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New Findings: What is the central question of this study?Does combining endurance and hypertrophic stimuli blunt the adaptations to both modalities and is this effect greater in muscles with larger baseline fibre cross sectional area?What is the main finding and its importance?Endurance exercise and hypertrophic stimuli can be combined to increase fatigue resistance and fibre size without blunting either adaptation regardless of baseline fibre size. Previous studies have demonstrated that fibre cross‐sectional area (FCSA) is inversely related to oxidative capacity, which is thought to be determined by diffusion limitations of oxygen, ADP and ATP. Consequently, it is hypothesised that (1) when endurance training is combined with a hypertrophic stimulus the response to each will be blunted, and (2) muscles with a smaller FCSA will show a larger hypertrophic response than those with a large FCSA. To investigate this, we combined overload with endurance exercise in 12‐month‐old male mice from three different strains with different FCSA: Berlin High (BEH) (large fibres), C57BL/6J (C57) (normal‐sized fibres) and Berlin Low (BEL) (small fibres). The right plantaris muscle was subjected to overload through denervation of synergists with the left muscle acting as an internal control. Half the animals trained 30 min per day for 6 weeks. The overload‐induced hypertrophy was not blunted by endurance exercise, and the exercise‐induced increase in fatigue resistance was not impaired by overload. All strains demonstrated similar absolute increases in FCSA, although the BEH mice with more fibres than the C57 mice demonstrated the largest increase in muscle mass and BEL mice with fewer fibres the smallest increase in muscle mass. This study suggests that endurance exercise and hypertrophic stimuli can be combined without attenuating adaptations to either modality, and that increases in FCSA are independent of baseline fibre size. [ABSTRACT FROM AUTHOR]

Prolonged low‐frequency force depression (PLFFD) induced by fatiguing exercise is characterized by a persistent depression in submaximal contractile force during the recovery period. Muscle glycogen depletion is known to limit physical performance during prolonged low‐ and moderate‐intensity exercise, and accelerating glycogen resynthesis with post‐exercise carbohydrate intake can facilitate recovery and improve repeated bout exercise performance. Short‐term, high‐intensity exercise, however, can cause PLFFD without any marked decrease in glycogen. Here, we studied whether recovery from PLFFD was accelerated by carbohydrate ingestion after 60 minutes of moderate‐intensity glycogen‐depleting cycling exercise followed by six 30‐seconds all‐out cycling sprints. We used a randomized crossover study design where nine recreationally active males drank a beverage containing either carbohydrate or placebo after exercise. Blood glucose and muscle glycogen concentrations were determined at baseline, immediately post‐exercise, and during the 3‐hours recovery period. Transcutaneous electrical stimulation of the quadriceps muscle was performed to determine the extent of PLFFD by eliciting low‐frequency (20 Hz) and high‐frequency (100 Hz) stimulations. Muscle glycogen was severely depleted after exercise, with a significantly higher rate of muscle glycogen resynthesis during the 3‐hours recovery period in the carbohydrate than in the placebo trials (13.7 and 5.4 mmol glucosyl units/kg wet weight/h, respectively). Torque at 20 Hz was significantly more depressed than 100 Hz torque during the recovery period in both conditions, and the extent of PLFFD (20/100 Hz ratio) was not different between the two trials. In conclusion, carbohydrate supplementation enhances glycogen resynthesis after glycogen‐depleting exercise but does not improve force recovery when the exercise also involves all‐out cycling sprints. [ABSTRACT FROM AUTHOR]

We investigated the acute neuromuscular and stress responses to three different high-intensity interval training sessions in young (age 19.5±1.3 years) and older (age 65.7±2.8 years) women. Cycling exercise comprised either 6 × 5 s or 3 × 30 s all-out, or 3 × 60 s submaximal, efforts each performed 5 weeks apart in randomized order. Peak and average power was higher in young than in older women and was largest during the 6 × 5 s strategy in both groups (p<0.05). The decrease in the ratio of torques evoked by 20 and 100 Hz electrical stimulation, representing low-frequency fatigue, was more evident after the 3 × 30 and 3 × 60 s than the 6 × 5 s bout in both groups and was larger in young than in older women (p<0.05). Both groups preferred 6 × 5 s cycling for further training. In conclusion, in young women, very low volume (6 × 5 s) all-out exercise induces significant physiological stress and seems to be an effective means of training. For older women, longer exercise sessions (3 × 60 s) are more stressful than shorter ones but are still tolerable psychologically. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study was to follow circulating brain-derived neurotrophic factor (BDNF) and interleukin-6 (IL-6) levels in response to severe muscle-damaging exercise.Methods: Young healthy men (N = 10) performed a bout of mechanically demanding stretch-shortening cycle exercise consisting of 200 drop jumps. Voluntary and electrically induced knee extension torque, serum BDNF levels, and IL-6 levels were measured before and for up to 7 days after exercise.Results: Muscle force decreased by up to 40% and did not recover by 24 hours after exercise. Serum BDNF was decreased 1 hour and 24 hours after exercise, whereas IL-6 increased immediately and 1 hour after but recovered to baseline by 24 hours after exercise. IL-6 and 100-Hz stimulation torque were correlated (r = -0.64, P < 0.05) 24 hours after exercise.Discussion: In response to acute, severe muscle-damaging exercise, serum BDNF levels decrease, whereas IL-6 levels increase and are associated with peripheral fatigue. Muscle Nerve 57: E46-E51, 2018. [ABSTRACT FROM AUTHOR]