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Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance
Martin J. Gibala1, Jonathan P. Little1, Martin van Essen1, Geoffrey P. Wilkin1, Kirsten A. Burgomaster1, Adeel Safdar2, Sandeep Raha2 and Mark A. Tarnopolsky2
http://jp.physoc.org/content/575/3/901.long
Abstract
Brief, intense exercise training may induce metabolic and performance adaptations comparable to traditional endurance training. However, no study has directly compared these diverse training strategies in a standardized manner. We therefore examined changes in exercise capacity and molecular and cellular adaptations in skeletal muscle after low volume sprint-interval training (SIT) and high volume endurance training (ET). Sixteen active men (21 ± 1 years, ) were assigned to a SIT or ET group (n = 8 each) and performed six training sessions over 14 days. Each session consisted of either four to six repeats of 30 s ‘all out’ cycling at ∼250% with 4 min recovery (SIT) or 90–120 min continuous cycling at ∼65% (ET). Training time commitment over 2 weeks was ∼2.5 h for SIT and ∼10.5 h for ET, and total training volume was ∼90% lower for SIT versus ET (∼630 versus ∼6500 kJ). Training decreased the time required to complete 50 and 750 kJ cycling time trials, with no difference between groups (main effects, P ≤ 0.05). Biopsy samples obtained before and after training revealed similar increases in muscle oxidative capacity, as reflected by the maximal activity of cytochrome c oxidase (COX) and COX subunits II and IV protein content (main effects, P ≤ 0.05), but COX II and IV mRNAs were unchanged. Training-induced increases in muscle buffering capacity and glycogen content were also similar between groups (main effects, P ≤ 0.05). Given the large difference in training volume, these data demonstrate that SIT is a time-efficient strategy to induce rapid adaptations in skeletal muscle and exercise performance that are comparable to ET in young active men.
Regular endurance training induces numerous physiological adaptations that facilitate improved exercise capacity, i.e. the ability to sustain a given submaximal workload for a longer period of time or achieve a higher average power output over a fixed distance or time (Coyle, 1995; Hawley, 2002). One of the most prominent adaptations to training is a change in skeletal muscle substrate metabolism (Holloszy & Coyle, 1984). For example, even a short period of endurance training (5–7 days) increases glycogen availability but reduces the rate of glycogen catabolism during matched-work exercise (Green et al. 1992; Chesley et al. 1996), resulting in improved endurance capacity (Green et al. 1995). Training-induced shifts in substrate utilization are classically attributed to the improved respiratory control sensitivity that results from an increase in mitochondrial density, as reflected by changes in the maximal activity or protein content of enzymes in the tricarboxylic acid cycle and electron transport chain (Saltin & Gollnick, 1983; Holloszy & Coyle, 1984). However, other factors must also contribute to the training response, as shown by studies that show metabolic (Green et al. 1992; Clark et al. 2004) or performance adaptations (Coyle et al. 1988; Weston et al. 1997) despite no change in muscle oxidative capacity.
In contrast to traditional endurance training (ET), high-intensity sprint interval training (SIT) is generally thought to have less of an effect on muscle oxidative capacity, substrate utilization and endurance performance (Gleeson, 2000; Kubukeli et al. 2002). However, SIT increases the maximal activities of mitochondrial enzymes (Henriksson & Reitman, 1976; Saltin et al. 1976; Burgomaster et al. 2005), reduces glycogen utilization and lactate accumulation during matched-work exercise (Harmer et al. 2000; Clark et al. 2004; Burgomaster et al. 2006) and improves performance during tasks that primarily rely on aerobic metabolism (Burgomaster et al. 2005; Burgomaster et al. 2006; Eddy et al. 1977). SIT may also be more effective than ET for improving other important determinants of endurance performance, such as muscle buffering capacity (Weston et al. 1997; Edge et al. 2006). Low volume SIT may therefore represent a time-efficient strategy to induce muscle and performance adaptations similar to high volume ET (Coyle, 2005). However, no study has directly compared these diverse training approaches in a standardized manner.
