The primary aim of this study was to compare rating of perceived exertion (RPE) values measuring repetitions in reserve (RIR) at particular intensities of 1 repetition maximum (RM) in experienced ...(ES) and novice squatters (NS). Furthermore, this investigation compared average velocity between ES and NS at the same intensities. Twenty-nine individuals (24.0 ± 3.4 years) performed a 1RM squat followed by a single repetition with loads corresponding to 60, 75, and 90% of 1RM and an 8-repetition set at 70% 1RM. Average velocity was recorded at 60, 75, and 90% 1RM and on the first and last repetitions of the 8-repetition set. Subjects reported an RPE value that corresponded to an RIR value (RPE-10 = 0-RIR, RPE-9 = 1-RIR, and so forth). Subjects were assigned to one of the 2 groups: (a) ES (n = 15, training age: 5.2 ± 3.5 years) and (b) NS (n = 14, training age: 0.4 ± 0.6 years). The mean of the average velocities for ES was slower (p ≤ 0.05) than NS at 100% and 90% 1RM. However, there were no differences (p > 0.05) between groups at 60, 75%, or for the first and eighth repetitions at 70% 1RM. In addition, ES recorded greater RPE at 1RM than NS (p = 0.023). In ES, there was a strong inverse relationship between average velocity and RPE at all percentages (r = -0.88, p < 0.001), and a strong inverse correlation in NS between average velocity and RPE at all intensities (r = -0.77, p = 0.001). Our findings demonstrate an inverse relationship between average velocity and RPE/RIR. Experienced squatter group exhibited slower average velocity and higher RPE at 1RM than NS, signaling greater efficiency at high intensities. The RIR-based RPE scale is a practical method to regulate daily training load and provide feedback during a 1RM test.
Muscle fibers are generally fractionated into type I, IIA, and IIX fibers. Type I fibers specialize in long duration contractile activities and are found in abundance in elite endurance athletes. ...Conversely type IIA and IIX fibers facilitate short-duration anaerobic activities and are proportionally higher in elite strength and power athletes. A central area of interest concerns the capacity of training to increase or decrease fiber types to enhance high-performance activities. Although interconversions between type IIA and IIX are well recognized in the literature, there are conflicting studies regarding the capacity of type I and II fibers to interconvert. Therefore, the purpose of this article is to analyze the effects of various forms of exercise on type I and type II interconversions. Possible variables that may increase type II fibers and decrease type I fibers are discussed, and these include high velocity isokinetic contractions; ballistic movements such as bench press throws and sprints. Conversely, a shift from type II to type I fibers may occur under longer duration, higher volume endurance type events. Special care is taken to provide practical applications for both the scientist and the athlete.
The primary aim of this study was to compare 2 daily undulating periodization (DUP) models on one-repetition maximum (1RM) strength in the squat, bench press, deadlift, total volume (TV) lifted, and ...temporal hormone response. Eighteen male, college-aged (21.1 ± 1.9 years) powerlifters participated in this study and were assigned to one of 2 groups: (a) traditional DUP training with a weekly training order: hypertrophy-specific, strength-specific, and power-specific training (HSP, n = 9) or (b) modified DUP training with a weekly training order: hypertrophy-specific, power-specific, and strength-specific training (HPS, n = 9). Both groups trained 3 nonconsecutive days per week for 6 weeks and performed the squat, bench press, and deadlift exercises. During hypertrophy and power sessions, subjects performed a fixed number of sets and repetitions but performed repetitions until failure at a given percentage during strength sessions to compare TV. Testosterone and cortisol were measured at pretesting and posttesting and before each strength-specific day. Hypertrophy, power, and strength produced greater TV in squat and bench press (p ≤ 0.05) than HSP, but not for deadlift (p > 0.05). For squat and deadlift, there was no difference between groups for 1RM (p > 0.05); however, HPS exhibited greater increases in 1RM bench press than HSP (p ≤ 0.05). Effect sizes (ES) showed meaningful differences (ES > 0.50) in favor of HPS for squat and bench press 1RM. Testosterone decreased (p ≤ 0.05) at weeks 5 and 6 and cortisol decline at weeks 3 and 4. However, neither hormone was different at posttesting compared with pretesting (p > 0.05). Our findings suggest that an HPS configuration of DUP has enhanced performance benefits compared with HSP.
