Repetition Maximum Research Articles

The Influence of Lower-Limb Strength and Power on the Speed and Heat Results of Professional Brazilian Surfers.

To correlate speed and heat scores with anthropometric variables and lower-limb strength and power in professional surfers. A total of 19 men participated in simulated competitions on different days. All surfed waves were scored, and each athlete's best 2 were used for their total heat score. Speed values were extracted by global positioning system and adjusted by Z score. Squat jump, countermovement jump, and drop jump were executed. Anthropometric variables and 1-repetition maximum (1RM) in the half squat were measured. Pearson product-moment correlation was used to analyze the relationships. Height had a significant (P < .05) inverse association with speed indicators (r = -.36 to - .68), and body mass index had a moderate association with maximum wave speed of the highest score. Significant correlations with moderate to large magnitudes were found between maximum speed and vertical jumps (r = .46 to .56), average speed and vertical jumps (r = .48 to .59), and both maximum and average speed with 1RM (r = .52-.53). Athletes' best score and total heat score showed moderate to large associations with vertical jumps and 1RM (r = .48-.64), whereas second scores were correlated with the reactive strength index of the drop jump (r = .48) and 1RM (r = .51). Shorter surfers with lower center of gravity and those with superior lower-limb strength and power achieved greater speed and higher scores. Accordingly, surf coaches may consider prescribing dynamic strength and balance training based on an athlete's profile to improve performance.

Acute Responses to Different Velocity-Loss Thresholds During Squat Training With and Without Blood-Flow Restriction.

To compare the acute effects on mechanical, metabolic, neuromuscular, and muscle contractile responses to different velocity-loss (VL) thresholds (20% and 40%) under distinct blood-flow conditions (free [FF] vs restricted [BFR]) in full squat (SQ). Twenty strength-trained men performed 4 SQ protocols with 60% 1-repetition maximum that differed in the VL within the set and in the blood-flow condition (FF20: FF with 20% VL; FF40: FF with 40% VL; BFR20: BFR with 20% VL; and BFR40: BFR with 40% VL). The level of BFR was 50% of the arterial occlusion pressure. Before and after the SQ protocols, the following tests were performed: (1)tensiomyography, (2)blood lactate, (3)countermovement jump, (4)maximal voluntary isometric SQ contraction, and (5)performance with the load that elicited a 1m·s-1 at baseline measurements in SQ. No "BFR × VL" interactions were observed. BFR protocols resulted in fewer repetitions and lower increases in lactate concentration than FF protocols. The 40% VL protocols completed more repetitions but resulted in lower mechanical performance and electromyography median frequency during the exercise than the 20% VL protocols. At postexercise, the 40% VL protocols also experienced greater blood lactate concentrations, higher alterations in tensiomyography-derived variables, and accentuated impairments in SQ and countermovement-jump performances. The 20% VL protocols showed an increased electromyography median frequency at postexercise maximal voluntary isometric contraction. Despite BFR-accelerated fatigue development during exercise, a given VL magnitude induced similar impairments in the distinct performance indicators assessed, regardless of the blood-flow condition.

A Comparison of Three Protocols for Determining Barbell Bench Press Single Repetition Maximum, Barbell Kinetics, and Subsequent Measures of Muscular Performance in Resistance-Trained Adults

Background: One repetition maximum (1RM) is a vital metric for exercise professionals, but various testing protocols exist, and their impacts on the resulting 1RM, barbell kinetics, and subsequent muscular performance testing are not well understood. This study aimed to compare two previously established protocols and a novel self-led method for determining bench press 1RM, 1RM barbell kinetics, and subsequent muscular performance measures. Methods: Twenty-four resistance-trained males (n = 12, 24 ± 6.1 years) and females (n = 12, 22.5 ± 5.5 years) completed three laboratory visits in a randomized crossover fashion. During each visit, a 1RM was established using one of the three protocols followed by a single set to volitional fatigue using 80% of their 1RM. A Sex:Protocol repeated measures ANOVA was used to determine the effects of sex and differences between protocols. Results: No significant differences were observed between the protocols for any measure, except for 1RM peak power (p = 0.036). Post hoc pairwise comparisons failed to identify any differences. Males showed significantly higher 1RM, average, and peak power (ps &lt; 0.001), while females demonstrated a greater average concentric velocity (p = 0.031) at 1RM. Conclusions: These data suggest the protocol used to establish 1RM may have minimal impact on the final 1RM, 1RM barbell kinetics, and subsequent muscular endurance in a laboratory setting.

