It was unknown whether ultrasound-measured forearm muscle thickness was impacted by pronation of the forearm. The aim of this study was to investigate the influence of forearm pronation on two forearm muscle thicknesses (MT-ulna and MT-radius).
Participants and Methods
Fourteen healthy children and adolescents sat on a chair with their right arm comfortably on a table, and their hands were fixed to the board with elastic bands. The probe was placed perpendicularly over the forearm, and the angle of the board was then pronated in 5° increments from −10° to 30°. The average value of the two measures at each angle was used.
There was evidence that MT-ulna differed across measurement sites (F = 51.086, P < 0.001). For example, the values of the MT-ulna were 2.58 (SD 0.40) cm in standard position (0°), 2.56 (SD 0.41) in −10°, 2.62 (SD 0.41) in 10°, 2.65 (SD 0.42) in 20°, and 2.71 (SD 0.43) in 30°. Follow-up tests found that all sites differed from each other except for −10° and −5° (P = 0.155) and 10° and 15° (P = 0.075). There was also evidence that the MT-radius differed across measurement sites (F = 22.07, P < 0.001). Follow-up tests found that many but not all sites differed from each other.
Our results suggest that MT-ulna increases and MT-radius decreases due to forearm pronation from the standard position (0°). When determining the forearm position using the 95% limits of agreement, we recommend the forearm position within ±5° of the standard forearm position when measuring forearm MT.
Grip strength is a marker of future health conditions and is mainly generated by the extrinsic flexor muscles of the fingers. Therefore, whether or not there is a relationship between grip strength and forearm muscle size is vital in considering strategies for grip strength development during growth. Thus, this study aimed to examine the association between changes in grip strength and forearm muscle thickness in young children.
Two hundred eighteen young children (104 boys and 114 girls) performed maximum voluntary grip strength and ultrasound-measured muscle thickness measurements in the right hand. Two muscle thicknesses were measured as the perpendicular distance between the adipose tissue-muscle interface and muscle-bone interface of the radius (MT-radius) and ulna (MT-ulna). All participants completed the first measurement and underwent a second measurement one year after the first one.
There were significant (P < 0.001) within-subject correlations between MT-ulna and grip strength [r = 0.50 (0.40, 0.60)] and MT-radius and grip strength [r = 0.59 (0.49, 0.67)]. There was no significant between-subject correlation between MT-ulna and grip strength [r = 0.07 (−0.05, 0.20)], but there was a statistically significant (P < 0.001) between-subject relationship between MT-radius and grip strength [r = 0.27 (0.14, 0.39)].
Although we cannot infer causation from the present study, our findings suggest that as muscle size increases within a child, so does muscle strength. Our between-subject analysis, however, suggests that those who observed the greatest change in muscle size did not necessarily get the strongest.
Low-intensity blood-flow restriction (BFR) resistance training significantly increases strength and muscle size, but some studies report it produces exercise-induced muscle damage (EIMD) in the lower body after exercise to failure.
To investigate the effects of a pre-set number of repetitions of upper body concentric and eccentric exercise when combined with BFR on changes in EIMD.
Ten young men had arms randomly assigned to either concentric BFR (CON-BFR) or eccentric BFR (ECC-BFR) dumbbell curl exercise (30% one-repetition maximum (1-RM), 1 set of 30 repetitions followed by 3 sets of 15 repetitions). Maximal isometric voluntary contraction force (MVC), muscle thickness (MTH), circumference, range of motion (ROM), ratings of perceived exertion (RPE), and muscle soreness were measured before, immediately after, and daily for 4 days post-exercise.
MVC decreased by 36% for CON-BFR and 12% for ECCBFR immediately after exercise but was not changed 1–4 days post-exercise (p > 0.05). Only CON-BFR had significant changes in MTH and circumference immediately after exercise (p < 0.05). Muscle soreness was observed in the ECC-BFR arm at 1 and 2 days after exercise.
