High-intensity Training versus Traditional Exercise Interventions for Promoting Health

Lars Nybo; Emil Sundstrup; Markus D. Jakobsen; Magni Mohr; Therese Hornstrup; Lene Simonsen; Jens Bülow; Morten B. Randers; Jens J. Nielsen; Per Aagaard; Peter Krustrup

Disclosures

Med Sci Sports Exerc. 2010;42(10):1951-1958. 

In This Article

Discussion

The present investigation reveals that INT is an effective training stimulus for improvement of cardiorespiratory fitness and glucose tolerance, and in untrained subjects it may induce a significant reduction in systolic blood pressure. However, in relation to the treatment of hyperlipidemia and obesity, it is less effective than prolonged training, and in contrast to strength training, 12 wk of INT had no impact on muscle mass or indices of skeletal health.

Blood Pressure, Aerobic Fitness, and CV Risk Factors

The present results reveal that brief but intense training has the potential to reduce arterial blood pressure and counteract the development of hypertension. Thus, the group that completed the high-intensity training intervention had a significant reduction in systolic blood pressure and consequently a lowering of the MAP. The 8-mm Hg reduction in systolic pressure was similar to the changes in the MOD and STR groups, whereas diastolic pressure appeared to be less affected in the INT group compared with the MOD group. However, from a statistical perspective, the study included relatively few subjects, and therefore we cannot conclude whether brief intense training is less or equally efficient compared with prolonged moderate-intensity exercise interventions. In contrast, it seems clear that reduction in systolic or MAP after aerobic training is not directly related to the concomitant improvements in cardiorespiratory fitness. Accordingly, the study by Cornelissen et al.[7] supports the findings that reductions in systolic blood pressure are not correlated to changes in V̇O2max because they reported similar reductions in systolic blood pressure after moderate-intensity exercise training and training with a very low intensity, although the low-intensity training had a lower impact on V̇O2max as compared with the moderate-intensity training.[7]

The improvement of maximal oxygen consumption and performance during incremental treadmill running test was superior in the INT group compared with the MOD and STR groups, supporting the notion that the training intensity is more important than the training volume for the development of cardiorespiratory fitness.[33] However, the larger improvement of cardiorespiratory fitness was not accompanied by superior adaptations in relation to metabolic fitness. Thus, CS and HAD activity as well as fat oxidation during walking was not significantly altered in any of the three training groups, and only the MOD group appeared to have an improved capacity for fat oxidation during submaximal running. The lack of significant change in CS and HAD activity is in opposition to previous observations in our laboratory after bicycle[24] and soccer training[19] in subjects with a similar starting level. Considering the relatively low number of subjects, there is a risk of a type II error. However, the divergence may also relate to the different exercise modes because soccer and especially bicycling training may provide a strong stimulus for metabolic changes in vastus lateralis, whereas the training modes investigated in the present study do not appear to be as effective for vastus lateralis oxidative enzyme adaptations.

In contrast to the prolonged training program, the intense intermittent training intervention failed to lower the ratio between total and HDL cholesterol. Intense but short-lasting training therefore seems to be less efficient than prolonged training for improving the plasma lipoprotein-lipid profiles in untrained subjects, and in contrast to the stimuli for cardiorespiratory fitness, it seems that training volume rather than intensity is of importance for the improvement of the plasma lipoprotein-lipid profile.[9] The observed lipoprotein responses may relate to the concomitant changes in the subjects fat percentage, which was lowered in the MOD group but remained unaltered in the INT group. Accordingly, previous training studies have observed correlations between changes in lipoprotein-lipid profile and loss of body fat,[17] and the higher training volume and the larger total energy turnover in MOD compared with INT may explain both the significant loss of body fat and the improved lipoprotein-lipid profile in the MOD group, whereas total energy expenditure may have been insufficient in the INT group. The American College of Sports Medicine concludes that between 150 and 250 min of moderate physical activity per week is needed to counteract weight gain,[8] and although the INT intervention induced a significant increase in the subjects aerobic metabolic capacity, it included only 40 min of training per week, with 20 min of high-intensity running and 20 min of low-intensity warm-up activities. It has been speculated that short-term high-intensity interval training could be a time-efficient strategy for health promotion,[10] and the present results support that such training may influence some health parameters. However, it also demonstrates that in relation to treatment of hyperlipidemia and obesity, a certain training volume is needed, and the present study therefore supports the previously mentioned recommendations from the American College of Sports Medicine.[8,13] Nevertheless, for individuals with the metabolic syndrome and overweight subjects, it appears that an exercise program that includes high-intensity training is more effective than a program that only includes moderate-intensity exercise.[28,30,31] Consequently, the total weekly training time may be reduced to some extent when high-intensity bouts are included, but it appears that a certain volume is needed and that the total energy utilization is also of importance.