The effect of menstrual cycle phase-based rehabilitation for females following anterior cruciate ligament reconstruction: A randomised controlled trial

Research reports that follicular phase-based resistance training, where females predominantly perform resistance training in the first half of their menstrual cycle (MC), appears to result in better responses than regular training. The objective of this study was to compare the effects of MC phase-based rehabilitation (MCPBR) versus usual care (UC), following anterior cruciate ligament reconstruction (ACLR). Forty-three females participated in a 12-week intervention commencing six weeks post-ACLR. The primary outcome was knee extension strength limb symmetry index (LSI), and the secondary outcome was self-reported function (measured using the Knee Injury and Osteoarthritis Outcome Score, International Knee Documentation Committee Questionnaire, and Knee Self Efficacy Scale), measured at baseline and endpoint. Participants were randomly assigned to MCPBR (n = 21) or UC (n = 22). Participants’ MCs were monitored using calendar tracking, basal body temperature tracking, and urinary ovulation testing. Thirty-six females provided data for the final analysis. The M (SD) knee extension LSI for participants following MCPBR was 81.2% (13.2%), compared to 73.5% (21.8%) for those following UC (p = 0.17). The M (SD) one repetition maximum knee extension of the injured leg was 38.8 kg (14.1 kg) following MCPBR and 30.4 kg (11.7 kg) following UC (p = 0.06). Self-reported function was similar between groups. The findings of this study show that MCPBR and UC result in similar knee extension LSI and function and therefore do not support the recommendation of MCPBR for ACL rehabilitation in a New Zealand context. Future research should investigate females’ experience of MCPBR following ACLR.

Eccentric Resistance Exercise Effects on Older Adults With Metabolic Syndrome

Background This nonrandomized pilot study explored how whole-body eccentric resistance exercise training (ECC-RT) would change physical fitness and health parameters of older adults with metabolic syndrome symptoms. We hypothesized that ECC-RT would effectively improve neuromuscular and cardio-metabolic parameters. Methods Six men and 11 women aged between 62 and 79 (70.0 ± 5.0) years with body mass index &amp;gt;25 kg · m−2, dyslipidemia, and some indications of metabolic syndrome participated in this study. All performed 8 ECC-RT exercises of the major muscle groups twice a week for 8 weeks with a gradual increase in intensity from 10% to 100% of their maximal concentric strength assessed by 1-repetition maximum (1-RM) for each exercise. Before and after the training intervention, 1-RM strength of all exercises, physical function tests, sensory organization test (SOT) for balance, body composition, and some cardio-metabolic blood markers were measured. Results All participants completed 16 training sessions without any injuries or adverse effects. The concentric 1-RM strength increased (P &amp;lt; 0.05) for all exercises from baseline by 34.1% ± 13.8% (lateral pulldown) to 115.8% ± 108.7% (calf raise). Significant (P &amp;lt; 0.05) improvement of 400-m walk (12.8% ± 6.7%), repeated chair rise (18.6% ± 16.4%), timed up and go (13.6% ± 6.0%), and vestibular (26.1% ± 37.9%) and total score (6.5% ± 8.3%) in SOT were evident, although large variations in responses were observed among participants. However, no significant changes in body composition and blood markers were found. Conclusion The ECC-RT was tolerable for all participants and was effective for improving muscle strength and some physical function tests, but did not affect the metabolic syndrome parameters, possibly because of the short intervention period and small sample size.

Effects of Cluster vs. Traditional Sets Complex Training on Physical Performance Adaptations of Trained Male Volleyball Players.

