Carbohydrate intake during endurance exercise has long been recognized as a robust strategy to enhance exercise performance >1 hr, with studies consistently demonstrating beneficial effects ( Burke et al., 2011 ; Cermac & Van Loon, 2013 ; Jeukendrup, 2011 ; Stellingwerf & Cox, 2014 ). The
Kirsty M. Reynolds, Tom Clifford, Stephen A. Mears, and Lewis J. James
Andy J. King, Joshua T. Rowe, and Louise M. Burke
= carbohydrate. To be eligible for this review, studies were required to have investigated a CHO hydrogel compound during prolonged, endurance exercise defined as continuous running, cycling, triathlon, rowing, swimming, and cross-country skiing greater than 1-hr duration. Studies with exercise durations lasting
Laura Hottenrott, Sascha Ketelhut, Christoph Schneider, Thimo Wiewelhove, and Alexander Ferrauti
Postexercise recovery is a fundamental component of high-intensity and endurance exercise and is crucial for continuous performance enhancement. An acute bout of endurance exercise modulates different functional systems and leads to an increase in heart rate, lactate, body temperature, blood flow
Emma Brooks, Gilles Lamothe, Taniya S. Nagpal, Pascal Imbeault, Kristi Adamo, Jameel Kara, and Éric Doucet
availability of carbohydrates (CHO), knowing that this is the primary energy source during high-intensity exercise and is required to sustain longer duration or endurance exercise of higher intensities ( Cermak & van Loon, 2013 ; Romijn et al., 1993 ). Reductions in CHO availability (i.e., muscle and liver
Jason T. Penry and Melinda M. Manore
Choline plays a central role in many physiological pathways, including neurotransmitter synthesis (acetylcholine), cell-membrane signaling (phospholipids), lipid transport (lipoproteins), and methyl-group metabolism (homocysteine reduction). Endurance exercise might stress several of these pathways, increasing the demand for choline as a metabolic substrate. This review examines the current literature linking endurance exercise and choline demand in the human body. Also reviewed are the mechanisms by which exercise might affect blood choline levels, and the links between methyl metabolism and the availability of free choline are highlighted. Finally, the ability of oral choline supplements to augment endurance performance is assessed. Most individuals consume adequate amounts of choline, although there is evidence that current recommendations might be insufficient for some adult men. Only strenuous and prolonged physical activity appears sufficient to significantly decrease circulating choline stores. Moreover, oral choline supplementation might only increase endurance performance in activities that reduce circulating choline levels below normal.
Stefan M. Pasiakos, Holly L. McClung, James P. McClung, Maria L. Urso, Matthew A. Pikosky, Gregory J. Cloutier, Roger A. Fielding, and Andrew J. Young
This study examined alterations in skeletal-muscle growth and atrophy-related molecular events after a single bout of moderate-intensity endurance exercise. Muscle biopsies were obtained from 10 men (23 ± 1 yr, body mass 80 ± 2 kg, and VO2peak 45 ± 1 ml · kg−1 · min−1) immediately (0 hr) and 3 hr after a 60-min bout of cycle exercise (60% ± 5% VO2peak). Corresponding muscle biopsies were also obtained under resting conditions. The phosphorylation status of insulin/IGF-PI3K molecular-signaling proteins, ubiquitin-proteasome-related gene expression, FOXO transcription factors, and myogenic regulatory factors in muscle samples was analyzed using multiplex analysis, Western blotting, and quantitative real-time polymerase chain reaction (qRT-PCR). A condition–time interaction was observed for Akt phosphorylation (p < .05) with multiplexing. Regardless of endurance exercise, Akt phosphorylation decreased and ERK phosphorylation increased at 3 hr compared with 0 hr (p < .05). Levels of p70S6K phosphorylation were 110% greater (p < .05) at 3 hr than at 0 hr using Western blots. MuRF mRNA expression postexercise increased; levels were 4.7- and 5.7-fold greater (p < .05) at 0 hr and 3 hr, respectively, than at rest with qRT-PCR. Atrogin mRNA expression was up-regulated 3.2-fold 3 hr postexercise compared with rest. These findings demonstrate modest changes in the molecular responses to moderate endurance exercise in the absence of nutrition. This study provides the groundwork for future investigations designed to optimize the metabolic conditions necessary to positively influence the cellular mechanisms specific to skeletal-muscle protein turnover during recovery from endurance exercise.
Katrien De Bock, Bert O. Eijnde, Monique Ramaekers, and Peter Hespel
The purpose of this study was to investigate the effect of acute and 4-week Rhodiola rosea intake on physical capacity, muscle strength, speed of limb movement, reaction time, and attention.
