By Nick Tumminello
It is widely believed among exercise enthusiasts and fitness professionals alike that not only does cardio have minimal effects on skeletal muscle size, but also that it actually causes us to lose our hard-earned muscle. This is important to note because unless someone is training for an endurance sport, the majority of people are doing cardio to help them burn some extra calories in order to accelerate fat loss and show off their lean muscle. Remember: There’s weight loss and there’s fat loss. When people say they want to lose weight, they mean they want to lose fat, because you certainly don’t want to lose lean muscle.
That said, a 2014 study published in Exercise and Sport Sciences Reviews demonstrated that aerobic (cardio) exercise acutely and chronically alters protein metabolism and induces skeletal muscle hypertrophy, and can also serve as an effective countermeasure for populations prone to muscle loss.1 Another earlier study had found that aerobic exercise created improvements in lean muscle and aerobic capacity.2
Additionally, a 2012 study published in the International Journal of Sports Medicine found that adding low-impact aerobic exercise, such as cycling, will not jeopardize improvements in lean muscle mass.3 Not to mention that aerobic training increases your aerobic fitness, and, as said above, also helps you burn more calories to accelerate the fat loss process.
Now, we must keep these study results in perspective because they involved untrained individuals. So, this question is: What impact does cardio have on muscle for trained individuals? After all, fitness professionals often do bouts of cardio while prepping for their shows and are able to maintain lean muscle mass while doing so.
Polarized Training: Hard-Easy Cardio
Put simply, “polarized training” is a training concept used in the endurance training world that involves training either at low intensity (aerobic) work or high intensity (anaerobic work), but keeps the moderate training time between these extremes relatively small.
The research shows that polarized training seems to be a more effective approach at improving aerobic performance than emphasizing medium-intensity work.4 For example, a 2013 study published in the International Journal of Sports Physiology and Performance found that the group using polarized training improved their 10-kilometer race times by 41 seconds more than the group that emphasized more moderate (between high-intensity and low-intensity) training. Interestingly, the high-intensity training time was about the same for both groups. The only thing that differed was how much time was spent in the low- and moderate-intensity ranges.5
Polarized training is a battle-tested concept used in the endurance training world. But it can also be adapted by non-endurance athletes who are simply looking to incorporate some cardio training along with strength training to increase aerobic capacity and (mainly) to accelerate fat loss while maintaining lean muscle.
Combining Polarized Training with Undulating Strength Training
For a trained individual (i.e., someone who currently exercises) who’s looking to lose fat while also maintaining or even building muscle, strength training is a must. That said, a 2002 study published in the Journal of Strength and Conditioning Research compared linear periodization and daily undulating periodization for strength gains and found that making program alterations on a daily basis was more effective in making improvements to lean muscle mass than doing so every four weeks.6
Additionally, other more recent studies have not only also found that daily intensity and volume variations was more effective than weekly volume variations for increases in maximal strength, but using daily undulating periodization also may lead to greater gains in lean muscle mass.7,8,9 So the strength training portion of your workouts should mix up set/rep schemes— for instance, one day using 2-3 sets of 12-15 reps per exercise and another day doing 4-5 sets of 6-8 reps per exercise.
Now, because of this, the strength-training portion of your strength workouts will take longer than others, as it takes less time to perform 2 sets of 15 reps than it does to perform 4 sets of 6 reps. This is where polarized training comes in, and fits together with your undulating strength training perfectly.
Polarized Training Protocols
Below are the two types of hard-easy, cardio-conditioning methods you can perform in order to incorporate polarized training (after your strength training) into your workouts:
Bike Intervals: You’ll do these as the hard, anaerobic training portion of your polarized training. Using a medium resistance level, pedal as fast as you can for 15-20 seconds, then pedal lightly (as active recovery) for 40-45 seconds, equaling one interval per minute. Perform 9-12 rounds with a 3-5 warm-up (prior to starting) and a three- to five-minute cool-down (after finishing your last interval. If you do 9 interval than use a five-minute warm-up and cool-down, and if you do 12 interval, then use only a three-minute warm-up and cool-down. That’s a total of 18-19 minutes.
Elliptical Trainer or Treadmill: This will be your steady state, easy, aerobic training portion of your polarized training. Work at roughly 70 percent of your maximum heart rate for approximately 30-40 minutes.
When using the polarized training in conjunction with strength training as described here, the type of cardio-conditioning you do corresponds to the set/rep scheme used in the preceding strength training portion of the workout. In that, on the days where you spend the most time on the strength-training portion, which are the workouts where you do the highest amount of sets (4-5 sets each of exercise), you’ll do the hard portion of your polarized training since it takes the least amount of time of the cardio-conditioning protocols. In contrast, on the days where you do the least amount of sets (2-3 sets per exercise), which is are shorter strength-training sessions, you’ll perform the easy, steady-state cardio portion of your polarized training because it takes the longest of the cardio-conditioning protocols.
In short, polarized training uses an undulating cardio-conditioning (i.e., easy-hard) model just like undulating the strength training. On the days where your strength training workouts are the longest, your cardio-conditioning activities are the shortest and vice versa. Using both methods in conjunction not only keeps your workout time consistent, but it also varies your workout activities, which keeps things fresh, more interesting, and, as the research demonstrates, also more effective.
A Quick Word on Diet
When discussing fat loss, I want to make it clear that fat loss is determined by burning more calories each day than you consume. And, there are two ways to create a caloric deficit— eat fewer calories and increase your activity level to burn more calories. And, since we’re talking about training with the goal of losing fat while keeping the lean muscle— if you’re not obese, maybe just a bit overweight, or you’re already fairly lean and simply looking to lose that extra bit of fat, a large caloric deficit will generally make you lose some lean muscle even with strength training and adequate protein.10,11
So, in order to achieve fat loss without lean muscle loss, the goal is to be in a caloric deficit without starving yourself. Make sure your diet delivers plenty of protein, and focus your exercise efforts on performing regular strength training, and you can use the polarized training strategies described in this article to complement it.
Nick Tumminello is the owner of Performance University in Fort Lauderdale, Florida. He’s also the author of the new book Strength Training for Fat Loss and the DVD by the same name. For More information visit www.NickTumminello.com.
1. Adam R Konopka, Matthew P Harber. Skeletal Muscle Hypertrophy after Aerobic Exercise Training. Exerc Sport Sci Rev. 2014 Apr;42(2):53-61.
2. Harber MP, et al. Aerobic exercise training induces skeletal muscle hypertrophy and age-dependent adaptations in myofiber function in young and older men. J Appl Physiol (1985). 2012 Nov;113(9):1495-504
3. Mikkola J, Rusko H, et al. Neuromuscular and cardiovascular adaptations during concurrent strength and endurance training in untrained men. Int J Sports Med. 2012 Sep;33(9):702-10.
4. Neal CM, et al. Six weeks of a polarized training-intensity distribution leads to greater physiological and performance adaptations than a threshold model in trained cyclists. J Appl Physiol (1985). 2013 Feb 15;114(4):461-71.
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10. Willis et al., Effects of aerobic and/or resistance training on body mass and fat mass in overweight or obese adults. J App Phys., vol. 113 no. 12: 1831-1837; 2012
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