This study aimed to examine the impact of different set configurations during combination of resistance and plyometric training (complex [COX]) on jumping ability, power output, strength, and hormonal adaptations in young male volleyball players after a 6-week training period. A randomized controlled trial was conducted with twenty-four trained male volleyball players under the age of 19, who were assigned to one of two groups for lower-body COX training: cluster sets (CS-COX: n = 8) or traditional sets (TS-COX: n = 8), with an additional active control group (CON: n = 8). The players underwent evaluations for countermovement vertical jump (CMVJ), spike jump (SPJ), T-test change of direction speed (T-test CODS), one repetition maximum (1RM) in the back squat and leg press, and the Wingate Anaerobic Test before and after the 6-week training intervention (12 sessions in total). Blood samples were also collected before and after training to assess resting testosterone and cortisol responses. Following the training, both the CS-COX and TS-COX groups exhibited significantly greater (p = 0.001) changes than the CON group in the variables, while similar improvements in maximal strength, mean power output, and testosterone adaptations were observed following the training (p < 0.05). Moreover, the CS-COX group demonstrated greater improvements in CMVJ (effect size [ES] = 0.36), SPJ (ES = 0.06), T-test CODS (ES = -0.60), and peak power output (ES = 0.72), along with greater reductions in resting cortisol (ES = -0.30) levels compared to the TS-COX group after the 6-week intervention (p < 0.05). In conclusion, the results indicate that incorporating cluster sets during COX training sessions led to more favorable changes in bio-motor ability, peak power output, and cortisol adaptations, with greater consistency and uniformity in adaptations among the players compared to traditional set configurations.

The influence of photobiomodulation on upper body muscular performance in collegiate athletes.

Photobiomodulation (PBM), has been shown to improve muscular performance during single-joint resistance exercises. It is unclear whether this benefit extends to multiple-joint exercises, such as the barbell bench press. In a within-group design, 15 collegiate athletes (mean±SD; age 20.2±1.6 yrs; BMI 26.0±4.5 kg.m-2) received PBM or sham treatment six hours prior and then immediately preceding a bench press protocol. Two treatment sites each on the pectoralis major, triceps, and deltoids were irradiated. Bench press one repetition maximum (1RM), volume load (VL) lifted during five sets to failure at 60% 1RM, and muscular soreness were compared between PBM and sham conditions. Testing was conducted over three sessions separated by a week each, with a baseline testing day occurring first, and the PBM and sham condition testing days following in a counterbalanced fashion. A repeated measures ANOVA was applied for analysis (alpha level=0.05). No significant differences were observed between PBM and sham conditions for bench press 1RM or soreness (P≥0.05). VL was greater in both PBM and sham conditions compared to baseline (P≤0.05). VL was not significantly different between PBM and sham. These findings suggest that muscular performance during multi-joint resistance exercises such as the bench press may not benefit from PBM in the same fashion as single-joint resistance exercises.

High-Fatigue Dynamic Resistance Exercise Induces Significant Hypoalgesia Effect.

Hogge, R, Mascheri, M, Shurik, D, Hanney, WJ, and Anderson, AW. High-fatigue dynamic resistance exercise induces significant hypoalgesia effect. J Strength Cond Res XX(X): 000-000, 2024-Although dynamic resistance exercise is a recommended treatment for patients with musculoskeletal pain, optimal intensity to create hypoalgesia has not been established. Response to exercise may also be affected by biopsychosocial factors that modulate pain response. The first purpose was to compare the immediate effects of a high-fatigue/exertion leg extension, low-fatigue/exertion leg extension, and control condition on pressure pain threshold (PPT) applied to the quadriceps (local effects) and trapezius (systemic effects). The second purpose was to examine if psychological and pain sensitivity factors affected response to exercise. As a within-subject design, subjects completed psychological questionnaires, a control condition, and a 1-repetition maximum (1RM) during the first session. Subjects attended 2 more sessions where they completed 3 sets of a leg extension exercise at 50% of their 1RM until they reached a fatigue level of high fatigue (8/10 on the Borg CR-10) or low fatigue (3/10) with a randomized session order. A within-subject repeated-measures ANOVA was conducted (significance set at p < 0.05). High-fatigue exercise produced significantly higher PPT at the quadriceps than quiet rest after each set (F[6,162] = 3.25, p < 0.01, partial eta2 = 0.11). During low-fatigue exercise, individuals with an efficient endogenous pain inhibitory capacity displayed significantly higher PPT at the trapezius (F[2.14, 55.61] = 3.31, p = 0.03, partial eta2 = 0.11). Lower fear of pain was moderately associated with greater PPT increases at the trapezius (r = -0.38, p = 0.04). Although high-fatigue exercise produces immediate local hypoalgesia, systemic hypoalgesia is affected by variability in pain inhibition and fear of pain.

