Quantification of training-induced alterations in body composition via automated machine learning analysis of MRI images in the thigh region: A pilot study in young females

The maintenance of an appropriate ratio of body fat to muscle mass is essential for the preservation of health and performance, as excessive body fat is associated with an increased risk of various diseases. Accurate body composition assessment requires precise segmentation of structures. In this study we developed a novel automatic machine learning approach for volumetric segmentation and quantitative assessment of MRI volumes and investigated the efficacy of using a machine learning algorithm to assess muscle, subcutaneous adipose tissue (SAT), and bone volume of the thigh before and after a strength training. Eighteen healthy, young, female volunteers were randomly allocated to two groups: intervention group (IG) and control group (CG). The IG group followed an 8-week strength endurance training plan that was conducted two times per week. Before and after the training, the subjects of both groups underwent MRI scanning. The evaluation of the image data was performed by a machine learning system which is based on a 3D U-Net-based Convolutional Neural Network. The volumes of muscle, bone, and SAT were each examined using a 2 (GROUP [IG vs. CG]) × 2 (TIME [pre-intervention vs. post-intervention]) analysis of variance (ANOVA) with repeated measures for the factor TIME. The results of the ANOVA demonstrate significant TIME × GROUP interaction effects for the muscle volume (F1,16 = 12.80, p = 0.003, ηP 2 = 0.44) with an increase of 2.93% in the IG group and no change in the CG (-0.62%, p = 0.893). There were no significant changes in bone or SAT volume between the groups. This study supports the use of artificial intelligence systems to analyze MRI images as a reliable tool for monitoring training responses on body composition.

Inter-set rest configuration effect on acute physiological and performance-related responses to a resistance training session in terrestrial vs simulated hypoxia

Background

Metabolic stress is considered a key factor in the activation of hypertrophy mechanisms which seems to be potentiated under hypoxic conditions.This study aimed to analyze the combined effect of the type of acute hypoxia (terrestrial vs simulated) and of the inter-set rest configuration (60 vs 120 s) during a hypertrophic resistance training (RT) session on physiological, perceptual and muscle performance markers.

Methods

Sixteen active men were randomized into two groups based on the type of hypoxia (hypobaric hypoxia, HH: 2,320 m asl; vs normobaric hypoxia, NH: FiO2 of 15.9%). Each participant completed in a randomly counterbalanced order the same RT session in four separated occasions: two under normoxia and two under the corresponding hypoxia condition at each prescribed inter-set rest period. Volume-load (load × set × repetition) was calculated for each training session. Muscle oxygenation (SmO2) of the vastus lateralis was quantified during the back squat exercise. Heart rate (HR) was monitored during training and over the ensuing 30-min post-exercise period. Maximal blood lactate concentration (maxLac) and rating of perceived exertion (RPE) were determined after the exercise and at the end of the recovery period.

Results

Volume-load achieved was similar in all environmental conditions and inter-set rest period length did not appreciably affect it. Shorter inter-set rest periods displayed moderate increases in maxLac, HR and RPE responses in all conditions. Compared to HH, NH showed a moderate reduction in the inter-set rest-HR (ES > 0.80), maxLac (ES > 1.01) and SmO2 (ES > 0.79) at both rest intervals.

Conclusions

Results suggest that the reduction in inter-set rest intervals from 120 s to 60 s provide a more potent perceptual, cardiovascular and metabolic stimulus in all environmental conditions, which could maximize hypertrophic adaptations in longer periods of training. The abrupt exposure to a reduced FiO2 at NH seems to reduce the inter-set recovery capacity during a traditional hypertrophy RT session, at least during a single acute exposition. These results cannot be extrapolated to longer training periods.

Effects of Resistance Training in Hypobaric vs. Normobaric Hypoxia on Circulating Ions and Hormones

Hypobaric hypoxia (HH) seems to lead to different responses compared to normobaric hypoxia (NH) during physical conditioning. The aim of the study was to analyze the hormonal and circulating ion responses after performing high-intensity resistance training with different inter-set rest under HH and NH condition. Sixteen male volunteers were randomly divided into two training groups. Each group completed two counterbalanced resistance training sessions (three sets × ten repetitions, remaining two repetitions in reserve), with both one- and two-minute inter-set rest, under HH and NH. Blood samples were obtained to determine hormones and circulating ions (Ca²⁺, Pi, and HCO₃⁻) at baseline and after training sessions (5, 10, and 30 min). Resistance training with one-minute rest caused greater hormonal stress than with two-minute rest in cortisol and growth hormone, although the hypoxic environmental condition did not cause any significant alterations in these hormones. The short inter-set rest also caused greater alterations in HCO₃⁻ and Pi than the longer rest. Additionally, higher levels of Ca²⁺ and Pi, and lower levels of HCO₃⁻, were observed after training in HH compared to NH. Metabolic and physiological responses after resistance training are mediated by inter-set rest intervals and hypoxic environmental condition. According to the alterations observed in the circulating ions, HH could cause greater muscular fatigue and metabolic stress than NH.

