Effects of strength training on bioenergetics parameters determined at velocity corresponding to maximal oxygen uptake in endurance runners

Summary

Objectives

The present study analyzes the impact of a strength training program on bioenergetics parameters determined at velocity corresponding to maximal oxygen uptake ($\text{v}\dot{\text{V}}{\text{O}}_2\max$).

Methods

Sixteen recreational long-distance runners were divided into strength training (STG, n = 9) and control (CG, n = 7) groups. Before and after 8 weeks, the volunteers performed: maximal incremental treadmill test, constant-speed running at pre-training $\text{v}\dot{\text{V}}{\text{O}}_2\max$, and maximum dynamic strength test (1RM). Energy cost of running (ECr), and aerobic (A_MET) and anaerobic (AN_MET) metabolism contributions were estimated at $\text{v}\dot{\text{V}}{\text{O}}_2\max$.

Results

No differences were observed at baseline between groups (P > 0.05). After experimental period, there was an increase in 1RM for STG (27 ± 18%, P = 0.008), but not for CG (P > 0.05). The changes in ECr (pre = 0.254 ± 0.038 vs. post = 0.255 ± 0.037 kJ·m⁻¹), A_MET (pre = 191.5 ± 26.2 vs. post = 193.0 ± 31.7 kJ), and AN_MET (pre = 20.9 ± 6.4 vs. post = 21.0 ± 5.7 kJ) were not significant different (P > 0.05) to STG; as well as to CG (ECr - pre = 0.260 ± 0.046 vs. post = 0.259 ± 0.034 kJ·m⁻¹, A_MET - pre = 209.7 ± 30.2 vs. post = 203.3 ± 26.6 kJ, and AN_MET - pre = 19.3 ± 6.4 vs. post = 23.9 ± 4.6 kJ).

Conclusions

These findings suggest that 8 weeks strength training improved the maximum dynamic strength and did not alter bioenergetics parameters measured at $\text{v}\dot{\text{V}}{\text{O}}_2\max$ in recreational endurance runners.

Résumé

Objectif

La présente étude analyse l’impact d’un programme d’entraînement en force sur paramètres bioénergétiques du jogging déterminés à la vitesse correspondant à l’absorption maximale d’oxygène ($\text{v}\dot{\text{V}}{\text{O}}_2\max$).

Méthodes

Seize coureurs récréatifs à longue distance ont été divisés en groupes musculaires (STG, n = 9) et de contrôle (CG, n = 7). Avant et après 8 semaines, les bénévoles ont effectué : un test de tapis roulant d’augmentation maximal, un jogging à vitesse constante à pré-entraînement $\text{v}\dot{\text{V}}{\text{O}}_2\max$ et un test de résistance dynamique maximum (1RM). Le coût énergétique de faire du jogging (ECr) et les contributions au métabolisme aérobie (A_MET) et anaérobie (AN_MET) ont été estimés à $\text{v}\dot{\text{V}}{\text{O}}_2\max$.

Résultats

Aucune différence n’a été observée à la base entre les groupes (p > 0,05). Après la période expérimentale, il y a eu une augmentation de 1RM pour STG (27 ± 18 %, p = 0,008), mais pas pour CG (p > 0,05). Les changements dans ECr (pré = 0,254 ± 0,038 vs post = 0,255 ± 0,037 kJ·m⁻¹), A_MET (pré = 191,5 ± 26,2 vs post = 193,0 ± 31,7 kJ) et AN_MET (pré = 20,9 ± 6,4 vs post = 21,0 ± 5,7 kJ) n’étaient pas significatifs (p > 0,05) à STG ; ainsi que CG (ECr - pre = 0,260 ± 0,046 vs post = 0,259 ± 0,034 kJ·m⁻¹, A_MET - pré = 209,7 ± 30,2 vs post = 203,3 ± 26,6 kJ, et AN_MET - pré = 19,3 ± 6,4 vs poste = 23,9 ± 4,6 kJ).

Conclusions

Ces résultats suggèrent que l’entraînement en force de 8 semaines a amélioré la force dynamique maximale et n’a pas modifié les paramètres de bioénergie mesurés à $\text{v}\dot{\text{V}}{\text{O}}_2\max$ dans les coureurs d’endurance récréative.

