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- Author or Editor: Jeremy P. Loenneke x
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Abstract
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.
Purpose
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.
Methods
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.
Results
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.
Conclusions
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.
Abstract
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.
Abstract
Background and Aim
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.
Results
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.
Conclusion
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.
Abstract
Background
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.
Methods
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.
Results
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).
Conclusion
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.
Abstract
Background
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).
Purpose
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.
Methods
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.
Results
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.
Conclusion
Blood flow restriction applied in this study increased blood pressure in a pressure-dependent manner upon head-up tilt.
Abstract
Previous work has found that wide cuffs produce greater discomfort with elbow flexion exercise than narrower cuffs. It is our hypothesis that this is due to the balling up of the biceps underneath the cuff that is more pronounced with a wider cuff. One method to test this is through an upper body exercise where there is no contraction of the biceps.
Purpose
To investigate the effects of cuff width on discomfort following isometric handgrip exercise.
Methods
One hundred participants completed this experiment. In a randomized order, the participants performed four sets of two-minute isometric handgrip contractions with thirty seconds of rest at thirty percent of their maximal voluntary contraction with a 5 and 12 cm cuff inflated to 40% of arterial occlusion pressure. Discomfort ratings (0–100) were given after the fourth set of exercise. Average force was recorded for all four sets.
Results
There was no difference in discomfort (BF10 = 0.158) [median difference (95% credible interval) −0.997 (−3.360, 1.283) arbitrary units], or in average force (BF10 = 0.132) [median difference (95% credible interval) 0.08 (−0.199, 0.372) kilograms], between cuff conditions. There did not appear to be a greater preference for either cuff. Forty people preferred the narrow cuff (BF10 = 0.325), forty people preferred the wide cuff (BF10 = 0.325), and twenty people had no preference (BF10 = 7.719).
Conclusion
Cuff width does not appear to influence discomfort or the average force produced. This provides support for our hypothesis that the shape of the muscle may interact with wider cuff sizes, leading to greater discomfort.
