Endurance runners are generally not crazy about the idea of carrying out consistent, progressive, running-specific strength training. Part of the reason for this is a wide spread belief in two of the pervasive myths associated with running- that strength training can harm aerobic development and endurance and that aerobic training makes it nearly impossible to upgrade raw muscular strength. However, research reveals that the "conflict" between strength and endurance training is often imaginary.

If you go to the gym to lift weights four or five days a week, your muscles will begin to travel in a certain direction. They'll decide to upgrade their diameter and volume, and as a result your strength may improve dramatically. If you are only pushing weights around in the gym, and nothing more, however, you will sink when you undertake an activity which requires considerable endurance, in spite of your enhanced muscular strength. Your muscles won't know how to behave in a 10-K race, for example, and you'll finish far behind individuals with considerably less sinuosity and strength.

On the other hand, if you eschew the gym and simply run at a moderate tempo for about an hour or so, five days a week, your muscles will take an entirely different trajectory. They'll get busy synthesizing increased quanities of aerobic enzymes and higher densities of mitochrondria, and they may signal surrounding capillaries to create bushy new networks of small blood vessels. If there are any fast-twitch fibers hanging around in your muscles, they'll go through at least a partial atrophy and may commence a kind of metamorphosis which makes them look more like their slow twitch cousins. After eight weeks or so, moderate-intensity endurance exercise will be a snap, but a trip into the gym would most likely reveal a surprising lack of strength and coordination. Your muscles would be far different and far weaker, compared with the sinews which would pop out after a steady diet of gymming.

Traditionally, many exercise physiologist and coaches have said that these two possible directions are contradictory, that is, that if you push muscles on a path toward strength it will retard their development of greater endurance, and vice-versa. As a result of this kind of thinking, many endurance athletes avoid strength training altogether.

This story concerning the potential conflicts associated with simultaneous strength and endurance training certainly goes back to the 1970s, when Dr. Robert Hickson, then a post-doc researcher at Washington University in St. Louis, discovered that the running workouts he was completing with his mentor, Dr. John Holloszy, were causing muscles to fall off his body like autumn leaves (1). Hickson went on to complete a study in which he demonstrated that endurance training had a negative impact on the gains in stength associated with concurrent resistance training (2). The "lesson" from this research was adopted by the running community: If you were a runner, it made little sense to carry out strength training, since endurance-running activities would throttle the possible emergence of greater strength. Furthermore, the two activities were too disparate - "aerobic" vs. "anaerobic" in the parlance of the day - to be joined together in any serious runner's training log.

However, it would seem to be incautious and a bit hasty to conclude from Hickson's initial research that all strength training should be cast aside by the running crowd. Indeed, Hickson's own follow-up study, published eight years later, has often been over looked. In that inquiry, experienced runners who had reached a "steady-state levels of performance" (e.g., who had stagnated) carried out strngth training three times a week for 10 weeks, with their regular endurance training remaining constant during this period (3). This research, far from revealing problems associated with synching strength training with endurance work, revealed that the addition of strength training was linked with a 13-percent enhancement of endurance during intense running.

Other studies failed to show that endurance training harmed the development of strength. In one of the most ingenious of these investigations, some subjects performed endurance training with the other leg. A second group of athletes carried out strength training on one leg and the combo of endurance and strength with the lower limb. The endurance training was composed of five three-minute bouts of cycling per workout at an intensity of 90 to 100% VO2max, while the strength training centered on six sets of 15-22 reps of leg presses with maximal resistance (4).

After 22 weeks (a beautifully long time frame in the exercise-science world), the legs which engaged in both endurance and strength training were just as strong as the lower appendages which performed strength training only. An interesting aspect of this research was that the same leg muscles were used for both the endurance and strength training, and the movements involved (pushing on a bike pedal and pressing a platform) were similar mechanically. This contradicted one view which had been held - that endurance-training's depressing effect on strength would be particularly strong if the same muscles were engaged in both types of training. After all, individual muscles could never go in two directions at once, right? If asked to do so, they would abandon gains in strength in favor of endurance-related changes, just as Hickson's quads lost mass when he became a serious runner.

In this study, however, muscles engaged in endurance training had no problem at all with the task of building up strength when they were asked to do so. It is very cool that the movements involved (pedaling and pressing) overlapping biomechanically, suggesting that the development of running-specific strength would not be retarded by high-quality running workouts.

