Effects of Training With Free Weights Versus Machines on Muscle Mass, Strength, Free Testosterone, and Free Cortisol Levels

Different Intensities of Physical Activity and Risk of Male Genital Cancers: Exploring Potential Causal Relationships

Physical activity is associated with cancer of the male genitalia. However, the genetic causality of this association remains unclear. In this study, Mendelian randomization (MR) was used to explore the potential causal relationship between different intensities of physical activity and cancer of the male genitalia. This study utilized single nucleotide polymorphisms (SNPs) associated with vigorous exercise obtained from published genome-wide association studies (GWAS) and summary genetic data associated with male genital cancer from published GWAS. The main analysis method used was the inverse variance weighted (IVW) method for two-sample MR analysis. The heterogeneity of the results was assessed using Cochran's Q statistic, while horizontal pleiotropy was assessed using MR-Egger. Sensitivity analysis included a "leave-one-out" test. The results showed that light DIY activity was a risk factor for male genital cancer (OR = 1.045, 95% confidence interval [1.004, 1.089], p = .033). The result passed the sensitivity test. This study found the effect of light DIY activities on male genital cancer. Future studies should further explore the impact of different types of physical activity on specific types of male genital cancer to improve relevant prevention strategies.

Sex differences in absolute and relative changes in muscle size following resistance training in healthy adults: a systematic review with Bayesian meta-analysis

Background

Muscle hypertrophy may be influenced by biological differences between males and females. This meta-analysis investigated absolute and relative changes in muscle size following resistance training (RT) between males and females and whether measures of muscle size, body region assessed, muscle fibre type, and RT experience moderate the results.

Methods

Studies were included if male and female participants were healthy (18-45 years old) adults that completed the same RT intervention, and a measure of pre- to post-intervention changes in muscle size was included. Out of 2,720 screened studies, 29 studies were included in the statistical analysis. Bayesian methods were used to estimate a standardised mean difference (SMD), log response ratio (lnRR) with exponentiated percentage change (Exp. % Change of lnRR), and probability of direction (pd) for each outcome.

Results

Absolute increases in muscle size slightly favoured males compared to females (SMD = 0.19 (95% HDI: 0.11 to 0.28); pd = 100%), however, relative increases in muscle size were similar between sexes (Exp. % Change of lnRR = 0.69% (95% HDI: -1.50% to 2.88%)). Outcomes were minimally influenced by the measure of muscle size and not influenced by RT experience of participants. Absolute hypertrophy of upper-body but not lower-body regions was favoured in males. Type I muscle fibre hypertrophy slightly favoured males, but Type II muscle fibre hypertrophy was similar between sexes.

Conclusion

Our findings strengthen the understanding that females have a similar potential to induce muscle hypertrophy as males (particularly when considering relative increases in muscle size from baseline) and findings of our secondary analyses should inform future research that investigates sex differences in highly trained participants and muscle fibre type-specific hypertrophy.

Comparative Effects of the Free Weights and Smith Machine Squat and Bench Press: The Important Role of Specificity for Strength Adaptations

PURPOSE

Although previous studies have compared strength-training adaptations between free weights (FW) and machine-guided exercises, those studies did not use a Smith machine (SM), which most closely replicates the exercises performed with FW. Thus, the aim of the present study was to investigate the chronic effects of strength-focused, velocity-based training regimens using FW versus SM.

METHODS

Thirty-seven sport-science students (14 female) were assigned, balanced by sex and relative strength, to either an FW or SM training group. The training program lasted 8 weeks (2 sessions/wk), and participants performed 4 sets per exercise (back squat and bench press) at 70% of their 1-repetition maximum with moderate effort levels (20%-25% velocity loss). Load-velocity profile parameters (load-axis intercept, velocity-axis intercept, and area under the load-velocity relationship line), cross-sectional areas of the vastus lateralis and pectoralis major muscles, and the number of repetitions to failure in the bench-press exercise were assessed before and after the training program. Mechanical variables were assessed using both FW and SM.

RESULTS

All variables, with the exception of back-squat velocity-axis intercept (P = .124), improved in both training groups. The changes in load-axis intercept and area under the load-velocity relationship line were more pronounced when the training and testing conditions matched. Failure in the bench-press exercise and cross-sectional areas of the vastus lateralis and pectoralis major showed comparable improvements for both training groups, while velocity-axis intercept tended to improve more in the SM group.

CONCLUSIONS

The general population, unconcerned with the specificity of strength adaptations, can choose a training modality (FW or SM) based on personal preferences.

Correlation between low testosterone levels and the risk of osteoarthritis: a cross-sectional analysis of NHANES data (2011-2016)

BACKGROUND

Osteoarthritis (OA) is a common degenerative joint disease that significantly impacts the quality of life, especially among older adults. Testosterone, a critical hormone for musculoskeletal health, has been suggested to influence OA pathogenesis. However, the relationship between low testosterone levels and OA risk remains underexplored in large, representative populations. This study aimed to investigate the association between low testosterone levels and OA risk using data from the National Health and Nutrition Examination Survey (NHANES, 2011-2016).

