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"Snacks Training": It takes little to improve his health

A sedentary lifestyle is a global problem that affects more and more adults and children, especially in developed countries. The World Health Organization estimated in 2010 that almost a quarter of adults were physically inactive. Since then, this number has not improved. Now it is clearly established that the cardiorespiratory fitness (generally estimated by VO_2MAX or VO_2Peak) is linked to the risk of all-cause mortality and the risk of cardiovascular diseases. One of the main reasons for not engaging in a regular physical activity is lack of time. However, official recommendations preconize a minimum of 150 minutes per week at moderate intensity (3-6 METs) or 75 minutes weekly at high intensity (> 6 METs), in increments of 10 minutes minimum, in addition to two minimum sessions of resistance training.

This is one of the reasons why High-Intensity Interval Training (HIIT) is so popular with researchers. In fact, it makes it possible to greatly reduce the duration of a workout, to work at higher intensities and to obtain results that are similar to or even greater than those obtained with steady-state training (i.e., moderate and continuous intensity). However, the very high intensity of some protocols is not suitable for everyone. That's why some researchers looked at even more economical solutions in terms of time. But how far is it possible to reduce the duration of training sessions while continuing to benefit from cardiorespiratory gains ?

The Study

To answer this question, Professor Gibala's team (McMaster University, Canada) set up an original protocol by dividing a HIIT workout into 3 sprints, separated by several hours (thus creating 3 micro-workouts, thus the term "snacks training"). For this, the researchers gathered 24 sedentary students without medical problems that they separated into 2 groups: a Control group (CON) that did nothing during the whole duration of the experimental protocol and an Experimental group (EXP) which carried out the protocol. Before and after the protocol, the VO2Peak and peak power (P_Peak, in watts) of all study participants were evaluated on cycle-ergometer. The test consisted of 3 minutes of warm-up at 50 Watts, then the resistance was increased by 1 Watt every 2 seconds until the pedaling rate dropped below 60 RPM, in which case the test was stopped and the VO₂ value measured was considered VO_2Peak (same for P_Peak).

The experimental protocol lasted 6 weeks. During these 6 weeks, the EXP group realized 3 times a day, 3 times a week, a stair climbing of 60 stairs at maximum speed. Each bout was separated by 1 to 4 hours of recovery. Before each bout, a warm-up was made and consisted of 10 Jumping Jacks, 10 Air Squats, 5 lunges on each side and 1 minute walking. The RPE (Rate of Perceived Exertion, Borg scale, between 1 and 10) was evaluated before and after each climb.

Results & Analyzes

The main results of this study show that 3 bouts of 60 steps per day, even with 1 to 4 hours recovery, are enough to allow a significant improvement in VO_2Peak and power of the lower limbs (Figs 1 and 2).

The improvement of the VO_2Peak is still modest with about 5% increase for the experimental group. This small increase was mainly due to the relatively long recovery periods which reduced the metabolic stress. This gain represents on average 91.7 ml / min, that represents for a subject of 70 kg, 1.31 ml/kg/min. Although this value is very low, epidemiological studies have already reported that an increase of 1 ml/kg/min in sedentary over 50 years allowed a 9% decrease in all-cause mortality.

The the lower limbs P_Peak increased by 12% for the experimental group. This implies a sizeable peripheral stimulus from the stair climbing. But this can be also due to the warm-up (done 3 times a day, too).

Practical Applications

This study shows that 3 bouts of 60 steps per day (3 x 20s), spaced by 1 to 4 hours of recovery allow an improvement of the cardiorespiratory fitness in young sedentary students. Although the improvement is minimal compared to more traditional methods of interval training, these results demonstrate that structured physical activity provides benefits regardless of the level at which one begins and even with very little of time.

A previous study of this same group of researchers showed that 3 x 20s stair climbing sessions with 2 minutes of recovery between each climb allowed a gain of about 12% VO_2Peak. Therefore, for a sedentary public who would like to start a regular and structured physical activity, it is quite possible to start with micro-sessions (fragments of a "normal" session) and to obtain gains, then to switch towards more metabolically stressful sessions, and thus greater gains.

References

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