Shibata, K, Yamaguchi, T, Takizawa, K, and Nosaka, K. Comparison in repetitions to failure between concentric-only and eccentric-only dumbbell arm curl exercise at four different relative intensities. J Strength Cond Res 37(9): 1754–1760, 2023—The repetitions to failure (RF) were compared between concentric-only (CON) and eccentric-only (ECC) arm curl exercise for different intensities based on CON and ECC 1 repetition maximum (1RM), respectively, with 2 different inter-repetition rests. Sixteen healthy male, university students (19–22 years) participated in 6 sessions. In sessions 1 and 2, CON and ECC 1RM strength were determined. In sessions 3 to 6, CON and ECC dumbbell arm curl exercises were performed until momentary failure at the intensity of either 70, 80, 90 or 95% of CON and ECC 1RM, respectively, with the inter-repetition rest of 3 seconds (R3) for one arm and 6 seconds (R6) for the other arm in a pseudo-randomized order. A significant (p < 0.01) muscle contraction type × intensity interaction effect was evident for both R3 and R6 conditions. RF was greater (p < 0.01) in ECC than in CON at 70% (34.2 ± 13.3 vs 20.9 ± 5.4), 80% (22.0 ± 6.7 vs 11.6 ± 2.7), 90% (10.1 ± 3.1 vs 5.2 ± 1.3), and 95% (6.8 ± 2.1 vs 2.7 ± 0.8) for R3. RF was also greater (p < 0.01) for ECC than for CON at 80% (24.5 ± 8.1 vs 15.6 ± 3.6), 90% (10.8 ± 2.8 vs 7.2 ± 1.8) and 95% (6.7 ± 2.4 vs 3.9 ± 1.5) for R6, with greater (p < 0.05) RF for R6 than R3. Significant (p < 0.01) correlations in RF were evident between CON and ECC for R3 (r = 0.86) and R6 (r = 0.76). Equations to estimate 1RM were derived for CON and ECC at R3 and R6 (e.g., ECC 1RM = Load × 110.0/[110.5-RF] for R3). These results suggest that fatigue is less in ECC than in CON performed at the same relative intensity.

Shibata, K, Takizawa, K, Tomabechi, N, Nosaka, K, and Mizuno, M. Comparison between two volume-matched squat exercises with and without momentary failure for changes in hormones, maximal voluntary isometric contraction strength and perceived muscle soreness. J Strength Cond Res 35(11): 3063–3068, 2021—The present study compared 2 squat exercises with and without momentary failure (MF) for changes in blood hormones, maximal voluntary isometric contraction (MVC) strength, and perceived muscle soreness (SOR). Ten physically active male students performed squat exercises at 75% of their 1 repetition maximum in 2 conditions. First, they performed each set to MF for 3 sets, and 2 weeks later, performed the same number of repetitions in 6 sets without MF (NMF). The rate of perceived exertion was assessed at 30 minutes after exercise. Blood lactate, serum concentrations of growth hormone (GH), testosterone, insulin-like growth factor 1 (IGF-1) and cortisol, MVC strength, and SOR were measured before and after each exercise. Rate of perceived exertion was higher (p < 0.01) in MF (8.3 ± 1.2) than in NMF (4.1 ± 1.4). Blood lactate was greater (p < 0.01) at 5 minutes after MF (7.2 ± 0.7 mM·L⁻¹) than NMF (3.6 ± 0.7 mM·L⁻¹). At 30 minutes after exercise, GH (MF: 12.3 ± 8.3 ng·ml⁻¹, NMF: 4.4 ± 5.2 ng·ml⁻¹) and cortisol (MF: 19.0 ± 4.3 μg·dl⁻¹, NMF: 14.2 ± 4.6 μg·dl⁻¹) were greater (p < 0.01) for MF than NMF, but no significant differences were observed between conditions for testosterone and IGF-1. Maximal voluntary isometric contraction strength decrease (6.1 ± 8.8%) at 24 hours after exercise was evident only for MF, but SOR at 24 hours after exercise was similar between MF (4.8 ± 3.3 cm) and NMF (2.5 ± 2.4 cm) conditions. These results suggest that mechanical and metabolic stimulus to the muscles were greater for MF than NMF condition.

The aim of this study is to clarify the effects of 3-week work-matched high-intensity intermittent cycling training (HIICT) with different cadences on the VO_2max of university athletes. Eighteen university athletes performed HIICT with either 60 rpm (n = 9) or 120 rpm (n = 9). The HIICT consisted of eight sets of 20 s exercise with a 10 s passive rest between each set. The initial training intensity was set at 135% of VO_2max and was decreased by 5% every two sets. Athletes in both groups performed nine sessions of HIICT during a 3-week period. The total workload and achievement rate of the workload calculated before experiments in each group were used for analysis. VO_2max was measured pre- and post-training. After 3 weeks of training, no significant differences in the total workload and the achievement rate of the workload were found between the two groups. VO_2max similarly increased in both groups from pre- to post-training (p = 0.016), with no significant differences between the groups (p = 0.680). These results suggest that cadence during HIICT is not a training variable affecting the effect of VO_2max.