METHODS

This cross-sectional analysis included 4,548 participants from NHANES, a nationally representative U.S.

DATASET

Testosterone levels were categorized as low or normal, with low testosterone defined as < 300 ng/dL for men and population-based cutoffs for women. The presence of OA was determined through self-reported physician diagnosis. Multivariable logistic regression models were used to examine the association between testosterone levels and OA risk, adjusting for demographic, socioeconomic, lifestyle, and clinical factors. Restricted cubic spline (RCS) analysis was conducted to evaluate non-linear relationships. Subgroup analyses were performed to assess consistency across key demographic and clinical strata.

RESULTS

Among the 4,548 participants, 812 (17.9%) were diagnosed with OA. Participants with OA were older, more likely to be female, and exhibited higher rates of obesity and hyperlipidemia. In fully adjusted models, low testosterone levels were significantly associated with increased OA risk (OR, 1.22; 95% CI, 1.02-1.46; P = 0.028). RCS analysis indicated a non-linear relationship, with a steep increase in OA risk at lower testosterone levels, suggesting a threshold effect. Subgroup analyses demonstrated consistent associations across demographic and clinical groups without significant interactions.

CONCLUSION

Low testosterone levels are independently associated with an increased risk of OA in the U.S.

POPULATION

These findings underscore the potential role of hormonal health in OA pathogenesis and highlight the need for longitudinal studies to clarify causal pathways. The observed non-linear relationship suggests that maintaining optimal testosterone levels may be important for joint health, and testosterone replacement therapy could be explored as a preventative strategy for individuals with testosterone deficiency.

Electromyographic Comparison of Traditional Fitness Machines, Outdoor Fitness Equipment Without Load Selectors, and Outdoor Fitness Equipment with Load Selectors in a Seated Chest Press Exercise in Trained Young Men

Outdoor fitness equipment (OFE) are strength training installations comparable to those found in indoor gyms but are located outdoors with greater accessibility. However, the scientific evidence supporting their effectiveness remains limited. The objective of this study was to analyze and compare the electromyographic (EMG) activity of upper limb muscle groups during the use of a traditional seated chest press (SCP) machine, a classic OFE SCP (OFE-SCP), and a new OFE-SCP featuring a load selector system (BIOFIT-SCP). The sample was composed of 34 active young men. EMG activity of five muscle groups was analyzed: the anterior deltoid (AD), the clavicular (CP) and sternal (SP) heads of the pectoralis major, and the lateral (LHTB) and long heads of the triceps brachii (LongHTB), under different intensities. The OFE-SCP showed significantly lower EMG activity compared with the SCP and BIOFIT-SCP in all muscles and phases (p < 0.001). Significantly lower EMG activity for the SP in all three phases was found on the BIOFIT-SCP compared with the SCP (p < 0.001), but it was significantly higher for the LHTB and AD in the BIOFIT-SCP compared with the SCP during the full and concentric phases (p < 0.05 to p < 0.001). In conclusion, training with the OFE-SCP generates less EMG activity than traditional machine training, while, in general, BIOFIT-SCP proved effective for strength training comparable to the SCP.

The role of anti-aging approaches in managing hypogonadism in sedentary older males

Introduction

With thirty percent of the world's population not getting enough exercise, Worldwide, physical inactivity ranks as one of the most common causes of premature mortality. Rapid drops in physical activity, decreased mobility, and early morbidity are aging characteristics. As the population over 80 continues to rise, aging raises the danger of age-related illnesses and changes in hormone release.

Aim

Understanding the aging process is useful in developing pharmacological therapies and identifying therapeutic targets for age-related testosterone deficiency. Therefore, this study's purpose is to present a thorough evaluation of the effects of anti-aging strategies on testosterone levels in older, inactive men.

Methods

A literature search was completed for clinical and preclinical studies published in English between 2014 and 2024 related to age, sedentary life, testosterone, and anti-aging strategies.

Results

A sedentary lifestyle and low testosterone are linked to a vicious cycle. A sedentary lifestyle lowers testosterone levels, which leads to depression, exhaustion, low energy, and weakened bone and muscle strength. These effects exacerbate the detrimental consequences of aging and physical inactivity. Anti-aging techniques can prevent and treat age-related diseases, including calorie restriction, a balanced diet, regular exercise, weight control, diabetes management, and quitting smoking. Regular exercise raises total testosterone, free testosterone, and muscle steroidogenesis. In older men, testosterone replacement treatment increases bone density, cholesterol, protein synthesis, strength, erectile function, sexual desire, and general cognitive performance. However, some studies suggest dehydroepiandrosterone supplementation may provide health improvements without negative effects, potentially reversing arterial aging and reducing cardiovascular disease risk.

Conclusion

This article evaluates the prospects for anti-aging procedures to assist in reducing the adverse effects of aging and physical inactivity in men.

