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Fruit supplementation reduces indices of exercise-induced muscle damage: a systematic review and meta-analysis.
Doma, K, Gahreman, D, Connor, J
European journal of sport science. 2021;(4):562-579
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Abstract
This systematic review and meta-analysis examined the effects of fruit supplements on indices of muscle damage and physical performance measures following muscle-damaging exercise protocols. The PEDro scale and Cochrane's risk of bias tool was used to critically appraise each study, whilst forest plots were generated to report on standardised mean differences (SMD) and p-values. The studies employed a crossover-randomised design, or a randomised controlled placebo design, with measures compared between the supplement (SUPP) and placebo (PLA) conditions at 24 and 48 h following the muscle-damaging exercise protocols. Compared to the PLA condition, the SUPP condition exhibited significantly lower levels of indirect muscle damage markers (p = 0.02; I2 = 44%), inflammatory markers (p = 0.03; I2 = 45%) and oxidative stress (p < 0.001; I2 = 58%), whilst antioxidant capacity was significantly increased (p = 0.04; I2 = 82%) at 24 h post-exercise. The maximal isometric voluntary contraction was significantly greater for the SUPP condition than the PLA at 24 h (p < 0.001; I2 = 81%) and 48 h (p < 0.001; 84%) post-exercise. Only a few studies reported on functional outcome measures (i.e. countermovement jump, cycling, sprint and running maximal oxygen uptake), and the findings appeared conflicting according to qualitative analyses. Fruit supplementation minimised the level of several biomarkers of muscle damage, inflammation and oxidative stress, whilst improved muscular contractility during periods of EIMD. These findings demonstrate that fruit supplements could be used as recovery strategies from strenuous exercise sessions.
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Age-related Deficits in Voluntary Activation: A Systematic Review and Meta-analysis.
Rozand, V, Sundberg, CW, Hunter, SK, Smith, AE
Medicine and science in sports and exercise. 2020;(3):549-560
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Abstract
Whether there are age-related differences in neural drive during maximal effort contractions is not clear. This review determined the effect of age on voluntary activation during maximal voluntary isometric contractions. The literature was systematically reviewed for studies reporting voluntary activation quantified with the interpolated twitch technique (ITT) or central activation ratio (CAR) during isometric contractions in young (18-35 yr) and old adults (>60 yr; mean, ≥65 yr). Of the 2697 articles identified, 54 were eligible for inclusion in the meta-analysis. Voluntary activation was assessed with electrical stimulation and transcranial magnetic stimulation on five different muscle groups. Random-effects meta-analysis revealed lower activation in old compared with young adults (d = -0.45; 95% confidence interval, -0.62 to -0.29; P < 0.001), with moderate heterogeneity (52.4%). To uncover the sources of heterogeneity, subgroup analyses were conducted for muscle group, calculation method (ITT or CAR), and stimulation type (electrical stimulation or transcranial magnetic stimulation) and number (single, paired, or train stimulations). The age-related reduction in voluntary activation occurred for all muscle groups investigated except the ankle dorsiflexors. Both ITT and CAR demonstrated an age-related reduction in voluntary activation of the elbow flexors, knee extensors, and plantar flexors. ITT performed with paired and train stimulations showed lower activation for old than young adults, with no age difference for the single electrical stimulation. Together, the meta-analysis revealed that healthy older adults have a reduced capacity to activate some upper and lower limb muscles during maximal voluntary isometric contractions; however, the effect was modest and best assessed with at least paired stimulations to detect the difference.