Long article on benefits & disadvantages of doing both cardio and resistance training:
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">The first and most important finding is that aerobic exercise — provided that you don't do too much of it — does not interfere with gains in muscle size. In fact, several studies show that it can actually help you build muscle faster.
In one 10-week trial carried in the journal Medicine and Science in Sports and Exercise, researchers assigned a group of 30 healthy (but untrained) male subjects to one of three groups [12].
• Group one lifted weights for three days each week. The training program involved eight exercises. Four sets of 5-7 repetitions were completed for each exercise. The first set served as a warm-up. Subsequent sets were taken to the point of muscular failure. Subjects rested for 60-90 seconds between sets.
• Group two completed three sessions of moderate-intensity aerobic exercise (cycling at 70% heart rate reserve) each week. Each workout lasted 50 minutes.
• Subjects in group three combined the two programs. Both workouts were performed on the same day, with the order of strength and aerobic exercise rotated each training day. Subjects rested for 10-20 minutes between workouts.
Combining aerobic and resistance exercise didn't impair muscle growth. In fact, growth in the quadriceps (the group of muscles on the front of your thighs) was greatest in the group combining the two workouts. What's more, when muscle fibers in the thigh were measured, those in the combined group were larger than those in the resistance-only group.
The same research group published similar findings several years previously [11]. One group of men trained with weights (4 sets per exercise, 5-7 repetitions per set), while an aerobics-only group performed 50 minutes of cycling at 70% of heart rate reserve. The combined group did both workouts in a single session. Both groups trained three times per week.
The men lifting weights made virtually identical strength gains in both the squat and bench press, irrespective of whether they did aerobic exercise. Gains in muscle mass were slightly greater in the combined group compared to those lifting weights.
A team of strength-training experts from Finland report similar findings [4]. The scientists, based at the University of Jyväskylä, tested the effect of 21 weeks of aerobic exercise on muscle size, strength and power in a group of healthy men [4]. One group lifted weights twice each week, while group two performed the same workout but did an extra 30-60 minutes of cycling on separate days twice per week.
The result? Aerobic exercise had no negative effect on muscle size or strength. Once again, muscle growth in the legs was greatest in the group combining aerobic and resistance exercise.
Research published in the Journal of Applied Physiology also shows that aerobic exercise has a beneficial effect on muscle growth [3]. Thirty physically active healthy men were assigned to one of three groups for 10 weeks. The men in one group spent three days a week running or jogging (25-40 minutes at 65-85% of their age-derived maximum heart rate), while a resistance-only group trained with weights. A combined group performed both routines on the same day of the week, always doing the weight training first.
The resistance exercise program involved a combination of free weights and fixed resistance machines. The program was divided into upper-body exercises (performed on Monday), lower-body exercises (performed on Wednesday), and both upper- and lower-body exercises (performed on Friday).
During the first two weeks of the program, subjects performed 10-15 repetitions per set, with three sets per exercise. During the final eight weeks, the resistance was set so that failure to lift the weight occurred at 10-12 repetitions on the first set, 8-10 repetitions on the second set, and 4-8 repetitions on the third set.
As with the previous studies, the combined group gained the most, completing the study with an extra seven pounds of muscle. The resistance-only group made slightly slower progress, averaging a five-pound gain by week ten.
So, what do these studies tell us?
Firstly, the addition of 1-2 hours of moderate-intensity aerobic exercise (such as cycling at 65-85% of your age-derived maximum heart rate) to a three-day per week weight training program does not impede gains in muscle size. On the contrary, it appears to help rather than hinder growth. The question is, how?
Both resistance and aerobic exercise increase the ability of your body to remove sugar and other nutrients from the blood [15]. However, both forms of exercise work in a different way. When you train with weights, you gain muscle. And it's this extra muscle that removes these nutrients from your blood.
Aerobic exercise, on the other hand, enhances nutrient uptake independently of changes in muscle mass, increasing both the number and function of glucose transporters. These help to transport glucose (sugar) from the blood into the muscle. It's possible that the rise in nutrient uptake translates into greater muscle growth.
Aerobic exercise also increases capillary density. Capillaries deliver oxygen, nutrients (such as protein, carbohydrate, and fat), and hormones (such as testosterone) to muscle cells. All are vital for muscle growth. Capillaries also remove heat and metabolic by-products from the active muscle tissue. The number of capillaries per muscle fiber increases to a greater extent after 12 weeks of combined training, compared to resistance exercise alone [18].
What's more, aerobic exercise has the potential to improve the quality of your weight training workouts. Studies show that the fitter you are, the faster your body can recover between sets when you're training with weights [17].
Muscle strength
On the flip side, there's some bad news for anyone wanting to gain strength and power. Although these studies show greater muscle growth with a combination of resistance and aerobic exercise, improvements in strength and power — in almost all cases — were reduced [3, 4, 11, 12].
In the early stages of an exercise program, differences in strength gains between resistance-only and combined training aren't easy to detect, usually becoming more pronounced after 9-10 weeks of training [5].
However, simultaneous training compromises gains in strength only when both modes of training use the same muscles. Some evidence for this comes from a research group based at Pennsylvania State University [9]. This study is especially interesting because all subjects were members of the US Army, and very physically active. What's more, the aerobic exercise program incorporated high-intensity interval exercise, which is a lot more physically demanding than conventional forms of aerobic exercise.
Training took place four days per week (Monday, Tuesday, Thursday, and Friday). The group combining both aerobic and resistance exercise trained twice per day, running in the morning and lifting weights 5-6 hours later. In other words, this was a very demanding program followed by a group of highly motivated individuals.
Although gains in lower body strength were reduced in the groups combining resistance and aerobic exercise, gains in upper body strength were similar in both the combined and resistance-only group.
Endurance exercise
But, that's only half the story. While concurrent aerobic and resistance exercise tends to limit gains in strength, the addition of explosive strength training to an endurance-training program actually enhances endurance performance [1, 6, 7, 8, 13].
A good example comes from research published in the Journal of Applied Physiology [14]. A group of elite cross-country runners was assigned to one of two groups. Group one replaced roughly one-third of their regular endurance-training program (which involved an average of 8-9 hours per week of exercise) with explosive-type strength training. This involved various sprints, jumping exercises, and leg exercises using light weights but fast lifting speeds. Group two continued with their regular training program.
The group using the explosive-type strength training improved their best five-kilometer (roughly three miles) race time without a change in their aerobic fitness. Instead, the faster race times were due to improvements in the neuromuscular system (the "chain of command" that transmits signals from the brain to the muscle). This reduced the energy cost of running — known as running economy.
Although strength and power are often confused, the two aren't the same thing. Strength is the ability to generate force, while maximal strength is the maximal force generated in a given action, such as the bench press. Power, on the other hand, refers to the work done per unit of time. It's often measured using the maximum rate of force development, which is a measure of your ability to produce maximal force in minimal time. High rates of force development are necessary for success in "explosive" activities such as sprinting, and throwing.</div>
