ECSS Paris 2023: OP-BM08
INTRODUCTION: Aging is associated with decreased physical activity, leading to muscle mass and strength loss, particularly in the lower extremities. However, the masseter, continuously engaged in mastication, may be less affected, making it a potential model for studying age-related muscle changes with minimal bias from activity. This cross-sectional study examines agings impact on masseter size and strength compared to the quadriceps femoris, a muscle more influenced by activity levels. METHODS: Thirty women were recruited and categorized into three age groups: young (26 ± 1.8 years), middle-aged (44.1 ± 3.4 years), and older (69.5 ± 3.1 years). Quadriceps and masseter cross-sectional area (CSA) were assessed via ultrasound, lower limb maximal isometric strength (MVIC) via an isokinetic dynamometer, and masseter strength via a bite force sensor. Muscle size and strength were expressed relative to the young group’s mean. Data were analyzed using two-way mixed-factorial ANOVAs (3 groups × 2 muscles or 3 groups × 2 strength tests) in SPSS (α = 0.05). Sidak’s post hoc tests were used for pairwise comparisons. Cohen’s d effect sizes were calculated to quantify the magnitude of differences between age groups. RESULTS: Both muscles exhibited a progressive reduction in size across age groups. Quadriceps CSA in the middle-aged and older participants was found to be 75 ± 14% and 56 ± 13% of that in the young participants (all p < 0.05). Similarly, masseter CSA in the middle-aged and older participants corresponded to 94 ± 15% and 79 ± 14% of that in the young individuals (all p < 0.05). Although the group × muscle interaction was not significant (p = 0.110), effect sizes were larger for the quadriceps (young vs. middle-aged: 1.56, young vs. old: 2.95, middle-aged vs. old: 1.47) than for the masseter (young vs. middle-aged: 0.29, young vs. old: 1.08, middle-aged vs. old: 1.09). For strength measures, no significant group × strength test interaction was observed (p = 0.541), but a significant main effect of group was found (p < 0.001). Strength was significantly lower in middle-aged and older participants compared to young adults (MVIC: 81 ± 14% and 62 ± 16%; bite force: 75 ± 15% and 68 ± 31%; all p < 0.05), with no significant differences between middle-aged and older participants (p = 0.186). Effect sizes were comparable between MVIC and bite force for the young vs. middle-aged comparison (MVIC = 1.20, bite force = 1.33), whereas a larger effect was observed for MVIC (1.25) than for bite force (0.27) when comparing middle-aged to older adults. CONCLUSION: This study demonstrates a progressive age-related decline in muscle size and strength. Although the lack of significant group × muscle interactions suggests limited statistical power, larger effect sizes in the quadriceps indicate a more pronounced reduction as compared to the masseter muscle. Further research is needed to determine whether aging affects these muscles differently and to explore the underlying mechanisms driving these differences.
Read CV Gustavo SchaunECSS Paris 2023: OP-BM08
INTRODUCTION: The age-related decline in muscle mass and function known as sarcopenia contributes greatly to the loss of quality of life within the older population(1). The pathogenesis of these alterations is related to several known factors contributing to varying degrees. Typical tests used to diagnose sarcopenia are based on muscle mass indexes (e.g. appendicular skeletal mass, ASM) and functional abilities (e.g. handgrip, HG). Nevertheless, these parameters cannot discriminate muscle alterations that lead to functional disability. Recent evidence suggests changes in neurophysiological processes to be major contributors (2). Therefore, the aim of this study is to explore possible correlations between motor units (MUs) properties and typical sarcopenic indexes in a non-sarcopenic group of elderly. METHODS: Fifty-two non-sarcopenic elder subjects (43F/9M, age=72.1±5.0 years, BMI=25.24±2.69 kg/m2) performed isometric knee extension maximal voluntary contractions (MVC) and trapezoidal contractions at 25% of the MVC. During the MVCs, maximum torque (MT) and rate of force development at 200ms (RFD200) were determined. MUs properties (i.e. recruitment and de-recruitment threshold, discharge rate during steady state, mean discharge rate) of the vastus lateralis (VL) were obtained during the submaximal contractions using high-density EMG. Moreover, participants underwent a dual-energy X-ray absorptiometry (DXA) scan to determine the ASM and performed HG