Androgen receptor regulates the differentiation of myoblasts under cyclic mechanical stretch and its upstream and downstream signals

Our previous studies have demonstrated the important roles of androgen receptor (AR) in myoblast proliferation regulated by 15 % (mimic appropriate exercise) and 20 % (mimic excessive exercise) mechanical stretches. Except for myoblast proliferation, differentiation is also an important factor affecting muscle mass and strength. But the role of AR in stretch-regulated myoblast differentiation and AR's upstream and downstream signals remain unknown. In the present study, firstly the differences of myogenic differentiation between C2C12 (with AR expression) and L6 (without AR expression) myoblasts induced by 15 % and 20 % mechanical stretches were compared; secondly, AR antagonist flutamide and AR agonist GTx-007 were used in 15 % and 20 % stretched myoblasts respectively to confirm AR's roles in stretch-regulated myoblast differentiation; thirdly, RNA-seq, molecular dynamic simulation (MD) and co-immunoprecipitation were performed to screen the downstream and upstream molecules of AR during stretches. We found that (1) 15 % stretch increased while 20 % stretch decreased myotube number in differentiating C2C12 and L6 myoblasts, with more significant changes in C2C12 cells than L6 cells; (2) in stretched C2C12 myoblasts, AR antagonist flutamide inhibited 15 % stretch-promoted differentiation while AR agonist GTx-007 reversed 20 % stretch-inhibited differentiation (reflected by changes in myotube number, MHC contents of fast-twitch and slow-twitch fiber, and the levels of myogenic regulatory factors (MRFs) such as MyoD and myogenin); (3) KEGG analysis of RNA-seq showed that the differently expressed genes (DEGs) in C2C12 cells induced by 15 % stretch were enriched in FoxO and JAK-STAT signaling pathways, while DEGs by 20 % stretch were enriched in FoxO and MAPK signaling pathways; (4) MD and co-immunoprecipitation showed that β1 integrin could interact with AR and influence AR's activity in C2C12 cells. In conclusion, AR plays important roles in myoblast differentiation promoted by 15 % stretch while inhibited by 20 % stretch, which was fulfilled through FoxO-MRFs. In addition, α7β1 integrin may be a bridge linking mechanical stretch and AR. This study is beneficial to deeply understand the roles and mechanisms of AR in stretch-regulated muscle mass and strength; and reports firstly that myoblasts sense mechanical stimulus and transmit into intracellular AR via α7β1 integrin.

Free-Weight Resistance Training Enhances Core Muscle Strength but Does Not Translate to Improved Athletic Performance in Adolescent Canoe/Kayak Athletes

BACKGROUND/OBJECTIVES

While previous evidence has shown that using free weights for resistance training is a more practical approach to enhancing strength, there is a relatively low prevalence of free-weight resistance training among adolescent kayak/canoe athletes. Therefore, this study aims to assess the impact of free-weight resistance training on body composition and various performance factors among adolescent canoe/kayak athletes.

METHODS

Twenty-seven young sprint kayakers and canoeists (14 ± 1 years; 164 ± 7 cm; 56 ± 8 kg) completed this study. Following baseline assessments, athletes were randomly divided into two training groups: the free-weight resistance training group (FW) or the control group (C). The FW group underwent free-weight resistance training sessions twice weekly for 24 weeks. The C group maintained their regular bodyweight training sessions during the same timeframe. All participants performed both the pre- and post-training assessments for the following dependent variables: body composition, upper-body power, upper-body isometric muscle strength, isometric mid-thigh pull, core strength, countermovement jump, balance, anaerobic ability, and aerobic performance.

RESULTS

After 24 weeks of training, the free-weight resistance training group exhibited a significant increase in body weight (from 56 ± 5 kg to 58 ± 4 kg, p < 0.05) and improvements in the number of straight leg raise repetitions (from 23 ± 6 to 26 ± 4, p < 0.05) compared to the control group. However, the two groups observed no significant differences between upper-body isometric muscle strength, power, balance, and anaerobic/aerobic performance.

CONCLUSIONS

A 24-week training duration might be insufficient for novice participants in resistance training. Future research should consider incorporating an adaptation period or a learning phase for movements before training, thereby enhancing the efficacy of free-weight resistance training in increasing strength.

The Association of Serum Calprotectin with Fitness Indicators and Biochemical Markers in High-Level Athletes: A Continuous Dynamic Monitoring during One Competitive Season

The objective was to determine the associations between several biochemical indicators and the dynamics of concentration change across four physical fitness phases over the period of a competitive season. Furthermore, associations between serum calprotectin and biomarkers of inflammation or muscle injury and physical indicators were examined.

SUBJECTS AND METHODS

Twenty professional male water polo players (median age: 28 (22-42)) were included in this study. Serum creatine kinase activity was determined by the automated photometric UV method. The concentrations of calprotectin, C-reactive protein, and myoglobin were measured using an automated immunoturbidimetric method, while an automated immunochemistry method was employed for interleukin-6, troponin I, and cortisol determination. Tests of repeated strength, maximal strength, and static strength were used to evaluate physical activity.

