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Previous studies have reported associations of polymorphisms in the IGF1 gene with phenotypes of body composition (BC). The purpose of this study was to identify phenotypes of BC and physical function that were associated with the IGF1 promoter polymorphism (rs35767, −C1245T). Subjects from the Health, Aging, and Body Composition Study, white males and females (n = 925/836) and black males and females (533/705) aged 70–79 years were genotyped for the polymorphism. Phenotypes of muscle size and function, bone mineral density, and BC were analyzed for associations with this polymorphism. To validate and compare these findings, a cohort of young (mean age = 24.6, SD = 5.9) white men and women (n = 173/296) with similar phenotypic measurements were genotyped. An association with BC was identified in elderly females when significant covariates (physical activity, age, smoking status, body mass index) were included. White women with C/C genotype had 3% more trunk fat and 2% more total fat than those with C/T (P

Purpose: To examine the validity of 2 linear position transducers, the Tendo Weightlifting Analyzer System (TWAS) and Open Barbell System (OBS), compared with a criterion device, the Optotrak Certus 3-dimensional motion-capture system (OC3D). Methods: A total of 25 men (age, 25 [3] y; height, 174.0 [6.7] cm; body mass, 89.0 [14.7] kg; squat 1-repetition maximum [1RM], 175.8 [34.7] kg) with ≥2 y of resistance-training experience completed a back 1RM and 1 set to failure at 70% of 1RM. Average concentric velocity (ACV) and peak concentric velocity (PCV) were recorded by all 3 devices during the final warm-up set, all 1RM attempts, and every repetition during the 70% set. Results: In total, 575 samples were obtained. Bland–Altman plots, mountain plots, a 1-way analysis of variance, SEM, and intraclass correlation coefficients were used to analyze validity. The analysis of variance showed no difference (P =.089) between devices for ACV. However, for PCV, TWAS was significantly different (ie, inaccurate) from OC3D (P <.001) and OBS (P =.001), but OBS was similar (P =.412) to OC3D. For ACV, intraclass correlation coefficients were higher for OBS than for TWAS. Bland–Altman plots showed agreement for ACV for both devices against OC3D but large limits of agreement for PCV for both devices. Mountain plots showed valid ACV for both devices, however, but slightly greater ACV and PCV accuracy with OBS than TWAS. Conclusions: Both devices may provide valid ACV measurements, but some metrics suggest more accurate ACV with OBS vs TWAS. For PCV, neither device is particularly accurate; however, OBS seems to be more accurate than TWAS. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the association of age with muscle mass and strength in a group of young adults before and after 12 weeks of progressive resistance training. Eight hundred twenty-six young males and females (age 24.34 [+ or -] 5.69 yr, range 18-39 yr) completed a strictly supervised 12-week unilateral resistance training program of the nondominant arm. Isometric (maximal voluntary contraction [MVC]) and dynamic strength (1 repetition maximum [1RM]) of the elbow flexors and cross-sectional area (CSA) of the biceps-brachii using magnetic resonance imaging (MRI) scans were measured before and after training. Pearson correlation coefficients were calculated for size and strength variables and age. In addition, the cohort was divided into groups according to decade of life and differences assessed by analysis of variance. Age correlated significantly and positively with all pretraining measures of muscle size and strength (CSA: r = 0.191, p < 0.001; MVC: r = 0.109, p = 0.002; 1RM: r = 0.109, p = 0.002). Age was not related to the training-induced changes in CSA or MVC but was negatively associated with the change in 1RM (r = -0.21 7, p < 0.001). The study indicates that age does have a significant positive relationship with muscle size and strength in untrained young adults. Although age was negatively associated with improvements in 1RM, the effect of age was small relative to the improvements induced through resistance training, thus suggesting age does not limit response to training in any practical way during early adulthood. KEY WORDS magnetic resonance imaging, muscle cross-sectional area, isometric strength, isotonic strength, supervised resistance training

