Concurrent Strength and Endurance Training
It's that time of year again when the debate on whether or not endurance athletes should lift weights begins. Both sides will toss out research and personal experience as evidence that it does or doesn't do the endurance athlete any good. I tend to come down on the side that it is beneficial, but with limitations.
Most of the research indicates that weight lifting does improve aerobic endurance performance, primarily by boosting economy rather than aerobic capacity/VO2max [1-5]. Not all research finds benefits, however [6,7]. I should point that while my 20-year research archive only includes two studies that found no benefit from strength training for endurance athletes, journals are less likely to publish research that reports no positive change in the conclusion. So while the research appears to be tilted toward lifting weights as a way of racing faster we may not be seeing the whole picture.
So it really isn't the research that causes me to come down on the side of strength for endurance athletes, it's my experience from 20 years of working with athletes of all abilities. But I do agree with the positive-finding research that the main reason for this benefit is improved economy.
What's "economy"? Let's put it in the context of the 3 most basic predictors of success in endurance sports--a large aerobic capacity, lactate threshold at a high percentage of aerobic capacity and economical movement. Improving any of these three will benefit performance in endurance sports. The latter-economy-essentially has to do with how much energy is wasted-or not wasted-during exercise.
How can energy be wasted during exercise? One way to waste energy is to use high levels of glycogen (carbohydrate-based fuel) during submaximal effort. It's sort of like the fuel economy rating of your car. Some cars are gas guzzlers and others are very efficient in their use of petrol. The fuel source you would like to primarily use during exercise is fat. How much fat you burn relative to glycogen during exercise at any intensity is a decent indicator of how economical--and fit--you are. Teaching your body to spare glycogen and preferentially use fat for fuel is one of the purposes of endurance training, especially in the Base period.
How can the body become better at using fat for fuel? There are a few ways, but let's look at one that has to do with strength work. The more the workload is done by slow twitch (type 1) muscles as opposed to fast twitch (type 2a and 2b) muscles the more fat you use as a percentage of the total energy expenditure.
So how can you get the type 1 muscles to carry more of the workload? I'm glad you asked. The stronger the type 1 muscles are the greater the percentage of the workload they can carry while you bike, run, swim, cross-country ski or do whatever your endurance sport involves. You can make these muscles stronger in many different ways--by training on hilly courses, by increasing the drag resistance in some way during workouts (for example, swimming while wearing a T-shirt or running with a parachute attached), and/or by lifting weights. If you go the latter route the exercises you do need to closely mimic the movements of your sport. Biceps curls will not make you a more economical runner.
Will weight lifting help every athlete become more economical and therefore faster? Nope. I've coached a few endurance athletes who came to their sport with a long history of body building or power lifting. These athletes had plenty of strength. They needed less. Athletes who are the peak of performance probably won't benefit either. If I took a Kenyan runner who had just won the New York City Marathon and put him on a weight lifting program for several weeks it's doubtful he would be a better runner. But if someone who was a complete novice--say to cycling--lifted weights doing cycling-related strength exercises for several weeks he or she would undoubtedly improve cycling performance without even turning the cranks once. Most of us fall between these extremes. And most of us will improve our endurance performances by lifting weights. My experience tells me this is so.
1. Hickson RC, et al. 1988. Potential for strength and endurance training to amplify endurance performance. J Apply Physiol 65(5):2285-2290.
2. Hoff J, et al. 1999. Maximal strength training improves work economy in trained female cross-country skiers. Med Sci Sports Exerc 31(6):870-877.
3. Johnston RE, et al. 1995. Strength training in female distance runners: Impact on running economy. Med Sci Sports Exerc 27(5):S47.
4. Tanaka H and Swensen T. 1988. Impact of resistance training on endurance performance. A new form of cross training? Sports Med 25(3):191-200.
5. Marcinik EJ, et al. 1991. Effects of strength training on lactate threshold and endurance performance. Med Sci Sports Exerc 23(6):739-743.
6. Bishop D, et al. 1977. The influence of resistance training on endurance cyclists. Med Sci Sports Exerc (29(5):S1502.
7. Bishop D, et al. 1999. The effects of strength training on endurance performance and muscle characteristics. Med Sci Sports Exerc 31(6):886-891.