|That's how your healthy "exercise snack" could look like - just make sure your boss knows that you're doing it to make sure you stay healthy and don't miss a day at the office ;-)|
Now the obvious questions are (1) what exactly is a "brief, intense exercise snack" and (2) what can you expect from having it before a meal?
To answer these questions we have to take a closer look at the experimental protocol the scientists used. In order to investigate whether three small doses of intense exercise before meals (aka ‘exercise snacking’) would result in better postprandial blood glucose control than a single bout of (energy-matched) prolonged, continuous, moderate-intensity exercise in individuals with insulin resistance, Francois et al. had their, 16 volunteers who met the inclusion criteria of being aged 18–55 years and not being medicated for blood glucose or high blood pressure participate in all of the following experimental conditions:
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- Exercise snacking (ES) -- Six 1 min work bouts, consisting of walking at 90% HRmaxwith 1 min recovery (slow walk) between each, were completed 30 min before breakfast, lunch and dinner. The total energy cost for CONT and ES were matched (based on metabolic calculations inV˙O2max test). The exercise was undertaken on an incline treadmill, with HR and RPE measured at the end of each interval.
- Composite exercise snacking (CES) -- Six 1 min work bouts alternating between walking and resistance-based exercise were performed, with 1 min recovery between each bout, 30 min before breakfast, lunch and dinner. The total number of 1 min work bouts balanced the ES regime. The resistance based exercise bouts were undertaken using resistance bands (as many reps as possible within 60 s), and walking was at 90% HRmax on an incline treadmill, with HR and RPE measured at the end of each interval. The resistance-band exercises worked the musculature of the arms, back and core. All exercise sessions included a 5min warm-up period and a 3 min cool-down period at a self-selected intensity on a treadmill.
As you can see in Figure 1, the exercise snacking protocols lowered the mean postprandial glucose (PPG) following breakfast (by 1.0±0.9 mmol/l [mean ±SD]) and dinner (by 0.5±0.8 mmol/l) but not following lunch (−0.0±0.7 mmol/l). Previous studies with somewhat more intense regimen showed improvement irrespective of the time of the day (Devlin. 1985), though. If you don't stick to running 1.2k, but hop on a treadmill for 3-5 sets of 1 min all out running or a tabata style workout, you should see improvements on every meal.
"For their first trial, participants consumed their habitual diet under free-living conditions while completing a 5-day dietary log. The diet was then replicated for the second and third trials, so that timing, composition and quantity of all food and drink consumed were matched between the three trials. Subsequent dietary analysis (Kai-culator Enhanced 2010 Food Composition Database v0.43; Dunedin, New Zealand) for the main days of interest is shown in Table 1. Physical activity levels for the three trials were monitored using pedometers and activity logs." (Francois. 2014)
Table 1: Total daily macronutrient intake for the participants’first experimental trial (Francois. 2014)
|Figure 1: The 3 h PPG AUC for breakfast (a), lunch (b) and dinner (c) on the exercise day for CONT, ES and CES trials. Data are means ± SD,n=9. *p<0.05 for ES vs CONT for breakfast and dinner PPG AUC (Francois. 2014)|
- Devlin, J. T., and E. S. Horton. "Effects of prior high-intensity exercise on glucose metabolism in normal and insulin-resistant men." Diabetes 34.10 (1985): 973-979.
- Francois, Monique E., et al. "‘Exercise snacks’ before meals: a novel strategy to improve glycaemic control in individuals with insulin resistance." Diabetologia (2014): 1-9.
- World Health Organization. "Global recommendations on physical activity for health." (2010).