RESULTS

Serum calprotectin concentrations expressed in median and IQR were significantly different: T1: 2.92 g/mL (2.47; 3.86); T2: 2.35 g/mL (1.26; 2.87); T3: 2.27 g/mL (1.60; 3.27); and T4: 1.47 g/mL (1.04; 2.85) (p = 0.004). Cortisol concentration and CK activity showed significant changes among phases (p = 0.049 and p = 0.014, respectively). Each physical activity examined showed a significant seasonal decrease (all p values were 0.001). Calprotectin serum concentration and indicators of muscular injury, inflammation, and physical activity were found to be correlated during particular stages of the seasonal examination.

CONCLUSIONS

Calprotectin values determined throughout one competitive season decreased as training intensity among water polo players increased. Serum calprotectin concentrations and indicators were related to biochemical markers of inflammation and muscle damage.

Free-Weight and Machine-Based Training Are Equally Effective on Strength and Hypertrophy: Challenging a Traditional Myth

PURPOSE

This study aimed to compare the effects of free-weight and machine-based resistance training on strength, hypertrophy, and joint discomfort.

METHODS

Thirty-eight resistance-trained men participated in an 8-wk resistance program allocated into free-weight ( n = 19) or machine-based ( n = 19) groups. Training variables were identical for both modalities, so they only differed in the use of barbells or machines to execute the full squat, bench press, prone bench pull, and shoulder press exercises. The velocity-based method was implemented to accurately adjust the intensity throughout the program. Strength changes were evaluated using eight velocity-monitored loading tests (four exercises × two modalities) and included the relative one-repetition maximum (1RM Rel ), as well as the mean propulsive velocity against low (MPV Low ) and high (MPV High ) loads. Ultrasound-derived cross-sectional area of quadriceps (proximal and distal regions), pectoralis major, and rectus abdominis was measured to examine hypertrophy. Complementarily, Western Ontario and McMaster Universities and Disabilities of the Arm, Shoulder and Hand questionnaires were administrated to assess changes in lower- and upper-limb joint discomfort. Outcomes were compared using ANCOVA and percentage of change (∆) statistics.

RESULTS

Each group significantly ( P < 0.001) increased 1RM Rel , MPV Low , and MPV High for both modalities tested, but especially in the one they trained. When considering together the eight exercises tested, strength changes for both modalities were similar (∆ differences ≤1.8%, P ≥ 0.216). Likewise, the cross-sectional area of all the muscles evaluated was significantly increased by both modalities, with no significant differences between them (∆ difference ≤2.0%, P ≥ 0.208). No between-group differences ( P ≥ 0.144) were found for changes in stiffness, pain, and functional disability levels, which were reduced by both modalities.

CONCLUSIONS

Free-weight and machine-based modalities are similarly effective to promote strength and hypertrophy without increasing joint discomfort.

Lifting velocity predicts the maximum number of repetitions to failure with comparable accuracy during the Smith machine and free-weight prone bench pull exercises

This study compared the accuracy of the fastest mean velocity from set (MVfastest) to predict the maximum number of repetitions to failure (RTF) between 2 variants of prone bench pull (PBP) exercise (Smith machine and free-weight) and 3 methods (generalized, individualized multiple-point, and individualized 2-point). Twenty-three resistance-trained males randomly performed 2 sessions during Smith machine PBP and 2 sessions during free-weight PBP in different weeks. The first weekly session determined the RTF-MVfastest relationships and subjects completed single sets of repetitions to failure against 60-70-80-90%1RM. The second weekly session explored the accuracy of RTFs prediction under fatigue conditions and subjects completed 2 sets of 65%1RM and 2 sets of 85%1RM with 2 min of rest. The MVfastest associated with RTFs from 1 to 15 were greater for Smith machine compared to free-weight PBP (F ≥ 42.9; P < 0.001) and for multiple-point compared to 2-point method (F ≥ 4.6; P ≤ 0.043). The errors when predicting RTFs did not differ between methods and PBP variants, whereas all RTF-MVfastest relationships overestimated the RTF under fatigue conditions. These results suggest that RTF-MVfastest relationships present similar accuracy during Smith machine and free-weight PBP exercises and it should be constructed under similar training conditions.

Effect of free-weight vs. machine-based strength training on maximal strength, hypertrophy and jump performance - a systematic review and meta-analysis

BACKGROUND

The effectiveness of strength training with free-weight vs. machine equipment is heavily debated. Thus, the purpose of this meta-analysis was to summarize the data on the effect of free-weight versus machine-based strength training on maximal strength, jump height and hypertrophy.

METHODS

The review was conducted in accordance with the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, and the systematic search of literature was conducted up to January 1st, 2023. Studies that directly compared free-weight vs. machine-based strength training for a minimum of 6 weeks in adults (18-60 yrs.) were included.

