Muscle activation was greater at 80 % 1RM. However, differences in volume, metabolic byproduct accumulation, and muscle swelling may help explain the unexpected adaptations in hypertrophy vs. strength observed in previous studies.

Jenkins, NDM, Housh, TJ, Buckner, SL, Bergstrom, HC, Cochrane, KC, Hill, EC, Smith, CM, Schmidt, RJ, Johnson, GO, and Cramer, JT. Neuromuscular adaptations after 2 and 4 weeks of 80% versus 30% 1 repetition maximum resistance training to failure. J Strength Cond Res 30(8): 2174-2185, 2016-The purpose of this study was to investigate the hypertrophic, strength, and neuromuscular adaptations to 2 and 4 weeks of resistance training at 80 vs. 30% 1 repetition maximum (1RM) in untrained men. Fifteen untrained men (mean ± SD; age = 21.7 ± 2.4 years; weight = 84.7 ± 23.5 kg) were randomly assigned to either a high-load (n = 7) or low-load (n = 8) resistance training group and completed forearm flexion resistance training to failure 3 times per week for 4 weeks. Forearm flexor muscle thickness (MT) and echo intensity, maximal voluntary isometric (MVIC) and 1RM strength, and the electromyographic, mechanomyographic (MMG), and percent voluntary activation (%VA) responses at 10-100% of MVIC were determined at baseline, 2, and 4 weeks of training. The MT increased from baseline (2.9 ± 0.1 cm) to week 2 (3.0 ± 0.1 cm) and to week 4 (3.1 ± 0.1 cm) for the 80 and 30% 1RM groups. MVIC increased from week 2 (121.5 ± 19.1 Nm) to week 4 (138.6 ± 22.1 Nm) and 1RM increased from baseline (16.7 ± 1.6 kg) to weeks 2 and 4 (19.2 ± 1.9 and 20.5 ± 1.8 kg) in the 80% 1RM group only. The MMG amplitude at 80 and 90% MVIC decreased from baseline to week 4, and %VA increased at 20 and 30% MVIC for both groups. Resistance training to failure at 80 vs. 30% 1RM elicited similar muscle hypertrophy, but only 80% 1RM increased muscle strength. However, these disparate strength adaptations were difficult to explain with neuromuscular adaptations because they were subtle and similar for the 80 and 30% 1RM groups.

Estimates of critical power (CP) and anaerobic work capacity (AWC) from the power output vs. time relationship have been derived from various mathematical models. The purpose of this study was to examine estimates of CP and AWC from the multiple work bout, 2- and 3-parameter models, and those from the 3-minute all-out CP (CP3min) test. Nine college-aged subjects performed a maximal incremental test to determine the peak oxygen consumption rate and the gas exchange threshold. On separate days, each subject completed 4 randomly ordered constant power output rides to exhaustion to estimate CP and AWC from 5 regression models (2 linear, 2 nonlinear, and 1 exponential). During the final visit, CP and AWC were estimated from the CP3min test. The nonlinear 3-parameter (Nonlinear-3) model produced the lowest estimate of CP. The exponential (EXP) model and the CP3min test were not statistically different and produced the highest estimates of CP. Critical power estimated from the Nonlinear-3 model was 14% less than those from the EXP model and the CP3min test and 4-6% less than those from the linear models. Furthermore, the Nonlinear-3 and nonlinear 2-parameter (Nonlinear-2) models produced significantly greater estimates of AWC than did the linear models and CP3min. The current findings suggested that the Nonlinear-3 model may provide estimates of CP and AWC that more accurately reflect the asymptote of the power output vs. time relationship, the demarcation of the heavy and severe exercise intensity domains, and anaerobic capabilities than will the linear models and CP3min test.

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These findings suggest CP and RCP demarcate the heavy from severe exercise-intensity domain and result from a different mechanism of fatigue than that of GET and VT, possibly hyperkalemia.

Dinyer, TK, Byrd, MT, Garver, MJ, Rickard, AJ, Miller, WM, Burns, S, Clasey, JL, and Bergstrom, HC. Low-load vs. high-load resistance training to failure on one repetition maximum strength and body composition in untrained women. J Strength Cond Res 33(7): 1737–1744, 2019—This study examined the effects of resistance training (RT) to failure at low and high loads on one repetition maximum (1RM) strength and body composition (bone- and fat-free mass [BFFM] and percent body fat [%BF]) in untrained women. Twenty-three untrained women (age: 21.2 ± 2.2 years; height: 167.1 ± 5.7 cm; body mass: 62.3 ± 16.2 kg) completed a 12-week RT to failure intervention at a low (30% 1RM) (n = 11) or high (80% 1RM) (n = 12) load. On weeks 1, 5, and 12, subjects completed 1RM testing for 4 different exercises (leg extension [LE], seated military press [SMP], leg curl [LC], and lat pull down [LPD]) and a dual-energy x-ray absorptiometry scan to assess body composition. During weeks 2–4 and 6–7, the subjects completed 2 sets to failure for each exercise. During weeks 8–11, the subjects completed 3 sets to failure for each exercise. The 1RM strength increased from week 1 to week 5 (LE: 18 ± 16%; SMP: 9 ± 11%; LC: 12 ± 22%; LPD: 13 ± 9%), week 1 to week 12 (LE: 32 ± 24%; SMP: 17 ± 14%; LC: 23 ± 26%; LPD: 25 ± 13%), and week 5 to week 12 (LE: 11 ± 9%; SMP: 7 ± 9%; LC: 10 ± 7%; LPD: 11 ± 11%) in each exercise, with no significant differences between groups. There were no significant changes in BFFM (p = 0.241) or %BF (p = 0.740) for either group. Resistance training to failure at 30% 1RM and 80% 1RM resulted in similar increases in 1RM strength, but no change in BFFM or %BF. Untrained women can increase 1RM strength during RT at low and high loads, if repetitions are taken to failure.

The close association between f b and RPE throughout the run at CHR - 5 and during the last 50 % of the run at CHR + 5 indicated that muscle afferents may have provided feedback from metabolic and mechanical stimuli that contributed to the perceptual responses. In addition, only RPE consistently indicated exhaustion and the current findings supported its use to monitor exercise performed at a constant HR.