Recent evidence suggests that resistance training with light or heavy loads to failure results in similar adaptations. Herein, we compared how both training modalities affect the molecular, neuromuscular, and recovery responses following exercise. Resistance‐trained males (mean ± SE: 22 ± 2 years, 84.8 ± 9.0 kg, 1.79 ± 0.06 m; n = 15) performed a crossover design of four sets of leg extensor exercise at 30% (light RE) or 80% (heavy RE) one repetition maximum (1RM) to repetition failure, and heavy RE or light RE 1 week later. Surface electromyography (EMG) was monitored during exercise, and vastus lateralis muscle biopsies were collected at baseline (PRE), 15 min (15mPOST), and 90 min following RE (90mPOST) for examination of molecular targets and fiber typing. Isokinetic dynamometry was also performed before (PRE), immediately after (POST), and 48 h after (48hPOST) exercise. Dependent variables were analyzed using repeated measures ANOVAs and significance was set at P ≤ 0.05. Repetitions completed were greater during light RE (P < 0.01), while EMG amplitude was greater during heavy RE (P ≤ 0.01). POST isokinetic torque was reduced following light versus heavy RE (P < 0.05). Postexercise expression of mRNAs and phosphoproteins associated with muscle hypertrophy were similar between load conditions. Additionally, p70s6k (Thr389) phosphorylation and fast‐twitch fiber proportion exhibited a strong relationship after both light and heavy RE (r > 0.5). While similar mRNA and phosphoprotein responses to both modalities occurred, we posit that heavy RE is a more time‐efficient training method given the differences in total repetitions completed, lower EMG amplitude during light RE, and impaired recovery response after light RE.

Previous investigations have reported a relationship between skeletal muscle phenotype and motor unit (MU) firing parameters during submaximal contractions. The purpose of the current investigation, however, was to examine the relationships between motor unit firing behavior during a maximal voluntary contraction, Myosin Heavy Chain (MHC) isoform content, and various molecular neuromuscular targets of the vastus lateralis (VL) muscle in resistance‐trained men. Ten resistance‐trained males completed a trapezoidal ramp contraction up to 100% of their maximal voluntary isometric strength (MVIC). Surface electromyography was recorded from the VL using a multichannel electrode array and decomposed to examine the firing characteristics of individual MUs. A skeletal muscle biopsy of the VL was also collected from each subject. Regression analyses were performed to identify relationships between type II fiber area and the slopes and/or intercepts of the mean firing rate (FRMEAN) versus recruitment threshold (RT), max firing rate (FRMAX) versus RT, and RT versus MU action potential amplitude (MUAPPP) relationships. There were significant inverse relationships between type II fiber area and the y‐intercept of the FR versus RT relationship (P < 0.05). Additionally, strong relationships (r > 0.5) were found between type II fiber area and FRMEAN versus RT slope and RT versus MUAPPP slope and intercept. These data further support the hypothesis that skeletal muscle phenotype is related to MU behavior during isometric contraction. However, our data, in concert with previous investigations, may suggest that these relationships are influenced by the intensity of the contraction.

Background: We sought to determine if a pre-workout supplement (PWS), containing multiple ingredients thought to enhance blood flow, increases hyperemia associated with resistance training compared to placebo (PBO). Given the potential interaction with training loads/time-under-tension, we evaluated the hyperemic response at two different loads to failure. Methods: Thirty males participated in this double-blinded study. At visit 1, participants were randomly assigned to consume PWS (Reckless™) or PBO (maltodextrin and glycine) and performed four sets of leg extensions to failure at 30% or 80% of their 1-RM 45-min thereafter. 1-wk. later (visit 2), participants consumed the same supplement as before, but exercised at the alternate load. Heart rate (HR), blood pressure (BP), femoral artery blood flow, and plasma nitrate/nitrite (NOx) were assessed at baseline (BL), 45-min post-PWS/PBO consumption (PRE), and 5-min following the last set of leg extensions (POST). Vastus lateralis near infrared spectroscopy (NIRS) was employed during leg extension exercise. Repeated measures ANOVAs were performed with time, supplement, and load as independent variables and Bonferroni correction applied for multiple post-hoc comparisons. Data are reported as mean ± SD. Results: With the 30% training load compared to 80%, significantly more repetitions were performed (p < 0.05), but there was no difference in total volume load (p > 0.05). NIRS derived minimum oxygenated hemoglobin (O 2 Hb) was lower in the 80% load condition compared to 30% for all rest intervals between sets of exercise (p < 0.0167). HR and BP did not vary as a function of supplement or load. Femoral artery blood flow at POST was higher independent of exercise load and treatment. However, a time*supplement*load interaction was observed revealing greater femoral artery blood flow with PWS compared to PBO at POST in the 80% (+56.8%; p = 0.006) but not 30% load condition (+12.7%; p = 0.476). Plasma NOx was~3-fold higher with PWS compared to PBO at PRE and POST (p < 0.001).

Background The U.S. Air Force physical fitness assessment (PFA) is used to determine the overall fitness of their personnel. It is currently unknown to what extent the PFA scores of Reserve Officers’ Training Corps (ROTC) cadets are affected by mandatory physical training. The purpose of this investigation was to longitudinally examine the PFAs of ROTC cadets over a four-year period, evaluate the results across class ranks, and evaluate the sensitivity of the classification of the tests. Methods Air Force ROTC cadets performed the PFAs (abdominal circumference, 1-min pushups, 1-min sit-ups, and a 1.5-mile run) in both the spring (n = 26) and fall (n = 22) semesters. PFAs were compiled over a four-year period (Spring 2014 – Fall 2017) and were performed in accordance with Air Force Instruction 36–2905. A one-way repeated measures ANOVA was performed separately for the fall and spring groups for each dependent variable across the 4 years. Additionally, a one-way between groups ANOVA was performed for each dependent variable during the time point (fall 2015; N = 46) with the most recorded cadets for each class rank. Results Longitudinal assessments revealed a main effect of time (P = 0.010) on abdominal circumference; cadets had a smaller abdominal circumference in their freshman year than in their senior year. A main effect of time (P = 0.006) was also observed on sit-up quantity; cadets performed more sit-ups in their junior year than in their freshman year. Examining between class ranks during the same year (between-subjects ANOVA) revealed a main effect of class rank on sit-up quantity (P = 0.003); the freshmen completed fewer repetitions than the sophomores (P = 0.018) and the juniors did (P = 0.001). Conclusion The results indicated that only the sit-up component showed differences between class ranks. These findings suggest that the Air Force PFA may not be sensitive enough to detect changes in physical fitness or distinguish between class ranks regarding physical performance, even after years of training. This limitation may be in part due to the limited duration of training incorporated by the ROTC program (2 h per week), which provided a maintenance effect rather than improvement in physical performance. We recommend that more attention be directed to the efficacy of physical training, the sensitivity of measures included in the PFA, or both.

The results of the present study indicated that only knee extension RTD was able to discriminate between the two groups. These findings suggest that rapid force production may be more sensitive at distinguishing training-specific muscular adaptations than peak acceleration or velocity.