ECSS Paris 2023: OP-BM05
INTRODUCTION: 17beta-estradiol (E2), progesterone (P4) and testosterone (T), whose concentrations differ according to sex, oral contraceptive (OC) use and menstrual cycle phase, may influence the severity of exercise-induced muscle damage (1). However, muscle damage is not uniformly distributed among the muscles activated during exercise (2). Shear wave elastography provides a muscle-specific evaluation of muscle damage through changes in mechanical properties. This study aimed to examine changes in those properties after eccentric exercise according to sex, OC use and menstrual cycle phase. METHODS: Ninety-one healthy females and twenty males participants performed an eccentric exercise of the knee flexors, during the early follicular (EF), late follicular (LF) or mid-luteal (ML) phase, or while using OC for females, and at an arbitrary time point for males. Serum E2, P4 and T concentrations, blood creatine kinase activity, isometric maximal voluntary contraction (iMVC) force of the knee flexors and shear wave speed (SWS) of the biceps femoris, semitendinosus and semimembranosus were assessed before (PRE), immediately after (POST), two days (D2) and seven days (D7) after the exercise. SWS was measured during isometric contractions performed at 50% of the session-specific iMVC and at 50% of the PRE-iMVC (to standardize absolute force level across sessions) as well as during passive stretches to end-range of motion. RESULTS: In eumenorrheic females, E2 and P4 levels followed the typical menstrual cycle pattern, with lower levels observed in OC users and males (p < 0.001). T concentration was higher in males (p < 0.001). Creatine kinase activity increased similarly in all groups (p < 0.001). iMVC force decreased and partially recovered between POST and D7 in all groups but ML (p < 0.001). At 50% of the session-specific iMVC, changes in semitendinosus SWS mirrored the loss of iMVC force (p < 0.05). Conversely, at 50% of PRE iMVC force, semitendinosus SWS decreased from PRE and POST to D2 only in ML (p < 0.05). Resting semitendinosus SWS increased at D2 for all groups but returned to baseline by D7 only for LF and ML (p < 0.01). CONCLUSION: Active muscle mechanical properties and neuromuscular function were more impaired in the ML group when E2 levels decreased, which may partly reflect the beneficial role of E2 on muscle regeneration (1). In contrast, alterations in passive semitendinosus SWS resolved by D7 only in the groups with the highest E2 levels, consistent with a potential effect of E2 on connective tissue (3). Interestingly, higher T levels in males did not appear to alleviate the force loss related to exercise-induced muscle damage and the higher ethinylestradiol concentration in the OC group did not result in different mechanical or functional behavior compared with the EF group. 1) Jomard C., Gondin J. (2023). Physiol Rep, 11(19):e15798. 2) Goreau V. et al. (2022). Scand J Med Sci Sports, 32(9):1335-1345. 3) Fede C. et al. (2019). Plos One, 14(9):e0223195.
Read CV Jérémie BouvierECSS Paris 2023: OP-BM05
INTRODUCTION: Persistent quadriceps weakness after ACL rupture is well documented and hinders functional recovery. These deficits likely reflect structural and neuromuscular alterations, with neural activation impairments evolving from predominantly spinal to more central mechanisms from acute to subacute phases [1]. However, neural activation has been mainly studied during isometric contractions and after reconstruction rather than after rupture alone. This study aimed to extend knowledge on neuromuscular contributions to strength asymmetries during anisometric contractions in patients following ACL rupture. METHODS: This abstract reports preliminary data from sixteen patients assessed 2-6 weeks after ACL rupture and sixteen healthy subjects. Participants performed maximal quadriceps contractions under three conditions: isometric at 80° knee flexion, and concentric and eccentric at 20°/s from 60° to 100° knee flexion. For each condition, we measured at 80°: torque, voluntary activation, electromyographic activity (RMS) of knee extensor muscles, and doublet-evoked torque. For each variable, side-to-side asymmetries were calculated using the asymmetry index ((stronger − weaker)/stronger) and analyzed with a two-way repeated-measures ANOVA with contraction mode (isometric, concentric, eccentric) as a within-subject factor and group (patients, controls) as a between-subject factor. Finally, we assessed covariations between torque asymmetries and asymmetries in doublet