Low-intensity ECC-BFR produces significant muscle soreness at 24 h but neither ECC-BFR nor CON-BFR exercise produces significant changes in multiple indices of EIMD.
To investigate the relationships between site-specific muscle loss in the thigh, muscle quality and zigzag walking performance, 40 men and 41 women aged 65–79 years had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. Skeletal muscle mass (SM) was estimated from an ultrasoundderived prediction equation. Site-specific thigh sarcopenia was calculated using ultrasound-measured MTH at the anterior/posterior aspects of the thigh (AP-MTH ratio). Zigzag walking time (ZWT) and maximum isometric knee extension (KE) and flexion (KF) torques were measured. Muscle quality (torque/thigh SM) and knee joint strength index (torque/body mass) were calculated. There were no significant correlations between SM index and ZWT. However, AP-MTH ratio was inversely correlated (P < 0.05) to ZWT in men (r = −0.335) and women (r = −0.309). ZWT was also inversely correlated (P < 0.05) to KE-strength index in both sexes (men, r = −0.328; women, r = −0.372). Similarly, ZWT was correlated to KF-strength index (r = −0.497) and muscle quality (r = −0.322) in women, but not in men. After adjusting for age, height and body mass, AP-MTH ratio was inversely correlated to ZWT in men (r = −0.325) and tended to be correlated to ZWT in women (r = −0.263). Zigzag walking performance may be associated with site-specific thigh sarcopenia in older men and women.
Previous studies reported that aerobic-type exercise such as walking or cycling with blood flow restriction (BFR) has been shown to elicit increases in leg muscle hypertrophy and strength, as well as improved aerobic capacity. Although previous studies investigated cardiovascular responses during a relatively short duration of exercise (∼5 min), the effects of prolonged leg muscular BFR have remained unknown. The purpose of this study was to examine the cardiovascular effects of longer duration low intensity exercise combined with BFR. Eight men performed 30 min of exercise at 40% of a predetermined maximal oxygen uptake under both BFR and normal flow (CON) conditions. Cardiovascular parameters were measured at rest and every 10 min during exercise. The main findings were that 1) the SV and HR did not change significantly between 10 to 30 min of exercise in BFR and CON conditions, although BFR-induced reduction of SV and increased HR were found at 10 min exercise compared with normal flow, 2) blood pressure was increased at 10 min of exercise in BFR compared to the CON, however the blood pressure decreased gradually with BFR from 10 to 30 min of exercise, and 3) blood lactate and RPE increased gradually during exercise with BFR. In conclusion, our results suggest that the BFR-induced reduction of SV and increased HR within the first 10 min of exercise are representative of changes in these parameters.
The purpose of this study was to investigate the time course of hypertrophic adaptations in both the upper arm and trunk muscles following high-intensity bench press training. Seven previously untrained young men (aged 25±3 years) performed free-weight bench press training 3 days (Monday, Wednesday and Friday) per week for 24 weeks. Training intensity and volume were set at 75% of one repetition maximum (1-RM) and 30 repetitions (3 sets of 10 repetitions, with 2–3 min of rest between sets), respectively. Muscle thickness (MTH) was measured using B-mode ultrasound at three sites: the biceps and triceps brachii and the pectoralis major. Measurements were taken a week prior to the start of training, before the training session on every Monday and 3 days after the final training session. Pairwise comparisons from baseline revealed that pectoralis major MTH significantly increased after week-1 (p=0.002), triceps MTH increased after week-5 (p=0.001) and 1-RM strength increased after week-3 (p=0.001) while no changes were observed in the biceps MTH from baseline. Significant muscle hypertrophy was observed earlier in the chest compared to that of the triceps. Our results indicate that the time course of the muscle hypertrophic response differs between the upper arm and chest.