RESULTS

Thirteen studies (outcomes: maximal strength [n = 12], jump performance [n = 5], muscle hypertrophy [n = 5]) with a total sample of 1016 participants (789 men, 219 women) were included. Strength in free-weight tests increased significantly more with free-weight training than with machines (SMD: -0.210, CI: -0.391, -0.029, p = 0.023), while strength in machine-based tests tended to increase more with machine training than with free-weights (SMD: 0.291, CI: -0.017, 0.600, p = 0.064). However, no differences were found between modalities in direct comparison (free-weight strength vs. machine strength) for dynamic strength (SMD: 0.084, CI: -0.106, 0.273, p = 0.387), isometric strength (SMD: -0.079, CI: -0.432, 0.273, p = 0.660), countermovement jump (SMD: -0.209, CI: -0.597, 0.179, p = 0.290) and hypertrophy (SMD: -0.055, CI: -0.397, 0.287, p = 0.751).

CONCLUSION

No differences were detected in the direct comparison of strength, jump performance and muscle hypertrophy. Current body of evidence indicates that strength changes are specific to the training modality, and the choice between free-weights and machines are down to individual preferences and goals.

Connective Adaptive Resistance Exercise (CARE) Machines for Accentuated Eccentric and Eccentric-Only Exercise: Introduction to an Emerging Concept

Eccentric resistance exercise emphasizes active muscle lengthening against resistance. In the past 15 years, researchers and practitioners have expressed considerable interest in accentuated eccentric (i.e., eccentric overload) and eccentric-only resistance exercise as strategies for enhancing performance and preventing and rehabilitating injuries. However, delivery of eccentric resistance exercise has been challenging because of equipment limitations. Previously, we briefly introduced the concept of connected adaptive resistance exercise (CARE)-the integration of software and hardware to provide a resistance that adjusts in real time and in response to the individual's volitional force within and between repetitions. The aim of the current paper is to expand this discussion and explain the potential for CARE technology to improve the delivery of eccentric resistance exercise in various settings. First, we overview existing resistance exercise equipment and highlight its limitations for delivering eccentric resistance exercise. Second, we describe CARE and explain how it can accomplish accentuated eccentric and eccentric-only resistance exercise in a new way. We supplement this discussion with preliminary data collected with CARE technology in laboratory and non-laboratory environments. Finally, we discuss the potential for CARE technology to deliver eccentric resistance exercise for various purposes, e.g., research studies, rehabilitation programs, and home-based or telehealth interventions. Overall, CARE technology appears to permit completion of eccentric resistance exercise feasibly in both laboratory and non-laboratory environments and thus has implications for researchers and practitioners in the fields of sports medicine, physiotherapy, exercise physiology, and strength and conditioning. Nevertheless, formal investigations into the impact of CARE technology on participation in eccentric resistance exercise and clinical outcomes are still required.

Adaptive changes in bodybuilders in conditions of different energy supply modes and intensity of training load regimes using machine and free weight exercises

Background

The research was aimed at comparing the effect of using two types of training load different in intensity and energy supply. We studied the influence of the proposed load variations (machine and free weight exercises) on long-term adaptation of the body at the stage of specialized basic training in bodybuilding.

Methods

A total of 64 athletes aged 18-20 years were examined. The research participants were randomly divided into four groups, 16 athletes in each group. Athletes of group 1 and 3 used a complex of free weight exercises. Group 2 and 4 participants performed machine exercises. Bodybuilders of group 1 and 2 were trained in conditions of medium intensity training load (R a  = 0.58) in the anaerobic-glycolytic mode of energy supply. Athletes of the 3rd and 4th groups used high intensity load (R a  = 0.71) in the anaerobic-alactate mode of energy supply. We managed to determine the nature of adaptation processes using methods of control testing of strength capabilities, bioimpedansometry, anthropometry, biochemical analysis of blood serum (LDH, creatinine).

Results

The study showed that the difference in the dynamics of the participants' maximum strength development (on example of chest muscles) did not depend on the content of machine or free weight exercises, but on the features of training load regimes. Thus, the controlled indicator of strength capabilities in athletes of groups 3 and 4 increased by 5.1% compared to groups 1 and 2. During all stages of the study, the indicators of the projectile working mass in athletes of groups 3 and 4 exceeded the results observed in groups 1 and 2 by 25.9%. At the same time, the amount of load in a set is on average 2 times higher in athletes of groups 1 and 2. Group 4 athletes, who used machine exercises and high intensity training load, increased the circumferential body measurements by 3.8 times (the chest), compared to the results recorded in group 1 athletes. Athletes of group 1 and 2 showed increasing in body fat by 3.4% compared to the initial level on the background of large load volume. The basal creatine level in bodybuilders of groups 3 and 4 increased by 3.7 times after 12 weeks of study, which indicates an accelerated growth of muscle mass.

Conclusion

The most pronounced adaptive body changes in bodybuilders at the stage of specialized basic training occurred during high intensity training load and anaerobic-alactate energy supply mode. Machine exercises contributed to increasing the morpho functional indicators of athletes more than free weight exercises.