and chair stand tests. Muscle architecture of VL was also assessed at rest at 50% of the femur length. Pearson’s correlation coefficient was used to determine the association between MUs properties and DXA and functional and muscle architecture parameters RESULTS: Recruitment and de-recruitment thresholds are related to ASM (r=-0.30,P=0.048; r=-0.33,P=0.030), HG (r=-0.32,P=0.036; r=-0.35,P=0.020), MT (r=-0.67,P<0.001; r=-0.63,P<0.001) and RFD200 (r=-0.31,P=0.040; r=-0.32,P=0.035). Moreover, the recruitment threshold is associated with VL thickness (r=-0.31,P=0.044) and the de-recruitment threshold correlates with the chair stand score (r=-0.32,P=0.031). The discharge rates (i.e. mean and during the steady state) correlate with the fascicle length (r=-0.30,P=0.049; r=-0.31,P=0.044). All the relationships are classified as weak correlations, except those that include the MT, which are strong correlations. CONCLUSION: In the elderly, MUs properties of VL could represent significant parameters related to functional abilities and skeletal muscle mass. Our results suggest that among the MUs properties, recruitment and de-recruitment thresholds of MUs can relate better to functional scores and anthropometric characteristics than other. Nevertheless, further studies are necessary to improve the knowledge about muscle alterations related to functional disability in the elderly including a population of sarcopenic individuals. REFERENCES 1-Pattermann-Rocha et al., 2022, J Cachexia Sarcopenia Muscl 2-Pratt J., et al., 2021, J Gerontol A Biol Sci Med Sci
Read CV Riccardo MagrisECSS Paris 2023: OP-BM08
INTRODUCTION: Proper control of the trunk muscles is essential for maintaining stability and performing daily activities, particularly in the presence of muscle fatigue1. However, the effects of ageing on trunk muscle force control remain largely unexplored. Force control primarily depends on the common synaptic input received by motoneurons2 and therefore high-density surface electromyography (HDsEMG)-force relationships provide insights into the association between muscle activity and the generated force. This study investigates the relationship between oscillations in lumbar erector spinae (LES) HDsEMG activity and force in young and older participants during a fatiguing task. METHODS: Twelve older (O, age: 69±4) and twelve young (Y, age: 26±2) participants performed an isometric trunk extension at 30% of their maximal voluntary isometric force until failure. HDsEMG signals were recorded using a 13x5 grid of electrodes placed over the LES. Muscle fibre conduction velocity (MFCV) values were measured. Force steadiness was quantified using the coefficient of variation of force (CoV). Coherence analysis was applied to examine the relationship between HDsEMG and force signals in the delta (0-5 Hz) frequency bandwidth. A mixed-model ANOVA was used to analyse differences in MFCV, CoV and coherence values (Coh) over time (3 epochs of equal duration) and between groups. The Wilcoxon test was used to compare endurance time between groups. Regression analysis examined the association between the percent variation in Coh and CoV values from the beginning to the end of the task. RESULTS: Endurance time did not differ between groups (O: 90.56 ± 34.75 s; Y: 100.71 ± 49.20 s; p=0.41). MFCV significantly decreased throughout the fatiguing task in both groups (p<0.01), indicating LES fatigue. CoV increased significantly at the end of the task in both groups (p<0.01) with O showing greater values than Y (p<0.01). Coh values decreased significantly at the end of the task in both groups (p<0.01), with a significant Time*Group interaction (p<0.05) revealing lower Coh values in O in the middle phase of the contraction. Lastly, a greater decline in Coh was associated with a larger increase in CoV values in both O (R2=0.86; p<0.01) and Y (R2=0.75; p<0.01). CONCLUSION: Despite similar endurance between groups, older participants showed greater force variability. In both groups, coherence values declined with fatigue, likely reflecting the recruitment of synergistic muscles to prolong endurance. However, this decline occurred earlier in older participants, suggesting earlier disruptions in common synaptic input to the LES. This may contribute to the age-related increase in force variability, as the decline in coherence is associated to greater force fluctuations. REFERENCES: 1 Johanson E. et al., Eur Spine J, 2011. 2 Farina D., Negro F., Exerc Sport Sci Rev, 2015. Scholarship CUP: H83C22000370001
Read CV Martina ParrellaECSS Paris 2023: OP-BM08