Stair-Climbing Versus Machine-Based Resistance Exercise to Improve Muscle Power Among Older Adults: A Noninferiority Trial.

Van Roie, E, van Uffelen, J, and Delecluse, C. Stair-climbing versus machine-based resistance exercise to improve muscle power among older adults: a non-inferiority trial. J Strength Cond Res XX(X): 000-000, 2024-Machine-based resistance training (RT) can reduce the age-related loss in muscle power (Pmax). However, weight-bearing exercises have greater potential for implementation. This study investigated whether stair-climbing exercise (STAIR) was non-inferior to improve Pmax compared with machine-based RT among older adults. Functional capacity tests were secondary outcomes. Older adults (30♂ and 16♀; 70.9 ± 4.3 years) were randomly assigned to RT or STAIR (n = 23 per group). Supervised laboratory-based training sessions were performed 2 times per week for 12 weeks. In week 1-4, exercises were performed at controlled speed (hypertrophy-oriented; 4 × 12-15 repetitions; 55% of 1 repetition maximum (1RM) in RT; step-up exercise with height of 30-40 cm in STAIR), in week 5-12 as fast as possible (power-oriented, 4 × 12 repetitions; 40% of 1RM for RT and 4 × 2 flights of 6 steps for STAIR). Leg-extensor Pmax and functional capacity were measured pre-intervention and post-intervention, and Pmax also after 4 weeks of training. Gains in Pmax were not statistically different in RT (19.5 ± 12.2%) and STAIR (13.7 ± 16.5%) (d = 0.39, pint = 0.086), whereas non-inferiority analyses were inconclusive (between-group difference in gains: 5.8% (95% CI -3.1 to 14.6); non-inferiority limit 3.9%). STAIR increased more in stair ascent performance (d = 0.45-0.61, pint < 0.05) than RT. STAIR and RT improved similarly on 10-m fast walk, 5-repetition sit-to-stand, and countermovement jump (pint > 0.05). To conclude, STAIR and RT both induced significant changes in Pmax and functional capacity in older adults. STAIR was beneficial over RT for gains in stair-climbing performance. Future research should investigate the effects of STAIR in a home-based unsupervised setting.

Is inertial training more effective than traditional resistance training in young healthy males?

Inertial training, also called flywheel training is more and more popular among sportsmen. The available data concerning the effectiveness of inertial training compared to conventional resistance strength training are contradictory. The aim of this study was to compare the impact of inertial training (IT) vs. traditional gravity-dependent resistance training (TRT) on elbow flexor and knee extensor strength. Twenty-six young, recreationally active males were randomized into IT group (n = 13) or TRT group (n = 13). Both groups performed strength training three times a week for 6 weeks. Before and after training, the maximum force of the trained muscles was evaluated under training conditions (one repetition maximum under gravity-dependent conditions and maximal force under inertial conditions) and isometric conditions. Countermovement jump, squat jump, pull-up test, and limb circumference were also evaluated. Elbow flexor muscle strength and arm circumference increased significantly in both IT and TRT over the course of training. There were no significant differences in relative muscle strength increases between groups. Knee extensor muscle strength also improved significantly in IT, regardless of the tested conditions, while TRT showed significant changes in one repetition maximum and isometric force but no significant changes in force obtained under inertial conditions. Thigh circumference increased in IT (P ≤ 0.05) but was unchanged in TRT. Jumping abilities improved significantly in both groups, without any differences between groups. We cannot confirm the superiority of inertial training over traditional resistance training definitively. Nevertheless, inertial training had a slight advantage over traditional resistance training when knee extensor muscle training was considered.

