The effects of single versus twice daily short term heat acclimation on heat strain and 3000m running performance in hot, humid conditions

Abstract

The effects of single versus twice daily short term heat acclimation on heat strain and 3000m running performance in hot, humid conditions, Journal of Thermal Biology, http://dx.doi.org/10. 1016/j.jtherbio.2016.01.001 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. .min -1 2peak , once daily for 4d (SDHA) and twice daily for 2d (TDHA), in 35°C, 60% relative humidity (RH), and once daily for 4d (CON) in 21°C, 40% RH. Participants completed a pre-and post-intervention 5 km treadmill run trial in 30°C, 60% RH, where the first 2 2peak and the final 3 km was selfpaced.No statistically significant interaction effects occurred within-or between-groups over the 2-4d intervention. While within-group differences were found in physiological and perceptual measures during the fixed intensity trial post-intervention, they did not statistically differ between-groups. Similarly, TDHA (-36±34s [+3.5%]) and SDHA (-26±28s [+2.8%]) groups improved 3 km performances (p=0.35), but did not differ from CON (-6±44s [+0.6%]). This is the first study to investigate the effects of HA twice daily and compare it with traditional single session per day STHA. These STHA protocols may have the ability to induce partial adaptive responses to heat stress and possibly enhance performance in environmentally challenging conditions, however, future development is warranted to optimise the administration to provide a potent stimuli for heat adaptation in athletic and military personnel within a rapid regime.

Once- and twice-daily heat acclimation confer similar heat adaptations, inflammatory responses and exercise tolerance improvements

“…Our data indicate no advantage but more importantly, no disadvantage of nonconsecutive TDHA over consecutive ODHA, agreeing with our previous STHA investigation (Willmott et al. ). Further to this, as outlined above, these observations are true even when the session duration is 60 min (this study), as opposed to 90–100 min which has been previously described as preferable (Racinais et al.…”

“…Seminal work by Lind and Bass (Lind and Bass 1963) demonstrated the benefits of continuous, once-daily HA (i.e., 100-min sessions), as opposed to longer and shorter intermittent times (e.g., twice-daily, 2 9 50 min), which contributed to duration recommendations for optimal heat adaptations . Our data indicate no advantage but more importantly, no disadvantage of nonconsecutive TDHA over consecutive ODHA, agreeing with our previous STHA investigation (Willmott et al 2016). Further to this, as outlined above, these observations are true even when the session duration is 60 min (this study), as opposed to 90-100 min which has been previously described as preferable .…”

Physiological and perceptual responses to exercising in restrictive heat loss attire with use of an upper-body sauna suit in temperate and hot conditions

“…~1.4-2.0 W.kg -1 ) elicit rates of heat storage, that increase Tre by 1.0-1.9°C.hr -1 in a range of participants including trained athletes and recreationally active individuals, and both males (Gibson et al 2015b;Willmott et al 2016Willmott et al , 2017James et al 2016) and females (Mee et al 2015. These data, which are similar to the current experiment (Table 1 and 2, Figure 1 and 3) give confidence that "overdressing" by utilising upper-body vinyl suits, or perhaps additional layers of regular clothing can elicit comparable physiological responses to experiments where heat adaptation has occurred.…”

Short-term heat acclimation prior to a multi-day desert ultra-marathon improves physiological and psychological responses without compromising immune status

“…The numerous physiological advantages induced by HA have been discussed in detail elsewhere (Sawka et al, 2011;Garrett et al, 2014;Taylor, 2014;Racinais et al, 2015). Short-term HA (STHA) can confer up to 75% of physiological adaptations typically seen following long-term HA (LTHA) (Pandolf, 1998), and appears effective across a range of populations (Costa et al, 2014;Garrett et al, 2014;Gibson et al, 2015a;Mee et al, 2015a;Neal et al, 2015;Willmott et al, 2016). Ultra-endurance athletes may benefit from STHA prior to competition (Costa et al, 2014), particularly when optimal controlled hyperthermia methods (Taylor, 2014;Racinais et al, 2015) are implemented, due to reduced training volume for equal physiological (Gibson et al, 2015a) and cellular adaptations (Gibson et al, 2015b).…”