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Charging up hills boosts leg-muscle strength and improves your running economy, but what about running down hills? If you carry out repeats on a neighborhood incline, you've got to jog back down the hill before you surge upward again. Does such downhill ambling do anything special for you - aside from giving your knees a good jarring?

Of course! As we have mentioned previously in the pages of Running Research News, downhill running can help prevent leg-muscle soreness, especially in the quadriceps muscles in the front of the thigh. Soreness often results when one's muscles are challenged by a greater-than-normal number of eccentric contractions, in which the muscles attempt to shorten while they are actually being elongated.

The "quads" are notorious soreheads, mainly because gravity pulls the knee downward (e.g., produces knee flexion) with every footstrike during the act of running. This flexing stretches out the quads at the exact time they are contracting (attempting to shorten) to prevent excessive knee flexion. The resulting, repetitive strain (which occurs about 90 times per minute per leg) can produce significant quadriceps-muscle damage. If you simply complete your usual volume of training, your quads have already adapted to that amount of strain and ordinarily don't protest too much. However, if you run more miles than you are accustomed to, your quads tend to complain quite loudly. If you have ever boosted your mileage quickly or run a marathon, you know the feeling.

Downhill running actually magnifies this eccentric, "pulling-apart" stress on the quads, because the leg "falls" a little farther than normal with each stride. Thus the accelaration of the leg is greater at impact (footstrike), and the forces which produce knee flexion are consequently greater. The quads, of course, are still trying to carry out their yeoman-like work of resisting knee flexion, but the stress on them is much higher. Microscopic tears in the quads' muscle fibers and connective tissues can occur, and considerable soreness can result.

That doesn't mean that downhill running is bad for you, though: In the long run, it is actually good, because those old quads of yours adapt fairly readily. Once they've been exposed to some downhill running, they'll be sore, sure, but if you run downhill a few weeks later, the quads will be considerably "tougher" - and less apt to get sore. In addition, if - after your downhill exposure - you run longer than usual on the flat, your quads will also be less likely to get hurt. The soreness protection gained from downslope running does seem to carry over to regular efforts. Down Hill

                                                             The Six-Week Factor

In fact, for yet-to-be-explained reasons, the soreness insurance provided by a single bout of downhill running can often last for six weeks or more. Several years ago, scientists at the University of Massachusetts asked 109 individuals to perform two sets of 35 maximal, eccentric contractions of the biceps muscle in the upper part of one arm. Basically, these eccentric contractions consisted of lowering a very heavy weight, which forced the biceps muscles to elongate as the weight was lowered at the same time they were attempting to shorten to stabilize the weight's movement.

After this unusual workout, biceps soreness and tightness peaked about two to three days later, and maximal swelling occurred a few days after that. Biceps strength declined immediately after the rigorous session and stayed below-par for 10 days.

However, when the individuals tried the same biceps routine six weeks later (with no intervening biceps training), there was appreciably less soreness and little loss of muscle strength. The biceps muscles were somehow protected from problems as a result of that initial eccentric session.

Interestingly enough, the protection didn't last much longer than six weeks. When a second group of subjects waited 10 weeks after their initial eccentric workout to stress their biceps again, their biceps were thrown into uncontrollable agony and lost most of their strength. What was going on? Why could the bicep "remember" what happened six weeks before - but not 10 weeks before?

The Massachusetts researchers speculated that a strenuous bout of eccentric exercise "teaches" the nervous system how to better control and distribute the forces that are acting on particular muscles. In theory, this lessens the strain on individual muscle fibers when eccentric activity tries to "tear them apart" - and thereby reduces muscle damage and consequent pain. Just as the nervous system can learn to do this, it can also forget, and this forgetting seems to take place after six to 10 weeks. Six-Week Factor

                                           Australian Rats Reveal Sarcomere Secrets

Nice theory, but does it really work that way? To check it out, scientists at Monash University in Australia asked 16 laboratory rats to work out on treadmills over a five-day period. Eight of these rats participated only in "uphill" (inclined) running, while the other eight ran only "downhill" (declined running). Actual workouts consisted of five-minute work intervals with 1.5-minutes recoveries, starting with three work intervals on the fifth day. Running speed during the work intervals was a rather modest 16 meters per minute. After five days, the rats' quadriceps muscles  were tested for strength and then biopsied.

