Effect of 3 weeks of detraining on the resting metabolic rate and body composition of trained males

Abstract

Objective: To examine the hypothesis that detraining decreases the resting metabolic rate (RMR) of long-term exercisers. Design: Eight pairs of subjects were matched for age, mass and training volume. They were then randomly allocated to either a control group (continue normal training) or detraining group (stop normal training but continue activities of daily living). Setting: Exercise Physiology Laboratory, The Flinders University of South Australia. Subjects: Sixteen male subjects (age 23.1 AE 4.7 y (s.d.); mass 73.73 AE 8.9 kg; V Ç O 2max 60.2 AE 6.3 ml. kg 71 . min 71 ; height 180.3 AE 5.0 cm; body fat 14.6 AE 5.4%) were selected from a pool of respondents to our advertisements. Interventions: Each pair of subjects was measured before and after a 3-week experimental period. Results: Two (groups) 6 3 (2-, 3-and 4-compartment body composition models) ANOVAs were conducted on the difference between the pre-and post-treatment scores for percentage body fat, fat-free mass (FFM) and relative RMR (kJ.kg FFM 71 .h 71 ). No signi®cant between-group differences were identi®ed except for the detraining group's small decrease in FFM (0.7 kg, P 0.05). The main effects for body composition model were all signi®cant; but the overall differences between the multicompartment models and the 2-compartment one were less than their technical errors of measurement. No signi®cant interaction (P 0.51) resulted from a 2 6 2 ANOVA on the pre-and post-treatment absolute RMR data for the control (315.2 and 311.9 kJah) and detraining groups (325.4 and 325.5 kJah). Conclusions: 3-weeks detraining is not associated with a decrease in RMR (kJah, kJ.kg FFM 71 .h 71 ) in trained males; hence, our data do not support a potentiation of the RMR via exercise training. The greater sensitivity of the multicompartment models to detect changes in body composition was of marginal value.

Cambios de la composición corporal tras un periodo de desentrenamiento deportivo

“…Los cambios significativos del porcentaje de grasa corporal total tras el DT están en concordancia con los datos aportados por otros autores en diversas modalidades deportivas y tras periodos de DT (3,4,6,9,14). El ligerísimo aumento no significativo de la MME podría ser debido a la asociación del ACT con la masa muscular y sus componentes tanto extra como intracelular que se observa tras el DT, habiéndose descrito modelos de regresión múltiple de los cambios del peso corporal a través de cambios del AEC que explicarían un 55% de la varianza en el cambio del peso corporal (13).…”

“…Un periodo de DT puede producir cambios de la masa grasa (MG) y de la masa libre de grasa (MLG); sin embargo, los cambios de la MLG son difíciles de evaluar con el método clásico de dos componentes (14). Por ejemplo, el análisis individual de algunos componentes de la MLG puede ayudar a explicar cambios asociados al proceso de entrenamiento.…”

“…Utilizando modelos de CC multicompartimental para evaluar los componentes de la MLG después de un periodo de desentrenamiento, LaForgia detectó pequeñas alteraciones hídricas que en ocasiones pueden ser significativas (14). Por el contrario, en otro estudio no fue posible detectar la pérdida de fluidos corporales tras un entrenamiento, tanto con el control de las variaciones del peso corporal como por medio de medidas de ACT, AEC y AIC mediante BIA (17).…”

Impact of indexing resting metabolic rate against fat-free mass determined by different body composition models

“…Hydrodensitometry has been the method of choice for the majority of cross-sectional and longitudinal studies that have attempted to determine the link between exercise status and RMR independent of FFM. Only a small number of cross-sectional (Smith et al, 1997(Smith et al, , 1999Withers et al, 1998b) Impact of indexing resting metabolic rate J LaForgia et al and longitudinal Westerterp et al, 1992;LaForgia et al, 1999) studies have employed the more valid multicompartment models. The robustness of the conclusions reached by those studies, which utilised hydrodensitometry, is therefore diminished given that small but physiologically significant (5-10%) differences in RMR resulting from exercise training may be masked or falsely created due to errors in estimating FFM.…”

“…While all these studies were generally robust in their experimental designs and controls for the measurement of RMR, the majority have employed twocompartment body composition models that are generally prone to significant errors in the determination of the FFM. Only three studies Westerterp et al, 1992;LaForgia et al, 1999) utilised more valid multicompartment body composition models.…”