Keywords: resistance training; movement; performance; biomechanics; strength testing EN resistance training movement performance biomechanics strength testing 201 212 12 04/29/22 20220415 NES 220415 Introduction The one-repetition maximum (1RM) test, a reliable measure of muscular strength for compound movements (i.e., back squat and bench press) ([30]), can be used to track strength progress and to calculate percentage-based loading ([8]). Like SEM, the ICC 95% confidence intervals suggest that bench press predictions were more accurate than squat preictions; however, 95% CI ranges were still wide for the bench press. Back Squat and Bench Press Technique The back squat and bench press were performed in accordance with International Powerlifting Federation standards ([16]). [Extracted from the article]

The purpose of this study was to validate the percentage of body fat (%BF) values estimated from the BOD POD (BP) with those obtained from hydrostatic weighing (HW) in athletic American high school boys. Additionally, the %BF values measured via near-infrared interactance (NIR), bioelectrical impedance (BIA), and skinfold (SF) were compared to HW to determine the validity of these measures. Thirty white boys (mean age [+ or -] SD = 15.8 [+ or -] 1.0 years) who where currently participating in organized sports volunteered to have their %BF estimated. Measurements were obtained from NIR, BP, BIA, and SF in random order and concluded with HW. The findings from the present study indicated that the NIR and BIA instruments produced significant (P < 0.008) constant error (CE) and total error (TE) values that were too large to be of practical value (TE > 4.0%BF). The BP produced a significantly (P < 0.008) higher CE with acceptable TE values compared to HW, but compared to all three SF estimations, the BP TE values were higher. Two of the SF equations were nonsignificant (P > 0.008) and had the lowest TE values compared to HW. These data suggest that the BP can produce acceptable body fat measures for athletic white boys but is not superior to estimates made by the SF equations used in this study. KEY WORDS air d splacement plethysmography, near-infrared interactance youth, biolectrical impedance, skinfold

The purpose of this study was to examine the effects of 28 days of beta-alanine (b-Ala) and creatine monohydrate (CrM) supplementation on the onset of neuromuscular fatigue by using the physical working capacity at neuromuscular fatigue threshold ([PWC.sub.FT]) test in untrained men. Fifty-one men (mean age [+ or -] SD = 24.5 [+ or -] 5.3 years) volunteered to participate in this 28-day, double-blind, placebo-controlled study and were randomly assigned to 1 of 4 groups: placebo (PLA; 34 g dextrose; n = 13), CrM (5.25 g CrM plus 34 g dextrose; n = 12), b-Ala (1.6 g b-Ala plus 34 g of dextrose; n = 12), or b-Ala plus CrM (CrBA; 5.25 g CrM plus 1.6 g b-Ala plus 34 g dextrose; n = 14). The supplement was ingested 4 times per day for 6 consecutive days, then twice per day for 22 days before posttesting. Before and after the supplementation, subjects performed a continuous incremental cycle ergometry test while a surface electromyographic signal was recorded from the vastus lateralis muscle to determine [PWC.sub.FT]. The adjusted mean posttest [PWC.sub.FT] values (covaried for pretest [PWC.sub.FT] values) for the b-Ala and CrBA groups were greater than those for the PLA group (p [less than or equal to] 0.05). However, there were no differences between the CrM vs. PLA, CrBA vs. b-Ala, CrM vs. b-Ala, or CrM vs. CrBA groups (p > 0.05). These findings suggested that b-Ala supplementation may delay the onset of neuromuscular fatigue. Furthermore, there appeared to be no additive or unique effects of CrM vs. b-Ala alone on [PWC.sub.FT] KEY WORDS. carnosine, ergogenic aids, electromyography, cycle ergometry

Ratings of perceived exertion (RPE) are used for exercise programming of cardiac rehabilitation patients, whenever it is difficult to use heart rate to set intensity due to medication or other factors. This investigation examined the physiological responses to two stepping exercise modes (upright and recumbent) at the same RPE. Analysis indicated significant physiological differences between the modes of exercise which may be mediated by postural differences. Specifically, the physiological responses to the recumbent exercise, but not the upright exercise, had the expected relationship with RPE, with recumbent stepping requiring less physiological effort than the upright stepping at the same RPE. As such, we cannot recommend with confidence that the prescription for upright exercise be made based on data from recumbent exercise or vice-versa.