Sunday, August 2, 2015

From BodyPump to HIIT, From Weight Lifting to Cardio - How Much Energy & Fat Do You Burn During & After Your Workouts and How do PWO Carbs or Protein Affect This

BodyPump is a fast paced workout with barbells. Light(er) weights, high reps, loud music and a drill instructor... if you know one, you'll know all of these group based "resistance training" workouts.
Sunday and time for a brief review of the latest exercise-related publications. Today, I picked two studies that took a closer look at something I would never suggest you'd consider a primary measure of the quality of your training: The energy expenditure during and after your workouts.

While exercise and the exercise-induced increase in energy-expenditure is an important pillar of diet (+ exercise) induced weight loss. The dietary component is what makes you lose weight, while the exercise component is meant to (a) maximize the retention of lean muscle tissue and (b) improve your overall fitness and health. If you're just "working out to burn energy" you're destined to fail; not least because you will never be able to tell exactly how many kcals you've "left in the gym". And beware: Especially while dieting, it's usually much less than you think ;-)
Read more about exercise-related studies at the SuppVersity

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  • People overestimate the energetic demands of "intense" exercise (Berthiaume. 2015) - In view of the fact that everyone knows the (inaccurate) rule of thumb that says that the amount of energy (in kcal) you expend when you're jogging is roughly your body weight times 10 (it's actually rather body weight times 7, unless you're running really fast, by the way), it's not surprising that Berthiaume et al.'s latest study shows that their subjects, 40 healthy men and women (age: 31.7±5.8 years, body mass index [BMI]: 24±2.6 kg/m²), significantly overestimated the amount of energy they expended during a (perceived) "intense" BodyPump(TM) workout.
    Figure 1: Young, healthy BodyPump practitioners overestimate the energetic demands of this kind of equipment based group workouts by over 36% (Berthiaume. 2015).
    Instead of the 394.1±116 kcal, the subjects thought they'd burned, the scientists measurements yielded an average energy expenditure of only 250.3±67.8 kcal during the 60 minute workout. Now, that's not really a problem if do BodyPump, because you like group workouts like these. In view of the fact that the typical clientele of programs like these tends to charge the energy they expend during workouts against the energy from extra food they'd like to eat (BIG mistake, learn why), this may be problematic.
    Figure 2: Just a reminder: The energy expenditure (kcal per kg of body weight per hour) due to body weight exercises calculated based on oxygen uptake during the exercises (traditional) or during the rest periods has been shown to be rather under- than overestimated (Vezina. 2014 | read more)
    Now, you may remember the results of Vezina's 2014 study (see Figure 2 and previous article). In said paper they used a much more precise method to arrive at the actual energy expenditure. In Berthiaume's study, a simple SenseWear armband was used. That's not the "traditional calc." in Figure 2 that proved to be so unreliable in Vezina's study, but it may still suffer from the same shortcomings when it comes to measuring anaerobic vs. aerobic energy expenditure. It would thus be prudent to be at least somewhat skeptical of the exactness of Berthiaume's results.
  • Exercise type and post-workout supplementation influence post-exercise resting energy expenditure and respiratory exchange ratio (Wingfield. 2015) - I know, I have written about EPOC, which is actually nothing else than the total post-exercise energy expenditure in relation to the respiratory exchange ratio, repeatedly. There is a reason, though, that the latest study from the University of North Carolina still made it into the SuppVersity news: It compared six exercise sessions, consisting of three exercise modalities and two acute nutritional interventions - that's extraordinary, for sure.
    • AEE - aerobic endurance exercise - 30-min on the treadmill at 45% to 55% of the heart rate reserve), high-intensity interval running 
    • HIIT - ten rounds of a 60-s treadmill run at 85% to 95% HRR with a 60-s passive rest period), and 
    • HIRT - high-intensity resistance training consisting of leg presses and bench presses, lunges, shoulder presses, biceps curls, and triceps extensions using free weights for three sets of 6RM to 8RM followed by a 20- to 30-s rest for each set of a given exercise and 2.5 min between each exercise 
    • CHO and PRO (25 g of CHO (maltodextrin) or PRO (whey isolate) mixed with 6 oz of water in an opaque bottle. 
    With its s randomized, crossover, double-blind design, the study is also pretty well-powered, even though it had only twenty female, recreationally active participants (mean ± SD; age 24.6 ± 3.9 years; height 164.4 ± 6.6 cm; weight 62.7 ± 6.6 kg).
