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Science of Sport: Challenging, "Anaerobic" Strength Training Produces Improvements In Aerobic Endurance

It's a Shock to Conventional Ways of Thinking about Training

By Owen Anderson

Recent research indicates that very demanding strength training, the kind of work which utilizes fairly heavy resistance, is likely to lead to major gains in endurance running performance.

At first glance, of course, this proposition would appear to be absurd. After all, heavy-duty strength training revolves around high-load efforts, slow movements, and small numbers of reps. In contrast, competitive endurance running is associated with nothing more than body weight for resistance, relatively quick movements, and incredible numbers of reps (180 to 200 steps per minute, or 6300 to 7000 "reps" in a 35-minute 10K). In addition, high-resistance strength training is carried out for a few seconds at a time, with a relatively low rate of oxygen consumption, whereas 10-K running is usually sustained for 30 or more minutes, with an oxygen consumption rate of more than 90 percent of maximal. How can there be a close connection between anaerobic strength training and aerobic endurance running?

To find out, let's look at the actual research. In a study carried out at the Norwegian University of Science and Technology in Trondheim by Jan Hoff (at right) and his colleagues, 19 cross-country skiers were randomly assigned to either a training group (nine skiers) or a control group (10 athletes). The training-group members carried out three high-resistance, close-to-maximal strength-training sessions per week for eight weeks, while the control athletes conducted their usual strength work with much-lighter resistance; otherwise, the two groups trained in identical fashion (1). The maximal strength training was carried out with a modified cable-pulley apparatus which was designed to simulate the double-poling movements required for cross-country skiing.

For the maximal-strength-training group, about 45 minutes per week out of a total weekly training time of approximately 10 hours were devoted to the pull-downs on the cable-pulley apparatus (thus, each of the three weekly strength-training sessions lasted for about 15 minutes). The beginning intensity for these resistance workouts was set at 85 percent of 1RM, i. e., 85 percent of the resistance which could be lifted (with a pull-down movement) one and only one time; the 1RM was established before the eight-week training period began. When an athlete could perform three sets of six reps @ 85 percent of the original 1RM, the resisting load was increased by three kilograms for the next training session.

As mentioned, control-group members conducted traditional strength training with lighter resistances; both groups averaged close to 10 hours per week of endurance training, which revolved around regular skiing, roller skiing, and running.

After the eight weeks of training, the changes in the maximal-strength-training group were impressive. For one thing, the high-resistance group upped maximal strength (measured on the cable-pulley skiing device) by 10 percent, while the control group failed to boost max strength at all. In addition, the peak muscular force produced when the athletes were working at 80 percent of 1RM increased significantly by 34 percent over the eight weeks for the max-strength athletes but stagnated for the control individuals.

Very importantly, changes in the rate of force development were also significantly different between the groups. The key variable used to assess the rate of force development is something called TPF (time to peak force), which basically quantifies the amount of time required for muscles to reach their highest force production during a movement. As you might expect, very brief TPFs are associated with explosive performances and high rates of motion, while fat TPFs are linked with sluggish movements. Even though the rate of movement utilized in the max-strength training (i. e., during the pull-downs on the modified cable-pulley apparatus) was quite slow (since the resistance, at 85 percent of 1RM, was set so high), the max-strength group reduced TPF by 50 percent at a resistance of 80 percent of 1RM (from 180 down to just 90 milliseconds) and pared down TPF by 60 percent at a resistance of 60 percent of 1RM (from 200 to only 80 milliseconds)!! In other words, it was taking much less time for the max-strength trainers to generate substantial muscular forces.

Meanwhile, the control group failed to improve TPF at 80 percent of 1RM and improved TPF at 60 percent of 1RM by a smaller amount, compared with the max-strength Norsemen. To put it simply, the max-strength trainees were much quicker and more powerful during skiing-specific movements. How about actual performances, though?

No problem: The max-strength skiers upgraded their average time to exhaustion during a very rugged test from 6.5 to 10.2 minutes, a 56-percent upgrade; this test involved working for as long as possible on a ski ergometer at an intensity which produced VO2max (in effect, at vVO2max). Control skiers got better, too (after all, they carried out a lot of skiing and ski rolling during the eight-week study), but their 25-percent improvement was significantly smaller, compared with the gain achieved by the max-trainers.