A key finding was that the quadriceps muscle cells of the decline-trained rats contained almost 10-percent more sarcomeres per cell, compared to the quads of the inclined rodents. To understand what sarcomeres are, bear in mind that a muscle cell is a barrel-shaped structure, and each "barrel" is filled with several hundred to several thousand cyclindrical, threadlike structures called myofibrils. To picture this, simply imagine a pipe-shaped structure (the muscle cell) stuffed with countless numbers of small cylindrical wires (the myofibrils). Incidentally, when we say that a muscle cell is shaped like a pipe, we are referring to a section of cylindrical water pipe, not to a pipe used for smoking purposes.

The myofibrils themselves are composed of microscopic, cylindrical compartments laid end to end (picture tiny cyclinders or spools glued together at their ends to make one long cylinder). These compartments are called the sarcomeres, and within the sarcomeres are the proteins (filaments) which actually allow muscles to both shorten and elongate. As special filaments slide inward (toward the middles of the sarcomeres), the myofibrils and overall muscle cell shorten, but when the filaments slide outward, the muscle gets longer.

As mentioned, downhill running induced the muscle cells to add more sarcomere to their myofibrils. Why is this increase in number of sarcomeres beneficial, and how can it prevent muscle damage and soreness? Since muscle-cell length itself didn't change significantly as a result of the downhill running, the fact that there were more sarcomeres per muscle cell was elongating, each sarcomere in a downhill-trained muscle would have to elongate less, and thus each sarcomere would be less likely to sustain internal damage. Sarcomere Secrets

To learn more about how WHAT HAPPENS WHEN YOUR RUNNING GOES DOWNHILL (the full article can be read by purchasing Vol.14-6 of Running Research News) and many more running related topics, simply click-on the Back Issues link, and select the volume and issues number, from the drop-down menu. A subscription to Running Research News is another way to receive valuable information about running.

Manys runners loathe the idea of dropping mileage and replacing the "lost" miles with explosive strength training, but new research from Finland reveals that such a strategy can significantly improve maximal running speed and leg muscle power - workout any loss in maximal aerobic capacity. In the new investigation, experienced runners reduced weekly mileage by 20 percent and upgraded maximal running velocity by 3 percent. REPLACING MILES WITH EXPLOSIVE MOVES

What happens if you suddenly decided to chop 20 percent of your usual miles from your weekly log - and then replaced that lost mileage with explosive training which required a comparable amount of time? Many runners would suggest that such a move would deplete maximal aerobic capacity (VO2max), because of the lower overall volume of endurance training which would be conducted. Furthermore, many coaches and runners would say that the change would produce a drop in fitness and race performances, because of the necessarily abridged maximal aerobic capacity. Given such thinking, it is not at all surprising that so few runners carve away at their mileage and substitute explosive work for their endurance-type training.

However, there have been various hints in the scientific literature that such substitutions could produce surprising benefits. Some research, for example, has shown that "anaerobic work capacity" (the kind of thing which is fostered by explosive training) can have an important impact on endurance performance (1). In addition, Tim Noakes' now classic paper revealed that "neuromuscular characteristics" {basically, the ability of muscles to produce high amounts of force very quickly) could predict endurance-performance capability more successful than good-old VO2max (2). Producing force quickly is a key adaptation associates with explosive training. Thus, these inquires suggest that the traditional thinking about mileage and high-power work might be wrong.

Fortunately, the question of what really happens when endurance work is replaced by explosive training intrigued by Jussi Mikkola, Heikki Rusko, and their colleagues at the Research Institute for Olympic Sports in Jyvaskyla, Finland. Recently, Mikkola, Rusko, and their co-workers asked 13 well-trained young runners (nine males, four females) who were training about 8.8 hours per week to pare 1.7 hours from their weekly logs (leaving about 7.1 hours of endurance training) - and then to incorporate 1.7 hours of explosive training into their schedules each week for a period of eight weeks (thus maintaining the usual 8.8 total hours of effort). These runners were young (average age = 17.3 years) and fit (mean VO2max = 62.4 ml'kg-1 min-1). REPLACING MILES WITH EXPLOSIVE MOVES

The explosive training was carried out three times a week (which meant that each session lasted for about 34 minutes). The workouts consisted of high-speed sprint intervals ((5 to 10) X (30 to 150 meters)), jumping exercises with no additional resistance (alternate-leg jumps, and hurdle jumps), and "gym exercises" with fairly light resistance (half squats, knee extensions, knee flexions, calf raises, abdominal curls, and back extensions). For the gym exertions, two to three sets of six to 10 repetitions were utilized, and the underlying philosophy for all of the explosive movements was to use very high action velocities.