To test the hypothesis that sit-up performance is associated with sarcopenia classification measures, 93 older women aged 53–78 years were divided into three groups based on achieved repetitions (30 s) for the sit-up performance test: Group 0 (G 0, n = 33) performed 0 repetitions, Group 1–9 (G 1–9, n = 30) performed between 1 and 9 repetitions, and Group 10+ (G 10+, n = 30) performed over 10 repetitions. Dual-energy X-ray absorptiometry-derived appendicular lean soft tissue mass (aLM), handgrip strength (HGS), usual walking speed, and chair stand were measured, and low muscle mass (aLM index) and poor physical function were defined according to previous studies. Age and body mass index were similar among the three groups. HGS was higher in G 10+ compared with G 0. The prevalence rate of low muscle mass was 30% for G 0, 20% for G 1–9, and 3% for G 10+. Low HGS was observed in both G 0 (24%) and G 1–9 (20%), but not in G 10+. Only two persons in G 0 were classified as slow walking speed. Our results suggest that sit-up performance may be a useful indicator to determine the extent of sarcopenia because low muscle mass and poor function were almost non-existent in individuals who could perform over 10 sit-ups.
It has been observed that gluteal-femoral adipose tissue has a protective effect against risk factors for cardiovascular disease but has not yet been concluded how different evaluation methods of fat distribution affect the results.
To test the hypothesis that B-mode ultrasound-measured subcutaneous adipose tissue distribution is associated with cardiovascular risk factors, 326 Japanese unmedicated postmenopausal women aged 50–70 years were analyzed. Subcutaneous adipose tissue thickness at 6 sites (anterior and posterior aspects of trunk, upper-arm, and thigh) and serum total (TC) and high-density lipoprotein cholesterol (HDLC) was measured, and a ratio of HDLC to TC (HDLC/TC) was calculated. We used Bayesian linear regression with 4 separate models with each model predicting HDLC/TC.
Our first model provided evidence for an inverse correlation (r = –0.23) between ultrasound measured body fat (6 site measurement) and HDLC/TC. The second model noted evidence for an inverse correlation between trunk fat and HDLC/TC and found evidence for the null with respect to the correlation between thigh fat and HDLC/TC. Therefore, we added thigh fat to the null model to produce Distribution Model 2. Within this model, we noted an inverse correlation (r = –0.353) between trunk fat and HDLC/TC. Our last model determined that within the trunk fatness, the abdominal area (anterior trunk) was a larger predictor than the subscapular site (posterior trunk).
These results support the evidence that ultrasound-measured abdominal subcutaneous adipose tissue thickness is a non-invasive predictor for monitoring the risk for dyslipidemia in postmenopausal women.
Orthostatic intolerance occurs in some astronauts following space flight. Although orthostatic blood pressure responses should normalize in the weeks following the return to Earth, there may be situations where an immediate short-term solution is necessary (e.g., emergency evacuation).
The purpose of this study was to examine different levels of blood flow restriction on changes in blood pressure and heart rate when transitioning from supine to a head-up tilt and determine whether this change differs based on sex.
Eighty-nine participants (45 men, 44 women) completed the three visits with different pressures (Sham, Moderate, and High) in a randomized order. Cuffs were placed on the most proximal area of the thighs. Brachial blood pressure was measured at baseline, upon inflation of the cuffs in a supine position, immediately after tilt (70°), and eight more times separated by 45 seconds.
Data are presented as mean (SD). The change in systolic (High > Moderate > Sham) [High vs Sham: 5.5 (7.4) mmHg, High vs Moderate: 3 (7.4) mmHg, and Moderate vs Sham: 2.4 (8.4) mmHg] and diastolic pressure (High > Moderate = Sham) [High vs Sham: 2.4 (5.3) mmHg, High vs Moderate: 1.9 (6.3) mmHg] differed across applied pressures. The change in heart rate was initially greatest in the sham-pressure but increased the greatest in the high-pressure condition by the end of the head-up tilt period. Additionally, there was no influence of sex.
Blood flow restriction applied in this study increased blood pressure in a pressure-dependent manner upon head-up tilt.