Strength training: how beneficial is it for endurance athletes?

The 150-pound person who runs the marathon in five hours is just as strong as the 150-pound runner who completes the race in two hours and eight minutes. After all, the slower runner has shown that he can accomplish the same task completed by the elite competitor - the work of transporting a 150-pound weight 26.2 miles.' - Jim Bledsoe, noted American exercise physiologist.The majority of endurance athletes accept the idea that strength training is beneficial for their sport, but some athletes, coaches, and scientists remain unconvinced.

On an anecdotal level, it does seem odd that the best endurance athletes in the world - the Kenyan runners - rarely report to the gym, and on a more scientific level it seems clear that training for endurance and training for strength and power are at opposite 'poles' of the conditioning spectrum.

To run a marathon in two hours and eight minutes, for example, a runner's leg muscles need to develop the capacity to take about 23,000 rapid but submaximal steps without stopping ('submaximal steps' means strides taken with fairly moderate force production), while training for strength often consists of hoisting a close-to- maximal weight fairly slowly - and no more than eight to 10 times - before stopping.

How could lifting a weight slowly for eight to 10 reps, even if done for several sets, really prepare a runner's muscles to optimally handle the thousands of quick contractions needed to run a marathon - or even a 10K?

That question is not easily answered, but exercise physiologists have certainly attempted to do so. A variety of different studies with endurance swimmers, skiers, rowers, cyclists, and runners have tried to determine what - if any - benefits are associated with strength training. We'll guide you on a painless 'trip' through the best of these investigations and tell you what they really mean to you and your training.

Does it help rowers?

We'll start with rowing, primarily because strength training is advocated by most respected rowing coaches and because strength - rather than pure endurance - seems to be such an important aspect of rowing competitions. Research studies have suggested that anaerobic energy production (the type of energy production associated with very forceful muscular contractions rather than continuous submaximal ones) creates up to 23 per cent of the energy needed for many rowing competitions.

Strength training for rowers also has an interesting history. In the late 1960s, many serious rowers followed a programme of high- resistance, low-repetition training during their pre-seasons and then gradually shifted over to low-resistance, high-repetition efforts during the competitive season. That was a reasonable approach: The idea was simply that the ultra- strength developed during those pre-season, high-resistance, close-to-maximal exertions could be converted to real power during the competitive season by shifting over to quicker, more explosive, submaximal movements. To put it another way, the pre-season was designed to build up brute muscle strength, while the in- season was supposed to develop the ability to apply all of that strength in a very quick, coordinated way, ie, with great power.

A digression on strength and power

Speaking of strength and power, we probably should define those two key terms to avoid possible confusion. The strength of an athlete is determined by measuring how much 'work' he/she can perform. The work might involve lifting a 400-pound weight overhead; if two athletes can each lift 400 pounds - but no more than that - overhead, they are equally strong. If one can lift only 300 pounds, he is less strong.

In endurance sports, the work involves transporting one's body (or one's body plus bike or boat) from one point to another. That's why we must say that the 150-pound marathoner who moves his body 26.2 miles in five hours is just as strong as the 2:08 elite marathoner of similar weight; the amount of time required to accomplish the work just doesn't matter when we are talking about strength.

In fact, we would have to contend that the 200- pound marathoner who finishes the race in five hours is actually stronger than the 120-pound competitor who crosses the finish line in 2:08, since the heavier runner has done more total work. He has shown that he can move a much greater weight over the entire marathon distance, and we're not sure that the little 120-pound fella could do the same thing with an 80-pound weight attached to his body.

Power, though, is completely different: It is the amount of work performed per unit of time. Thus, the 150-pound marathoner who finishes in 2:08 is considerably more powerful than the 150- pounder who clocks five hours, since the denominator is considerably smaller in the first case ( it's just 128 minutes versus 300 minutes), and therefore the quotient (the work performed per minute and the actual power in Watts) will be higher.

As athletes develop the ability to generate more muscular force in shorter periods of time, they become more powerful. Although we tend not to think of endurance sports as power events, competitive endurance athletes are in fact very concerned about power, since higher power equates with faster race times. In contrast, devotees of training programmes like the Galloway (run-walk) system are mainly concerned about strength, since their primary goal is merely to get their body weight across the finish line.

