Author(s): DEMEUSOY, P., BONTEMPS, B., ERSKINE, R.M., NICOL, C., PIPONNIER, E., Institution: AIX-MARSEILLE UNIVERSITÉ, Country: FRANCE, Abstract-ID: 1752

INTRODUCTION:
Repeated sprints are crucial regarding physical performance in many sports but result in reversible hamstrings muscle damage (HsMD) (1). In females, the hamstring-to-quadriceps ratio decreases at high knee angular velocities (2), which could lead to greater HsMD following sprinting. Eccentric preconditioning is reported to reduce muscle damage in response to subsequent exercise - a phenomenon known as the repeated bout effect. Thus, this study aimed to investigate whether performing a hamstring-specific eccentric exercise a few days before a repeated-sprint task could attenuate HsMD to a greater extent for females than males.
METHODS:
Participants were randomly assigned to either a preconditioning (PC; n=21; 11 females; age=20.1±2.1) or a control group (CT; n=22; 11 females; age=20.6±3.1) and underwent 3 visits scheduled according to the menstrual cycle. The first visit included a familiarisation with the procedures but only the PC group performed a preconditioning exercise (4x10 eccentric hamstring contractions). Fourteen days later, participants performed a repeated sprint task (3 sets of 5x30m) (1). To assess the acute and delayed effects of HsMD, participants were tested before (PRE), immediately after (POST) and two days (2D) after the strenuous sprinting task. Indirect markers of HsMD included muscle soreness (MS; assessed via visual analogue scale), muscle swelling (decreased echo-intensity; EI), maximal voluntary isometric torque (MVT) and low-frequency fatigue (myostimulation trains: 10-50Hz; T10 to T50). Linear mixed models were performed fitted with time, group and sex as independent factors and participant as random intercept.
RESULTS:
No significant differences were found between PC and CT groups over time for any of the measures. Regardless of group, MVT decreased by -13.4±8.9% (p<.001) at POST and -4.4±9.1% (p<.01) at 2D, respectively. Evoked responses to T10, T20 and T30 decreased at POST (-9.6%±23.6%, -15.0±19.6%, -7.6±12.8%; p<.05) but returned to baseline at 2D, in all groups. A time x sex interaction effect was found for EI and MS. Only females showed significant loss of EI (i.e. increased muscle swelling) at 2D (-5.8±5.0%; p<.001). Moreover, females showed increased MS at POST and 2D (+2.9±2.4 and +3.6±2.8, respectively; p<.05), whereas MS increased only at 2D for males (+2.2±1.5; p<.05).
CONCLUSION:
Our results do not support a repeated bout effect from hamstring-specific eccentric preconditioning against future HsMD induced by repeated sprinting. Nevertheless, only females showed indirect signs of hamstring swelling at 2D (associated with increased MS), which reinforces their higher sensitivity to HsMD (3). These findings highlight the necessity for sex-specific strategies to prevent HsMD. For females, longitudinal eccentric training may serve as an effective approach to mitigate HsMD following running-based activities.
REFERENCES
1. Baumert et al., Sci. Rep., 2021
2. Hewett et al., J. Sci. Med. Sport, 2008
3. Macchi et al., Front. Physiol., 2021