Shibata, K, Yamaguchi, T, Takizawa, K, and Nosaka, K. Comparison between eccentric-concentric and eccentric-only dumbbell arm curl exercise training for their effects on neuromuscular adaptations. J Strength Cond Res XX(X): 000–000, 2026—Eccentric-concentric (ECC-CON), low-load (ECC-Low), and high-load eccentric-only (ECC-High) dumbbell arm-curl exercise training were compared to test the hypothesis that ECC-Low would induce similar neuromuscular adaptations to ECC-CON and ECC-High. Thirty-four male university students without regular elbow flexor resistance exercise training were placed to ECC-CON ( n = 11), ECC-Low ( n = 11), or ECC-High ( n = 12) group, and trained twice weekly for 6 weeks. The training load was progressively increased from 30 to 90% of concentric-only one-repetition maximum (CON1-RM) for ECC-CON and ECC-Low, and of eccentric-only 1-RM (ECC1-RM) for ECC-High. Rating of perceived exertion (RPE) was recorded after each set and averaged RPE was obtained. Changes in elbow flexion CON1-RM and ECC1-RM, maximal voluntary isometric contraction (MVIC) strength at 30°, 60°, and 90° elbow flexion, concentric peak power at 30% MVIC, and biceps brachii and brachialis muscle thickness (MT) were compared between groups by split-plot analyses of variance. RPE was lower ( p < 0.05) in ECC-Low (4.0 ± 0.7) and ECC-High (5.1 ± 1.1) than ECC-CON (6.2 ± 1.1). ECC1-RM, MVIC strength at all angles, and concentric peak power increased ( p < 0.01) similarly between groups (e.g., ECC1-RM, ECC-CON: 9.8 ± 4.8%, ECC-Low: 10.3 ± 4.9%, ECC-High: 12.8 ± 7.1%), but increases ( p < 0.01) in CON1-RM (ECC-CON: 11.8 ± 7.1%, ECC-High: 9.9 ± 5.3%) and MT (3.9 ± 3.1%, 5.4 ± 4.4%) were evident only after ECC-CON and ECC-High without a difference. These results did not fully support the hypothesis, but ECC-Low was effective for improving 6 of 8 measures similarly to ECC-High and ECC-CON with lower RPE. This suggests the efficacy of eccentric-only resistance exercise training for individuals who are novice in elbow flexor resistance exercise training.

Shibata, K, Yamaguchi, T, Takizawa, K, and Nosaka, K. Comparison between eccentric-concentric and eccentric-only (ECC-only) dumbbell arm curl exercise for the number of repetitions to failure over five sets. J Strength Cond Res XX(X): 000–000, 2026—We compared eccentric-concentric (ECC-CON) and ECC-only dumbbell arm curl exercises for the number of repetitions to failure (RF) over 5 sets with 1- and 3-minute rest between sets. Twelve healthy male university students participated in 3 sessions. In session 1, one-repetition maximum (1-RM) of ECC-CON for one arm and ECC-only for the other arm was assessed. In sessions 2 and 3, the number of RF over 5 sets of ECC-CON and ECC-only at 80% of respective 1-RM load until failure in each set was investigated. The rest interval between sets was 1-minute or 3-minute in a pseudo-randomized order in the 2 sessions. The number of RF in ECC-only (17.5 ± 7.1 for 1-minute, 18.4 ± 7.9 for 3-minute rest) was greater ( p < 0.01) than that in ECC-CON (9.8 ± 2.0, 10.3 ± 2.2) in the first set. The number of RF decreased greater ( p < 0.01) for ECC-only (−13.1 ± 6.4, −13.9 ± 6.4) than ECC-CON (−6.2 ± 2.1, −3.8 ± 1.7) from the first to the second set. The number of RF was smaller ( p < 0.01) for ECC-only than ECC-CON in the third to the fifth sets in 3-minute rest condition (e.g., 3.2 ± 1.0 vs. 0.8 ± 1.3 in the fifth set) and was greater ( p < 0.01) in 3-minute than in 1-minute rest condition for ECC-CON alone (e.g., 3.2 ± 1.0 vs. 1.3 ± 1.0 in the fifth set). These results suggest that the less fatigable characteristics in ECC-only were limited to the first set, and ECC-only induced greater decrease in the number of RF over sets. Prolonging the rest interval between sets did not increase the number of RF in ECC-only.

The aim of this study was to clarify effects of 3-week work-matched high-intensity intermittent cycling training (HIICT) with different cadences on VO2max in university athletes. Eighteen university athletes performed HIICT with either 60 rpm (n = 9) or 120 rpm (n = 9). HIICT consisted of eight sets of 20-s exercise with a 10-s passive rest between each sets. The initial training intensity was set at 135% of VO2 max and was decreased by 5% every two sets. Athletes in both groups performed 9 sessions of HIICT during 3-week. The total work-load and achievement rate of the work load calculated before experiments in each group were used for analysis. VO2max was measured pre and post-training. After 3-week of training, no significant differences in the total work-load and achievement rate of the work load were found between the two groups. VO2max similarly increased in both groups from pre to post training (p = 0.016), with no significant differences between the groups (p = 0.680). These results suggest that cadence during HIICT is not training variable affecting effect of VO2max.