Substantial evidence suggests crosstalk between reproductive and gut-axis but mechanisms linking metabolism and reproduction are still unclear. The present study evaluated the possible role of ...glucose-dependent-insulinotropic-polypeptide (GIP) and glucagon-like-peptide-1 (GLP-1) in reproductive function by examining receptor distribution and the effects of global GIPR and GLP-1R deletion on estrous cycling and reproductive outcomes in mice. GIPR and GLP-1R gene expression were readily detected by PCR in female reproductive tissues including pituitary, ovaries and uterine horn. Protein expression was confirmed with histological visualisation of incretin receptors using GIPR-Cre and GLP1R-Cre mice in which the incretin receptor expressing cells were fluorescently tagged. Functional studies revealed that female GIPR
and GLP-1R
null mice exhibited significantly (
< 0.05 and
< 0.01) deranged estrous cycling compared to wild-type controls, indicative of reduced fertility. Furthermore, only 50% and 16% of female GIPR
and GLP-1R
mice, respectively produced litters with wild-type males across three breeding cycles. Consistent with a physiological role of incretin receptors in pregnancy outcome, litter size was significantly (
< 0.001-
< 0.05) decreased in GIPR
and GLP-1R
mice. Treatment with oral metformin (300 mg/kg body-weight), an agent used clinically for treatment of PCOS, for a further two breeding periods showed no amelioration of pregnancy outcome except that litter size in the GIPR
group was approximately 2 times greater in the second breeding cycle. These data highlight the significance of incretin receptors in modulation of female reproductive function which may provide future targets for pharmacological intervention in reproductive disorders.
To date, research has examined the physiological determinants of performance in standardized CrossFit® (CF) workouts but not without the influence of CF familiarity. Therefore, the purpose of this ...present study was to examine the predictive value of aerobic fitness, body composition, and total body strength on performance of two standardized CF workouts in CF-naïve participants. Twenty-two recreationally trained individuals (males = 13, females = 9) underwent assessments of peak oxygen consumption (VO2 peak), ventilatory thresholds, body composition, and one repetition maximum tests for the back squat, deadlift, and overhead press in which the sum equaled the CF Total. Participants also performed two CF workouts: a scaled version of the CF Open workout 19.1 and a modified version of the CF Benchmark workout Fran to determine scores based on total repetitions completed and time-to-completion, respectively. Simple Pearson’s r correlations were used to determine the relationships between CF performance variables (19.1 and modified Fran) and the independent variables. A forward stepwise multiple linear regression analysis was performed and significant variables that survived the regression analysis were used to create a predictive model of CF performance. Absolute VO2 peak was a significant predictor of 19.1 performance, explaining 39% of its variance (adjusted R2 = 0.39, p = 0.002). For modified Fran, CF Total was a significant predictor and explained 33% of the variance in performance (adjusted R2 = 0.33, p = 0.005). These results suggest, without any influence of CF familiarity or experience, that performance in these two CF workouts could be predicted by distinct laboratory-based measurements of fitness.
Background and aims
Increased adipose tissue may promote catabolic events in skeletal muscle. The aim of this study was to test whether high-fat diet (HFD)-induced obesity would accelerate the onset ...of muscle wasting in middle-aged mice.
Methods
Muscle was collected from C57BL/6 mice at 9 months of age (baseline) and 14 months of age after consuming a control (C) or HFD. Mice in C and HFD were also subjected to evaluations of body composition and function before and after their respective diets.
