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Concurrent Resistance Training and Aerobic Training:
The Problem and the Science Behind the Solution

The Problem Resistance training provides numerous and important health benefits through multiple mechanisms that may reduce the risks for diabetes, heart disease, possibly some cancers, and disabilities. There is much more extensive and long-standing evidence, however, about the benefits of aerobic training and cardiovascular fitness and disease risk reduction, particularly for reducing the risks of heart disease and for premature death from heart disease. What has always been tricky for people primarily interested in resistance training is how to incorporate aerobic training into an overall program without undermining strength development or hypertrophy (gaining muscle mass). The evidence shows that reaching some modest level of cardiorespiratory fitness can substantially reduce your risk of heart disease and early death even in the face of other prominent risk factors such as a family history of heart disease, high blood cholesterol, and high blood pressure1. I've tried almost everything under the sun from long distance running to very brief, super high intensity interval training. There has never, however, been any combination ("concurrent") of resistance training and aerobic training that seemed to optimally work. Whatever I devised and in whatever arrangement such as doing resistance training and aerobic training on the same or alternate days just didn't seem to work well over an extended time. Something was always not quite right and that even pertains to my more recent use of the brief, prescriptive Graded Exercise Protocol (GXP) for aerobic training described on this site. My problems - and perhaps yours - with concurrent training are not unique. It's an area that has been researched for many years. The Science Reviews of studies that have examined how aerobic training when combined in the same training program with resistance training can interfere with strength gains and hypertrophy (muscle mass) have pointed out that there is a great deal of inconsistency in this area of research. Sometimes strength gains and hypertrophy are blunted and sometimes they're not. The studies though are difficult to compare because across studies the aerobic and resistance training protocols have used different frequencies, intensities, and volume, training has been on the same day or alternate days, resistance training may or may not precede aerobic training, there may be different rest periods between resistance and aerobic training, and participants with different characteristics have been used. Theorists who have postulated such rationales for interference as acute or chronic fatigue, overtraining, or more basically, hormonal mechanisms, are not only left with an inconsistently done set of studies to try to fit into their theories, but they also need to explain why some studies showed interference and some did not. Docherty and Sporer have recently attempted in an extensive review article to advance the science by postulating specific physiological mechanisms affected by different training protocols that can predict when there will and will not be interference between aerobic and resistance training2. They then saw if their predictions fit some recent studies that have shown no or minimal interference. Throughout their article, the authors' insights and conclusions provide some important training guidelines. Docherty and Sporer noted that aerobic training to increase maximum oxygen consumption and hence the body's ability to transport and use oxygen is dependent upon both a central component involving adaptations in the cardiopulmonary system and a peripheral component involving adaptations in muscle tissues. Central and peripheral adaptations are, in turn, dependent upon different mechanisms. It does appear that the higher the intensity of the stimulus used to increase maximum oxygen consumption (e.g., high intensity interval training), the greater the increase in oxygen consumption. However, the location of the adaptation to aerobic training may shift depending upon the intensity of the stimulus. At lower levels of intensity, it appears that most of the adaptations occur centrally. With higher intensity training, more adaptations occur peripherally. Docherty and Sporer noted that research suggests that training at between 70% to 80% of VO2max (70% to 80% of heart rate reserve; about 80% to 85% of maximum heart rate; just slightly below the anaerobic threshold) results in maximal contractile force in the heart and thus maximizes central adaptations important for health benefits. These findings are critical and suggest how concurrent training can be optimized. If you're using aerobic training to favorably influence your health through central adaptations, there may be no reason to train at levels that will result in more peripheral adaptations. The ability to perform at higher levels (e.g., run, bike, or swim very fast) does require training at high levels of intensity and specific peripheral adaptations, but such performance levels are not the goal of most people. I know