ECSS Paris 2023: OP-BM05
INTRODUCTION: Hyperglycemia in Type 2 diabetes (T2D) leads to an increase in non-enzymatic glycation products (e.g., glycated hemoglobin: HbA1c) that accumulate irreversibly, damaging musculoskeletal tissues. Couppé et al. [1] found that Achilles tendon stiffness is higher in diabetic patients, potentially altering gait and increasing the metabolic energy cost of locomotion (Cnet). The present study used ultrasound, kinematic, and metabolic measurements during walking to test the hypothesis that higher HbA1c in T2D affects muscle and tendon behavior, with increased energy expenditure. METHODS: Twenty-three well compensated T2D patients (age 62±5 years; weight 79±12 kg; height 1.73±0.09 m; HbA1c: 55±9 mmol/mol; IPAQ 1596±432 MET/week) and 14 healthy matched controls (64±5 years; 73±12 kg; 1.73±0.09 m; HbA1c: 36±3 mmol/mol; IPAQ 14896±532 MET/week) walked on a treadmill at 4 km/h for 5 minutes. Kinematic and metabolic data were collected using a 3D motion capture system and breath-by-breath metabolimeter. Ultrasound images of the gastrocnemius medialis were recorded. Stride length (SL), stride frequency (SF), contact time (CT), and swing time (ST) were obtained from kinematic analysis. Cnet was calculated as net oxygen uptake per walking speed. Fascicle length was measured via ultrasound, and series-elastic element (SEE) length was estimated. An unpaired SPM t-test assessed differences in fascicle and SEE behavior during the stance phase. Maximum fascicle shortening, SEE strain, and SEE recoil were also analyzed. RESULTS: No significant differences were observed in SL, SF, CT and ST between populations. Cnet showed no significant differences between populations. SPM analysis revealed significant differences in fascicle and SEE behavior during the stance phase: healthy participants exhibited shorter fascicle lengths (20–100% stance phase, P<0.01), while T2D patients showed greater SEE lengths throughout the stance phase (P<0.001). Maximum fascicle shortening and SEE strain were lower in T2D patients (P<0.05), but no differences were found in tendon recoil. Significant negative (R2=-0.37, P<0.05) and positive associations (R2=0.43, P<0.05) were observed between HbA1c and tendon strain or maximum fascicle shortening, respectively. CONCLUSION: People with T2D walked with longer fascicle lengths and less strain of the SEE compared to healthy individuals. While a reduction in maximum fascicle shortening could reduce the metabolic energy cost during the stance phase, a decrease in elastic strain is likely to increase energy expenditure [2]. Our findings indicate that these two opposing mechanisms may balance each other out. Indeed, despite higher HbA1c levels being associated with muscle fascicle and SEE behavior, we found no significant differences in kinematic or energetic parameters during walking between individuals with well controlled diabetes and controls. REFERENCES: 1) Couppè et al. J Appl Physiol, 2016 2) Monte et al. Exp Physiol, 2023
Read CV Andrea MonteECSS Paris 2023: OP-BM05
INTRODUCTION: Muscle volume is an important determinant for its’ power generation capacity and is typically investigated in various population groups to evaluate the effectiveness of different interventions to enhance muscle function. Previous studies (1) have indicated that some muscles can adapt to training with a region-specific hypertrophy (changes in its shape), which would indicate different fiber type distribution as well as distinct innervation patterns within the muscle during exercise. The current study examined whether a triceps surae (TS) high metabolic stress exercise at different operating lengths (consequently at either low or high muscle force potential) leads to distinct mechanical and region-specific morphological adaptive changes. METHODS: 12 young adults (27±5 yrs) underwent a 12-week exercise intervention 3x week consisting of 3 sets of cyclic unilateral isometric plantarflexion contractions at 80% of maximal voluntary contraction until failure to induce high muscle metabolic stress. Based on the TS muscle force-length-relationship (2), low and high levels of mechanical stress were respectively induced using a short (PF; 115⁰) or a long (DF; 85⁰) muscle-tendon unit (MTU) length for either legs. TS MTU mechanical and morphological properties were assessed via ultrasonography and dynamometry. Magnetic resonance imaging was used to reconstruct all three