Evaluating the evening carbohydrate dilemma: the effect of within-the-day carbohydrate periodization on body composition and physical fitness.

To assess the effects of carbohydrate timing and type on body composition and physical fitness. Forty-two healthy, trained male volunteers underwent a four-week intervention, randomly divided into three groups: (i) Sleep Low-No Carbohydrates (SL-NCHO): consuming all carbohydrate intake at regular intervals prior to evening training, (ii) Sleep High-Low Glycemic Index (SH-LGI), and (iii) Sleep High-High Glycemic Index (SH-HGI). In both SH-LGI and SH-HGI, carbohydrates were distributed throughout the day, both pre-(60% of total intake) and post-evening training (40% of total intake). The SH-LGI and SH-HGI groups diverged in evening carbohydrate quality, featuring LGI and HGI foods, respectively. All participants performed a standardized exercise program combining resistance exercise and high-intensity interval training. Body composition was assessed using skinfold measurements and bioelectrical impendence analysis. Physical fitness was assessed by measuring VO2max, Visual Reaction Time (VRT), Countermovement Jump (CMJ), and 1-repetition maximum (1RM) in hack squat, chest press, shoulder press, and lat-pulldown exercises. There was a significant time-effect on both body composition and physical fitness indices. Bodyfat percentage decreased by an average of 1.5% (p < 0.001), fat-mass by 1.4kg (p < 0.001) and fat-free mass increased by 0.9kg (p = 0.006). A time-effect was also observed in VO2max, CMJ, 1RM testing, and VRT (all p < 0.05). There were no significant differences among interventions. A balanced dietary plan with sufficient nutrient and energy intake promotes body composition optimization and physical fitness, independently of carbohydrate type or timing. This study points towards implementing flexible nutrition interventions, emphasizing the potential of tailored dietary strategies to optimize health and physical fitness. The trial was registered at clinicaltrials.gov as NCT05464342.

Current methods for the exercise dose equalization in resistance training drive to markedly different session-induced efforts.

Effects comparison of resistance exercises may require equalizing the exercise-induced dose, this is currently done by using methods based on total weight lifted or on sets performed until failure. Dose equalization of resistance training sessions by these methods was analyzed in the present study. Twelve trained participants performed five bench-press sessions with a similar relative endpoint determined by the inability to complete a set of 50% of the maximum repetitions number (MNR). Sessions were performed at 50 or 85% of one-repetition maximum (1-RM) with sets until failure or sets prescribing 50% of MNR. The last session was performed with a reduced recovery pause to match the exercise density (total weight lifted/pause duration) of a previous session. Sessions resulted in different total weight lifted (3158±1592 kg at 85% of 1-RM vs. 5330±1967 at 50%, P<0.001) and number of sets until failure (5.1±1.9 at 85% of 1-RM vs. 2.9±1.1 at 50%, P<0.001). Matching of sessions' density suppressed the differences in the number of sets performed (P=0.50). Protocols' equalization based on the total weight lifted is likely to result in exercise volumes close to maximums when performed with heavy loads, whereas equalization based on sets to failure could induce a sets number close to the maximum when performed with light loads. Current methods for protocols equalization rely on gross values of exercise volume without considering maximums, that can result in markedly unbalanced efforts and biased results. Prescribing each exercise volume according to its maximum might optimize the training protocols' equalization.