And, yes, this was a Heikki Rusko study, so there was a very nice control group - 12 individuals in all (nine men and three women) who were also young (17.3 years) and fit (VO2max = 61.8 ml'kg-1min-1). These controls pretty much stayed away from the explosive training during the eight-week period, instead focusing on 8.5 hours per week of endurnce training.

Muscle strength, jumping ability, and 30-meter running speed were measured in both the explosive and control groups at the beginning and end og the eight week period. And - since this was a Rusko study - all runners performed a maximal anaerobic running test, or MART (Rusko is one of the primary developers of the MART). A MART can be completed on a treadmill (3 & 4), but in this research the testing took place on an indoor track. Basically, a MART is a series of 150-meter runs, with 100-second recoveries between runs and a five meter flying start before each 150-meter effort. The velocities of the 150-meter runs are tightly controlled. In this research, the first was carried out at 39.4 meters per second (101.5 seconds per 400 meters) for females and 4.75 meters per second (84 seconds per 400 meters) for males. After that, the velocity was increased by .41 meters per second for each consecutive 150-meter effort. At the well equipped Rusko lab in Jyvaskyla, the runners were guided into running at the correct velocity by a "light rabbit" (a moving light which moved around the track at the required speed). In a MART, the last 150-meter run is completed at maximal effort, and ordinarily about nine to 10n 150-meter surges are completed per test. Fairly fast speeds are attained during the test. For example, a male runner who manages to perform 10 150-meter runs would complete the last effort at no less than 8.44 meters per second (47 seconds per 400 meters, if he could "hold on" that long).

Over the course of eight weeks, the explosive training paid major dividends. The maximal speed in the MART (the velocity attained for the last 150-meter sprint) increased by 3 percent in the explosively trained runners - but failed to budge at all in the regular, endurance-trained subjects. Furthermore, 30-meter speed (the top velocity achieved in a 30-meter sprint which was preceded by a 20-meter flying start) advanced by 1.1 percent for the explosive runners - but was stagnant for control individuals. REPLACING MILES WITH EXPLOSIVE MOVES

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In theory, triathletes should have fewer overuse injuries, compared to other endurance athletes. After all, "cross training" is believed to minimize the risk of injury (and is even prescribed for injured athletes as a way to recovery), and triathletes cross train routinely. A triathlete whose main strength is running, for example, could be described as cross training for two-thirds of all workouts (if running, swimming, and cycling workouts occur with equal frequencies). Indeed, initial reports indicate that overuse injuries may be lower for triathletes; one study found an annual overuse- injury frequency of 41 percent in a group of triathletes, compared with the usual 50 to 65 percent injury rates found in "pure" runners ("An Epidemiological Investigation of Training and Injury Patterns in British Triathletes, "British Journal of Sports Medicine, Vol.28, pp. 191-196,). TRIATHLETES

However, other research has identified a 90 percent (!) injury rate in triathletes, well above the norm for endurance-sport participants ("Overuse Injuries in Ultraendurance Triathletes," American Journal of Sports Medicine, Vol. 17, pp. 514-518). Indeed, some sports-medicine experts argue that triathletes are more prone to injury, since each of the three triathlon sports tends to trigger a particular type of malady.

Swimming, for example, is known to induce shoulder injuries, which are seldom seen in running. Biking is associated with a higher risk of low-back problems, which are usually not a problem in endurance swimmers. In addition, triathletes often carry out more total workouts per week, compared with " straight" swimmers, runners, or cyclists. From these perspectives, triathlon competition might be considered a "high-risk" sport.

So the question remains: Do triathletes get injured more or less often, compared with "specialist" endurance athletes? In addition, which triathletes are at the highest risk for injury? Do psychological state, physical build, age, and gender play a role in determining risk? How about the number of years of triathlon experience, the time spent competing, training pace, and even stretching?

