Scientific Programme

Abstract-ID: 2266

SEX DIFFERENCES IN MUSCLE FUNCTION AND MYOCELLULAR RESPONSE TO A STRENUOUS MILITARY FIELD EXERCISE [2266]

Author(s): LANDER, E.1, VIKMOEN, O.2, TEIEN, H.2, HELKALA, K.3, RAASTAD, T.1, Institution: NORWEGIAN SCHOOL OF SPORT SCIENCE, Country: NORWAY


INTRODUCTION:
Exposure of extreme stress during military operations can affect the soldiers’ operability for several weeks (1). However, there is limited information on the myocellular response to arduous military operations and the molecular regulation in the recovery phase. Furthermore, it is not known whether there are sex differences to such extreme stress. Therefore, the objective of this study was to investigate the impact of a strenuous military field exercise on muscle function and regulators of autophagy, protein synthesis and energy production, and to identify possible sex differences in the acute response and in the recovery phase.
METHODS:
Soldiers (F=8, M=10) from the Norwegian Defence Cyber Academy conducted a 10 days long strenuous military field exercise. Maximal leg extension force was tested before (Pre), after (Post0), one week after (Post1) and two weeks after (Post2) the exercise. Skeletal muscle biopsies were obtained from m. vastus lateralis at Pre, Post 0 and Post 1. Biopsies were analyzed for the following proteins by western blots: 4E-BP1, S6Kp70, AMPK, Ulk1, COX-IV, HADH, Citrat Synthase, Na+K+, SERCA1, SERCA2 and αB-Crystallin. Data was analyzed by a two-way ANOVA for sex differences and one-way ANOVA for time differences.
RESULTS:
Maximal force was reduced for the whole group by 9±11% at Post 0(p<0.05) and was still 8±12% lower than Pre at Post 2 (p<0.05), with no sex differences. The ratio pAMPK/totAMPK increased 39±40% at Post 0 (p<0.05) and 48±46% at Post 1 (p<0.001). Na+K+ decreased at the same time points with 7±12% (p<0.05) and 12±13% (p<0.05) respectively. Other significant changes from Pre to Post 1 were a 14±32% increase in 4E-BP1 (p<0.01), a 17±29% reduction in COX-IV (p<0.05) and a 18±21% reduction in citrate synthase (p<0.05). The only significant difference between sexes was found for Ulk1 at Post 0 (p<0.05), where women decreased 22±15% and men increased 16±17%. There was a tendency for differences between sexes in Na+K+ at Post 0 (p=0.065) where women at the same time point had a 14±9% reduction in Na+K+ (p<0.05). There were no significant changes in S6Kp70, αB-Crystallin, SERCA1, SERCA2 or HADH.
CONCLUSION:
These results indicate that a strenuous military field exercise leads to similar reductions in maximal force for men and women together with increased catabolism and/or inhibited anabolism, which last for at least one week. There was a sex difference in the change in protein levels of Ulk1, but this was not related to any difference in reduction of maximal force. The results indicate that there may be sex differences in the myocellular response to a military field exercise, but further investigations are needed.
1. Hamarsland, H., et al., MSSE 50; 2076-2084 (2018).