Concurrent adaptations in maximal aerobic capacity, heat tolerance, microvascular blood flow and oxygen extraction following heat acclimation and ischemic preconditioning.

We investigated the effects of: 1) Ischemic pre-conditioning (IPC) plus a concurrent five-day heat acclimation + IPC (IPC + HA), 2) five-day HA with sham IPC (HA), or 3) control (CON) on thermoneutral measurements of endurance performance, resting measures of skeletal muscle oxygenation and blood flow. Twenty-nine participants were randomly allocated to three groups, which included: 1) five-days of repeated leg occlusion (4 x 5-min) IPC at limb occlusive pressure, plus fixed-intensity (55% V˙ O2max) cycling HA at ~36 °C/40% humidity; 2) HA plus sham IPC (20 mmHg) or 3) or CON (thermoneutral 55% V˙ O2max plus sham IPC). In IPC + HA and HA, there were increases in maximal oxygen consumption (O2max) (7.8% and 5.4%, respectively; P < 0.05), ventilatory threshold (VT) (5.6% and 2.4%, respectively, P < 0.05), delta efficiency (DE) (2.0% and 1.4%, respectively; P < 0.05) and maximum oxygen pulse (O2pulse-Max) (7.0% and 6.9%, respectively; P < 0.05) during an exhaustive incremental test. There were no changes for CON (P > 0.05). Changes (P < 0.05) in resting core temperature (TC), muscle oxygen consumption (m V˙ O2), and limb blood flow (LBF) were also found pre-to-post intervention among the HA and IPC + HA groups, but not in CON (P > 0.05). Five-days of either HA or IPC + HA can enhance markers of endurance performance in cooler environments, alongside improved muscle oxygen extraction, blood flow, exercising muscle efficiency and O2 pulse at higher intensities, thus suggesting the occurrence of peripheral adaptation. Both HA and IPC + HA enhance the adaptation of endurance capacity, which might partly relate to peripheral changes.

The time course of adaptations in thermoneutral maximal oxygen consumption following heat acclimation.

PURPOSE: This study investigated the effects of a 10-day heat acclimation (HA) programme on the time course of changes in thermoneutral maximal oxygen uptake ([Formula: see text]O2max) during and up to 10 days post-HA. METHODS: Twenty-two male cyclists were assigned to a HA or control (Con) training group following baseline ramp tests of thermoneutral [Formula: see text]O2max. Ten days of fixed-intensity (50% baseline [Formula: see text]O2max) indoor cycling was performed in either ~ 38.0 °C (HA) or ~ 20 °C (Con). [Formula: see text]O2max was re-tested on HA days 5, 10 and post-HA days 1, 2, 3, 4, 5 and 10. RESULTS: [Formula: see text]O2max initially declined across time in both groups during training (P < 0.05), before increasing in the post-HA period in both groups (P < 0.05). However, [Formula: see text]O2max was higher than control by post-HA day 4 in the HA group (P = 0.046). CONCLUSIONS: The non-linear time course of [Formula: see text]O2max adaptation suggests that post-testing should be performed 96-h post-training to identify the maximal change for most individuals. In preparation for training or testing, athletes can augment their aerobic power in thermoneutral environments by performing 10 days HA, but the full effects will manifest at varying stages of the post-HA period.

Energy expenditure during a single-handed transatlantic yacht race.

BACKGROUND: The popularity of sports that expose people to consecutive days of high-intensity physical activity continues to increase. The ability to adequately nourish the human body to sustain the required level of competitive performance may be a key contributor to success in such events. METHODS: The energy expenditure of a male competitor in a single-handed, transatlantic race (Transat 2004) was assessed using the doubly-labelled water technique. RESULTS: Mean total daily energy expenditure (TDEE) during the race (13 days) was 14.5 MJ/day with a peak expenditure of 18.6 MJ during the most physically demanding 24-hour period. DISCUSSION: This mean TDEE was approximately 25% lower than that reported in a previous study (14.5 vs. 19.3 MJ/day) for a 13-day leg of a fully crewed offshore race. The difference in results was probably due to the fact that in the previous study, the crew operated in "watches" (work shifts), affording each crew member greater opportunity to eat, rest and sleep. Effective planning and efficient management of resources is essential to the success of the solo sailor. However, the extent to which maintenance of energy balance underpins competitive success remains to be established. To maintain energy balance during the race, a mean daily energy intake of 14.5 MJ/day was necessary for the subject in this study. However, this mean value for energy intake would have been inadequate to match the peak energy expended during the most physically demanding 24 hours of the race.