that's not one of my goals. Aerobic training at very high intensities through its effects on mechanisms associated with peripheral adaptations may be the cause of blunting of strength gains and hypertrophy when aerobic training is done along with resistance training. Docherty and Sporer then discussed the mechanisms that appear involved in increasing strength and hypertrophy. The basic theory holds that high intensity aerobic training such as interval training affects specific mechanisms in peripheral adaptations such as those involved in increasing a muscle's oxidative capacity while a resistance training protocol for hypertrophy would try to increase protein synthesis and also stress the anaerobic energy system. The combination of the two training protocols is literally trying to force the muscles to adapt in very different ways. However, adaptations to steady state aerobic training below the anaerobic threshold may be primarily central and have little or no interference with strength or hypertrophy since different mechanisms are involved. The authors next reviewed several relatively recent studies where concurrent training was done in order to see if the interference model they developed was supported by the outcomes of these investigations. Although there was not a perfect fit to the model, it did appear that steady state training below the anaerobic threshold does not compromise strength gains. There are not yet enough data on hypertrophy to draw similar conclusions but this is likely to be the case. The Solution Strength athletes and bodybuilders may be great at high intensity interval training, but such training may be contraindicated if our goals involve maximizing strength and muscle mass while doing just enough aerobic training to protect our health and prevent disease It appears that training just below the anaerobic threshold, for example doing the several to five-minute work part in the Graded Exercise Protocol (GXP) at that level, is likely to provide health benefits associated with increased transport and use of oxygen through central adaptations and have minimal or no compromising effects on strength and hypertrophy. Thus, if your primary reasons for doing aerobic training revolve around health, there is a simple, efficient, relatively stress free way to do aerobic training that will allow you to still maximize strength and most likely, hypertrophy. So, given that I've been doing the GXP two to three times per week for over a year, what was I doing wrong that still created obvious interference with resistance training? It's really quite simple and once again exercise science had the answer. While really good endurance athletes can train just below their lactate threshold at 80% and even 85% of maximum oxygen consumption (VO2max; about 80% to 85% of heart rate reserve, and about 90% of HRmax), those of us not training for endurance events can not train at those levels and still be in relative steady state. As suggested by Docherty and Sporer and supported by research3, a top level for steady state training is likely to be about 75% of VO2max and heart rate reserve - the same level that optimizes central adaptations to the cardiopulmonary system. Even with the GXP I was still training at too high a level of intensity and experiencing interference (namely soreness form mechanical stress) with my resistance training. Using the heart rate reserve method, I now do a 5-minute graded warm-up to 70% of heart rate reserve, a five-minute steady state work segment at 75%, and then do a 5-minute cooldown that reverses the warm-up. You can easily experiment and find the appropriate level for your steady state work piece. It's a level that is challenging but one you could maintain for longer than the 5 minutes (perhaps 7 or 8 minutes or more) and where your heart rate is literally holding steady or only very slowing climbing upward. Using an old but still important heuristic, it's a level where you still can talk ("the talk test"). I've found that this slight alteration in my aerobic training is paying big dividends. I no longer experience any soreness or interference from aerobic training. It's also made aerobic training alot more flexible because I can do it almost anytime. I can do aerobic training after resistance training, or the next day, early in the day or late in the day. It doesn't seem to matter. I still make aerobic training challenging and interesting by having certain goals that I want to achieve over time for the 5-minute work part of the GXP that will indicate a good level of cardiovascular fitness. But, armed with information from exercise science I'll achieve this fitness goal without interfering with resistance training. References Williams P T. Physical fitness and activity as separate heart disease risk factors: a meta-analysis. Medicine and Science in Sports and Exercise. 2001: 33: 754-761 Docherty D, Sporer B. A proposed model for examining the interference phenomenon between concurrent aerobic and strength training. Sports Medicine. 2000; 30: 385-394. McArdle WD, Katch FI, Katch VL. Exercise Physiology: Energy, Nutrition, and Human Performance. (4th edition). 1996; Baltimore: Williams & Wilkins.