PHASE I: A double blind placebo-controlled randomized study (n = 24) was performed, consisting of 2 sessions (2 days per session). Day 1: One hour after acute Rhodiola rosea intake (R, 200-mg Rhodiola rosea extract containing 3% rosavin + 1% salidroside plus 500 mg starch) or placebo (P, 700 mg starch) speed of limb movement (plate tapping test), aural and visual reaction time, and the ability to sustain attention (Fepsy Vigilance test) were assessed. Day 2: Following the same intake procedure as on day 1, maximal isometric knee-extension torque and endurance exercise capacity were tested. Following a 5-day washout period, the experimental procedure was repeated, with the treatment regimens being switched between groups (session 2). PHASE II: A double blind placebo-controlled study (n = 12) was performed. Subjects underwent sessions 3 and 4, identical to Phase I, separated by a 4-week R/P intake, during which subjects ingested 200 mg R/P per day.
PHASE I: Compared with P, acute R intake in Phase I increased 0 < -05) time to exhaustion from 16.8 ± 0.7 min to 17.2 ± 0.8 min. Accordingly, VO2peak (p < .05) and VCO2peak(p< .05) increased during R compared to P from 50.9 ± 1.8 ml • min-1 • kg−1 to 52.9 ± 2.7 ml • min-1 • kg"’ (VO2peak) and from 60.0 ± 2.3 ml • min-1 • kg-’ to 63.5 ± 2.7 ml • min-1 kg-1 (VCO2peak). Pulmonary ventilation (p = .07) tended to increase more during R than during P(P: 115.9±7.7L/min; R: 124.8 ± 7.7 L/min). All other parameters remained unchanged. PHASE II: Four-week R intake did not alter any of the variables measured.
Acute Rhodiola rosea intake can improve endurance exercise capacity in young healthy volunteers. This response was not altered by prior daily 4-week Rhodiola intake.
Jeremy C. Young, Nicholas G. Dowell, Peter W. Watt, Naji Tabet, and Jennifer M. Rusted
While there is evidence that age-related changes in cognitive performance and brain structure can be offset by increased exercise, little is known about the impact long-term high-effort endurance exercise has on these functions. In a cross-sectional design with 12-month follow-up, we recruited older adults engaging in high-effort endurance exercise over at least 20 years, and compared their cognitive performance and brain structure with a nonsedentary control group similar in age, sex, education, IQ, and lifestyle factors. Our findings showed no differences on measures of speed of processing, executive function, incidental memory, episodic memory, working memory, or visual search for older adults participating in long-term high-effort endurance exercise, when compared without confounds to nonsedentary peers. On tasks that engaged significant attentional control, subtle differences emerged. On indices of brain structure, long-term exercisers displayed higher white matter axial diffusivity than their age-matched peers, but this did not correlate with indices of cognitive performance.
Bettina Mittendorfer and Samuel Klein
Endurance exercise increases the use of endogenous fuels to provide energy for working muscles. Elderly subjects oxidize more glucose and less fat during moderate intensity exercise. This shift in substrate use is presumably caused by age-related changes in skeletal muscle, including decreased skeletal muscle respiratory capacity, because adipose tissue lipolysis and plasma fatty acid availability are not rate limiting. Endurance training in elderly subjects increases muscle respiratory capacity, decreases glucose production and oxidation, and increases fat oxidation thereby correcting or compensating for the alterations in substrate oxidation associated with aging.
Sharon L. Miller, Carl M. Maresh, Lawrence E. Armstrong, Cara B. Ebbeling, Shannon Lennon, and Nancy R. Rodriguez
The interaction of substrates and hormones in response to ingestion of intact proteins during endurance exercise is unknown. This study characterized substrate and hormone responses to supplementation during endurance exercise. Nine male runners participated in 3 trials in which a non-fat (MILK), carbohydrate (CHO), or placebo (PLA) drink was consumed during a 2-hour treadmill >· run at 65% V̇O2max. Circulating levels of insulin, glucagon, epinephrine, norepi-nephrine, growth hormone, testosterone, and cortisol were measured. Plasma substrates included glucose, lactate, free fatty acids, and select amino acids. Except for insulin and cortisol, hormones increased with exercise. While post-exercise insulin concentrations declined similarly in all 3 trials, the glucagon increase was greatest following MILK consumption. CHO blunted the post-exercise increase in growth hormone compared to levels in MILK. Free fatty acids and plasma amino acids also were responsive to nutritional supplementation with both CHO and MILK attenuating the rise in free fatty acids compared to the increase observed in PLA. Correspondingly, respiratory exchange ratio increased during CHO. Essential amino acids increased significantly only after MILK and were either unchanged or decreased in CHO. PLA was characterized by a decrease in branched-chain amino acid concentrations. Modest nutritional supplementation in this study altered the endocrine response as well as substrate availability and utilization following and during an endurance run, respectively.