The unique purpose of the present study was to compare changes in exercise capacity and molecular and cellular adaptations in skeletal muscle after low volume SIT and high volume ET. The SIT protocol was based on recent work from our laboratory (Burgomaster et al. 2005, 2006) and consisted of six sessions of brief, repeated ‘all out’ 30 s cycling efforts, interspersed with a short recovery, over 14 days. The ET protocol was modelled after work by others (Green et al. 1992; Spina et al. 1996) and consisted of six sessions of 90–120 min of moderate intensity cycling exercise, with 1–2 days of recovery interspersed between training sessions. As a result, subjects in both groups performed the same number of training sessions on the same days with the same number of recovery days; however, total training volume was ∼90% lower in the SIT group. Needle biopsy samples were obtained before and after training to examine changes in muscle factors related to exercise tolerance, including muscle oxidative capacity and buffering capacity (Hawley, 2002). Performance tests included 50 kJ and 750 kJ cycling time trials, which required ∼2 min and ∼1 h to complete, respectively, and thus differed considerably in the relative energy contribution from oxidative and non-oxidative metabolism. We hypothesized that both SIT and ET would increase muscle oxidative capacity and 750 kJ time trial performance, given the major contribution from aerobic metabolism during this task. In contrast, we hypothesized that SIT but not ET would increase muscle buffering capacity and 50 kJ time trial performance given the large contribution from non-oxidative metabolism during this task.
In conclusion, the most striking finding from the present study was that two very diverse forms of training induced remarkably similar changes in exercise capacity and selected muscle adaptations that are related to exercise tolerance. Given the markedly lower training volume in the SIT group, our results suggest that intense interval training is indeed a time-efficient strategy to induce rapid muscle and performance adaptations comparable to traditional endurance training. Additional research is warranted to clarify the effect of different acute exercise ‘impulses’ on molecular signalling events in human skeletal muscle, and the precise time course and mechanisms responsible for the contraction-induced changes that facilitate the training adaptation.
Thought it would be good for discussion. I realize the brevity of the study but it does lend itself to some pretty cool findings.
Martin J. Gibala1, Jonathan P. Little1, Martin van Essen1, Geoffrey P. Wilkin1, Kirsten A. Burgomaster1, Adeel Safdar2, Sandeep Raha2 and Mark A. Tarnopolsky2
http://jp.physoc.org/content/575/3/901.long
Abstract
Brief, intense exercise training may induce metabolic and performance adaptations comparable to traditional endurance training. However, no study has directly compared these diverse training strategies in a standardized manner. We therefore examined changes in exercise capacity and molecular and cellular adaptations in skeletal muscle after low volume sprint-interval training (SIT) and high volume endurance training (ET). Sixteen active men (21 ± 1 years, ) were assigned to a SIT or ET group (n = 8 each) and performed six training sessions over 14 days. Each session consisted of either four to six repeats of 30 s ‘all out’ cycling at ∼250% with 4 min recovery (SIT) or 90–120 min continuous cycling at ∼65% (ET). Training time commitment over 2 weeks was ∼2.5 h for SIT and ∼10.5 h for ET, and total training volume was ∼90% lower for SIT versus ET (∼630 versus ∼6500 kJ). Training decreased the time required to complete 50 and 750 kJ cycling time trials, with no difference between groups (main effects, P ≤ 0.05). Biopsy samples obtained before and after training revealed similar increases in muscle oxidative capacity, as reflected by the maximal activity of cytochrome c oxidase (COX) and COX subunits II and IV protein content (main effects, P ≤ 0.05), but COX II and IV mRNAs were unchanged. Training-induced increases in muscle buffering capacity and glycogen content were also similar between groups (main effects, P ≤ 0.05). Given the large difference in training volume, these data demonstrate that SIT is a time-efficient strategy to induce rapid adaptations in skeletal muscle and exercise performance that are comparable to ET in young active men.