Despite the whopping expansion of performance, the max-strength athletes enjoyed no positive upswing in VO2max, but they did manage to enhance economy (by 28 percent!) while skiing at an intense pace (control skiers failed to move either VO2max or skiing economy). After the top-end strength training, it was costing the max-strength skiers considerably less oxygen to move along at high-quality speeds.

Why did economy improve in Hoff’s skiers? Most likely, the motor units (collections of muscle cells) involved in the poling action were stronger after the eight weeks of max-strength training. As a result, fewer motor units needed to be recruited to carry out various intensities of work, lowering overall energy (and oxygen) cost. In general, if you can make yourself stronger during the movements involved in your sport, you will need to activate fewer motor units for any specific speed, your economy will be better, and your fatigue-resistance will consequently head north.

What is the explanation for why max strength training – with slow movements – manages to improve TPF, i. e., quickness of force production? When high resistance (i. e., 85 percent of 1RM or more) is utilized during a movement, all or at least most of the motor units involved in the motion are immediately activated in order to handle the heavy load. This includes the so-called high-threshold motor units, the ones which are rather reluctant to get involved in activity. Motor units which contain fast-twitch muscle fibers are high-threshold, and thus the high resistance causes the fast fibers to become highly trained in the movement, increasing the rate at which force is produced.

What if you believe that you are a slow-twitch "slug", with few or no fast-twitch muscles? It is reasonable to argue that the instantaneous, all-the-motor-unit-activation effect (associated with the initiation of a movement against heavy resistance) will enhance your TPF anyway, since all-possible motor units are “in on the action” from the start (they are not recruited gradually as the movement proceeds). Indeed, it is likely that the skiers in Hoff’s study possessed muscles which were composed primarily of slow-twitch cells, and yet Hoff's acolytes upgraded TPF to an incredible degree!

How would you put Hoff’s findings into practice in your own training as a runner? Naturally, pull-downs on a cable apparatus are not going to be the premier movement you want to emphasize. While it is clear that max-strength training works as a means of improving TPF, a “neural component” must be involved in the max-strength work for it to be effective. Just as Hoff’s cable-apparatus movements bore a strong resemblance to the poling motions of cross-country skiing, the strengthening movement(s) you select should be closely allied with the gait cycle of running. If that is not the case, the coordination component of strengthening will be lost, and the effects on TPF, economy, and performance will be considerably smaller, if not non-existent (2).

Squatting is perhaps the top-of-the-line strengthening movement for athletes who run, and so it is reasonable to begin with squats. First, of course, it is important to get a feeling for how much squatting strength you already have. You can experiment in the gym until you find your 1RM for two-leg squatting and then proceed as Hoff’s athletes did, beginning with an attempt at 3 X 6 @ 85 percent of your 1RM and adding two to three additional kilograms of resistance whenever you can actually complete all three sets of six repetitions.

Finding 1RM can be tough for some runners, though (and can also increase the risk of injury), so another approach would be to simply choose a resistance which produces a challenge when you attempt three sets of six reps; this resistance should be pretty close to your current 85-percent-1RM intensity. Once you have managed the full 3 X 6, you can then increase the resistance for the next workout (by approximately 2.5 to five pounds). Two- to three-minute recoveries are fine between sets. Note that it is wise to carry out a warm-up, with 10 minutes or so of jogging, before the squatting actually begins; it is also sensible to perform a warm-up set of squats, with very light resistance, before the three tough sets are actually attempted. You can perform your squats on a light day of running training or before you begin a quality running workout; it is important not to do them when you are fatigued. Over time, you will shift from two-leg to one-leg squats to enhance specificity. Naturally, you will add other running-specific exercises to your routine, as well.

When in your overall training cycle should you perform challenging strength training? One logical time is during a period when you are about to introduce higher-speed training into your overall program. By boosting TPF to an incredible degree, by enhancing coordination (as long as the exercises you choose mimic the movements of running), and by enhancing efficiency of movement, max-strength training creates an incredible platform upon which high-intensity training can by played out – and race PRs achieved.

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Copyright © 2006 Running Research News, All rights reserved. Posted with permission.

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