Estimating the relative load from movement velocity in the seated chest press exercise in older adults

AIM

This study aimed to i) determine the load-velocity relationship in the seated chest press in older adults, ii) compare the magnitude of the relationship between peak and mean velocity with the relative load, and iii) analyze the differences between sexes in movement velocity for each relative load in the chest press.

MATERIAL AND METHODS

Thirty-two older adults (17 women and 15 men; 79.6±7.7 years) performed a chest press progressive loading test up to the one-repetition maximum (1RM). The fastest peak and mean velocity reached with each weight were analyzed. Quadratic equations were developed for both sexes and the effectiveness of the regression model was analyzed through a residual analysis. The equations were cross-validated, considering the holdout method. The independent samples t-test analyzed i) the differences in the magnitude of the relationship between peak and mean velocity with the relative load and ii) the differences between sexes in the peak and mean velocity for each relative load.

RESULTS

It was possible to observe very strong quadratic load-velocity relationships in the seated chest press in women (peak velocity: r2 = 0.97, standard error of the estimate (SEE) = 4.5% 1RM; mean velocity: r2 = 0.96, SEE = 5.3% 1RM) and men (peak velocity: r2 = 0.98, SEE = 3.8% 1RM; mean velocity: r2 = 0.98, SEE = 3.8% 1RM) without differences (p>0.05) in the magnitude of the relationship between peak and mean velocity with the relative load. Furthermore, there was no overfitting in the regression models due to the high and positive correlation coefficients (r = 0.98-0.99). Finally, men presented higher (p<0.001) lifting velocities than women in almost all relative loads, except for 95-100% 1RM (p>0.05).

CONCLUSION

Measuring repetition velocity during the seated chest press is an objective approach to estimating the relative load in older adults. Furthermore, given the velocity differences between older women and men at submaximal loads, it is recommended to use sex-specific equations to estimate and prescribe the relative loads in older adults.

EFFECT OF AIR ENDURANCE TRAINING ON ATHLETE’S LOWER LIMB EXPLOSIVE STRENGTH

ABSTRACT Introduction: The explosion force is the neuromuscular system's capacity to overcome resistance with the highest possible contraction speed. It is the result of a kinetic combination between power and speed. The effect of outdoor resistance training is used in several athletics areas to improve the explosive power of the lower limbs. However, there are still few studies focused on basketball athletes. Objective: Verify the effect of outdoor resistance training on the explosive power of the lower limbs of basketball players. Methods: The article uses mathematical statistics and randomized controlled trials by analytical comparison to explore the influence of compound training methods on basketball players’ lower explosive limb power. Results: There was no performance gain in the control group at 30 days. Was an improved ability in the experimental group jumping after high-intensity composite training. Conclusion: Compound training plays a crucial role in improving lower limb explosive power in college basketball players. Evidence Level II; Therapeutic Studies - Investigating the result.

Resistance training and Down Syndrome: A narrative review on considerations for exercise prescription and safety

The current manuscript reviews the literature on the health effects of resistance training (RT) for individuals with Down syndrome (DS), focusing on this training modality’s methodology, application, and safety. The literature has mentioned that early aging in this population is associated with loss of muscle strength, lower lean and bone mass, and increased obesity. It is necessary to propose non-pharmacological measures for prevention and health promotion. Thus, this review suggests a current research-based RT guide for individuals with DS. This review is divided into three sections: Section 2 briefly reviews DS and the effects on structural and functional decline and how exercise and physical activity can influence health aspects in this population; Section 3 summarizes the evidence for RT prescription; Section 4 briefly reviews the health and potential benefits of RT in individuals with DS. The findings from this review suggest that most individuals with DS should engage in moderate-intensity RT at least 2 days a week and perform RT on the major muscle groups and include balance training. The RT program should be modified and adapted according to individuals’ characteristics and limitations. RT promotes positive, health-related benefits such as increasing strength, improving body composition, improving functional capacity and balance, reducing inflammatory status and oxidative stress, and improving the immune system. The RT protocols summarized in this current review provide guidance, critical conclusions, and novel research settings, which could be useful to coaches, clinicians, and researchers to effectively design RT program for individuals with DS.

Plasma microRNA-320a as a Potential Biomarker of Physiological Changes during Training in Professional Volleyball Players