Feasibility of utilizing pectoral muscle thickness as a predictor for one repetition maximum bench press in trained men

ABSTRACT The aim of the present study was to develop prediction equations for the one repetition maximum (1RM) Bench Press (BP) in resistance-trained men based on muscle thickness and simple anthropometric parameters. 83 men (age: 26.2 ± 4.9y, height: 175.9 ± 6.3 cm, body mass: 82.9 ± 11.2 kg) participated in the present investigation and were assessed for anthropometric measurements and for muscle thickness of pectoral major (MTP). Then, the participants performed the 1RM BP test. A very large correlation was detected between MTP and 1RM BP (r = 0.83–0.88). A prediction equation based on MTP and body mass (EQ1) was developed: 1RM BP = –15.2460565 + (32.0751388 * MTP) + (0.6364405 * Body Weight) with R2 = 0.79. Another prediction equation was developed using MTP only (EQ2): 1RM BP = 20.36167 + (39.36532 * MTP) with R2 = 0.69. Bland-Altman analysis and paired sample t test provided insufficient evidence to support differences between the predicted and the measured 1RM BP in both the equations (p > 0.05). This study showed that both MTP based (EQ2) and MTP and body mass based (EQ1) methods can be used to predict 1RM BP and may represent important tools for the evaluation of maximal strength. These findings support the potential use of non-performance-based parameters to predict maximal dynamic strength in trained individuals.

Effects of resistance training vs high intensity interval training on body composition, muscle strength, cardiorespiratory fitness, and quality of life in survivors of breast cancer: a randomized trial.

Breast cancer treatments often lead to unfavourable changes in body composition, physical fitness, and quality of life (QoL). We compared the effects of resistance training (RT) and high-intensity interval training (HIIT) on these outcomes in survivors of breast cancer. Twenty-eight survivors of breast cancer, post-treatment (Stage I-III), aged 55.5 ± 8.8 years and body mass index 27.9 ± 5kg/m2 were randomly allocated to a 12-week supervised RT (n = 14) or HIIT (n = 14) intervention, 3 days per week. Body composition (dual energy x-ray absorptiometry), upper and lower body muscle strength (1-repetition maximum), cardiorespiratory fitness (CRF) (Ekblom Bak Cycle Test), and QoL domains (EORTC QLQ-C30 and EORTC QLQ-BR45) were assessed at baseline and 12 weeks. There were no significant differences between groups at baseline. Exercise attendance ranged from 81 to 85%. Between groups, there were significant differences (p ≤ 0.001) after 12 weeks in chest press strength for RT (mean difference [MD] = 4.7 kg) and CRF for HIIT (MD = 1.9ml/min/kg). Within groups, there were significant improvements (p < 0.05) for % lean mass and % fat mass in both RT and HIIT, as well as for upper and lower body muscle strength, CRF, and QoL domains. No major adverse events were noted. Both exercise groups improved body composition, physical fitness, and QoL domains over 12 weeks of RT or HIIT, although mode-specific benefits were apparent with more substantial improvements in lean mass and muscle strength with RT and reductions in % fat mass and improved CRF with HIIT. Tailored exercise programs should address the specific health needs of each patient.

Effects of horizontally versus vertically loaded resistance exercises on performance and muscle architecture.

The aim of this study was to compare a training program based on horizontally (HT) versus vertically (VT) loaded exercises on performance and muscle architecture of the lower body muscles. Nineteen resistance trained individuals were randomly assigned to HT (N.=10; age: 25.9±4.2 y; body mass: 72.7±11.4 kg; height: 174.0±6.0 cm) or VT group (N.=9; age: 26.9±4.4 y; body mass: 76.2±10.8 kg; height: 174.2.0±5.8 cm). Both 6-week training programs included 4 training sessions per week and were equated for the total number of repetitions. One repetition maximum (1RM) was assessed for squat and hip thrust, together with vertical and horizontal jumps and sprint. Muscle thickness (MT) and echo intensity (EI) of vastus lateralis, vastus medialis and gluteus were also evaluated pre- and post-training period. A significantly greater increase in 1RM hip thrust was detected in HT (+17.9%; P=0.004) while greater increases in 1RM squat were found in VT (+10.5%; P=0.007). A greater increase (P=0.009) in vastus medialis MT was detected in VT (4.1%) compared to HT (-7.9%). Similar increases in MT of gluteus were registered in both groups (P<0.05). A greater improvement in standing long jump (P=0.004) was detected in HT (+7.6%) compared to VT (+1.6%), while both groups significantly improved vertical jump performance. Combining both groups, strong correlations were detected between gluteus EI and 20-m sprint (r=0.79; P<0.001). Results indicate that HT was more effective than VT for horizontal jumps while both HT and VT were equally effective on vertical jumps. Both HT and VT promoted similar changes in muscle architecture of the gluteus, but not of the vastus medialis.

