In last week’s guest post on muscle building , reader Charlotte raised the issue  of gender differences in exercise benefits. Are men and women the same when it comes to the effects of cardiovascular exercise? What about the most effective ways to burn fat? These were just a few questions that got the comment board going full throttle. Thanks to Charlotte and everyone who contributed their expertise and experience. (It’s what I love about doing MDA!)
So, what about the question of gender? Let me first say that the Primal Blueprint is fully intended for and applicable to both men and women. Sure, women naturally have a higher percentage of body fat and tend to carry it in places where it’s not as readily burned as abdominal fat. It’s true, also, that our relative hormones levels have some influence on our body’s use of fat for fuel, our resting metabolism, and our sensitivity to other hormones key to exercise response. But these gender-based differences have been found to be relatively modest. And ultimately, we are not necessarily trying to be body-builders or runway models, but simply trying to find that mix of diet and exercise that achieves the healthiest levels of low body fat and balanced, useful and well-sculpted muscles for each or our unique bodies.
Our similarities, when it comes to fitness, are much more numerous than our differences. A strength training study out last week highlights this fact. Researchers put to rest  an assumption that women should use a (lighter and) low velocity routine for weight training. What do you know? The traditional routine (heavier load, fewer repetitions) is most effective for building muscle in women. On that subject, it’s important to note that strength training is key to resting metabolism in both sexes. Although men as a whole tend to gain muscle mass more easily than women (the testosterone factor primarily), women have the absolute ability to increase muscle strength and even mass. Weight training is essential in the Primal Blueprint because of the importance of resting metabolism, insulin sensitivity and lean muscle mass for both genders.
What about the role of cardio in fat oxidation? Research suggests that women’s bodies use a higher proportion of fat for fuel than men do during low to moderate intensity exercise, but they may not experience the same level of fat oxidation following exercise. As you know, the Primal Blueprint includes low to moderate intensity exercise as a cornerstone of everyday “active” living. While this kind of exercise is part of the overall Primal Blueprint fitness picture, women seem to benefit more than men in terms of fat oxidation, at least in “real time”.
But that doesn’t mean women don’t derive benefit from moderate-high and high intensity exercise as well. High intensity exercise, while it doesn’t derive as great a percentage of energy from fat, results in greater overall total energy expenditure. In the period following exercise, the body primarily burns fat, and this oxidation is elevated to a higher degree after high intensity aerobic activity.
Earlier this year in More Chronic Cardio Talk , I mentioned a study from the University of New South Wales that compared fat oxidation in women who performed continuous and interval cycling routines. The women who performed interval training (twenty minutes of exercise in which they repeated eight seconds of high intensity “sprint” cycling and twelve seconds of rest) lost three times the body fat as those in the continuous group who performed a consistent cycling routine. (The continuous group worked at a low-moderate 60% capacity.) The researchers associated  the success of the interval training with its associated higher levels of catecholamines, a compound that plays a role in fat oxidation. This makes sense, given the possibility that women’s bodies respond more to the lipolytic role of catecholamines. I’m a firm believer in interval training because of the supporting research and because of the real life impact I see in myself and my clients. And it appears that women, at least in the area of fat oxidation, may again reap the most benefit.
The issue of adrenal burnout and thyroid function came up in the comments last week. I couldn’t agree more with what was said. While high intensity workouts can offer a leg up in terms of fat burning, going overboard can end up putting you in a worse situation over time. The Primal Blueprint takes this risk into account. Regular (traditional) weight training, a substantial dose of low to moderate aerobic activity, and brief sessions of high intensity interval training together should do the trick. If you find that an added boost of high intensity work (say, running or cycling at 80-85% max) provides substantial benefit for you, go ahead and add it as long as it doesn’t exceed 45 minutes or so for the reasons a number of readers mentioned last week (cortisol increase, muscle breakdown, etc.). Then again, you might reap the same benefit by adding more low to moderate activity during the week or adding some high intensity bursts at the end of your other workout days just to boost the post-workout oxidation. That’s where your “experiment of one” keeps you fully tuned to the day-to-day and week-to-week changes in your body.
Thanks to everyone for the great comments, questions, and suggestions. Keep ‘em coming!
Subscribe to Mark’s Daily Apple feeds 
This post was brought to you by the Damage Control Master Formula , independently proven as the most comprehensive high-potency antioxidant multivitamin available anywhere. With the highest antioxidant per dollar value and a complete anti-aging, stress, and cognition profile, the Master Formula is truly the only multivitamin supplement you will ever need. Toss out the drawers full of dozens of different supplements with questionable potency and efficacy and experience the proven Damage Control difference!