The Influence of Movement Tempo on Acute Neuromuscular, Hormonal, and Mechanical Responses to Resistance Exercise-A Mini Review

Wilk, M, Tufano, JJ, and Zajac, A. The influence of movement tempo on acute neuromuscular, hormonal, and mechanical responses to resistance exercise-a mini review. J Strength Cond Res 34(8): 2369-2383, 2020-Resistance training studies mainly analyze variables such as the type and order of exercise, intensity, number of sets, number of repetitions, and duration and frequency of rest periods. However, one variable that is often overlooked in resistance training research, as well as in practice, is premeditated movement tempo, which can influence a myriad of mechanical and physiological factors associated with training and adaptation. Specifically, this article provides an overview of the available scientific literature and describes how slower tempos negatively affect the 1-repetition maximum, the possible load to be used, and the number of repetitions performed with a given load, while also increasing the total time under tension, which can mediate acute cardiovascular and hormonal responses. As a result, coaches should consider testing maximal strength and the maximal number of repetitions that can be performed with each movement tempo that is to be used during training. Otherwise, programming resistance training using various movement tempos is more of a trial-and-error approach, rather than being evidence or practice based. Furthermore, practical applications are provided to show how movement tempo can be adjusted for a variety of case study-type scenarios.

High-Load Resistance Exercise Augments Androgen Receptor-DNA Binding and Wnt/β-Catenin Signaling without Increases in Serum/Muscle Androgens or Androgen Receptor Content

The purpose of this study was (1) to determine the effect of single bouts of volume- and intensity-equated low- (LL) and high-load (HL) full-body resistance exercise (RE) on AR-DNA binding, serum/muscle testosterone and dihydrotestosterone, muscle androgen receptor (AR), and AR-DNA binding; and, (2) to determine the effect of RE on sarcoplasmic and nucleoplasmic β-catenin concentrations in order to determine their impact on mediating AR-DNA binding in the absence/presence of serum/muscle androgen and AR protein. In a cross-over design, 10 resistance-trained males completed volume- and intensity-equated LL and HL full-body RE. Blood and muscle samples were collected at pre-, 3 h-, and 24 h post-exercise. Separate 2 × 3 factorial analyses of variance (ANOVAs) with repeated measures and pairwise comparisons with a Bonferroni adjustment were used to analyze the main effects. No significant differences were observed in muscle AR, testosterone, dihydrotestosterone, or serum total testosterone in either condition (p > 0.05). Serum-free testosterone was significantly decreased 3 h post-exercise and remained significantly less than baseline 24 h post-exercise in both conditions (p < 0.05). In response to HL, AR-DNA binding significantly increased at 3 h post-exercise (p < 0.05), whereas no significant differences were observed at any time in response to LL (p > 0.05). Moreover, sarcoplasmic β-catenin was significantly greater in HL (p < 0.05) without significant changes in nucleoplasmic β-catenin (p > 0.05). In conclusion, increases in AR-DNA binding in response to HL RE indicate AR signaling may be load-dependent. Furthermore, despite the lack of increase in serum and muscle androgens or AR content following HL RE, elevations in AR-DNA binding with elevated sarcoplasmic β-catenin suggests β-catenin may be facilitating this response.

Postural Control and Stress Exposure in Young Men: Changes in Cortisol Awakening Response and Blood Lactate

Background: It has recently been noticed that the quantity of stress affects postural stability in young women. The study was conducted with the goal of investigating whether increased stress may damagingly effect posture control in 90 young men (71 right-handed and 19 left-handed) while maintaining an upright bipedal posture, while keeping their eyes open or closed. Perceived Stress Scale (PSS) was administered and changes in free cortisol levels were monitored (Cortisol Awakening Response, CAR) in order to evaluate the amount of stress present during awakening, while the Profile of Mood States (POMS) was used to estimate distress on the whole. Posture control was evaluated with the use of a force platform, which, while computing a confidence ellipse area of 95%, was engaged by the Center of Pressure through five stability stations and was sustained for a minimum of 52 s, with and without visual input. Another goal of the experiment was to find out whether or not cortisol increases in CAR were linked with rises of blood lactate levels. Results: CAR, PSS and POMS were found to be extensively related. Furthermore, it has been observed that increases in salivary cortisol in CAR are associated with small but significant increases in blood lactate levels. As expected, stress levels did affect postural stability. Conclusions: The results of the present study confirm that the level of stress can influence postural stability, and that this influence is principally obvious when visual information is not used in postural control.

Postural Control and Stress Exposure in Young Men: Changes in Cortisol Awakening Response and Blood Lactate

BACKGROUND

It has recently been noticed that the quantity of stress affects postural stability in young women. The study was conducted with the goal of investigating whether increased stress may damagingly effect posture control in 90 young men (71 right-handed and 19 left-handed) while maintaining an upright bipedal posture, while keeping their eyes open or closed. Perceived Stress Scale (PSS) was administered and changes in free cortisol levels were monitored (Cortisol Awakening Response, CAR) in order to evaluate the amount of stress present during awakening, while the Profile of Mood States (POMS) was used to estimate distress on the whole. Posture control was evaluated with the use of a force platform, which, while computing a confidence ellipse area of 95%, was engaged by the Center of Pressure through five stability stations and was sustained for a minimum of 52 s, with and without visual input. Another goal of the experiment was to find out whether or not cortisol increases in CAR were linked with rises of blood lactate levels.

