This randomized, double-blinded, placebo-controlled study aimed to investigate the effect of strength training (ST) combined with vitamin C and E supplementation on perceived and performance fatigability in breast cancer survivors (BCS). Twenty-five BCS were randomly assigned to one of two groups: vitamins (VIT; n = 12; 51.0 ± 9.0 years); or placebo (PLA; n = 13; 48.2 ± 8.3 years). Both groups performed a 10-week ST protocol, twice a week. VIT was supplemented with vitamins C (500mg/day) and E (180mg/day) and PLA with polydextrose (1g/day), once a day after breakfast. At the beginning and at the end of training period, perceived fatigability was assessed using MFI-20 (general fatigue and physical fatigue). Performance fatigability was assessed during 30 maximal isokinetic knee extension at 120º/s-1. General fatigue reduced similarly in VIT (p = 0.004) and PLA (p = 0.011). Physical fatigue reduced similarly in both, VIT (p = 0.011) and PLA (p = 0.001). Performance fatigability also decreased similarly in VIT (p = 0.026) and PLA (p < 0.001). There was no difference between groups in any moment (p > 0.05). In summary, antioxidants supplementation does not add any positive synergistic effect to ST on improving perceived or performance fatigability in BCS. Novelty: -Strength training with maximal repetitions reduces perceived and performance fatigability of BCS. -Vitamins C and E supplementation does no add any positive synergistic effect to ST on reducing fatigability in BCS.

AbstractThis study investigated the acute effects of seated and supine knee extension exercise on muscle swelling, torque, and work output. Twelve resistance-trained men performed two isokinetic concentric-only knee-extension training protocols at different hip positions in a counter-balanced order. They completed the knee extension exercise in the seated (hip angle at 85°) and supine (hip angle at 180°) positions. The torque and work output were assessed during each set. Moreover, muscle thickness of the middle and proximal vastus lateralis and rectus femoris were evaluated before and after each protocol and used as an indicator of muscle swelling. Middle rectus femoris and proximal vastus lateralis thickness increased significantly (p=0.01) with no difference between exercise variations. However, the middle vastus lateralis thickness increased (p=0.01) only after the seated knee extension exercise (~7%). Knee extensors’ peak torque and work output were approximately 8% higher (p=0.04) in the seated when compared to the supine hip position. There was a similar decrease in torque and work output throughout both protocols (p=0.98). In conclusion, seated knee extension exercises produced greater torque, work output, and muscle swelling in the vastus lateralis when compared to the supine knee extension exercise.

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Aging is associated with neurodegeneration and a loss of muscle function, especially in lower-limb muscles. While caffeine may augment muscle force generation through multiple effects on the central nervous system, no studies have yet compared the effects of caffeine on force-generating capacity between younger and older men, who might respond differently due to age-related changes in the structures on which caffeine acts. In a double-blind, controlled trial, 22 younger (25 ± 5 years) and 21 older (68 ± 6 years) men were tested for isometric plantarflexor torque on two separate days (2–7 days apart) before and 60 min after ingesting 3 mg/kg (∼2 cups of coffee) of caffeine or placebo. No effects of caffeine ingestion on peak torque or rate of torque development were detected in either older or younger men. Therefore, 3 mg/kg of caffeine may not acutely counteract age-related decreases in force capacity of the functionally important plantarflexor muscles.

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Purpose To determine the amount of familiarization sessions required by breast cancer survivors to achieve a reliable measurement of muscle function assessed using isokinetic dynamometry. Methods Twenty-six breast cancer survivors performed three isokinetic knee extension tests separated by, at least, 48 h. The isokinetic testing protocol included one warm-up set of 10 submaximal knee extensions at 120°/s, followed by two sets of four maximal knee extensions at 60°/s, with 2-min rest interval between sets. Peak torque (PT), time to peak torque (TPT), angle of peak torque (APT), and average power (AP) of each trial was used for the assessment of testing reliability. Percentage change in the mean, typical error, coefficient of variation and intraclass correlation coefficients (ICC 2.1 ) were calculated to determine test-retest reliability. Results For PT, change in mean was lower between trials 2 and 3 than between trials 1 and 2 (4.18% and 13.18%, respectively), and ICC was greater between trials 2 and 3 than between trials 1 and 2 (0.962 and 0.818, respectively). For TPT and APT, ICC was clinically acceptable only between trials 2 and 3 (0.757 and 0.803, respectively). For AP, change in mean was clinically acceptable between trials 2 and 3 (9.84%), while ICC met acceptable reliability between both, trials 1 and 2 and, trials 2 and 3 (0.756 and 0.891, respectively). Conclusion At least one familiarization session is adequate to achieve reliable measurements of muscle function using isokinetic dynamometry, while avoiding the impact of learning effect of the measurements in breast cancer survivors.