Triction (BFR). Methods Six young healthy males performed three sets of knee extensions on a dynamometer (50% one-repetition maximum) separated by 90-s rest periods in three conditions: 1) until fatigue without BFR (fatigue), 2) until fatigue with BFR (100 mm Hg cuff constriction around thigh (BFR)), 3) same number of repetitions from condition 2 without BFR (matched). Each condition was performed on a separate visit. Results BFR was associated with higher [HbR] at the oblique fibers of the vastus medialis muscle (rest 1: 57.8 (BFR) vs 35.0 μM (matched); P < 0.0001) and a significantly lower stO2 during recovery periods between sets (7.5%–11.2 % lower than non-BFR conditions for rest 1 and 2, P < 0.0001). Using a piecewise linear spline method, a spike in [HbR] was observed before the onset of HbR clearance during recovery, causing HbR clearance to begin at a higher concentration (81 (BFR) vs 62 μM (matched), P = 0.029). [HbO2] kinetics during recovery were also affected by BFR, with longer duration (BFR, 51 s; matched, 31 s; P = 0.047) but lower rate of increase (BFR, 58 μM·min−1; matched, 89 μM·min−1; P = 0.004) during recovery. In the prefrontal cortex, BFR was associated with increased [HbR], diminished increase in [HbO2], and higher subjective exertion. Conclusions These findings yield insight into possible physiological mechanisms of BFR and suggest a role of time-resolved near-infrared spectroscopy in monitoring and optimization of BFR exercise on an individual basis....

The purpose of this study was to examine the affective responses to acute resistance exercise (RE) performed at self-selected (SS) and imposed loads in recreationally trained women. Secondary purposes were to (a) examine differences in correlates of motivation for future participation in RE and (b) determine whether affective responses to RE were related to these select motivational correlates of RE participation. Twenty recreationally trained young women (mean age = 23 years) completed 3 RE sessions involving 3 sets of 10 repetitions using loads of 40% of 1 repetition maximum (1RM), 70% 1RM, and an SS load. Affective responses were assessed before, during, and after each RE session using the Feeling Scale. Self-efficacy and intention for using the imposed and SS loads for their regular RE participation during the next month were also assessed postexercise. Results revealed that although the SS and imposed load RE sessions yielded different trajectories of change in affect during exercise (p < 0.01), comparable improvements in affect emerged after RE. Additionally, the SS condition was associated with the highest ratings of self-efficacy and intention for future RE participation (p < 0.01), but affective responses to acute RE were unrelated to self-efficacy or intention. It is concluded that acute bouts of SS and imposed load RE resulted in comparable improvements in affect; recreationally trained women reported the highest self-efficacy and intention to use the load chosen in SS condition in their own resistance training; and affective responses were unrelated to motivational correlates of resistance training.

F knee flexion. Our aim was to compare the net peak external knee flexion moments (pEKFM) experienced over typical ranges of squat loads and depths. Sixteen recreationally trained men (n = 16; age, 22.7 ± 1.1 years; body mass, 85.4 ± 2.1 kg; height, 177.6 ± 0.96 cm; mean ± SEM) with no previous lower-limb surgeries or other orthopedic issues and at least 1 year of consistent resistance training experience while using the squat exercise performed single-repetition squat trials in a random order at squat depths of above parallel, parallel, and below parallel. Less than 1 week before testing, 1RM values were found for each squat depth. Subsequent testing required the subjects to perform squats at the 3 depths with 3 different loads: unloaded, 50% 1RM, and 85% 1RM (9 total trials). Force platform and kinematic data were collected to calculate pEKFM. To assess the differences among loads and depths, a 2-factor (load and depth) repeated measures analysis of variance with significance set at the p < 0.05 level was used. Squat 1RM significantly decreased 13.6% from the above-parallel to the parallel squat and another 3.6% from the parallel to the below-parallel squat (p < 0.05). Net peak external knee flexion moments significantly increased as both squat depth and load were increased (p ≤ 0.02). Slopes of pEKFM were greater from unloaded to 50% 1RM than when progressing from 50% to 85% 1RM (p < 0.001). The results suggest that typical decreases in squat loads used with increasing depths are not enough to offset increases in pEKFM....

