The present study investigated the contribution of myofibrillar protein synthesis (MyoPS) and associated gene signaling to recovery from 300 muscle-damaging, eccentric contractions. Measured with D2O, MyoPS rates were elevated during recovery and observed alongside expression of inflammatory and regenerative signaling pathways. A nutritional intervention accelerated recovery; however, MyoPS and gene signaling were unchanged compared with placebo. These data indicate that MyoPS and associated signaling do not explain accelerated recovery from muscle damage.

Context The early events regulating the remodelling programme following skeletal muscle damage are poorly understood. Objective The objective of this study was to determine the association between myofibrillar protein synthesis (myoPS) and nuclear factor-kappa B (NF-κB) signalling by nutritionally accelerating recovery of muscle function following damage. Design, setting, participants, and interventions Healthy males and females consumed daily post-exercise and pre-bed protein-polyphenol (PP; n=9; 4 females) or isocaloric maltodextrin placebo (PLA; n=9; 3 females) drinks (parallel design), 6 days before and 3 days after 300 unilateral eccentric quadriceps contractions (EC) during complete dietary control. Main outcome measures Muscle function was assessed daily, and skeletal muscle biopsies were taken after 24, 27 and 36 h for measurements of myoPS rates using deuterated water, and gene ontology and NF-κB signalling analysis using an RT-qPCR gene array. Results EC impaired muscle function for 48 h in PLA, but for just 24 h in PP (P=0.047). EC increased myoPS compared to the control leg during post-exercise (24–27 h; 0.14±0.01 vs 0.11±0.01%·h -1, respectively; P=0.075) and overnight periods (27–36 h; 0.10±0.01 vs 0.07±0.01%·h -1, respectively; P=0.020), but was not further increased by PP (P>0.05). PP decreased post-exercise and overnight muscle IL1R1 (PLA=2.8±0.4, PP=1.1±0.4 and PLA=1.9±0.4, PP=0.3±0.4 log2 fold change, respectively) and IL1RL1 (PLA=4.9±0.7, PP=1.6±0.8 and PLA=3.7±0.6, PP=0.7±0.7 log2 fold change, respectively) mRNA expression (P<0.05) and downstream NF-κB signalling compared to PLA. Conclusion PP ingestion likely accelerates recovery of muscle function by attenuating inflammatory NF-κB transcriptional signalling, possibly to reduce aberrant tissue degradation rather than increase myoPS rates.

Animal-derived dietary protein ingestion and physical activity stimulate myofibrillar protein synthesis rates in older adults. We determined whether a non-animal-derived diet can support daily myofibrillar protein synthesis rates to the same extent as an omnivorous diet. Nineteen healthy older adults (age 66±1 y; BMI 24±1 kg·m-2; m=12, f=7) participated in a randomised, parallel-group, controlled trial during which they consumed a 3-day isocaloric high-protein (1.8 g·kg body mass-1·d-1) diet, where the protein was provided from predominantly (71%) animal (OMNI; n=9; m=6, f=3) or exclusively vegan (VEG; n=10; m=6, f=4; mycoprotein providing 57% of daily protein intake) sources. During the dietary control period participants conducted a daily bout of unilateral resistance-type leg extension exercise. Prior to the dietary control period participants ingested 400 mL deuterated water, with 50 mL doses consumed daily thereafter. Saliva samples were collected throughout to determine body water deuterium (2H) enrichments, and muscle samples were collected from rested and exercised muscle to determine daily myofibrillar protein synthesis rates. Deuterated water dosing resulted in body water 2H enrichments of ~0.78±0.03%. Daily myofibrillar protein synthesis rates were 13±8 (P=0.169) and 12±4% (P=0.016) greater in the exercised compared with rested leg (1.59±0.12 vs 1.77±0.12 %·d-1 and 1.76±0.14 vs 1.93±0.12 %·d-1) in OMNI and VEG groups, respectively. Daily myofibrillar protein synthesis rates did not differ between OMNI and VEG in either rested or exercised muscle (P>0.05). Over the course of a three day intervention, omnivorous or vegan derived dietary protein sources can support equivalent rested and exercised daily myofibrillar protein synthesis rates in healthy older adults consuming a high-protein diet.

Background Pre-exercise supplements containing low doses of caffeine improve endurance exercise performance, but the most efficacious time for consumption before intense endurance exercise remains unclear, as does the contribution of caffeine metabolism. Methods This study assessed the timing of a commercially available supplement containing 200 mg of caffeine, 1600 mg of β-alanine and 1000 mg of quercetin [Beachbody Performance Energize, Beachbody LLC, USA] on exercise performance, perception of effort and plasma caffeine metabolites. Thirteen cyclists (V̇O2max 64.5 ± 1.4 ml kg− 1 min− 1 (± SEM)) completed four experimental visits consisting of 30 min of steady-state exercise on a cycle ergometer at 83 ± 1% V̇O2max followed by a 15-min time trial, with perceived exertion measured regularly. On three of the visits, participants consumed caffeine either 35 min before steady-state exercise (PRE), at the onset of steady-state (ONS) or immediately before the time trial (DUR) phases, with a placebo consumed at the other two time points (i.e. three drinks per visit). The other visit (PLA) consisted of consuming the placebo supplement at all three time points. The placebo was taste-, colour- and calorie-matched. Results Total work performed during the time trial in PRE was 5% greater than PLA (3.53 ± 0.14 vs. 3.36 ± 0.13 kJ kg− 1 body mass; P = 0.0025), but not ONS (3.44 ± 0.13 kJ kg− 1; P = 0.3619) or DUR (3.39 ± 0.13 kJ kg− 1; P = 0.925), which were similar to PLA. Perceived exertion was lowest during steady-state exercise in the PRE condition (P < 0.05), which coincided with elevated plasma paraxanthine in PRE only (P < 0.05). Conclusion In summary, ingestion of a pre-exercise supplement containing 200 mg caffeine 35 min before exercise appeared optimal for improved performance in a subsequent fatiguing time trial, possibly by reducing the perception of effort. Whether this was due to increased circulating paraxanthine requires further investigation. Trial registration ClinicalTrials.Gov,NCT02985606; 10/26/2016.

Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. The present study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n=15; age, 24 ± 1 years; BMI, 22.3 ± 0.7 kg·m-2) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults. Versus isocaloric placebo (PLA; n=14; age, 25 ± 2 years; BMI, 23.9 ± 1.0 kg·m-2), PPB increased 48 h MyoPS rates after the first RET session measured using deuterated water (2.01 ± 0.15 %·d-1 vs. 1.51 ± 0.16 , respectively; P<0.05). Additionally, PPB increased isokinetic muscle function over 10 sessions of training relative to the untrained control leg (%U) from 99.9 ± 1.8 pre-training to 107.2 ± 2.4 %U at session 10 (versus 102.6 ± 3.9 to 100.8 ± 2.4 %U at session 10 in PLA; interaction P<0.05). Pre-to-post-training, PPB increased type II fCSA (PLA: 120.8 ± 8.2 to 109.5 ± 8.6 %U; PPB: 92.8 ± 6.2 to 108.4 ± 9.7 %U; interaction P<0.05), but the gain in quadriceps muscle volume was similar between groups. Similarly, PPB did not further increase peak isometric torque, muscle function or MyoPS measured post-training. This suggests that although PPB increases MyoPS and early adaptation, it may not influence longer term adaptations to unilateral RET.