Abstract
Sports limit the length of breaks between halves or periods, placing substantial time constraints on cooling effectiveness. This study investigated the effect of active cooling during both time-limited and prolonged post-exercise recovery in the heat. Ten recreationally-active adults (VO2peak 43.6 ± 7.5 ml·kg−1·min−1) were exposed to thermally-challenging conditions (36°C air temperature, 45% RH) while passively seated for 30 min, cycling for 60 min at 51% VO2peak, and during a seated recovery for 60 min that was broken into two epochs: first 15 min (REC0−15) and total 60 min (REC0−60). Three different cooling techniques were implemented during independent recovery trials: (a) negative-pressure single hand-cooling (~17°C); (b) ice vest; and (c) non-cooling control. Change in rectal temperature (Tre), mean skin temperature (), heart rate (HR), and thermal sensation (TS), as well as mean body temperature (), and heat storage (S) were calculated for exercise, REC0−15 and REC0−60. During REC0−15, HR was lowered more with the ice vest (−9 [−15 to −3] bts·min−1, p = 0.002) and single hand-cooling (−7 [−13 to −1] bts·min−1, p = 0.021) compared to a non-cooling control. The ice vest caused a greater change in compared to no cooling (−1.07 [−2.00 to −0.13]°C, p = 0.021) and single-hand cooling (−1.07 [−2.01 to −0.14]°C, p = 0.020), as well as a greater change in S compared to no cooling (−84 [−132 to −37] W, p < 0.0001) and single-hand cooling (−74 [−125 to −24] W, p = 0.002). Across REC0−60, changes in (−0.38 [−0.69 to −0.07]°C, p = 0.012) and (−1.62 [−2.56 to −0.68]°C, p < 0.0001) were greater with ice vest compared to no cooling. Furthermore, changes in in (−0.39 [−0.70 to −0.08]°C, p = 0.010) and (−1.68 [−2.61 to −0.74]°C, p < 0.0001) were greater with the ice vest compared to single-hand cooling. Using an ice vest during time-limited and prolonged recovery in the heat aided in a more effective reduction in thermo-physiological strain compared to both passive cooling as well as a single-hand cooling device.
Highlights
Both professional and recreational sporting events frequently take place in thermally-stressful environments, including the familiar summer Olympic Games (Barwood et al, 2009)
Thermoregulation Stored heat (S) reduction during REC0−15 was different between cooling conditions, with the application of an ice vest eliciting a significantly greater reduction of stored heat across timelimited recovery (REC0−15) compared to a non-cooling control (−84 [−132 to −37] W, p < 0.0001) and single-hand cooling (−74 [−125 to −24] W, p = 0.002)
A deeper look into the components of time-limited recovery indicates that heat loss was increased across the first 5 min of ice vest application when compared to both control (−44 [−73 to −15] W, p = 0.001) and single-hand cooling (−31 [−61 to −0.3] W, p = 0.047)
Summary
Both professional and recreational sporting events frequently take place in thermally-stressful environments, including the familiar summer Olympic Games (Barwood et al, 2009). Heated exercise-induced core and skin temperatures elevations contribute to the deterioration of aerobic exercise capacity, the exact cardiovascular mechanisms by which this decrement occurs appears to be a function of both exercise intensity and duration (Nybo et al, 2011). Augmentation of skin blood flow to facilitate heat loss impairs cardiac filling, reducing central venous pressure, and maximal cardiac output, and competitively impairs arterial oxygen delivery to exercising skeletal muscle. At prolonged submaximal intensities when muscle blood flow and oxygen consumption are often not significantly changed relative to a more temperate environment, high skin temperatures likely influence the perception of fatigue via alterations in afferent feedback (Nybo et al, 2011). The most serious heat related syndrome, is designated by a severely elevated core temperature and failure of an individual’s sweating mechanisms (Coris et al, 2004)
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