Ubjects (10 males and 9 females; 21.0 ± 2.5 yr, 65.4 ± 12.2 kg) were separated into two groups: 1) 10-d ULLS only (n = 9) and 2) 10-d ULLS plus aerobic and resistance training (ULLS + EX, n = 10). Exercise was performed on a single gravity-independent Multi-Mode Exercise Device (M-MED) with alternating days of high-intensity interval aerobic training and maximal exertion resistance training. Results Aerobic capacity increased by 7% in ULLS + EX (P < 0.05). Knee extensor and ankle plantar flexor three-repetition maximum increased in the ULLS + EX group (P < 0.05), but this change was only different from ULLS in the plantar flexors (P < 0.05). Peak torque levels decreased with ULLS but were increased for the knee extensors and attenuated for the ankle plantar flexors with ULLS + EX (P < 0.05). A shift toward type IIx myosin heavy-chain mRNA occurred with ULLS and was reversed with ULLS + EX in the vastus lateralis (P < 0.05) but not the soleus. Myostatin and atrogin increased with ULLS in both the vastus lateralis and soleus, but this change was mitigated with ULLS + EX only in the vastus lateralis (P = 0.0551 for myostatin, P < 0.05 for atrogin). Citrate synthase was decreased in the soleus during ULLS but was increased with ULLS + EX (P < 0.05). Conclusion These results indicate that an M-MED class countermeasure device appears to be effective at mitigating the deconditioning effects of microgravity simulated during a modified ULLS protocol....

Flores, V, Becker, J, Burkhardt, E, and Cotter, J. Knee kinetics during squats of varying loads and depths in recreationally trained women. J Strength Cond Res 34(7): 1945–1952, 2020—The back squat exercise is typically practiced with varying squat depths and barbell loads. However, depth has been inconsistently defined, resulting in unclear safety precautions when squatting with loads. In addition, women exhibit anatomical and kinematic differences to men, which may predispose them to knee joint injuries. The purpose of this study was to characterize peak knee extensor moments (pKEMs) at 3 commonly practiced squat depths of above-parallel, parallel, and full depths, and with 3 loads of 0 (unloaded), 50, and 85% depth-specific 1 repetition maximum (1RM) in recreationally active women. Nineteen women (age, 25.1 ± 5.8 years; body mass, 62.5 ± 10.2 kg; height, 1.6 ± 0.10 m; mean ± SD) performed squats of randomized depth and load. Inverse dynamics were used to obtain pKEMs from 3-dimensional knee kinematics. Depth and load had significant interaction effects on pKEMs (p = 0.014). Significantly greater pKEMs were observed at full depth compared with parallel depth with 50% 1RM load (p = 0.001, d = 0.615) and 85% 1RM load (p = 0.010, d = 0.714). Greater pKEMs were also observed at full depth compared with above-parallel depth with 50% 1RM load (p = 0.003, d = 0.504). Results indicate that effect of load on female pKEMs do not follow a progressively increasing pattern with either increasing depth or load. Therefore, when high knee loading is a concern, individuals must carefully consider both the depth of squat being performed and the relative load they are using.

Cotter, JA, Garver, MJ, Dinyer, TK, Fairman, CM, and Focht, BC. Ratings of perceived exertion during acute resistance exercise performed at imposed and self-selected loads in recreationally trained women. J Strength Cond Res 31(8): 2313–2318, 2017—Resistance exercise (RE) is commonly used to elicit skeletal muscle adaptation. Relative intensity of a training load links closely with the outcomes of regular RE. This study examined the rating of perceived exertion (RPE) responses to acute bouts of RE using imposed (40% and 70% of 1 repetition maximum [1RM]) and self-selected (SS) loads in recreationally trained women. Twenty physically active women (23.15 ± 2.92 years), who reported regular RE training of at least 3 weekly sessions for the past year, volunteered to participate. During the initial visit, participants completed 1RM testing on 4 exercises in the following order: leg extension, chest press, leg curl, and lat pull-down. On subsequent visits, the same exercises were completed at the SS or imposed loads. The RPE was assessed after the completion of each set of exercises during the 3 RE conditions using the Borg-15 category scale. Self-selected loads corresponded to an average of approximately 57%1RM (±7.62). Overall, RPE increased with load (40%1RM = 11.26 [±1.95]; SS 57%1RM = 13.94 [±1.58]; and, 70%1RM = 15.52 [±2.05]). Reflecting the linear pattern found between load and perceived effort, the present data provide evidence that RPE levels less than 15 likely equate to loads which are not consistent with contemporary American College of Sports Medicine (ACSM) guidelines for enhancing musculoskeletal health which includes strength and hypertrophy. Women desiring increases in strength and lean mass likely need to train at an exertion level at or surpassing a rating of 15 on the Borg-15 category. This article examined the modification of training load on perceived exertion, but other variables, such as the number of repetitions completed, may also be targeted to achieve a desired RPE. The primary understanding is that women who engage in RE may not self-select loads that are consistent with the ACSM recommendations for musculoskeletal health.