Author(s): FERRO, M., RAIMO, M., BERTOLLO, M., PAPINI, G.B., SARTOR, F., Institution: UNIVERSITY OF STUDIES D'ANNUNZIO CHIETI-PESCARA, Country: ITALY, Abstract-ID: 1228

INTRODUCTION:
The relation between muscle fatigue and marathon running is well established [1], but not all individuals respond to it in the same way. Overall fatigue, muscle fatigue, and muscle soreness are commonly experienced by marathoners. This analysis aimed to observe whether perceived overall muscle fatigue and soreness ratings over 8 weeks would differ in marathoners responding or not to a muscle fatigue protocol.
METHODS:
Data from 17 habitual marathoners (15 males, aged: 38±12 y, height: 1.81±0.09 m, weight: 70±9 kg, VO2max: 64±12 ml/kg/min) were analyzed. Training workload was measured using a chest strap. HR was used to compute total TRIMP (tTRIMP), composed of anaerobic TRIMP (anTRIMP) and aerobic TRIMP (aTRIMP), where (aTRIMP = z1+z2; anTRIMP = z3+z4+ z5). Runners kept a diary where they self-reported on a 0 to 10 scale overall fatigue, muscle fatigue and soreness every morning, evening, and before and after each training. Prior to the 8-week observation period (W38-45), they visited our laboratory twice for VO2max and muscle fatiguability tests. The fatiguability tests consisted of a 10-minute baseline submax run and baseline maximal voluntary contractions (MVCs), then 100 drop jumps from a 40 cm height step with a 20-second rest between each jump, followed by an isometric contraction to muscle failure at 30% MVC output. This fatigue protocol was immediately followed by post-MVCs and a 10-minute run at the same speed as baseline.
RESULTS:
Runners were divided into responders (R) who showed an MVC drop ≥20% and non-responders (NR) who did not. Pre- and post-fatigue MVCs, as well as pre- post-fatigue submax run HR, differ between R and NR (ΔMVC for R was -38%, and for NR=-2%, ΔHR for R was 10 bpm and for NR 4 bpm). During the 8 weeks a difference was found between the R and NR groups in overall fatigue ratings (F(1,382)=10.34, p<0.001); once followed-up it revealed differences at: W40 F(1,53)=4.88 p<0.05; W42 F(1,53)=4.27 p<0.05; W43 F(1,51)=7.01 p<0.011. Muscle soreness ratings showed a significant effect of group R vs. NR (F(1,382)=9.89 p=0,002); when followed up, there were not significant effects. Muscle fatigue ratings showed a significant difference between R and NR (F(1,382) =20.43 p<0.05), and follow-up showed differences at W38, W40, and W43 (F(1,41)=7.29 p=0.01; F(1,53)=9.91 p=0.003; F(1,51)=4.57 p<0.05). Overall (r=0.40, r =0.26, p<0.001), muscle fatigue (r=0.40, r =0.37, p<0.001), and muscle soreness ratings (r=0.40, r =0.24, p<0.001) significantly (within-subject) correlated with tTRIMP and anTRIMP, but not with aTRIMP.
CONCLUSION:
This study confirms that not all athletes respond to muscle fatigue equally. Interestingly, those who did not respond in the lab had higher overall fatigue and muscle fatigue ratings in training, while muscle soreness did not differ from responders. Future studies should investigate the reasons behind these differences and whether they differ in competition results.

1. Del Coso et al., (2017)