Real research on strength training

Getting back to rowing, strength training has evolved somewhat from the model we described above. Currently, it seems that more rowers are doing extensive amounts of low-resistance, high- repetition work during the pre-season and then shifting over to an emphasis on 'specific movements' (those that mimic the biomechanics of rowing) during the competitive season. Actual research concerning strength training for rowing hasn't exactly been exhaustive, with the best study probably being the one carried out by researchers at the University of Alberta and the University of Victoria in Canada in the late 1980s.

In that study, 18 equally strong male college oarsmen (average age 22) were divided into three groups - a high-velocity (and low-resistance) strength training group, a low-velocity (and high- resistance) strength training group, and a control group which carried out no strength training at all. The first two groups strength-trained four times a week, and each workout consisted of 'circuits' of 12 different exercises which worked the key muscles involved in rowing (two to three circuits were completed per training session). Within a circuit, each exercise was carried out continuously for two 20-second intervals (with a 20-second rest between intervals) before an individual moved on to a new exertion. The high- velocity, low-resistance trainers completed about 18 to 22 reps in 20 seconds, while the low- velocity, high-resistance athletes finished six to eight closer-to-maximal repetitions during each 20-second period.

After five weeks of such training, the high- velocity rowers improved their strength during high-velocity movements, while the low-velocity oarsmen improved their strength during low- speed motions (surprise, surprise!). However, high-velocity athletes were not stronger while doing low-velocity movements, and low-velocity ones were not stronger during high-velocity actions (again, surprise, surprise!).

These results are in exact concordance with the critically important specificity of training principle, which basically says that you get better at doing only those things which you specifically practise in training. To use a running example, training fast makes you a faster runner, while running loads of relatively slow miles makes you skilled in the fine art of running slowly.

Unfortunately, actual rowing performances were not measured in this Canadian study. However, all 18 oarsmen did climb aboard rowing ergometers for tests which evaluated their lactate productions and power outputs during 15 seconds of maximal rowing and 90 seconds of full-tilt effort. These check-ups revealed a slight trend toward improved power outputs (and greater lactate production) in the high-velocity trainers after the five weeks of training, but the changes were not statistically significant. The low-velocity trainees also failed to hike power, and the control subjects actually lost power over the five-week period.

The lack of significant improvement in power output has been taken by many to mean that strength training is not really that important for rowing. The naysayers contend that the strengthening activities ordinarily carried out by rowers, even though they involve the same arm, shoulder, and leg muscles involved in rowing, are not specific enough to rowing to make any difference. In other words, an athlete gains strength from the strengthening activities (one would certainly hope so!), but this strength doesn't carry over from the simple moves utilized in the gym to the complex act of rowing.

Too short a study

This conclusion is logical enough and does represent a strict interpretation of the important specificity of training principle, but it is also premature. We shouldn't forget that the Alberta- Victoria study went on for only five weeks; it's asking quite a lot of a strength programme to expect it to produce statistically significant performance improvements in just 35 days! A more reasonable time frame for this study would have been at least 12 weeks.

In addition, the strength programmes utilized in this rowing research were totally lacking in sophistication. As we mentioned earlier in this article, optimal power development for endurance sports depends on two key things - the development of greater strength and the evolution of quicker application of that strength. The low-velocity, high-resistance rowers were working on the greater-strength-development portion of the equation, while the high-velocity, low-resistance oarsmen worked solely on the quick-application end of the formula, so neither programme was complete!

The researchers, in addition to extending their study for a longer time period, should have added a third group of trainees who first went for the high-resistance routines and then graduated to low resistance with fast movement. We could call the first part of this overall scheme (the high- resistance part) the 'muscle' portion of power development, and we could call the last part (the quick-movement portion) the 'neural' piece of the puzzle. You need both to maximize your power! Your muscles supply the raw force, and your nerves supply the coordination of that force - and the rate at which it is applied.

A baseball elucidation

To illustrate this more clearly, take the case of a group of baseball pitchers who underwent some rather unique training. Instead of using only regular baseballs, they threw both heavier- and lighter-than-normal balls during their conditioning. Throwing the heavier balls strengthened their muscles appreciably, which was great, but it did have one drawback: actual arm motion was slower with heavier balls, compared to regular or light ones, and thus if the players had used only heavy balls in their training they would have been fine-tuning their nervous systems' abilities to coordinate strong - but slow - movements.