Acute Effect of Oral N-Acetylcysteine Supplementation on Fatigue Effect and Isometric Force Production in Physically Active People

The main objective of this study was to assess the ergogenic effect of N-acetylcysteine (NAC) on myotendinous isometric force production in physically active people after being subjected to a fatigue protocol. Twenty-three physically active people were randomly divided into the following two groups: NAC (n = 12; age = 26.8 ± 4.5 years, height = 173.1 ± 7.2 cm, and weight = 75.5 ± 7.5 kg), who received 2400 mg oral NAC, and control (n = 11; age = 23.4 ± 5.8 years, height = 175.9 ± 4.5 cm, and weight = 72.3 ± 9.9 kg), who received a placebo, for eight days. The isometric force production was assessed pre- and post-NAC supplementation during a maximal voluntary contraction test (MVC) and also during a fatigue protocol composed of seven sets of ten maximal isometric contraction repetitions of 5 s, with 5 s of rest between repetitions and 20 s between sets. No differences were observed between the groups in the force production values at any moment, and no side effects were found after NAC supplementation. After supplementation, a significant decrease in force was observed in both groups, but this significant loss of force started one set later in the NAC group compared to the control group (4th set vs. 5th set), which could be an ergogenic effect of the treatment. Therefore, oral daily supplementation with 2400 mg of NAC for eight days, could delay the decrease in force production during an isometric exercise protocol and without adverse side effects.

The effect of eight weeks of circuit resistance training on Apo-B/A ratio and inflammatory status of sedentary postmenopausal women

Abstract Exercise can be an effective non-pharmacological method to reduce the complications of menopause. This study aimed to investigate the effect of 8 weeks of circuit resistance training (CRT) on the levels of C-reactive protein (CRP), intercellular adhesion molecule 1 (ICAM-1), apolipoprotein A (Apo-A), Apo-B, and their ratio in sedentary postmenopausal women. Thirty postmenopausal women (age 54 ± 3 years, body mass index 27.6 ± 1.97 kg/m2) without any serious diseases and no hormone therapy volunteered to participate in the research. The subjects were randomly divided into two groups: circuit resistance training (n = 15, CRT) and Control (n = 15) groups. Resistance training was performed for 8 weeks, 3 days a week, including 12 stations for the whole body in 3 sets and 8-12 repetitions. The exercises started at 40% of one repetition maximum (1RM) and gradually reached 75% of 1RM in the last week. Blood samples were taken before and 48 hours after the end of both interventions to measure CRP, ICAM-1, Apo-A-I, and Apo-B. To analyse the data, a two-way analysis of variance test was used. The CRT intervention by reducing Apo-B (−8.9% vs −0.1%; change percentage relative to pre-to-post values in each group) and increasing Apo-A1 (+4.7% vs −0.1%) led to a significant increase in the Apo-B/A ratio (−13.0% vs −0.08%) compared to the Control group. In addition, a substantial decrease in the inflammatory levels of CRP (−21.0% vs +6.3%) and ICAM-1 (−22.7% vs +1.6%) was observed after 8 weeks of CRT compared to the Control group. The observed changes were consistent with a reduction in body mass and an improvement in the waist-hip ratio (WHR). The findings indicated that CRT could reduce the complications of menopause by reducing inflammatory markers and improving the lipid profile.

