ECSS Paris 2023: OP-PN27
INTRODUCTION: In team sports, horizontal deceleration (DEC) is a critical locomotor skill underlying sudden changes of velocity [1]. However, the effects of DEC during a repeated-sprint ability (RSA) test on muscle damage and underlying recovery kinetics are underexplored, despite the potentially damaging nature of recurrent DEC [2] due to the predominant eccentric muscle contractions [3]. This study therefore aimed to investigate the effects of different DEC intensities during an overground RSA test on subsequent kinetics of rectus femoris (RF) stiffness and serum creatine kinase levels ([CK]) to assess muscle damage. METHODS: Twelve participants (25±3.5 yrs) randomly performed a running RSA test [3 sets of 8 × 20 m; 20-s passive recovery between sprints, 5-min rest between sets] i) without DEC constraint after 20-m sprint (DECfree), ii) with enforced DEC of moderate intensity (DEC10; 10-m braking distance), and iii) with enforced DEC of intense intensity (DEC5; 5-m braking distance). Sprint time and DEC performances were assessed using timing gates and radar gun, respectively. RF stiffness and [CK] were assessed at rest before RSA test (baseline) and post 24 h, 48 h and 72 h using ultrasound elastography and dry-chemical colorimetry, respectively. RESULTS: There was no significant effect of condition (p=0.463) for the best sprint time in each set, but a significant effect of time (p=0.004). Mean DEC was significantly lower in DEC5 (-3.57±0.32 m/s2) than DEC10 (-2.52±0.37 m/s2, p<0.001) and DECfree (-1.82±0.30 m/s2, p<0.001), and lower in DEC10 than DECfree (p<0.001). There were significant effects of condition, time and interaction (all p<0.001) for relative stiffness vs. baseline. Relative stiffness were significantly higher in DEC5 than DEC10 and DECfree post 24 h (+16.4±3.2 vs. +9.8±4.2 and +4.5±5.7 %, respectively, p=0.007 and p<0.001), 48 h (+15.9±4.7 vs. +6.5±5.1 and +3.3±4.8 %, respectively, both p<0.001) and 72 h (+10.8±4.9 vs. +3.6±5.4 and +0.2±3.8 %, respectively, both p<0.001). There were significant effects of condition (p=0.012) and time (p<0.001) for relative [CK] vs. baseline. Pooled relative [CK] for all time points were significantly higher in DEC5 than DECfree (+141±180 vs. +66±98 %, p=0.019), while DEC10 (121±144 %) was not significantly different from either DEC5 (p=1.00) or DECfree (p=0.053). Pooled relative [CK] for all three conditions significantly increased at post 24 h (+171±151 %, p<0.001), 48 h (+111±175 %, p<0.001) and 72 h (+51±80 %, p=0.002). CONCLUSION: Repeated intense decelerations during repeated sprints induced an exacerbation of relative stiffness and creatine kinase levels over several days, peaking after 24 h and remaining elevated above baseline after 72 h. These findings indicate that the intensity of deceleration should be considered in order to adequately prepare the musculotendinous system and mitigate the damaging effects. [1] Harper, Sports Med, 2019 [2] Howatson, J Strength Cond Res, 2009 [3] Hewit, Strength Cond J, 2011
Read CV Johan GarciaECSS Paris 2023: OP-PN27
INTRODUCTION: During running, a greater mechanical stress (i.e., vertical load) is applied to the lower extremity at each ground contact, which promotes exercise-induced muscle damage and hemolysis. It has been shown that Advanced Footwear Technology (AFT) improve running performance by reducing the metabolic demand of running [1]. These shoes are designed with a combination of several components, including a compliant and resilient midsole foam. Thus, AFT shoes have a high cushioning function compared to traditional racing flats. Considering that the softer surface during running reduces the mechanical stress on the musculoskeletal system and the sole [2], the AFT shoes may attenuate exercise-induced muscle damage and hemolysis compared to traditional racing flats. Therefore, the purpose of present study was to determine the effect of AFT shoes on exercise-induced muscle damage and hemolysis after 2-h running. METHODS: Nine endurance athletes performed a 2-h treadmill running at 70% of maximal oxygen uptake (VO2max) wearing AFT shoes (METASPEED SKY PARIS, ASICS) (AFT trial) or conventional running shoes (HYPER SPEED 2, ASICS) (CON trial) on different days (Days 1 and 