To answer these questions, researchers at Staffordshire University in Stoke-on-Trent recently examined the five-year training programs of 12 elite triathletes from British National Squad, 17 national-development-team memebrs, and 87 male club triathletes ("Injury and Training Characteristics of Male Elite, Development Squad, and Club Triathletes," International Journal of Sports Medicine, Vol. 19, pp. 8-42). An injury was defined as any musculoskeletal problem causing cessation of training for at least one day, a reduction in training mileage, the taking of pain medicine, or the seeking of mediacl aid. Overuse injuries were recorded separately from traumatic injuries, such as those resulting from bicycle accidents. TRIATHLETES

As it turned out, injury prevalence did not differ significantly between the ability groups; 75 percent of elite, 75 percent of developmental, and 56 percent of club athletes suffered an overuse injury during the five-year period ( the downturn in injury rate in the club athletes was not statistically significant); total time taken off from training as a result of injury was also not different between groups.

In addition, there was no significant difference between the three groups in the proportions of athletes sustaing injury in particular parts of the body; for example, club athletes were no more likely to sustain Achilles-tendon injuries, compared with developmental and elite triathletes. The knee, Achilles tendon, and lower back tended to be the most-injured body areas for the athletes overall. Injury occurrence was not linked to age, height, weight, or body-mass index.

                                            The Curse of Running

As you might expect, running injuries were responsible for most of the problems, accounting for from 58 to 64 percent of all injuries in the three groups; cycling was far back with 16 to 34 percent, and swimming produced very few difficulties. A key question then was: What factors increased the risk of running injury? The Staffordshire-University researchers were able to identify total weekly triathlon training distance (the sun of running, swimming, and biking mileage), weekly cycling distance (!), swimming distance per week, total number of workouts per week, cycling training pace, and number of weekly running workouts as key risk factors for running injury.

These findings might seem surprising at first. After all, why would an extra hour spent swimming or an extra 40K on the bike increase an athlete's risk of developing a running injury? The key, of course, is that while such efforts do not produce the kind of impact damage to muscles associated with running, they can - when carried out in large-enough volume - retard muscular recovery enough so that muscles respond less well to the stress of running and are thus more vulnerable to being injured as a result of run training. TRIATHLETES

Triathlon training is a true "balancing act;" workouts which ultimately improve cycling or swimming fitness can sometimes hurt running capacity or even increase the risk of sustaining a running injury by temporarily retarding muscular recovery. In such cases, it might be better to attempt to improve cycling or swimming fitness less avidly and thus maintain the ability to run strongly and without injury. When a triathlete plans a high-quality bike or swim workout, he/she needs to take into account not only the effect the session will have on bike/swim fitness but also the impact it will have on subsequent running efforts. If a killer bicycle exertion boosts cycling fitness a notch or two but prevents the completion og high-quality running workouts, what has actually been gained?

For many triathletes who want to improve overall performance - and who are training within limited time frames, the key may be to assess in which sport the greatest gain can be made, i.e., the sport in which the greatest improvement in overall race clocking can be attained. That sport will then be emphasized most heavily in training - and workouts in the other two activities which might hinder development in the "high-improvement" sport will be eschewed.

What about injury? Is the triathlon truly a high-risk sport? The 75-percent injury figures cited above seem high, but it's important to note that such a rate of overuse injury was observed over a five-year period; in comparsion, studies have found that 50 to 65 percent of endurance runners are injured during just one year of training. Thus, overuse-injury frequency often ranges from nine to 12 training sessions per week. Avoidance of a pattern of "hammering away" in a high impact sport such as running and an engagement with three different movement patterns (running, swimming, cycling) does indeed seem to be beneficial, from an injury-prevention standpoint. On the other hand, the three-movement plan probably does not give triathletes an advantage over pure swimmers and cyclists; since the latter do not include running in their training schemes, they are likely to have lower injury rates, compared with athletes.

Here is our final take-home point: Since triathlon injuries tend to revolve around the knee, lower back, and Achilles tendon, triathletes should spend extra time strengthening those parts of their bodies in functional ways, i.e., during movement patterns which mimic those occurring naturally in their sports. TRIATHLETES

To learn about Glucosamine and Chrondroitin Sulfate: Great Theraphy For Athletes' Joints?, Is The Use Of Variable Pace Better Than Keeping An Even Keel?, Or Rage Against The Machine: Re-Build Your Body Without Expense Exercise Equipment  (the full articles can be read by purchasing Vol. 17 Issue 8 of Running Research News) and many more running related topics, simply click-on the Back Issues link, and select the volume and issues number, from the drop-down menu, or type in another topic of interest. A subscription to Running Research News is another way to receive valuable information about running. BUY NOW.