A deeper insight into the mechanisms responsible for athlete performance that may serve as specific and detailed training indicators is still desired, because conventionally used biomarkers provide limited information about the adaptive processes that occur during exercise. The objective of our study was to assess insulin-like growth factor 1 receptors (IGF1R) gene expression and evaluate plasma concentration of selected microRNAs (miRNAs) during a 10-week training period (sampling times: week 1, 4, 7, and 10) in a group of 12 professional female volleyball players. Circulating miRNAs (miR-223, miR-320a, and miR-486) with established concentration in plasma and documented association with the IGF1 signaling pathway, which is involved in muscle development and recovery, were tested. The levels of analyzed miRNAs, tested by one-way ANOVA, were significantly different between four training periods during a 10-week training cycle (miR-223 p < 0.0001, miR-320a p = 0.00021, miR-486 p = 0.0037, respectively). The levels of IGF1R also appeared to be different (p = 0.00092), and their expression showed a trend to increase between the first and third periods. In the fourth period, the expression decreased, although it was higher compared with the baseline. Correlations between concentration levels of miR-223 and miR-320a (rs = 0.54, p < 0.001), as well as between miR-320a and miR-486 (rs = 0.73, p < 0.001) were also found. In the fourth period, a negative correlation between miR-223 plasma level and leucocyte IGF1R expression was found (rs = -0.63, p = 0.028). Multiple linear regression analysis showed that miR-320a (p = 0.024) and creatine kinase (p = 0.028) had the greatest impact on the expression levels of the IGF1R gene. Future studies are required to define whether these miRNAs, especially miR-320a, as well as IGF1R expression could be useful biomarkers of physiological changes during exercise and to discover their detailed biological roles in mode-specific exercise training adaptations of professional athletes.

Machines and free weight exercises: a systematic review and meta-analysis comparing changes in muscle size, strength, and power

INTRODUCTION

To compare changes in muscle size, strength, and power between free-weight and machine-based exercises.

EVIDENCE ACQUISITION

The online databases of Pubmed, Scopus, and Web of Science were each searched using the following terms: ""free weights" OR barbells OR dumbbells AND machines" up until September 15, 2020. A three-level random effects meta-analytic model was used to compute effect sizes.

EVIDENCE SYNTHESIS

When strength was tested using a free-weight exercise, individuals training with free-weights gained more strength than those training with machines [ES: 0.655; (95% CI: 0.269, 1.041)]. When strength was tested a machine-based exercise incorporated as part of the machine-based training program, individuals training with machines gained more strength than those training with free-weights [ES: -0.784 (95% CI: -1.223, -0.344)]. When strength was tested using a neutral device, machines and free-weight exercises resulted in similar strength gains [ES: 0.128 (95% CI: -0303, 0.559)]. There were no differences in the change in power [ES: -0.049 (95% CI: -0.557, 0.460)] or muscle hypertrophy [ES: -0.01 (95% CI: -0.525, 0.545)] between exercise modes.

CONCLUSIONS

Individuals looking to increase strength and power should take into account the specificity of exercise, and how their strength and power will be tested and applied. Individuals looking to increase general strength and muscle mass to maintain health may choose whichever activity they prefer and are more likely to adhere to.

Skeletal Muscle Quality: A Biomarker for Assessing Physical Performance Capabilities in Young Populations

Muscle quality (MQ), defined as the amount of strength and/or power per unit of muscle mass, is a novel index of functional capacity that is increasingly relied upon as a critical biomarker of muscle health in low functioning aging and pathophysiological adult populations. Understanding the phenotypical attributes of MQ and how to use it as an assessment tool to explore the efficacy of resistance exercise training interventions that prioritize functional enhancement over increases in muscle size may have implications for populations beyond compromised adults, including healthy young adults who routinely perform physically demanding tasks for competitive or occupational purposes. However, MQ has received far less attention in healthy young populations than it has in compromised adults. Researchers and practitioners continue to rely upon static measures of lean mass or isolated measures of strength and power, rather than using MQ, to assess integrated functional responses to resistance exercise training and physical stress. Therefore, this review will critically examine MQ and the evidence base to establish this metric as a practical and important biomarker for functional capacity and performance in healthy, young populations. Interventions that enhance MQ, such as high-intensity stretch shortening contraction resistance exercise training, will be highlighted. Finally, we will explore the potential to leverage MQ as a practical assessment tool to evaluate function and enhance performance in young populations in non-traditional research settings.

Dose-Response Relationship Between Velocity Loss During Resistance Training and Changes in the Squat Force-Velocity Relationship

PURPOSE

This study aimed to compare the adaptations provoked by various velocity loss (VL) thresholds used in resistance training on the squat force-velocity (F-V) relationship.

METHODS

Sixty-four resistance-trained young men were randomly assigned to one of four 8-week resistance training programs (all 70%-85% 1-repetition maximum) using different VL thresholds (VL0 = 0%, VL10 = 10%, VL20 = 20%, and VL40 = 40%) in the squat exercise. The F-V relationship was assessed under unloaded and loaded conditions in squat. Linear and hyperbolic (Hill) F-V equations were used to calculate force at zero velocity (F0), velocity at zero force (V0), maximum muscle power (Pmax), and force produced at mean velocities ranging from 0.0 to 2.0 m·s-1. Changes in parameters derived from the F-V relationship were compared among groups using linear mixed models.