Regular endurance training induces numerous physiological adaptations that facilitate improved exercise capacity, i.e. the ability to sustain a given submaximal workload for a longer period of time or achieve a higher average power output over a fixed distance or time (Coyle, 1995; Hawley, 2002). One of the most prominent adaptations to training is a change in skeletal muscle substrate metabolism (Holloszy & Coyle, 1984). For example, even a short period of endurance training (5–7 days) increases glycogen availability but reduces the rate of glycogen catabolism during matched-work exercise (Green et al. 1992; Chesley et al. 1996), resulting in improved endurance capacity (Green et al. 1995). Training-induced shifts in substrate utilization are classically attributed to the improved respiratory control sensitivity that results from an increase in mitochondrial density, as reflected by changes in the maximal activity or protein content of enzymes in the tricarboxylic acid cycle and electron transport chain (Saltin & Gollnick, 1983; Holloszy & Coyle, 1984). However, other factors must also contribute to the training response, as shown by studies that show metabolic (Green et al. 1992; Clark et al. 2004) or performance adaptations (Coyle et al. 1988; Weston et al. 1997) despite no change in muscle oxidative capacity.
In contrast to traditional endurance training (ET), high-intensity sprint interval training (SIT) is generally thought to have less of an effect on muscle oxidative capacity, substrate utilization and endurance performance (Gleeson, 2000; Kubukeli et al. 2002). However, SIT increases the maximal activities of mitochondrial enzymes (Henriksson & Reitman, 1976; Saltin et al. 1976; Burgomaster et al. 2005), reduces glycogen utilization and lactate accumulation during matched-work exercise (Harmer et al. 2000; Clark et al. 2004; Burgomaster et al. 2006) and improves performance during tasks that primarily rely on aerobic metabolism (Burgomaster et al. 2005; Burgomaster et al. 2006; Eddy et al. 1977). SIT may also be more effective than ET for improving other important determinants of endurance performance, such as muscle buffering capacity (Weston et al. 1997; Edge et al. 2006). Low volume SIT may therefore represent a time-efficient strategy to induce muscle and performance adaptations similar to high volume ET (Coyle, 2005). However, no study has directly compared these diverse training approaches in a standardized manner.
The unique purpose of the present study was to compare changes in exercise capacity and molecular and cellular adaptations in skeletal muscle after low volume SIT and high volume ET. The SIT protocol was based on recent work from our laboratory (Burgomaster et al. 2005, 2006) and consisted of six sessions of brief, repeated ‘all out’ 30 s cycling efforts, interspersed with a short recovery, over 14 days. The ET protocol was modelled after work by others (Green et al. 1992; Spina et al. 1996) and consisted of six sessions of 90–120 min of moderate intensity cycling exercise, with 1–2 days of recovery interspersed between training sessions. As a result, subjects in both groups performed the same number of training sessions on the same days with the same number of recovery days; however, total training volume was ∼90% lower in the SIT group. Needle biopsy samples were obtained before and after training to examine changes in muscle factors related to exercise tolerance, including muscle oxidative capacity and buffering capacity (Hawley, 2002). Performance tests included 50 kJ and 750 kJ cycling time trials, which required ∼2 min and ∼1 h to complete, respectively, and thus differed considerably in the relative energy contribution from oxidative and non-oxidative metabolism. We hypothesized that both SIT and ET would increase muscle oxidative capacity and 750 kJ time trial performance, given the major contribution from aerobic metabolism during this task. In contrast, we hypothesized that SIT but not ET would increase muscle buffering capacity and 50 kJ time trial performance given the large contribution from non-oxidative metabolism during this task.
In conclusion, the most striking finding from the present study was that two very diverse forms of training induced remarkably similar changes in exercise capacity and selected muscle adaptations that are related to exercise tolerance. Given the markedly lower training volume in the SIT group, our results suggest that intense interval training is indeed a time-efficient strategy to induce rapid muscle and performance adaptations comparable to traditional endurance training. Additional research is warranted to clarify the effect of different acute exercise ‘impulses’ on molecular signalling events in human skeletal muscle, and the precise time course and mechanisms responsible for the contraction-induced changes that facilitate the training adaptation.
Thought it would be good for discussion. I realize the brevity of the study but it does lend itself to some pretty cool findings.
