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If you're a runner, perhaps you want to be able to run for longer periods of time at your current race and workout paces. Perhaps you want to run faster during your competitions and training sessions. Or maybe you just want everything you do now to feel a little easier. Whatever the case, improving your running economy can be the solution to your problem: exercise physiologists tell us that upgraded economy lowers perceived effort at your current race paces and allows you to run for longer periods of time at those speeds. Better yet, enhanced economy lets you run faster than your customary competitive speeds, without feeling that the effort is any harder.

If you're a regular reader of PP, you'll recall that - in purely physiological terms - improved economy means using less oxygen to run at a particular pace. No, working on your economy doesn't mean that you're preparing yourself to compete in the first Mars Marathon; as your economy improves, you'll still be dragging oxygen into your lungs and pushing it out to your leg muscles with your heart. It's just that you need less of that life-giving gas to run at race-relevant speeds, which is great because it puts less pressure on your heart (which is glad to beat more modestly once it learns that your muscles don't need quite as much oxygen as before) and makes running feel more effortless (there's a direct relationship between oxygen consumption and perceived effort). As a result, a seemingly insignificant 2-per cent improvement in economy can carve a nifty 48 seconds from your 10-K time, if you're currently about a 40-minute 10Ker.

So how do you actually improve your economy? Traditionally, exercise scientists have believed that strength training might do the trick. In part, the theory has been that strength work improves whole-body stability during the act of running. Thus, less energy is required to correct inappropriate movements (e. g., a wobbly trunk or an ankle which is dorsiflexed to too great a degree), and a particular pace can be sustained with a lower total energy cost.

Enter Hickson's team
In the first study to explore the link between resistance training and economy, carried out at R.C. Hickson's famous laboratory at the University of Illinois at Chicago, nine men (aged 18-27) took part in a 10-week, five-workout per week programme which was designed to strengthen their quadriceps muscles. The men were described as 'active' (e. g., participating regularly in recreational sports), but none were involved in long-term running or cycling training ('Strength Training Effects on Aerobic Power and Short-Term Endurance,' Medicine and Science in Sports and Exercise, vol. 12(5), pp. 336-339, 1980).

Three days per week, the subjects completed parallel squats (5 sets of 5 repetitions), knee flexions (3 x 5), and knee extensions (3 x 5). On the other two days, the men performed leg presses (3 x 5) calf raises (3 x 20), and a few dead lifts and sit-ups to fortify their back and abdominal muscles. All sets were separated by three-minute recovery periods. Although this programme may seem to be somewhat minimal, it wasn't a complete piece of cake - because all of the exercises were performed with as much weight as possible. Initially, the resistance was set at 80 per cent of the one-repetition maximum (80 per cent of the maximal weight which could be lifted once and only once). As strength increased, additional weight was added to maintain this same relative resistance. The parallel squats and calf raises were conducted with Olympic-style weights, while the knee flexions, extensions, and presses were completed on a Universal Gym. At the beginning and conclusion of the study, strength was measured as the maximum amount of weight which could be lifted for one repetition.

The effect on cycling and running
The 10-week programme did have a dramatic impact on muscular strength, which burgeoned by 38 per cent for squatting, 42 per cent for knee flexion, and 50 per cent for knee extension. That was not a big surprise; the big shocker was that even though the subjects had not participated in a single cycling workout during the study, VO2max while cycling increased by 4 per cent after 10 weeks. However, VO2max during running was unchanged at the end of the 10-week period!

At the beginning and end of the 10-week study, the men took part in an interesting test of endurance: they tried to exercise for as long as possible at their initial VO2max (eg, the cycling intensity or running speed which produced VO2max at the beginning of the research). Of course, this meant they were cycling at an intensity a little below their true VO2max at the end of the study, since cycling VO2max had risen. Endurance time, as measured by this test, vaulted upward by 47 per cent on the bicycle (from 278 to 407 seconds) and increased by 12 per cent while running (from 291 to 325 seconds)!

Those large increases in endurance might seem a little unusual to you, especially since the subjects had not taken part in any cycling or running workouts during the research (the increases were certainly a puzzlement to Hickson and his crew, who could offer no real explanation for the gains). So, what should we conclude from this research? What caused the small increase in VO2max for the bikers? What caused the gains in endurance capacity during both cycling and running?

The easiest conclusion to draw is simply that strength training benefits cyclists and runners (to be more accurate, we should say that the study shows that strength training can help relatively inexperienced cyclists and runners who do not cycle or run regularly). We can also safely conclude that strength training of the type utilized in this study, with an emphasis on quadriceps strengthening, seems to benefit bikers to a greater extent, compared to runners (remember that endurance soared by 47 per cent during cycling, but just 12 per cent while running, and that VO2max increased only on the bike). While the caveat here is again that the athletes were inexperienced at cycling and running, the different responses should not be too surprising. The strength programme utilized in this research emphasized the development of quadriceps rather than whole-leg strength, and quadriceps power plays a much larger role in cycling than in running.

