Post workout burn

After you’ve finished a workout, your body is not finished working

Heart rate and respiration stay elevated for a while, muscles repair themselves and re-stock their stores of glycogen, your glands pump out increased quantities of ‘repair’ hormones such as cortisol and testosterone, and your nervous system often maintains a higherthan-usual activity state. As a result, even if you spend your recovery period in a deck-chair, your body will continue to expend calories at a greater rate than normal.

 For individuals who are interested in losing weight, this post-exercise calorie burn may help to shed a few extra pounds, so scientists have struggled for years to figure out which type of exercise produces the best follow-up burn. Exercise experts have been fairly certain that strenuous cycling, running and swimming can produce decent post-workout energy expenditures, but they’ve been less confident about strength training. Now, new research carried out at Colorado State University suggests that a strenuous bout of resistance training can produce a post-exercise burn which may in fact be more intense than that produced by traditional ‘aerobic’ workouts.

At Colorado State, a group of students and health-club members participated in a resistance-training workout and a cycling workout on different occasions. The strength-training session consisted of five sets of 10 different exercises (bench presses, bent-over rows, leg extensions, leg curls, military presses, sit-ups, biceps curls, triceps extensions, half-squats and lateral arm raises). The weight for each lift was set at 70 per cent of each individual’s onerepetition maximum, and subjects performed eight to 12 repetitions per set. There were about 500 actual lifts (repetitions) in the overall workout, which lasted for approximately 100 minutes.

The cycling workouts were designed to require about as many calories as the resistance sessions, so subjects pedalled along at an intensity of 50% V02max (65 per cent of maximal heart rate) for an average of 64 minutes. To control for the effects of dietary intake on metabolic rate, all subjects consumed similar meals during the time periods preceding and following the workouts.

During the five-hour period which followed the workouts, calorie burning was significantly higher than normal. The shocker was that calorie expenditure tended to be significantly greater after strength training than after cycling. The difference wasn’t huge – about 24 extra calories burned after strength training – but for individuals who train four times a week this disparity could produce an extra 5000-calorie ‘burn’ over a year. This might equate to about a pound and a half of extra body fat lost by weight trainers compared to cyclists training with similar energy expenditures.

The Colorado State study suggested that weight trainers burn at least six calories per minute as they conduct a vigorous workout, but other studies suggest the expenditures may be even greater – as much as 12 calories per minte when lifting heavy weights with the leg muscles and seven to nine calories per minute for upperbody routines. In addition, resting metabolic rate was slightly above normal almost 15 hours after the strength workout. Thus it appears that resistance training can be beneficial for those who want to burn lots of calories, raise metabolic rates, and lose weight.

However, before you shift from aerobic workouts to strength training in the hope of getting slimmer, bear in mind that it took the Colorado State strength trainers 100 minutes to burn about 600 calories, while the cyclists accomplished the same thing in slightly over 60 minutes. This is remarkable, since the strength session was quite vigorous and the cycling workout was quite light (at just 65 per cent of max heart rate). It’s clear that it’s easier to burn more total calories per minute sitting astride a bicycle than ‘playing the iron game’.

It’s also important to remember that your actual training session – not your post-exercise period – is when you expend most calories. In the Colorado State study, both the cycling and strength-training sessions burned about 600 extra calories, while the excess burns amounted to just 51 calories after weight training and 27 after cycling. In other words, the post-exercise burns were dwarfed by the within-workout expenditures. Thus, if you want to use up a lot more calories and lose weight, your first move is to increase the intensity or duration of your workouts instead of worrying too much about what happens afterwards.

(‘Post-exercise Energy Expenditure in Response to Acute Aerobic or Resistive Exercise’, Intemational Joumal of Sport Nutrition, vol. 4, pp 347-360, 1994)

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