That's why the light balls also had to be included in the training programme: throwing lighter balls improved coordination during quicker-than-usual arm movements and taught the athletes' nervous systems to 'recruit' muscular activity very quickly (faster movement was possible because the light balls offered less resistance). When these three elements - strength, coordination, and quickness - were put together, the those pitchers threw with much higher velocities compared to hurlers who trained only with regular balls (the difference in fastball speed was abou 6 to 8 per cent).

But how does one periodize such training? Should the heavy work really come first (that is, after an appropriate 'base' period of general- strength building but before the high-velocity training), should one simply combine low- and high-velocity work together, or is it ideal to start with fast work and then add on strength?

Surprisingly, these questions have been little researched, bllt investigations carried Ollt in the former Soviet Union suggest that it is probably advisable to go through a preliminary period of heavy-duty (low-velocity) training, followed by the lighter, faster work. In baseball, for example, the idea would be to build basic shoulder strength before subjecting the shoulder joint and muscles to the high forces involved in whipping the arm forward at higher-than-usual speeds. One could put forth a very similar argument for running, cycling, swimming, rowing, and skiing.

This question was looked at by the scientists from the University of Hawaii who carried out the baseball study. Their research involved 45 high school and 180 university baseball pitchers, who completed three workouts per week over a 10-week period. The specifics of the research were as follows: a control group utilized only a standard-weight (five-ounce) baseball, a second group trained with both a standard and heavy (six-ounce) baseball for five weeks, followed by five weeks with only a standard and light (four- ounce) ball. The final group worked out with standard, heavy, and light balls simultaneously throughout the 10-week period.

During a typical workout, the pitchers threw just 66 pitches. For the control group, each pitch was made with a standard ball. The group which simultaneously used standard, heavy, and light balls would throw (in order) 11 times with the regular ball, 22 times with the heavy, 22 times with the light, and then 11 times with the standard baseball during a single workout. The heavy-first-and-then-light group sandwiched 11 standard throws around 44 heavy throws during the five-week 'heavy' period and 11 standard throws around 44 light ones during the final, five- week 'light' period.

After 10 weeks, the control group failed to improve pitching velocity, but the other two groups raised throwing speeds by a similar amount - 6 to 8 per cent. This suggests that concurrent usage of high-resistance and low- resistance work is okay for power development, but whether this is also the case for more extensive training programmes and for endurance athletes remains to be seen.

What about swimming?

As is the case with rowing, most serious swimmers conduct regular resistance workouts, believing that such efforts give them stronger strokes and greater propulsive force in the water.

As we have suggested, however, this popular philosophy is not immune from criticism. For example, it's easy to see how high-quality strength workouts might produce enough muscular fatigue to lower the quality of regular swimming sessions (as it would for the other endurance sports, too). Reducing the quality of the actual work which is carried out in training is certainly not an optimal way to enhance performances.

Another possible problem is that strength training can increase bulk (muscle mass) and therefore decrease movement speed the added weight tends to resist motion - and requires greater force production by the muscles to maintain usual training and racing speeds). And a final gripe is that if you coax muscle cells into getting involved in the process of making themselves stronger (by increasing the number of contractile proteins inside the cells and widening muscle-fibre diameters), they might 'forget' to do the key work necessary to heighten endurance, such as building more mitochondria and synthesizing exorbitant quantities of aerobic enzymes.

Overall, the idea is that hitting the gym for strength workouts makes it hard to fully develop one's endurance. That hypothesis has never actually been supported by scientific research, but the 'reverse idea' - that endurance training makes it hard to develop strength - does have reasonable scientific support. As mentioned, the overall notion is that simultaneously training for strength and endurance makes muscle cells a little 'schizophrenic'; they don't know how to behave because they don't know exactly what their 'master' wants. Classic research by R. C. Hickson and his crew (of researchers, not rowers) at the University of Illinois-Chicago has shown that endurance trainees seldom gain as much strength as pure strength trainers, even when both groups are doing the exact same strength workouts.

Why does devoting oneself to endurance make it harder to develop strength? The energy demands of endurance training may 'rob' energy from the process of muscle-building, thwarting strength development, and of course the aerobic enzymes and structures (eg, mitochondria) which muscle cells devote themselves to creating and increasing as a result of endurance training have little positive effect on strength. As a result, strength training can not be a maximally productive endeavour during times when endurance work is being heavily stressed. And even if adding strength training to endurance work did produce major increases in strength, the key muscle transformation which actually creates greater strength (ie, larger-diameter muscle cells) shouldn't have a positive impact on endurance, say the sceptics, so why strength-train?