Unravelling the mystery
But what actually caused the hikes in cycling and running endurance? We can't assign the laurels to VO2max, since running VO2max didn't change at all, and cycling VO2max rose by only 4 per cent, a far cry from the 47-per cent lift in endurance. We also can't pin our hopes on sweeter lactate thresholds, since blood-lactate levels during strenuous running and cycling were not different at the end of the study, compared to the beginning. The only other key physiological variable left is economy, which, although not actually measured by the researchers, was probably superior after the strength training. Bolstered quad strength, plus gains in the fortitude of the abdominal and low-back muscles resulting from the crunches and dead lifts, probably improved economy by stabilizing movement and thwarting energy wastage. This pushed the final bicycle test even further below the original cycling VO2max and made the run 'at VO2max' actually use less energy - and therefore oxygen - than a true at-VO2max effort. Thus, heart rate and perceived effort were substantially lower after 10 weeks, permitting the athletes to cycle or run at a high intensity for a considerably longer period of time than before they had undertaken strength training.

However, we should point out that in addition to promoting stability, improved strength probably enhances economy in another key way, too (we'll use the cycling example to make our point). As mentioned, the individuals in the Hickson study could pedal for only 278 seconds (four minutes and 38 seconds) at their VO2max intensity when the research began. They then boosted their quadriceps strength dramatically over a 10-week period. This strength came not from growing more muscle cells in the quads but from strengthening the cells already present there. Since individual cells were stronger after the 10 weeks of strength training, fewer total cells were required to produce the force necessary to pedal at VO2max intensity, saving energy (and thus enhancing economy). The decrease in the number of cells required of course allowed some of the previously active muscle fibres to rest during activity. When the hard-working cells became fatigued during the endurance test, they could drop out of the action, but exercise could continue (the point of exhaustion was not yet reached), because the wearied cells could be adequately 'replaced' by the fibres which had been resting - and waiting for their chance to help. Putting it all together, we can say that increased strength not only aids economy by enriching stability and decreasing the number of muscle cells required to sustain activity; it also delays total fatigue by allowing collections of muscle cells to 'share the work' in an alternating fashion.

Answering the next question
If you're getting into this article, you're probably wondering why the delay in fatigue associated with increased strength was greater for cycling than it was for running. Shouldn't improved strength be equally valuable in the two sports?

To answer that question, first bear in mind that the boost in strength was greatest in the quadriceps muscles, which are more important for cycling than running. In addition, the strengthening exercises utilized in the study (knee extensions, flexions, and presses while seated at a Universal Gym), were more specific to cycling than running, since they were carried out in a seated, non-weight-bearing position. In cycling, you are perched on your bum, as you are on the Universal Gym, and your legs seldom have to support full body weight, but that is certainly not the case while running! Thus the integrated actions of the leg muscles and the control and coordination of those muscles by the nervous system during the prescribed strength training were much more similar to the actions and control required for cycling, compared to running. As a result, the magnitude of the benefits carrying over to running were naturally smaller. When thinking about strength training, it's important to remember that gains in strength are of course a function of enhanced muscle-fibre size, but they can also occur as a result of the nervous system's 'learning' to coordinate muscle activity in the most power-producing manner possible. If both factors (better pure muscle strength, better coordination of muscles by the nervous system) are not working together, your strength training will never optimally improve your strength in your favoured sport. To put it another way, you can bolster your sinews in a variety of different ways, but you had better make your resistance training specific to your sport if you really want to achieve a performance-improving advance in your strength.

No, we haven't forgotten about that other question: why did strength training boost VO2max on the bike? To put it simply, the strength upswing allowed the subjects to push against the pedals a little longer during the VO2max test (because each push represented a smaller fraction of total strength and was therefore more tolerable). The slightly longer duration of the test then got the athletes up to a higher oxygen consumption rate. As wise exercise physiologists like to say, you can almost always get to a higher VO2max - if your leg muscles will permit it!

The follow-up
In Hickson's follow-up research (which also happened to be the second major published study on the effects of strength training on economy), the Illinois researchers eliminated one of the problems associated with their earlier research by involving experienced athletes in their work. All of the new subjects were already carrying out a regular running and cycling programme; on average, they ran three times a week and also cycled three times weekly - and continued to do so as they embarked on their new strength-training programme. Since the subjects were already so active, they strength-trained just three times per week in this second investigation (against. five times a week in the first piece of research). As in the first study, the subjects' endurance capacities were tested during a very high-intensity, close-to-VO2max exertion, but they were also assessed during longer, submaximal efforts - either cycling at an intensity of 80 per cent of VO2max or running a 10-K race on an indoor track ('Potential for Strength and Endurance Training to Amplify Endurance Performance,' Journal of Applied Physiology, vol. 65(5), pp. 2285-2290, 1988).

Eight athletes (six men and two women) took part in this second investigation; their average age was 31, and they had above-average fitness (mean running VO2max was 60 ml/kg/min). The strength-training workouts were somewhat similar to the earlier ones, consisting of parallel squats ((5 sets of 5 reps), knee extensions (3 x 5), knee flexions (3 x 5), and toe raises (3 x 25), with two-minute recoveries between sets and 10 weeks of total training. As in the first study, as much weight as possible was utilized (if the subjects could perform more than five reps, additional weight was added). None of the participants had engaged in strength training during the six months before the study began, but - as mentioned - all had been carrying out regular running or cycling workouts and continued to do so as the strength training progressed.

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