    Figure 3: Overview of the study design (Wingfield. 2015).
    Next to the post-exercise resting energy expenditure (REE) and respiratory rate (RER), which were analyzed via indirect calorimetry at baseline, immediately post (IP), 30 minutes (30 min) post, and 60 minutes (60 min) post exercise, the scientists obtained salivary samples, as well (both didn't change sign.). The latter were used to determine estradiol-β-17 and cortisol levels before the workouts. To exclude any influence of dietary changes, the subjects were asked to eat diets similar to those they had consumed when they wrote their 3-day food logs at the beginning of the study. Practically speaking, this meant that, on average, subjects ingested 2,078.7 ± 679.9 kcal, 253.7 ± 97.6 g CHO (approximately 48.8% CHO), 84.3 ± 29.9 g PRO (approximately 16.2% PRO), and 80.9 ± 36.7 g of fat (approximately 35.0% fat) per day.
    Figure 4: Only the HIIT modality yielded sign. inter-group differences as far as the resting energy expenditure is concerned. Even those were very transient, though, and disappeared 30 min after the workout (Wingfield. 2015).
    Interestingly, a statistical significant effect for the resting energy expenditure (REE) was observed only in the HIIT, yet not in the HIRT trial (Figure 4, A). This is a result you may not have expected based on the assumption that any form of intense activity (like resistance training in this case) should have some sort of "afterburn" effect.
Cortisol is not your enemy - at least in the short run: As expected the hardest workout, the HIIT workout, produced the most significant increase in cortisol. The change was still not statistically significant, but I decided to mention it anyway, in order to take the chance and remind you of the fact that cortisol is a glucocorticoid that will not just gnaw away your muscles (it does so if it's chronically elevated), but is also involved in a host of beneficial processes including acute increases in performance and the facilitation of body fat loss (learn more).
  • What is less surprising is the relatively small, but "significant" (statistically, only!) increase in REE in response to protein vs. carbohydrate (Figure 4, B). So, protein is thermogenic even after a workout. Unfortunately, the increase in energy expenditure and the increase in fatty oxidation as signified by the reduced respiratory exchange ratio in Figure 5 B are way too small to be of any practical relevance.
    Figure 5: Effect of exercise modality and CHO vs. PRO supplement on the respiratory exchange ratio (RER); lower values indicate greater fat and lower carbohydrate oxidation (Wingfield. 2015).
    Eventually, the same can be said of the decrease in RER (=increase in fatty oxidation) in response to the HIIT and the increase in RER (=decrease in fatty acid oxidation) in response to the HIRT regimen. Both are statistically significant and look large enough to be relevant. When all is said and done, it does yet not really matter if you burn fat directly or glucose first. Whether you lose or gain body fat is after all a matter of the total energy balance over days and weeks, and not the fatty acid oxidation during and 60 minutes after your workouts.
So, what did we learn today? I guess the most important message is that even if it would make sense to charge the energy you expend at the gym against the amount of energy you consume in form of foods, you would fail miserably, because your estimation of how many kcals you've actually "left at the gym" are going to be hilariously inaccurate.

Five Good Reasons Why At Least 50% of Your 2015 'Cardio' Training Should Be High Intensity Interval Training (HIIT) | more
Against that background the results of the Wingfield study are still interesting, but of highly questionable practical value. Your decision whether you do steady state medium intensity cardio, resistance training or high intensity interval training should always be based on your training goals, not the energetic demands of the workouts. In that, fitter individuals (like yourself?) will see better results with high intensity interval training than classic cardio - assuming their training goal are increases in cardiovascular fitness. To maintain the fitness you have, steady state cardio can obviously still be an option; and weight training + optional protein supplements are the perfect choice for anyone who's interested in being and looking fit | Comment!
  • Berthiaume, M. P., et al. "Energy expenditure during the group exercise course BodypumpTM in young healthy individuals." The Journal of sports medicine and physical fitness 55.6 (2015): 563.
  • Vezina, Jesse W., et al. "An Examination of the Differences Between Two Methods of Estimating Energy Expenditure in Resistance Training Activities." Journal of strength and conditioning research/National Strength & Conditioning Association (2014).
  • Wingfield, et al. "The acute effect of exercise modality and nutrition manipulations on post-exercise resting energy expenditure and respiratory exchange ratio in women: a randomized trial." Sports Med Open. (2015)