Glucose Tolerance

The present results indicate that INT with a relatively low volume was equally efficient to moderate training with a substantially larger total training volume. Previously, Houmard et al.[16] suggested that the total exercise duration should be considered when designing training programs with the intent of improving insulin action. Thus, they observed that exercise prescription that incorporated approximately 170 min of exercise per week improved insulin sensitivity more substantially than a program using only 115 min of exercise per week-both exercise interventions with intensities comparable with the MOD group in the present study. However, recently the same group[2] concluded that although the weekly exercise duration may be of importance for insulin action measured less than 24 h after the last exercise bout, it appears that moderate-intensity exercise and vigorous-intensity exercise appear to result in similar beneficial long-term effects. The present study supports the later conclusion and indicates that when the intensity is close to maximal, as little as 40 min of training per week may result in similar improvements in glucose tolerance as 150 min of moderate intense exercise per week.

Muscle and Bone Mass

Both bone and muscle mass were significantly increased after the strength-training intervention, whereas both these parameters remained unchanged in the INT group as well as in the MOD running group. The observation of increased bone mass after 12 wk of strength training indicates that such training besides being an effective stimulus for muscle growth also provides a significant osteogenic stimulus. Similar effects have been demonstrated by intervention studies, which have included strength training for a prolonged period (in general, 1 yr or more [20]). Longitudinal studies also signify that exercise with a so-called high-impact load may provide an effective osteogenic stimulus. For example, it has been observed that short-term participation in intermittent sports such as soccer training increases bone mineral content,[19] and cross-sectional studies have demonstrated that participants in sports that are characterized by multiple turns, jumps, and short sprints with accelerations and decelerations have higher bone mass and mineral density compared with sedentary subjects or athletes participating in non-weight-bearing or so-called low-impact sports.[12,27] A high strain rate and a large magnitude of ground reaction and muscle forces seem to be important factors for providing the anabolic effect, and the loading pattern in sports that include running at different speeds and in multiple directions appears to be at least as effective as specific strength training.[32] However, the present investigation indicates that a training program with "normal" straight forward running, although performed in interval with a high intensity, does not provide the adequate stimulus for enhancing bone mass or strength. In opposition, a recent cross-sectional study by Rector et al.[27] concluded that that long-term running and resistance training increase BMD compared with cycling, and running may have a greater positive effect on BMD than resistance training. The contradicting observation from the cross-sectional study and the present longitudinal investigation may illustrate the pitfall from drawing conclusions from cross-sectional studies because these may be influenced by other factors than the actual training that the subjects have conducted.

In conclusion, the present study investigated various health effects of brief but very intense exercise training, and the marked improvements in cardiovascular fitness, glucose tolerance, and exercise endurance as well as the lowering of systolic blood pressure put emphasis on the potential benefits of high-intensity training and its ability to improve certain physiological health parameters. However, the intense low-volume training regimen had limitations, and for the short-term intervention period, it was less effective than prolonged training in relation to the treatment of hyperlipidemia and obesity. Furthermore, 12 wk of INT had no impact on muscle mass or leg bone mass, whereas strength training besides increasing the subjects muscle mass also provided a significant osteogenic stimulus that may have both acute and prolonged effects for musculoskeletal health.

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