Regional Differences of Mechanical Properties in a Biceps Brachii Following Eccentric Exercise

PURPOSE: This study aimed to examine the effects of eccentric exercise (ECC) on the indices of mechanical properties together with markers of exercise-induced muscle damage (EIMD) in different sites of the biceps brachii (BB) muscle.METHODS: ECC using an elbow joint was performed in 13 non-trained, college men. Global symptoms of EIMD were identified through changes in muscle soreness and serum creatine kinase (CK) activity, including muscle function following ECC. To evaluate regional EIMD, muscle swelling and tenderness as well as muscular echo intensity were measured at distal (4 cm above the elbow joint) and middle (30% of the distance from the antecubital crease to the acromion) sites within the BB muscle. A handheld myotonometer was used to estimate changes in mechanical properties, that is, oscillation frequency (F), dynamic stiffness (S), and relaxation time (R), of BB muscles after ECC.RESULTS: A significant difference in the major markers of EIMD, such as muscle soreness and serum CK activity, along with parameters of muscle function, was observed after ECC compared to baseline. Although all indirect markers of regional muscle damage demonstrated meaningful differences between before and after ECC, no statistically significant interaction between the distal and middle sites was observed in any of the markers. After ECC, both distal and middle sites showed significant changes in F, S, and R, but no statistical differences in changes in muscle mechanical properties were observed between localized muscle sites within BB muscles.CONCLUSIONS: Changes in mechanical properties, including regional muscle damage, seem to be uniformly influenced by different anatomical locations within the BB muscle, such as elbow flexors, following ECC.

Spatial-frequency Analysis of the Anatomical Differences in Hamstring Muscles

Spatial frequency analysis (SFA) is a quantitative ultrasound method that characterizes tissue organization. SFA has been used for research involving tendon injury, but may prove useful in similar research involving skeletal muscle. As a first step, we investigated if SFA could detect known architectural differences within hamstring muscles. Ultrasound B-mode images were collected bilaterally at locations corresponding to proximal, mid-belly, and distal thirds along the hamstrings from 10 healthy participants. Images were analyzed in the spatial frequency domain by applying a two-dimensional Fourier Transform in all 6.5 × 6.5 mm kernels in a region of interest corresponding to the central portion of the muscle. SFA parameters (peak spatial frequency radius [PSFR], maximum frequency amplitude [Mmax], sum of frequencies [Sum], and ratio of Mmax to Sum [Mmax%]) were extracted from each muscle location and analyzed by separate linear mixed effects models. Significant differences were observed proximo-distally in PSFR ( p = .039), Mmax ( p < .0001), and Sum ( p < .0001), consistent with architectural descriptions of the hamstring muscles. These results suggest that SFA can detect regional differences of healthy tissue structure within the hamstrings—an important finding for future research in regional muscle structure and mechanics.

Regional muscle-adipose distribution is different in patients with heart failure with preserved or reduced ejection fraction

Background Epicardial adipose tissue (EAT) has been recognized to contribute inflammatory activity and atherosclerosis. On the other hand, it has been reported that the volume of EAT is lower in non-ischemic heart failure (HF) patients than healthy individuals. However, the difference in regional muscle-adipose distribution including EAT between HF with preserved ejection fraction (HFpEF) and HF reduced ejection fraction (HFrEF) has not been investigated. In addition, we investigated whether distribution of body composition contributed to exercise capacity. Methods The study included 105 non-ischemic HF patients diagnosed by cardiac catheterization between September 2017 and November 2019. Epicardial, abdominal and thigh muscle and adipose tissue volume were measured by computed tomography (CT), and exercise tolerance was evaluated by symptom-limited cardiopulmonary exercise test. Results Patients were divided into 2 groups according to the left ventricular ejection fraction, ≥40% as HFpEF (n=28) or &lt;40% as HFrEF (n=77). There was no significant difference comorbidity, including hypertension, dyslipidemia, chronic kidney disease, and body mass index. Plasma B-type natriuretic peptide level was significantly higher in HFrEF than HFpEF group (146.2 vs 393.2 pg/ml, p&lt;0.01), whereas, high-sensitive troponin T level was not different between two groups. Although there was no significant difference in BMI between two groups, the volume of EAT was significantly higher in HFpEF than HFrEF group (81.8 vs 136.4 ml, p=0.01). On the other hand, HFpEF had more thigh adipose tissue compared with HFrEF group (54.6 vs 42.1 ml, p=0.03). There were negative correlations between EAT volume and parameters of exercise capacity such as anaerobic threshold (r=−0.42, p&lt;0.01) and peak VO2 (r=−0.32, p&lt;0.01). Muscle volume itself does not corelate with these parameters. Conclusion In patient with nonischemic HF, the pattern of regional adipose distribution may have important role in pathologically. HFpEF and HFrEF has different pattern despite similar body mass index. These differences may be related to impaired exercise tolerance in these 2 different types of HF. Correlation between EAT and AT, peak VO2 Funding Acknowledgement Type of funding source: None

Validation of Fabric-Based Thigh-Wearable EMG Sensors and Oximetry for Monitoring Quadriceps Activity during Strength and Endurance Exercises

Muscle oximetry based on near-infrared spectroscopy (NIRS) and electromyography (EMG) techniques in adherent clothing might be used to monitor the muscular activity of selected muscle groups while exercising. The fusion of these wearable technologies in sporting garments can allow the objective assessment of the quality and the quantity of the muscle activity as well as the continuous monitoring of exercise programs. Several prototypes integrating EMG and NIRS have been developed previously; however, most devices presented the limitations of not measuring regional muscle oxyhemoglobin saturation and did not embed textile sensors for EMG. The purpose of this study was to compare regional muscle oxyhemoglobin saturation and surface EMG data, measured under resting and dynamic conditions (treadmill run and strength exercises) by a recently developed wearable integrated quadriceps muscle oximetry/EMG system adopting smart textiles for EMG, with those obtained by using two “gold standard” commercial instrumentations for EMG and muscle oximetry. The validity and agreement between the wearable integrated muscle oximetry/EMG system and the “gold standard” instrumentations were assessed by using the Bland-Altman agreement plots to determine the bias. The results support the validity of the data provided by the wearable electronic garment developed purposely for the quadriceps muscle group and suggest the potential of using such device to measure strength and endurance exercises in vivo in various populations.