2). We measured blood samples and the drop jump (DJ) index before and after running to evaluate exercise-induced muscle damage and hemolysis. In addition, all subjects performed 15-30 straight running trials on a 50-m over-ground at 70% of VO2max on Day 3 (on different day than Days 1 and 2). Kinetic and kinematic data were collected simultaneously using a 24-camera motion capture system and three force plates during over-ground running. We also calculated vertical loading rate and negative muscle mechanical work (an indication of eccentric muscle contraction) by using the musculoskeletal simulation (OpenSim). RESULTS: Blood myoglobin (Mb) levels (an indication of muscle damage) significantly increased after 2-h running in both trials. However, blood Mb elevations following running tended to be lower in the AFT trial than in the CON trial (P = 0.07). Moreover, reduction in DJ index after 2-h running was significantly greater in the CON trial than in the AFT trial (P = 0.03). Blood haptoglobin (Hap) levels significantly decrease (an indication of hemolysis) after 2-h running in both trials. However, the CON trial showed a greater reduction in blood Hap levels compared to AFT trial (P = 0.02). Loading rate (P = 0.001) and negative muscle mechanical work in gastrocnemius (P = 0.006) and soleus (P = 0.02) during over-ground running were significantly lower in the AFT trial than in the CON trial. CONCLUSION: The AFT shoe attenuated exercise-induced muscle damage and hemolysis after 2 hours of running compared to the traditional racing flats. [1] Hoogkamer W, Kipp S, Frank JH, Farina EM, Luo G, Kram R. Sports Med 48(4):1009-1019, 2018. [2] Impellizzeri FM, Rampinini E, Castagna C, Martino F, Fiorini S, Wisloff, U. Br J Sport Med 42: 42-46, 2008.
Read CV DAICHI SUMIECSS Paris 2023: OP-PN27
INTRODUCTION: It is well established that severe intensity exercise performance is impaired following eccentric exercise-induced muscle damage (EIMD) [1, 2]. Given that performance during exercise within the severe intensity domain can be robustly predicted based on the hyperbolic power-duration relationship and its two parameters, critical power (CP) and the finite work capacity above CP (W’), it is likely that one or both of these variables are impaired with EIMD. However, no study has tested this hypothesis. This study assessed the effect of EIMD on CP and W’ measured during a 3-minute all-out test (3MT). METHODS: 15 recreationally active participants (age = 25 ± 4 years, 3 females, V̇O2peak = 46.8 ± 8.7 ml·kg·min-1) completed two, 3-minute all-out tests (3MT), one under control conditions (Control) and one 24 h following a bout of damaging eccentric exercise (Damage). CP, W’, peak power output (PPO), cardiopulmonary and electromyographic (EMG) data were collected during each 3MT. Potentiated twitch response (Qtw,pot) and maximal voluntary contractions (MVC) of the knee extensor muscles were used to assess the degree of damage incurred. RESULTS: EIMD reduced MVC and Qtw,pot by 32 and 30%, respectively (p < 0.001, d ≥ 1.14). Paired t-test results showed that EIMD resulted in a reduction in CP from 241 ± 72 W to 231 ± 66 W (p = 0.037, d = 0.15), W’ from 16.57 ± 4.5 kJ to 14.76 ± 3.9 kJ (p = 0.008, d = 0.45) and PPO by 776 ± 180 W to 696 ± 152 W (p = 0.023, d = 0.48). There was no difference in EMG during cycling between damage and control (p = 0.766). However, VO2, VCO2 and VE were lower for damage than control (p ≤ 0.02). CONCLUSION: These results demonstrate that EIMD reduces CP, W’ and PPO. Possible determinants of reduced CP with EIMD include a reduction in gross efficiency [3] and/or an impairment in muscle oxidative capacity [4]. Reductions in W’ might be attributable to reduced glycogen stores and/or a more rapid rate of accumulation of intramuscular metabolites [4, 5], while the reduced MVC and Qtw,pot 24hrs post damage suggest that impaired contractile function is at least partially responsible for these reductions in PPO. The results shown in this study add new insight into the determinants of reduced severe intensity exercise performance with EIMD. REFERENCES 1. Marcora et al., 2008; 2. Twist et al., 2009; 3. Horner et al., 2024; 4. Fouré et al., 2015 ; 5. Asp et al., 1998
Read CV Will PearmainECSS Paris 2023: OP-PN27