RESULTS

Linear equations showed increases in F0 (120.7 N [89.4 to 152.1]) and Pmax (76.2 W [45.3 to 107.2]) and no changes in V0 (-0.02 m·s-1 [-0.11 to 0.06]) regardless of VL. Hyperbolic equations depicted increases in F0 (120.7 N [89.4 to 152.1]), V0 (1.13 m·s-1 [0.78 to 1.48]), and Pmax (198.5 W [160.5 to 236.6]) with changes in V0 being greater in VL0 and VL10 versus VL40 (both P < .001). All groups similarly improved force at 0.0 to 2.0 m·s-1 (all P < .001), although in general, effect sizes were greater in VL10 and VL20 versus VL0 and VL40 at velocities ≤0.5 m·s-1.

CONCLUSIONS

All groups improved linear and hyperbolic F0 and Pmax and hyperbolic V0 (except VL40). The dose-response relationship exhibited an inverted U-shape pattern at velocities ≤0.5 m·s-1 with VL10 and VL20 showing the greatest standardized changes.

Integrating Transwomen and Female Athletes with Differences of Sex Development (DSD) into Elite Competition: The FIMS 2021 Consensus Statement

Sport is historically designated by the binary categorization of male and female that conflicts with modern society. Sport’s governing bodies should consider reviewing rules determining the eligibility of athletes in the female category as there may be lasting advantages of previously high testosterone concentrations for transwomen athletes and currently high testosterone concentrations in differences in sex development (DSD) athletes. The use of serum testosterone concentrations to regulate the inclusion of such athletes into the elite female category is currently the objective biomarker that is supported by most available scientific literature, but it has limitations due to the lack of sports performance data before, during or after testosterone suppression. Innovative research studies are needed to identify other biomarkers of testosterone sensitivity/responsiveness, including molecular tools to determine the functional status of androgen receptors. The scientific community also needs to conduct longitudinal studies with specific control groups to generate the biological and sports performance data for individual sports to inform the fair inclusion or exclusion of these athletes. Eligibility of each athlete to a sport-specific policy needs to be based on peer-reviewed scientific evidence made available to policymakers from all scientific communities. However, even the most evidence-based regulations are unlikely to eliminate all differences in performance between cisgender women with and without DSD and transwomen athletes. Any remaining advantage held by transwomen or DSD women could be considered as part of the athlete’s unique makeup.

Muscle Activation and Kinematic Analysis during the Inclined Leg Press Exercise in Young Females

Knee joint muscle activation imbalances, especially weakness in the vastus medialis oblique, are related to patellofemoral pain within the female population. The available literature presents the leg press as an exercise which potentially targets vastus medialis oblique activation, thus reducing imbalances in the quadriceps muscles. The main aim of the present study was to compare thigh muscle activation and kinematic parameters under different conditions during the inclined leg press exercise in a young female population. A cross-sectional study was conducted on 10 young, trained females. Muscle activation of the vastus medialis oblique, vastus lateralis, rectus femoris and gluteus medialis was analyzed under five different inclined leg press conditions, modifying the feet rotation (0–45° external rotation) and the stance width (100–150% hip width) on the footplate. All the conditions were performed at two different movement velocities: controlled velocity (2″ eccentric–2″ concentric) and maximal intended velocity. Mean propulsive velocity, maximum velocity and maximum power were also assessed. The results show that both controlled velocity conditions and maximal intended velocity conditions elicited a similar muscle activation pattern with greater activation during the concentric phase (p < 0.001, ηp² = 0.96). The maximal intended velocity conditions showed greater overall muscle activation (p < 0.001, ηp² = 0.91). The vastus medialis oblique presented the greatest muscle activation, followed by the rectus femoris, vastus lateralis and, the gluteus medialis. Furthermore, the inclined leg press condition with 0º feet rotation, 100% hip width distance and the maximal intended velocity generated the greatest kinematic parameter outputs. In conclusion, the inclined leg press exercise might be an optimal exercise to target vastus medialis activation regardless of the feet rotation and stance width conditions.

Evaluation of the Lower Limb Muscles' Electromyographic Activity during the Leg Press Exercise and Its Variants: A Systematic Review

The aim of this study was to analyze the literature on muscle activation measured by surface electromyography (sEMG) of the muscles recruited when performing the leg press exercise and its variants. The Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to report this review. The search was carried out using the PubMed, Scopus, and Web of Science electronic databases. The articles selected met the following inclusion criteria: (a) a cross-sectional or longitudinal study design; (b) neuromuscular activation assessed during the leg press exercise, or its variants; (c) muscle activation data collected using sEMG; and (d) study samples comprising healthy and trained participants. The main findings indicate that the leg press exercise elicited the greatest sEMG activity from the quadriceps muscle complex, which was shown to be greater as the knee flexion angle increased. In conclusion, (1) the vastus lateralis and vastus medialis elicited the greatest muscle activation during the leg press exercise, followed closely by the rectus femoris; (2) the biceps femoris and the gastrocnemius medialis showed greater muscular activity as the knee reached full extension, whereas the vastus lateralis and medialis, the rectus femoris, and the tibialis anterior showed a decreasing muscular activity pattern as the knee reached full extension; (3) evidence on the influence of kinematics modifications over sEMG during leg press variants is still not compelling as very few studies match their findings.