RESULTS

CAR, PSS and POMS were found to be extensively related. Furthermore, it has been observed that increases in salivary cortisol in CAR are associated with small but significant increases in blood lactate levels. As expected, stress levels did affect postural stability.

CONCLUSIONS

The results of the present study confirm that the level of stress can influence postural stability, and that this influence is principally obvious when visual information is not used in postural control.

Does rest interval between sets affect resistance training volume, density, and rating of perceived exertion when adopting the crescent pyramid system in young women?

BACKGROUND

The rest interval between sets can affect the responses to resistance training. Thus, the purpose of this study was to compare the effects of different rest intervals (RI) on volume, density, and rating of perceived exertion (RPE) when adopting a crescent pyramid (CP) system.

METHODS

Twenty young women (21.1±2.6 years, 1.59±0.06 m, 58.5±9.3 kg) participated in this study. All participants performed three experimental sessions of the leg press exercise in 5 sets until voluntary muscular failure at 60%, 65%, 70%, 75%, and 80% of one-repetition maximum (1RM). A randomized and crossover design was used so that in each session one of three RI (RI-1 = 1 min, RI-2 = 2 min, and RI-3 = 3 min) was tested.

RESULTS

The participants performed a significantly larger volume in the RI-3 (12820±3134 kg) when compared to RI-1 (10367±3053 kg) condition (P<0.05). The volume did not differ between RI-2 and RI-3 (P>0.05). The density was higher (P<0.05) in RI-1 (43.1±12.7 kg/s) when compared RI-2 (25.6±5.8 kg/s) and RI-3 (17.7±4.3 kg/s). The RI-2 presented higher density compared to RI-3 condition (P<0.05). The RPE was not different between the three conditions (P>0.05).

CONCLUSIONS

The use of 2 minutes of rest between sets allowed the performance of a high volume-load and density of the session in young women. In addition, the three experimental sessions provided a high perception of effort.

Individualized Whole-Body Vibration: Neuromuscular, Biochemical, Muscle Damage and Inflammatory Acute Responses

Objective. We aimed to investigate the acute residual hormonal, biochemical, and neuromuscular responses to a single session of individualized whole-body vibration (WBV) while maintaining a half-squat position. Methods. Twenty male sport science students voluntarily participated in the present study and were randomly assigned to an individualized WBV group (with the acceleration load determined for each participant) or an isometric group (ISOM). A double-blind, controlled parallel study design with repeated measures was employed. Results. Testosterone and growth hormone increased significantly over time in the WBV group (P < .05 and P < .01, respectively; effect size [ES] ranged from 1.00 to 1.23), whereas cortisol increased over time in both groups (P < .01; ES ranged from 1.04 and 1.36). Interleukin-6 and creatine kinase increased significantly over time only in the WBV group (P < .05; ES = 1.07). The maximal voluntary contraction decreased significantly over time in the ISOM group (P = .019; ES = 0.42), whereas in the WBV group, the decrease did not reach a significant level (P = .05). The ratio of electromyographic activity and power decreased significantly over time in the WBV group (P < .01; ES ranged from 0.57 to 0.72). Conclusion. Individualized WBV increased serum hormonal concentrations, muscle damage, and inflammation to levels similar to those induced by resistance training and hypertrophy exercises.

Seated row and biceps curl exercises present similar acute responses on muscle thickness, arm circumference, and peak force for elbow flexors after a resistance training session in recreationally-trained subjects

BACKGROUND

The primary purpose of this study was to measure the acute effects on muscle thickness, arm circumference, and peak force between unilateral seated row and unilateral biceps curl exercises for elbow flexors after a RT session in recreationally-trained subjects.

METHODS

Fourteen resistance-trained men (25.3±2.5years, 76.5±6.4kg, 174.6±7cm) performed 6 sets of 10RM and 2-min rest for one of two exercises (unilateral seated row exercise, USR or unilateral biceps curl, UBC). Muscle thickness (MT), arm circumference (AC), and peak force (PF) were measured before 10-min (control), pre-RT session and post-RT (immediately after, 15-min and 30-min). All acute RT variables were measured during both exercises: maximal number of repetitions (MNR), total number of repetitions (TNR), time under tension (TUT), rating of perceived exertion (RPE). Two-way ANOVAs were used to test differences between exercises and moments with an alpha of 5%.

RESULTS

For PF, there was a significant difference between pre- and post-0 for UBC and USR (P<0.001). For AC, there were significant differences between pretest × post-0-min for both exercises (P<0.001). For MT, there were significant differences between pretest × post 0-min (P<0.001), pretest × post 15-min (P<0.001) for both exercises and pretest × post 30-min only for UBC (P=0.006).

CONCLUSIONS

Both exercises induced similar increases in AC and MT for elbow flexors and reduction in peak force.