Heat suit training increases hemoglobin mass in elite cross‐country skiers

Abstract

Purpose The primary purpose was to test the effect of heat suit training on hemoglobin mass (Hbmass) in elite cross‐country (XC) skiers. Methods Twenty‐five male XC‐skiers were divided into a group that added 5 × 50 min weekly heat suit training sessions to their regular training (HEAT; n = 13, 23 ± 5 years, 73.9 ± 5.2 kg, 180 ± 6 cm, 76.8 ± 4.6 ml·min−1·kg−1) or to a control group matched for training volume and intensity distribution (CON; n = 12, 23 ± 4 years, 78.4 ± 5.8 kg, 184 ± 4 cm, 75.2 ± 3.4 ml·min−1·kg−1) during the five‐week intervention period. Hbmass, endurance performance and factors determining endurance performance were assessed before and after the intervention. Results HEAT led to 30 g greater Hbmass (95% CI: [8.5, 51.7], p = 0.009) and 157 ml greater red blood cell volume ([29, 285], p = 0.018) post‐intervention, compared to CON when adjusted for baseline values. In contrast, no group differences were observed for changes in work economy, running velocity, and fractional utilization of maximal oxygen uptake (V̇O2max) at 4 mmol·L−1 blood lactate, V̇O2max or 15‐min running distance performance trial during the intervention. Conclusion HEAT induced a larger increase in Hbmass and red blood cell volume after five weeks with five weekly heat suit training sessions than CON, but with no detectable group differences on physiological determinants of endurance performance or actual endurance performance in elite CX skiers.

High or hot—Perspectives on altitude camps and heat‐acclimation training as preparation for prolonged stage races

“…As illustrated by Figure 1 derived from a point-counter point discussion in 2016 in Journal of Physiology 36,37 both 10 days heat-acclimation 32,38 and 14 days with natural heat acclimatization 30 can induce a marked increase in plasma volume, but the PV-expansion in those studies was not associated with a change in peak power or time trial performance in trained cyclists. In opposition to our opponents in the abovementioned pointcounter point discussion 30 and their acclimation study, 33 we found no evidence for short to medium duration heat acclimatization to translate into improved performance in cooler settings, although the athletes had massive improvements in exercise performance tested in the heat. The evidence for "cool performance" transfer effects derived from plasma volume expansion or other acclimation effects achieved via short-medium duration acclimatization protocols are in our opinion still weak (see 36,37 for discussion or this paper 27 for meta-analysis).…”

“…Utilizing the prolonged heat-acclimation approach, accomplished either as part of the training (~1 h per day and at least five times per week) completed in hot climatic chambers 31,34 or via training with superimposed heat stress with increased clothing insulation, 33 we observe systematic increases in Hb-mass both in elite international and national level competitive cyclists (see Figure 2 for individual Hb-mass gains across the range of trained to highly trained athletes in the studies). On average the 5 week heat-training interventions, we have completed elicit a ~3% effect (30 g gain) on total Hb-mass, which is significantly different from matched controls and translate into elevated peak peak-powerpower during incremental testing (delta gain of 18 watt in heat-exposed groups compared to 6 watt in control; p < 0.05 both for the Hb-mass and peak power response).…”

“…The evidence for "cool performance" transfer effects derived from plasma volume expansion or other acclimation effects achieved via short-medium duration acclimatization protocols are in our opinion still weak (see 36,37 for discussion or this paper 27 for meta-analysis). The pointcounter point discussion did, however, prompt us to complete a series of prolonged heat-acclimation studies 31,[33][34][35] with durations of 5 weeks or more to test the idea that allowing sufficient time for adaptation, heat-acclimation and the associated plasma volume expansion would translate into an increased RBC-volume.…”

“…4,27 The abovementioned study by Karlsen et al 29 exemplifying natural acclimatization achieved via ecological exposure was completed as an intervention study where the HEAT-group for 2 week transferred from habitual cool training environment to training in dry heat (~35°C with 2-4 h exposure per day). However, similar physiological adaptations may be induced with shorter (~1 h/day) training in climatic chambers 31,32 or training with increased clothing 33,34 (so-called sweat suit training that hampers heat-dissipation to provoke hyperthermia). From a practical point of view and discussed below the later may be attractive for some athletes as it may induce physiological adaptations comparable to natural exposure and allow the athlete to complete the remaining of the weekly training in cooler conditions.…”

Implications of Heat Stress-induced Metabolic Alterations for Endurance Training

“…Increased RBCV and Hb mass represent critical endurance training adaptations, improving oxygen transport, and contributing to improved VO 2max , a key determinant of endurance performance. Interestingly, when implementing prolonged heat-acclimation protocols (5 weeks) using either environmental chambers [137,138] or 'heat suits' [139]…”