M et al., 2015) which might be partially related to the development of players’ fatigue during games. In comparison with substitutes, starters players showed lower LE at the end of matches, which might indicate that they alter their biomechanical running pattern, possibly due to fatigue, not experienced by substitutes due to their reduced match time exposure.
Read CV Marco MartinECSS Paris 2023: OP-AP10
INTRODUCTION: High training load (TL) is a potential risk factor for injury in non-elite adolescent team sport. A valid, easily applied measure of TL in this population is required where access to more sophisticated measures may be limited. TL may be calculated from the product of a rating of perceived exertion (RPE) score from a Borg CR-10 or CR-100 and session duration. There is limited research into the validity of this approach to determine TL in adolescent populations in field settings using paediatric specific scales of RPE. This study aimed to investigate the validity of the paediatric OMNI-RPE scale as a tool to calculate TL when compared to heart rate (HR) and velocity derived measures of TL in non-elite adolescent team sport athletes. METHODS: Part A involved completion of both an easy and hard version of a simulated team game circuit (each consisting of warm up, two sets of 5-minute intermittent running circuits and a cool down). Part B involved observations during usual team games. An OMNI-RPE (0 “not tired at all” to 10 “very very tired”) was taken 30 minutes post session. An OMNI TL, expressed in arbitrary units, was calculated as a product of the OMNI-RPE and session duration. This score was compared against other measures of TL namely, Edward’s Training Impulse (TRIMP), time spent in heart rate (HR) zones 4 and 5 (80-100% HR peak) and time spent in 0-25%, 25-50%, 50-70% and >70% velocity peak (VP). Heart rate and velocity were measured using Catapult Optimeye S5 units and compatible Polar T31 heart rate units. RESULTS: Twenty (age14.2±1.7 years; eight female) team sport athletes participated in Part A. For both the easy(E) and hard(H) versions of the circuit, low to moderate correlations were observed between OMNI TL and Edwards TRIMP (E r=0.2, H r=0.18) time in HR zones 4 and 5 (E r=0.33, H r=0.19), time spent in 25-100% VP (E r=0.46, H r=0.37), 50-100% VP (E r=0.39, H r=0.37) and 70-100% VP (E r=0.05, H r=-0.23). 34 different athletes (age15.2±1.5 years; 16 female) participated in Part B. Moderate to large correlations were observed between OMNI TL and Edwards TRIMP (r=0.53) time spent in HR zone 4/5 (r=0.45) time spent in 25-100% VP (r=0.42) and time spent in 50-100% VP (r=0.51). A low correlation was observed between OMNI TL and time in 70-100% VP (r=0.28). CONCLUSION: The larger correlations between OMNI TL and the HR and velocity derived measures of TL in the team game suggest OMNI TL may have greater utility in monitoring TL in a naturalistic setting rather than simulations. Compared to similar studies using Borg CR-10 or CR-100 RPE scales (perceived exertion from extremely weak to extremely strong), lower correlations between OMNI TL and HR derived measures of TL were observed in this study. This may be because the OMNI-RPE scale is anchored in perceptions of tiredness making it sensitive to weariness or fatigue, so may be influenced by other physical and psychosocial factors such as poor sleep and performance stressors.
Read CV David SainsburyECSS Paris 2023: OP-AP10
INTRODUCTION: The demanding nature of team sports can generate substantial fatigue, with recovery strategies being widely employed by practitioners to counteract fatigue accumulation during the competitive season [1]. However, the effectiveness of such strategies may partly stem from the placebo effect, which has been shown to produce moderate-to-large benefits on measures of performance (e.g., strength, aerobic/anaerobic capacity) [2,3] and well-being (e.g., muscle soreness) [4]. Despite the evidence linking the placebo effect to performance improvements, limited research is available regarding its role in post-exercise recovery strategies. Therefore, the aim of this study was to compare measures of performance, physiological and perceptual recovery between a placebo (PLA) and passive rest intervention (CON) after football matches. METHODS: Using a crossover design, 18 high-level, youth (i.e., under-16) male players completed two full-length (2x45-min halves) friendly football matches, followed by either PLA or CON. Specifically, PLA involved the use of a non-invasive vagus nerve stimulation device (Pulsetto, Vilnius, Lithuania) as a sham intervention, where no actual stimulation was delivered. To assess between-intervention differences, countermovement jump height (CMJ), 10 and 20-m sprint times, heart rate variability (Ln-rMSSD), perceived fatigue, static and dynamic (i.e., measured during a squat) muscle soreness were recorded at pre-match, post-match, post-recovery (i.e., shortly after PLA/CON) and 24 h post-match. Two goalkeepers participated in each match, but were not included in the analyses. RESULTS: Match-play induced substantial fatigue, with our main findings revealing significant deteriorations (p < 0.003) in CMJ (small-to-large effect size [ES]), 10- (moderate ES) and 20-m sprinting (moderate-to-large ES), Ln-rMSSD (moderate ES), perceived fatigue, static and dynamic soreness (large ES for all perceptual measures) in both interventions at post-match and post-recovery, compared to pre-match. Although no significant between-intervention differences were found for any variable at any time point (p > 0.05), perceived fatigue [ES (r) = 0.40] and dynamic soreness [ES (r) = 0.32] were moderately lower in PLA than CON at post-recovery. CONCLUSION: Our findings suggest that the placebo intervention did not directly affect the recovery of performance or heart rate variability. It did, however, show moderate benefits in reducing perceived fatigue and dynamic muscle soreness at post-recovery, compared to passive rest. While caution is warranted – due to the lack of statistically significant differences – these results highlight the importance of considering the placebo effect when designing research on recovery strategies and when employing them in applied settings, as even small effect sizes may offer meaningful benefits for athletes using placebo interventions [2]. REFERENCES: 1. Calleja-González et al. (2018); 2. Hurst et al. (2020); 3. Chhabra & Szabo (2024); 4. Nasser et al. (2023)
Read CV Marco PernigoniECSS Paris 2023: OP-AP10