compartments of the TS muscle in order to determine their volume and muscle specific shape factors (3). RESULTS: Similar adaptive increments (p<0.05) were found in TS muscle strength (~20-25%), pennation angle (~10%), maximal anatomical cross-sectional area (ACSAmax; ~5%) and muscle volume (on average ~6% across compartments) between DF and PF legs following the 12 weeks of exercise. Despite of the majority of muscle growth seemingly taking place closer to the belly region of the muscle, no clear region-specific adaptation was detected and ACSAmax demonstrated no significant shift in its position in relation to the muscle length in either of the trained legs or analysed compartments of the TS. Accordingly, no change in the individual muscle specific shape factors were found over the 12-week training period. CONCLUSION: The findings provide evidence that skeletal muscles are highly responsive to metabolic stimuli as even moderate mechanical tension and stress increases their force and power generation capacity. Moreover, exercising at different operating lengths of the contractile element within the force length-relationship seems not to cause inhomogeneous region-specific hypertrophy in skeletal muscles. REFERENCES: 1) Narici et al. (1996) Acta Physiol Scand 2) Csapo et al. (2010) J Exp Biol 3) Albracht et al. (2008) J Biomech
Read CV Gaspar EproECSS Paris 2023: OP-BM05
INTRODUCTION: The aging process promotes absolute decrease in fascicle length and angle [1] and changes in the morphology of the contractile and non-contractile tissues, which affects force capacity [2]. While muscle contractile elements are known to produce force, the intramuscular connective tissue has a key role in force transmission and in maintaining the structural integrity of the muscle. For pennate muscles to contract, changes in fascicle length (Lf) and angle (FA) and muscle thickness (MT) [3] occur. In this scenario, the age-related changes in muscle architecture and morphology impact on muscle shape changes during contraction [4] and the relative fascicle behavior during contraction. However, it is not known whether muscles of elderly individuals with high physical activity status, that is known to mitigate muscle loss and maintain fascicle length and angle [5], interfere in the fascicle behavior in comparison to a younger population reference. In this study we analyzed fascicle behavior during ramped isometric knee extension comparing elderly with high and low physical activity status to young adults. METHODS: In this preliminary analyses of an ongoing study, data of twenty-one elderly individuals, eleven (76.1±5.1 years old; 22.1±4.0 and 39.5±3.3 mL/min/Kg) with low aerobic capacity (EL), determined by VO2Max, ten (70.0±3.9 years old; 39.5±3.3 mL/min/Kg) with high physical activity capacity (EH) and eight young adults (Y; 25.6±2.3 years old) were analyzed. Ultrasound imaging was employed to measure changes in muscle architecture during isometric ramp contractions up to 30% of the maximum voluntary contraction (MVC), with slow force increase (2% MVC/s). The ultrasound recordings were synchronized to the force signal. Changes in fascicle behavior (Lf, FA and MT) were compared from the beginning of the force contractions to 10, 20 and 30% of MVC. RESULTS: Two-way ANOVA showed a decrease in Lf of EL with increasing force, with significantly lower Lf (p<0.05) at 30% of MVC compared to Y. MT was significantly decreased from the beginning of the contraction to 10, 20 and 30% (p<0.01) of MVC in both EH and EL. In addition, the decrease in MT showed a significant trend (p=0.06) only in EL compared to Y at 30% of MVC. CONCLUSION: These preliminary results show that changes in VL architecture during isometric submaximal tasks occur regardless of age, however the amount of change is higher in elderly individuals with lower aerobic capacity when compared to a young population. It is possible that the training status of the elderly individuals mitigates the architectural and morphological age-related changes in the contractile and non-contractile tissue, which will reflect in lower alterations is muscle fascicle behavior during contraction. References 1 Narici MV et al. (2021) J Cachexia. Sarcopenia Muscle 2 Fede C et al. (2022) Int J Mol Sci 3 Eng CM. et al. (2018) Integr Comp Biol. 4 Holt NC et al. (2016) J Exp Biol 5 Fragala et al (2019) J Strength Cond Res.
Read CV Clarissa M BruscoECSS Paris 2023: OP-BM05