The Temporal Effects of Altitude and Low Energy Availability Manipulation on Resting Metabolic Rate in Female Race Walkers

Abstract

Purpose To investigate the temporal effects of ~1,800 m altitude exposure and energy availability (EA) manipulation on resting metabolic rate (RMR). Methods Twenty elite female race walkers underwent a 3-week training camp at an altitude of ~1,800 m. During the first two weeks, athletes consumed a high EA (HEA) diet of 45 kcal·kg fat free mass (FFM)-1·day-1. During the final week, half the athletes consumed a low EA (LEA) diet of 15 kcal·kg FFM-1·day-1 while the others continued on a HEA diet. Athletes followed individualized training plans throughout the study. To assess the effect of altitude on RMR, athletes in the HEA group had RMR measured at baseline (~580 m) prior to altitude exposure (Pre-alt), at 36-hours (36 h-alt), 2 weeks (Wk2-alt) and 3 weeks into altitude exposure (Wk3-alt), and at 36 hours post-altitude exposure at ~580 m (36 h-post). To assess the effect of LEA exposure on RMR while at altitude, athletes in the LEA group underwent RMR measurements at Pre-alt and before (Wk2-alt) and after the 7-days of LEA (Wk3-alt). Results Compared to Pre-alt, the RMR of HEA athletes was increased at 36 h-alt (+5.3 ± 3.1%; p = 0.026) and Wk2-alt (+4.9 ± 4.9%; p = 0.049), but was no longer elevated at Wk3-alt (+1.7 ± 4.2%; p = 0.850). The RMR of HEA athletes at 36 h-post was lower than all timepoints at altitude (p < 0.05) but was not different from Pre-alt (-3.9 ± 7.2%; p = 0.124). The 7-day period of LEA exposure at altitude did not affect RMR (p = 0.347). Conclusions RMR was transiently increased with ~1,800 m altitude exposure in female athletes and was unaffected by short-term LEA. However, the altitude-induced increase was small (~25-75 kcal/day) and was unlikely to have clinically significant implications for daily energy requirements.