Strength and endurance: training both

Strength training is necessary for building lean muscle mass and increasing longevity. No argument there. But aerobic training – better known as “cardio” - is a necessary component of fitness and fat burning, particularly if your eating habits are less than perfect. Cardio-respiratory training is also critical to longevity because, as a growing body of science suggests, aerobic fitness helps combat all-cause mortality, especially but not limited to, death due to a cardiovascular event. There is no way around it: we must keep our heart muscle strong.

Perhaps you’ve been training hard at the gym several times a week, week in and week out, and going for long runs on your days off, and you’re wondering, “How do I balance my strength training with my aerobic conditioning?” Is it all right to do both on the same day? Or do you run on your “recovery” day? What’s best? What if I want to include high intensity intervals?

If you’re an endurance athlete and a strength athlete, you’ve got your work cut out for you. It’s a lot of training to fit in. And if you’re going to work that hard, you want to get the most bang for your workout buck. Most likely your goal is to improve your strength and performance. To do so, you must push your body beyond its comfort zone. This means overloading your musculoskeletal and cardiovascular systems.

Aerobic training (Cardio-respiratory training)

Aerobic means with oxygen; anaerobic means without oxygen. Aerobic activity tests the ability of the circulatory, respiratory, and muscular systems to supply oxygen during sustained physical exercise. Both aerobic and anaerobic exercise create energy through the process of glycolysis, which is the conversion of glucose into fuel.

Anaerobic Training (Strength training and High Intensity Intervals)

Anaerobic activities such as most types of strength training and high intensity intervals uses a different mechanism to fuel the body. Anaerobic glycolysis can’t be sustained for long. While aerobic exercise uses oxygen to break down glucose, anaerobic exercise uses other, less efficient but faster mechanisms.

Strength training is generally anaerobic and endurance training is aerobic.

If you do strength training say, 3-4 times a week, doing light aerobic activity afterwards is a good way to cool down and clear lactic acid from the blood. But, for best results, endurance activity (exercise lasting more than one hour) on the same day as you lift is not recommended. Save that for your off-days.

When you consider which systems are being stressed when you are lifting weights, you are stressing primarily your musculoskeletal system. When you are endurance training (running, cycling, swimming, etc.) you are stressing primarily your cardiovascular system.

It might seem logical to conclude that you could do both types of training on the same day since you are working different systems. But your nervous system is also involved. The neuromuscular system is under stress during both activities. Skeletal muscles contract and relax, actions controlled by the nervous system, which is composed of nerves called neurons. Any exercise which puts a demand on the muscular system, also puts a demand on the nervous system. The nerves are attached to muscle cells which receive and send signals between the muscles and the brain during physical activity, which means there will be considerable fatigue after strength training and after endurance activities.

For this reason, it may be best to train them on separate days. As for high intensity intervals, they are also best done on a day separate from strength training. What is your experience with combining these two types of training?