[This article originally appeared in the
issue of Northwest Runner
Strength training and endurance training teach your muscles to do very different things. The former requires them to exert very high forces for very brief periods of time, whereas the latter demands more modest forces for much longer periods. So what happens when both types of training are conducted simultaneously? Do they interfere with each other, or, alternatively, can strength training be used to enhance one's endurance?
The answer to this question is not immediately obvious; in theory, training the body for strength could lead to adaptations that either enhance or hinder endurance performance. For example, it is well-known that a traditional weightlifting program leads to muscle hypertrophy, i.e., one's muscles get bigger and stronger. For a typical distance runner, improved muscle power is a good thing, yet increased body weight is not. So the question remains: can this runner benefit from strength training?
To shed some more light on this issue, let's review a few key findings of the last 15 years.
First, Rusko & Bosco (European Journal of Applied Physiology 56: 412-418, 1987) examined the effect of wearing a "weight vest" on the metabolism of trained cross country skiers and distance runners. For four weeks, a group of 12 athletes carried out their normal training and daily activities while wearing vests weighing 9-10% of their body weight, while a vestless control group likewise went about their normal routine. The vest-donning athletes emerged from the study with an improved VO2max (a measure of the body's ability to consume oxygen) and lactate threshold (the exercise intensity at which lactate begins to accumulate in the blood), whereas these values were unchanged in the control subjects.
Second, Hickson et al. (Journal of Applied Physiology 65: 2285-2290, 1988) added a heavy-resistance weight training program to the regular running and cycling workouts of eight duathletes. At the end of the ten-week program, the participants were able to last 11-13% longer in an intense short-term (4- to 8-minute) cycling or running test than they had prior to the weight training, and they lasted 20% longer than before in a longer (60- to 90-minute), less intense cycling test.
Third, Hoff et al. (Medicine and Science in Sports and Exercise 31: 870-877, 1999) examined a group of eight female Norwegian cross-country skiers who in addition to their usual workouts spent nine weeks performing a strength-training exercise designed to simulate the "double-poling" technique used in skiing. By the end of the study, the strength-trained skiers had improved an average of 137% in a short, intense skiing test similar to those conducted on Hickson's duathletes, whereas the control group improved by "only" 58%. (The large improvement seen in the control group was not surprising given that this study was conducted at the start of the skiing season, when both groups were just beginning to train seriously.)
Finally, Paavolainen et al. (Journal of Applied Physiology 86: 1527-1533, 1999) obtained some astounding results from a study of elite Finnish orienteers with 5K times in the 18-minute range. In this study, training volumes (in hours per week) were similar for the experimental group and the control group, but the experimental group spent nearly a third of its training time on "explosive-strength" training sessions consisting of jumping drills, rapid leg-press and knee-extensor exercises, and 20-100m sprints. The rest of this group's training time (and essentially all of the control group's training time) was devoted to traditional endurance workouts, speedwork, and circuit training. After nine weeks of hopping and dashing around like hyperactive sprinters, the strength-trained Finns sliced over 30 seconds off their 5K times, while the control group showed no improvement whatsoever.
Taken together, these studies offer several important insights. The first is that, at least under some circumstances, strength training is indeed beneficial to endurance athletes. I find the Finnish orienteer data particularly exciting, since the experimenters were able to take a group of experienced, well-trained runners and improve their 5K times by over half a minute apiece.
A second point is that strength training is most likely to be effective if it mimics the movements and actions of the athlete's sport. Rusko's weight vest study is perhaps the ultimate example of this; the strength training consisted simply of running and walking with an added load, a very good imitation of normal running. Similarly, the Norwegian skiers used an apparatus that forced their arms to mimic the "double-poling" motion used in skiing. Non-specific strength training, on the other hand, may offer little or no benefit to endurance athletes. For example, Bishop et al. (Medicine and Science in Sports and Exercise 31: 886-91, 1999) found that 12 weeks of high-resistance squat workouts failed to boost the performances of trained female cyclists. The authors concluded that, although they strengthen the legs, heavy-weight squats may not resemble normal cycling enough to improve cycling performance.
We have just seen the importance of doing strength workouts that are relevant to one's sport. A related point is that the "explosive" strength training techniques employed by Paavolainen et al. develop neuromuscular strength without causing the marked muscle hypertrophy characteristic of high-resistance weight training (Hakkinen et al., Acta Physiologica Scandinavica 125: 587-600, 1985). Therefore, high-velocity, low-resistance exercises may help runners get stronger without putting on lots of extra muscle mass.
Finally, we must acknowledge that we don't yet know for sure whether strength training is useful in preparing for running races longer than 5
kilometers. (Although Hickson's weight-trained subjects improved their performance on the prolonged cycling test, they failed to improve their 10K running times.) Thus,
while the above studies show that strength training may give athletes an edge in events lasting four to 20 minutes, its impact on marathon performance is uncertain at