To summarize, the view is that when strength training is fitted into endurance training, the strength training is often fruitless, and even if it does work it won't help you run, cycle, swim, ski, or row any faster.

Back to swimming

That's a stupid view, because strength serves as the prelude to power for endurance athletes, but it is true that scientific research has shown that swimmers usually become less strong when their swimming training intensifies just before key competitive periods. Nonetheless, they often perform well during competitions, making sceptics wonder why raw strength is so highly valued.

Note that this is a very weak criticism of strength training, however. The lack of strength which appears just before the competitive season - after a very rugged period of training - is due to the overtraining to which swimmers are usually subjected, which damages muscles and aggrandizes fatigue; in fact the swimmers would probably perform much better if they backed down on their swimming volume and carried out additional (or higher-quality) strength workouts to prevent such 'strength black-outs'. But, does scientific research really support the idea that strength training is good for swimmers?
As with rowing, there is a relative paucity of relevant research. The most interesting study is certainly the one carried out by Hirofumi Tanaka, Dave Costill, and Bill Fink several years ago at Ball State University, in which 24 collegiate swimmers were divided into two groups of equal ability. One of these groups combined strength training with their usual swim workouts, while the second group refrained from strength training altogether. All athletes participated in six swimming workouts per week, while the strength-plus-swimming athletes completed three resistance sessions each week, too. The swimming season lasted for 14 weeks.

Total swimming volume started at about 2000 metres per day, steadily rose to 6000 metres per day by the end of the seventh week of training, stayed at 6000 daily metres for a total of three weeks, and then dropped progressively over the final four weeks, reaching a low point of 2000 metres per day during the 14th week, just before a major competition. The resistance-training group carried out their strength training on alternate days during the fourth through 11th weeks of the overall programme (for eight weeks total). No resistance training was completed during the final three weeks, and of course the resistance-free (control) swimmers carried out no strength training at all during the 14-week period.

The actual strength training, carried out with machines and free weights, consisted of dips, chin-ups, lat pull-downs, elbow extensions (for the triceps muscles), and bent-arm flys. Three sets of eight to 12 reps of each exercise were performed per workout, and resistance was progressively increased over the eight-week period (the average increase in resistance was 31 per cent).

And what happened?

At the end of the season, both groups had improved their strength by the same amount on a 'swim bench' (a dry-land resistance device which attempts to replicate the biomechanics of the front-crawl stroke in swimming). Both groups improved their power during 'tethered swimming' to the same extent, and both collections of swimmers reduced blood- lactate levels during high-speed, 365-metre swims by the same amount. However, distance moved per stroke (during front-crawl swimming) was unchanged for both the strength-trained and regularly trained swimmers.

Somewhat shockingly, sprint-swim velocity (speed measured during a maximal 22.9-metre swim) actually decreased by the same amount in both groups. How's that for an effective training programme?(!!) Such drop-offs in velocity (power) are one reason why venerable exercise physiologist Dave Costill (one of the Ball State researchers) began telling swim coaches that they were forcing their athletes to swim far too many metres per week during training (ie, the training volume was turned up way too high, causing overtraining and a lack of power).

Unfortunately, actual competitive perform- ances of the two groups of athletes in the Costill- Tanaka-Fink investigation were not compared, so the 'bottom line' in this piece of research was simply that strength training did not improve either swimming capacity or overall strength (measured while swimming) in these collegiate swimmers any more than did routine swim workouts.

Many observers of the competitive swimming scene have looked at this key study and declared that it shows that strength training has little value for serious swimmers. Of course, the key problem with this assertion is that the strength-training programme devised by Fink, Costill, and Tanaka does not represent strength training in toto; there are many other types of strength schemes which swimmers could follow. In fact, the overall strength programme was a very poor one. The key principle of progression was utilized in only one sense in Tanaka's plan: the swimmers did progress from lesser to greater resistance over the eight-week period. However, there was no progression from one type of strength training to another, eg, frorn general strengthening exertions to those more specific to the act of swimming, and in fact the exercises utilized by Tanaka's athletes resembled the actions required for swimming only in the sense that the major muscles needed for swimming were stressed during the strength training.

The exact (or nearly exact) movements required for swimming were not replicated during the strength training, and thus the neural (coordination) component of strengthening was absent. Movement speed was also not varied; the swimmers lifted weights at roughly the same speed throughout the whole eight-week period (there was no alternation of high-resistance, slow-velocity efforts with low-resistance, high- velocity ones). It's easy to see why Tanaka's programme made the swimmers stronger while doing the specific exercises in the programme - but not while swimming. The research would have been much more interesting if the swimmers had tried some quality strength training.