Bismuth telluride as a passive Q-switcher for neodymium-doped fiber laser

The scene of fiber laser has progressed very rapidly with the demonstration of various materials as saturable absorbers in a near- and mid-infrared laser cavity. However, the researchers focused on erbium-, ytterbium-, and thulium-doped fiber as a gain medium. Here, we proposed a neodymium-doped fiber laser setup to generate a Q-switched laser in a 1-μm regime. The laser utilized bismuth telluride, a topological insulator as a Q-switcher for pulse generation. With a linear absorption of approximately 5 dB at 1089 nm, this SA can generate a stable Q-switched laser in a neodymium-doped fiber laser cavity. It generates a stable Q-switched laser at 1089 nm when the pump intensity is adjusted between 167 and 190 mW. The pulsed laser owns the shortest pulse width of 6.48 μs with a maximum repetition rate of 40 kHz. The stability of the laser is promising since it has a signal-to-noise ratio of 40 dB. In the authors’ knowledge, this is the first demonstration of bismuth telluride as a saturable absorber in an all-fiberized neodymium-doped fiber laser cavity.

Cross-Validation of Equations for Estimating 1 Repetition Maximum From Repetitions to Failure for the Bench Press and Leg Extension.

Roberts, TD, Smith, RW, Arnett, JE, Ortega, DG, Schmidt, RJ, and Housh, TJ. Cross-validation of equations for estimating 1 repetition maximum from repetitions to failure for the bench press and leg extension. J Strength Cond Res XX(X): 000-000, 2024-Eighteen previously published equations (EQs) that estimate 1 repetition maximum (1RM) from repetitions to failure (RTF) were cross-validated for the bench press (BP) and leg extension (LE) movements. Forty-three recreationally active men (age: 20.58 ± 1.47 years; body mass [BM]: 81.66 ± 13.65 kg) completed a 1RM test and RTF at 80% of the 1RM test for the LE, and 39 of the 43 men (age: 20.61 ± 1.48 years; BM: 83.58 ± 12.73 kg) completed the same tests for the BP. The EQs were categorized as generic (the source did not indicate its applicability for a specific movement) or movement-specific (BP-specific and LE-specific EQs). The generic EQs were cross-validated for both movements, whereas the BP-specific and LE-specific EQs were cross-validated for their respective movements only. The cross-validation criteria included calculations of the constant error (CE) (mean differences between estimated and measured 1RM), Pearson Correlation Coefficient, standard error of the estimate, and total error. The level of significance was set at p ≤ 0.05. After the initial cross-validation analyses of the previously published EQs, the most accurate EQs were modified by subtracting their cross-validation CE from the original EQ to improve their accuracy for estimating BP and LE 1RM by eliminating systematic error. The modified EQs were then cross-validated using the same statistical procedures. Based on the cross-validation analyses, we recommend the following EQs: BP 1RM = (RTF0.1 × weight) + 1.49 and LE 1RM = (RTF0.1 × weight) + 1.06 using weights that result in 4-10 RTF.

Plantar flexor strength and size decrease following single-leg disuse in uninjured adults: A meta-analysis.

Plantar flexors play a pivotal role in human locomotion and balance. Several original research studies and systematic reviews have characterised the impact of single-leg disuse on plantar flexor strength and size. However, no meta-analysis has quantified the effects of single-leg disuse on changes in plantar flexor strength and size in uninjured adults. To quantify changes in plantar flexor strength and size in response to single-leg disuse. Data were extracted from 19 studies captured in our previous systematic review on studies that employed a unilateral lower limb immobilisation model (cast or brace) and were published up to January 30, 2022. Random-effects meta-analyses were performed on original research studies reporting measures of plantar flexor strength (isometric, isokinetic, or repetition maximum) and size (magnetic resonance imaging or computed tomography) in uninjured adults. Single-leg disuse decreased plantar flexor strength (Hedges gav = -0.71 [95% confidence interval: -0.93, -0.48], p < 0.001, 7-28 days, N = 16 studies, n = 121 participants including ≥13 females, ages 19-29) and plantar flexor size (-0.33 [-0.50, -0.15], p < 0.001, 14-35 days, N = 6, n = 49, 10 females, ages 22-27) across all durations of disuse. Single-leg disuse decreases plantar flexor strength and size in uninjured adults. This work adds to recent meta-analytic findings demonstrating the declines in knee extensors strength and size following single-leg disuse. The paucity of female and participants >30 years old in the single-leg disuse literature examining plantar flexors represents a priority of future work.