evoked torque and voluntary activation in patients and healthy controls using a linear mixed effects model. RESULTS: Repeated-measures ANOVA revealed significant group effects for asymmetries in torque, doublet-evoked torque, and voluntary activation (p ≤ 0.05), with greater side-to-side asymmetries in patients than controls, but no main effect of mode or mode × group interaction. RMS EMG asymmetries showed no significant group or mode effects and no group × mode interactions (p ≥ 0.05). For both patients and healthy subjects, torque asymmetry was positively associated with both voluntary activation and doublet-evoked torque asymmetries (p ≤ 0.05), and was not influenced by contraction mode (p ≥ 0.05). Model explained 65% of the variance (R² = 0.65). CONCLUSION: Our results indicate that the side-to-side deficits in torque and neuromuscular factors previously reported during isometric contractions in post-operative patients [2] extend to anisometric contractions early after ACL rupture. Furthermore, deficits in activation level and muscle capacity appear to contribute to torque asymmetries in both patients with ACL rupture and healthy controls, consistent with previous isometric findings [3]. This contribution was similar across isometric, concentric, and eccentric modes. REFERENCES 1. Lepley, A. S., et al. Scandinavian Journal Of Medicine And Science In Sports, 2015. 2. Lisee, C., et al. Sports Health, 2019. 3. Maffiuletti, N. A., et al. Journal Of Electromyography And Kinesiology, 2016.
Read CV Hadrien AlauxECSS Paris 2023: OP-BM05
INTRODUCTION: In addition to the loss of muscle size, ageing is associated with an increase in intramuscular fat, which results in a reduction of the contractile tissue contained within a muscle (Pinel et al, 2021). However, it is not well understood if certain muscles are more prone to fatty infiltration with age compared to others, which could lead to an underestimation of muscle atrophy for muscles prone to fat infiltration. Therefore, the aim of the current study was to compare the fatty infiltration and functional (non-fat) volume of the four quadriceps femoris and gluteus maximus muscles between young and older adults. METHODS: Participants were forty recreationally active, healthy adults, 20 young (Y, 23 ± 3 years, 10 males) and 20 older (O, 67 +/- 4 years, 10 males). MRI scans (3.0 T Discovery MR750w; GE Healthcare, Chicago, IL) of the dominant thigh were obtained (axial T1-weighted and IDEAL fat and water images, contiguous 4-mm slices). T1-weighted images were segmented to determine quadriceps and gluteus maximus muscle volume. Segmentations were then transposed onto the fat fraction image to quantify the fat fraction percentage (FF%) in each slice/image for each individual muscle, in order to calculate total FF% of each muscle ([fat volume / total volume] × 100). Functional volume was calculated by subtracting fat volume from total volume. RESULTS: FF% showed a main effect of age (p = 0.001) and muscle (p < 0.001), as well as an age × muscle interaction (p = 0.001). Post hoc interaction contrasts revealed that the gluteus maximus had a greater difference in FF% between young and older participants (Y 7.0%, O 12.0%) compared to the rectus femoris (p = 0.004; Y 1.6%, O 2.7%), vastus medialis (p = 0.007; Y 2.3%, O 3.7%), and vastus lateralis (p = 0.021; Y 2.4%, O 3.9%). However, the difference in FF% between young and older participants was similar across all the quadriceps muscles (p = 1.000). For total and functional volume, there was a main effect age (p < 0.001), as well as a significant age × muscle interaction (p ≤ 0.003). Post hoc comparisons revealed older adults had significantly lower total volume for the three individual vastii muscles (all p<0.001), but not the rectus femoris (p = 0.123) and gluteus maximus (p = 0.486). However, when fat infiltration of the gluteus maximus was accounted for older adults had lower functional volume compared to the young group (p = 0.037). CONCLUSION: The gluteus maximus appears to have a relatively high level of fat infiltration irrespective of age, and showed a markedly higher fat infiltration with age than the quadriceps. These findings indicate that the pattern of intramuscular fat deposition with age is muscle specific and for muscles prone to fat infiltration (e.g. gluteus maximus) the effect of age on muscle atrophy may be underestimated/erroneously assessed by total volume without accounting for fat infiltration. References Pinel S et al (2021) Exp Gerontol 156.
Read CV Ed SadulaECSS Paris 2023: OP-BM05