On to skiing

Can strength training help cross country skiers? Heikki Rusko and his colleagues at the University of Jyvaskyla in Finland checked out that possibility with a unique piece of research carried out in the late 1980s. Rusko's subjects were 15 national-level cross country skiers, seven of whom took part in a unique, six-week strength- training programme which combined both explosive (high-velocity, low-resistance) exertions and heavy-duty (low-velocity, high- resistance) work.

The explosive exertions consisted of sprint training, jumps, and other quickly conducted exercises, while the heavy-duty stuff involved squats with barbells and other basic resistance exercises using loads of 70 to 90 per cent of an athlete's 'one-repetition-max', 70 to 90 per cent of the greatest weight which an athlete could lift once.

Meanwhile, a control group of eight skiers spent most of their time engaged in routine endurance training for skiing but also completed some 'endurance strength training', which consisted of very-low-resistance abdominal, arm, and leg exercises with hundreds of repetitions.

After the six-week training period, the explosively trained group held a couple of advantages over the endurance group. First, the time required to develop significant muscular force, which was initially equal between groups, shortened in the explosive group, compared to the endurance group. Specifically, it took .41 seconds for the athletes' quadriceps muscles to produce 90 per cent of their maximal strength before the explosive training was carried out - but just .29 seconds after the extensive explosive training (a 29-per cent improvement).

Meanwhile, the endurance athletes were unable to improve their quickness of force production in their quads. That was no surprise, since the explosive group had been emphasizing quick, forceful movements in their training, while the endurance skiers had been moving more lethargically during their workouts. Basically, members of the explosive group improved the quickness with which their nervous systems stimulated their muscles to act. They became more powerful!

Similarly, the explosive group improved their vertical jumping ability by about 11 per cent over the course of six weeks, while the endurance group failed to jump any higher than before. As was the case with the upgraded rate of force development, this was not a huge surprise. The explosive athletes had been practising their jumps, and jumping capacity itself depends on one's ability to accelerate rapidly away from the ground in order to overcome the downward acceleration produced by gravity. Acceleration is dependent on power, and the explosive athletes had been working intently on power, while the endurance people had emphasized endurance and strength.

As with the rowing and swimming research, no actual performance tests were carried out with the athletes, an omission which seems rather puzzling. However, all athletes were tested for changes in V02max, aerobic threshold (the exercise intensity which caused blood-lactate levels to rise above 2 mmol/litre), and lactate threshold, and it was determined that neither the explosive nor endurance athletes improved in those key areas. Because of that, various individuals have contended that Rusko's research constitutes 'proof' that strength training is of little benefit to cross-country skiers (the cross- country skiers could jump higher than usual after Rusko put them through their paces, but shrewd sceptics have pointed out that there is little link between vertical jumping ability and cross- country skiing performance).

However, it's premature to say that strength training can't lift endurance-skiing capacity, since there were a number of problems with Rusko's research (in addition to the failure to test actual skiing performance). The total time devoted to strength training was short (six weeks), and the strength training, although it did include both low- and high-velocity work, failed to progress from general strengthening to exertions which closely paralleled the actual movements involved in skiing. Rusko's study only shows that a fairly limited strength-training programme has little impact on maximal aerobic capacity and lactate threshold in cross-country skiers.

Cycling next?

Research exploring the effects of strength training on cycling has been a 'mixed bag'. We have the study carried out by Ben Hurley and his co-workers at the University of Maryland, in which 10 healthy men took up strength training (bench presses, hip flexions, knee extensions, knee flexions, press-ups, leg presses, lat pulldowns, arm curls, parallel squats, and bent-knee sit-ups) for 12 weeks, while eight other healthy men served as controls. After 12 weeks, the strength-trained men improved their endurance while cycling at an intensity of 75 per cent V02max by 33 per cent and also lifted lactate threshold (the single best predictor of endurance performance) by 12 per cent.

However, these men were untrained prior to the study and did not carry out regular cycling workouts during the research, so the applicability of these findings to serious athletes is questionable.

The study carried out by R. C. Hickson and his colleagues at the University of Illinois at Chicago was considerably more practical. In that investigation, eight experienced cyclists added three days per week of strength training to their regular endurance routines over a 10-week pe