Introduction

It is well known that during long-distance events the athletes must be able to maintain relatively high velocities over the course of a race [1]. Previous studies have reported that the capacity to sustain a high percentage (90–100%) of the maximal oxygen uptake ($\dot{\text{V}}{\text{O}}_2\max$) can be considered one important factor for success in long-distance events [2], [3]. Consistent results have suggested that the ability to sustain the velocity at 100% of $\text{v}\dot{\text{V}}{\text{O}}_2\max$ ($\text{v}\dot{\text{V}}{\text{O}}_2\max$) is highly related to energy system contributions [4], [5]. Recently, It has been demonstrated that the contributions of the aerobic (A_MET) and anaerobic (AN_MET) systems were, respectively, 80 and 20% during a run performed at $\text{v}\dot{\text{V}}{\text{O}}_2\max$ [6]. These findings suggest that A_MET is the predominant energy system during exercise performed at $\text{v}\dot{\text{V}}{\text{O}}_2\max$, but that AN_MET could provide a significant portion of the muscle's ATP supply.

Over the past three decades, it has been shown that the ability of the skeletal muscle to produce force is another key component for success in short-term endurance performance (∼ 6-min) [1], [7]. This has lead the analysis of the impact of strength training programs (ST) on endurance performance become a popular research topic in sport sciences [7], [8], [9], [10]. It has been proposed that the improved strength after a ST could decrease the energy cost of running (ECr) and increases AN_MET during high-intensity running. For instance, Støren et al. [10] found that 8 weeks of ST enhanced the efficiency of the stretch-shortening cycle by increasing store and restitution of elastic energy during running, leading to an improvement of the ECr. Mikkola et al. [11] observed a significant increase in anaerobic performance after 8 weeks ST in endurance runners and confirmed previous findings suggesting that ST induces metabolic adaptations that contribute to an increased ability to provide a rapid resynthesis of muscle's ATP via anaerobic metabolism [12]. This adaptation could be especially relevant at phases of the race where the highest speeds are reached and energy demand may exceed the aerobic capacity.

Although these studies have elucidated some critical aspects concerning the beneficial effects of the ST on endurance performance, it is important to consider others that suggested the existence of the interference effect when attempting to perform the strength and endurance trainings concurrently. Despite not a universal finding [1], [7], it has been reported that ST may produce attenuated gain in aerobic capacity when compared with endurance training alone [13], [14]. It is well recognized that skeletal muscle is a highly malleable tissue and therefore, the metabolic and structural adaptations provided by athletic training are specific to the mode of performed exercise [13]. It has been shown that endurance training increases the oxidative capacity in type I fibers, while the ST promotes hypertrophy and stimulates anaerobic glycolysis preferentially in type II fibers [12], [15]. It is known that type II fibers are more fatigable and have a lower oxidative capacity than type I fibers [16], which could result in a compromised gain in aerobic capacity with the addition of ST in endurance training routines [13], [14], [17].

The abovementioned interference effect could be particularly important for bioenergetics parameters determined during the exercise performed at $\text{v}\dot{\text{V}}{\text{O}}_2\max$, because during high-intensity aerobic exercise (i.e. > 70% of $\dot{\text{V}}{\text{O}}_2\max$) there is an increased recruitment of the fast twitch fibers [16]. However, the analysis of the influence of the ST on ECr, A_MET, and AN_MET at $\text{v}\dot{\text{V}}{\text{O}}_2\max$ has been limited to a unique study, which used a 6-week ST program composed by only one strength exercise (i.e., half-squat) [8]. These training characteristics could provide an insufficient metabolic stimulus for peripheral adaptations. Therefore, whether ST changes bioenergetics parameters determined during high-intensity exercise, particularly at $\text{v}\dot{\text{V}}{\text{O}}_2\max$, still remains to be determined. Thus, the main purpose of the present study was to analyze the impact of an 8 weeks ST program on energy system contributions and ECr determined at $\text{v}\dot{\text{V}}{\text{O}}_2\max$. Considering previous studies suggesting a possible interference effect of the ST in endurance exercise [13], [14], it was hypothesized that ST could impair some bioenergetics parameters (i.e., aerobic system contribution) determined at $\text{v}\dot{\text{V}}{\text{O}}_2\max$ in endurance runners.