Results
HFD demonstrated significant (
p
< 0.05) losses of grip strength (−15 %) and sensorimotor coordination (−11 %), whereas C did not. Lean mass decreased to a greater degree in HFD although not significantly (C: −20.69 ± 7.94 vs. HFD: −31.14 ± 5.49 %,
p
> 0.05). Gastrocnemius, quadriceps, and hamstrings mass in C and HFD were significantly reduced from baseline (−27 to 43 and −39 to 47 %, respectively,
p
< 0.05) with no differences between the two; however, soleus mass was lower only in HFD (−24 %,
p
= 0.03). Myofiber area, satellite cells, and myonuclei of the gastrocnemius were lower only in HFD (−23, −19, and −16 %, respectively,
p
< 0.05) compared to baseline.
Conclusions
HFD-induced obesity adversely affected function in middle-aged mice. Atrophy of the soleus in HFD but not C suggests sensitivity of oxidative muscle to HFD-dependent catabolism more so than aging. In the muscles containing fast/mixed fibers, aging effects may have concealed the catabolic nature of HFD; however, morphological changes in the gastrocnemius including decreased fiber area, satellite cells, and myonuclei are consistent with an atrophic phenotype related to HFD.
Introduction: The purpose of this study was to investigate the efficacy of daily one-repetition maximum (1RM) training of the back squat on maximal strength. Material and methods: Three competitive ...lifters performed the squat for 37 consecutive days and are reported as individual cases. Participant 1 (P1) (body mass = 80.5 kg; age = 28 yrs.) and participant 3 (P3) (body mass = 108.8 kg; age = 34 yrs.) were powerlifters; participant 2 (P2) (body mass = 64.1 kg; age = 19 yrs.) was a weightlifter. Each participant had at least 5 years of training experience with the squat. During days 1-35, participants performed a 1RM squat followed by 5 volume sets of 3 repetitions at 85% or 2 repetitions at 90% of the daily 1RM. On day-36, participants performed only 1 set of 1 repetition at 85% of day-1 1RM; and a final 1RM was performed on day-37. Results: Absolute and percent changes for P1 from day-1 to day-37 were +5 kg/2.3%, and from day-1 to peak (greatest 1RM of the period) were +12.5 kg/5.8%. P2 experienced a 13.5 kg/10.8% increase in 1RM from both day-1 to day-37 and day-1 to peak. P3 demonstrated a 21.0 kg/9.5% increase from both day-1 to day-37 and day-1 to peak. All 3 participants exhibited significant (p < 0.05) correlations between time (days) and 1RM (P1: r = 0.65, P2: r = 0.78, P3: r = 0.48). Conclusions: Our findings suggest that daily 1RM training effectively produced robust changes in maximal strength in competitive strength athletes in a relatively short training period.
Fish oil (FO) has received great attention for its health-enhancing properties. However, its potential synergistic effects with resistance training (RT) are not well established. The purpose of this ...study was to investigate the effects of FO supplementation during 12-weeks of RT on handgrip strength, physical function, and blood pressure (BP) in community-dwelling older adults. Twenty-eight healthy older adults (10 males, 18 females; 66.5 ± 5.0 years) were randomly assigned to three groups: Control (CON), resistance training (RT), resistance training with FO (RTFO). Handgrip strength, physical function five times sit-to-stand (5T-STS), timed up and go (TUG), 6-m walk (6MW), 30-s sit-to-stand (30S-STS), and BP were measured pre- and post-intervention. ANOVA was used with significance set at P ≤ 0.05. Handgrip strength significantly increased in RT (+5.3%) and RTFO (+9.4%) but decreased in CON (-3.9%). All physical function outcomes increased in RT and RTFO. CON exhibited significantly decreased TUG and 30S-STS with no change in 5T-STS and 6MW. BP substantially decreased only in RTFO, systolic blood pressure (-7.8 mmHg), diastolic blood pressure (-4.5 mmHg), mean arterial pressure (-5.6 mmHg), while no change was found in CON and RT. Chronic RT enhanced strength and physical function, while FO consumption combined with RT improved BP in community-dwelling older adults.
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