High-intensity interval training improves VO2peak, maximal lactate accumulation, time trial and competition performance in 9–11-year-old swimmers

Training volume in swimming is usually very high when compared to the relatively short competition time. High-intensity interval training (HIIT) has been demonstrated to improve performance in a relatively short training period. The main purpose of the present study was to examine the effects of a 5-week HIIT versus high-volume training (HVT) in 9–11-year-old swimmers on competition performance, 100 and 2,000 m time (T100 m and T2,000 m), VO2peak and rate of maximal lactate accumulation (Lacmax). In a 5-week crossover study, 26 competitive swimmers with a mean (SD) age of 11.5 ± 1.4 years performed a training period of HIIT and HVT. Competition (P < 0.01; effect size = 0.48) and T2,000 m (P = 0.04; effect size = 0.21) performance increased following HIIT. No changes were found in T100 m (P = 0.20). Lacmax increased following HIIT (P < 0.01; effect size = 0.43) and decreased after HVT (P < 0.01; effect size = 0.51). VO2peak increased following both interventions (P < 0.05; effect sizes = 0.46–0.57). The increases in competition performance, T2,000 m, Lacmax and VO2peak following HIIT were achieved in significantly less training time (~2 h/week)

ANTIHISTAMINES INCREASE LEG BLOOD FLOW DURING EXERCISE

M.R. Ely1, S.M. Ratchford2, H.L. Clifton2, D.T. La Salle2, J.D. Trinity2, D.W. Wray2, J.R. Halliwill1FACSM. 1University of Oregon. Eugene, OR; 2University of Utah, Salt Lake City, UT Histamine mediated vasodilator pathways elevate microcirculatory blood flow during inflammation and immune responses as well as skeletal muscle blood flow following endurance exercises. During exercise, intramuscular histamine concentration increases, however, the contribution of histamine to exercise hyperemia is unknown. The production of intramuscular histamine is reported to be positively correlated with exercise intensity and duration. Therefore, elevations in intramuscular histamine may contribute to skeletal muscle blood flow as exercise increases in intensity and duration. PURPOSE: To compare limb blood flow during a ramped increase in exercise intensity before and after prolonged exercise under normal conditions and when histamine signaling is blocked. It was hypothesized that H1/H2antihistamines would decrease limb blood flow and the effect would be greater at high exercise intensities and following prolonged exercise. METHODS: Sixteen (7F) volunteers performed unilateral knee-extension exercise after consuming either Placebo or histamine (H1/H2) receptor antagonists (Blockade). The exercise consisted of two incremental ramp protocols at 20, 40, 60, and 80% of peak work rate, which were separated by 60 min of knee-extension exercise (60% of peak). Femoral artery blood flow (Logiq e9, GE Medical Systems) was measured during each exercise intensity and every 10 min during the 60 min of prolonged exercise. Data were analyzed with a 3-way RM ANOVA and are presented as Means±SEM. RESULTS: Femoral artery blood flow increased with exercise intensity from 1676±57, 2008±68, 2272±75, to 2660±97 ml/min at 20, 40, 60 to 80% of peak work rate during Placebo (PCONCLUSION:Contrary to the hypothesis, these results suggest that blocking histamine’s actions during exercise, regardless of the intensity or duration, increased skeletal muscle blood flow. Support provided by: The Eugene & Clarissa Evonuk Memorial Graduate Fellowship

The effect of acute pomegranate extract supplementation on oxygen uptake in highly-trained cyclists during high-intensity exercise in a high altitude environment

Abstract Background Recent research has indicated that pomegranate extract (POMx) may improve performance during aerobic exercise by enhancing the matching of vascular oxygen (O2) provision to muscular requirements. POMx is rich in ellagitannin polyphenols and nitrates (NO3 −), which are both associated with improvements in blood flow and O2 delivery. Primarily, this study aimed to determine whether POMx improves performance in a cycling time trial to exhaustion at 100%VO2max (TTE100%) in highly-trained cyclists. In addition, we investigated if the O2 cost (VO2) of submaximal exercise was lower with POMx, and whether any changes were greater at high altitude where O2 delivery is impaired. Methods Eight cyclists exercised at three submaximal intensities before completing a TTE100% at sea-level (SEA) and at 1657 m of altitude (ALT), with pre-exercise consumption of 1000 mg of POMx or a placebo (PLAC) in a randomized, double-blind, crossover design. Data were analysed using a three way (treatment x altitude x intensity) or two-way (treatment x altitude) repeated measures ANOVA with a Fisher’s LSD post-hoc analysis. Significance was set at p ≤ 0.05. The effect size of significant interactions was calculated using Cohen’s d. Results TTE100% performance was reduced in ALT but was not influenced by POMx (p > 0.05). Plasma NO3 − were 10.3 μmol greater with POMx vs. PLAC (95% CI, 0.8, 19.7,F 1,7 = 7.83, p  0.05). Submaximal VO2 values were not affected by POMx (p ≥ 0.05). Conclusions The restoration of SEA VO2 values at ALT is likely driven by the high polyphenol content of POMx, which is proposed to improve nitric oxide bioavailability. Despite an increase in VO2, no change in exercise performance occurred and therefore this study does not support the use of POMx as an ergogenic supplement

Integrative human cardiovascular responses to hyperthermia

Progressive whole-body hyperthermia with passive heat stress is associated with a host of physiological adjustments. These include large increases in peripheral blood flow and cardiac output and a smaller selective redistribution of blood flow from the cerebral and visceral tissues to the limbs, head, and torso, with perfusion pressure being only slightly reduced. Aerobic metabolism also increases in these conditions, but the magnitude is small in absolute terms, suggesting a predominant role of thermosensitive mechanisms in passive hyperthermia-induced cardiovascular adjustments. Although exercise heat stress requires substantially greater blood flow requirements compared to passive heat stress alone, the magnitude of this hyperemic response is less than would be expected given the extent to which both conditions independently increase blood flow in isolation. As a result, submaximal exercise limb blood flow is only slightly higher during small muscle-mass exercise in the heat, and is similar to control conditions during whole-body exercise. When exercise intensity is increased further towards maximal levels, the superimposition of heat stress leads to earlier reductions in regional and systemic blood perfusion, compromised locomotor limb aerobic metabolism, and ultimately results in impaired endurance capacity. This chapter provides an integrative overview of the human cardiovascular response to passive heat stress and exercise heat stress, with emphasis on its consequences on exercise performance in the heat