An odd thing about running is that many runners believe that the best way to optimize aerobic capacity (VO2max) is to run lots of miles. However, the scientific study which detected the greatest improvement ever recorded in VO2max in well trained runners actually linked an upswing in intense training and a decrease in mileage with the big jump in VO2max. BEST TRAINING FOR MAXIMIZING AEROBIC CAPACITY

The study of interest, completed by Timothy Smith, Lars McNaughton, and Kylie Marshall of the University of Tasmania in Australia and Kingston University in the United Kingdom, shook up the training of five experienced runners (1). These harriers were fit (average VO2max was 61.5 ml O2 kg-1min-1), and they were utilizing a variety of different training techniques prior to the onset of research, including long-slow distance work, speed work, tempo training, over speed efforts, and weight training. All five were primarily middle distance runners, and their average age was 23.

Before the investigation began, each runner completed three VO2max tests, which also were used to determine V max (the minimal running velocity which caused a runner to hit maximal aerobic capacity, or VO2max). These exams were completed on a Quinton treadmill. The initial treadmill speed was set at 10 kilometers per hour for two minutes, jumped to 12 kilometers per hour for one minute, and moved up to 14 kilometers for an additional minute. After that, the velocity increased by one kilometer per hour each minute until exhaustion was reached. Oxygen consumption was carefully measured during this incremental test, and VO2max was assumed to have been reached when a runner met at least two of the following three criterias: volitional exhaustion, a heart rate within five beats per minute of predicted max heart rate (using the familiar formulas of 220 - age), and an increase in running speed with no further increase in oxygen consumption. Vmax was defined as the slowest running speed (from the tests) which produced an oxygen-consumption rate equal to V)2max.

To make things interesting, each runner also completed a 3-K time trial and three Tmax tests. Tmax is simply the length of time a runner can keep going at Vmax, and each Tmax test was preceded by a 15-minute warm-up consisting of five minutes of running at 60 percent of Vmax. The treadmill velocity was then set at 18 kilometers per hour (lower than Vmax for each runner), the runner mounted the treadmill quickly, and the treadmill was up-regulated to Vmax within 10 seconds. Each runner then tried to hang on as long as possible, with verbal encouragement provided by the investigators. BEST TRAINING FOR MAXIMIZING AEROBIC CAPACITY

After all this testing, the runners were probably happy to embark on the four-week training program developed by Smith, McNaughton, and Marshall. This 28-day plan focused on two very intense sessions each week; within each workout, all six intervals were completed right at Vmax, a fairly scalding interval intensity. A notable aspect of this training was that the durations of the work intervals were set at anywhere from 60 percent of Tmax to 75 percent of Tmax! That's unusual: Traditionally, with Vmax training (also known as vVo2max training), runners set their work interval lengths at about 20 to 50 percent of Tmax and do not move above 15 minutes of total running at Vmax per workout.

Let's say, for example, that a runner's Vmax corresponds with a pace of 90 seconds per 400 meters (4.44 meters per seconds) and that his/her T max is six minutes. Obviously, 50 percent of six minutes is three minutes. Ordinarily, a "stringent" Vmax session for this runner would then be 5 work intervals with a duration of 50 percent of Tmax, i.e., X 800 in three minutes each, for a total dose of 15 minutes of Vmax running.

If we put this same runner on Smith-McNaughton-Marshall plan, however, things would get much rougher. In the fourth week of S-M2 plan, for example, one workout involved 6 work intervals at Vmax with durations of 75 percent of Tmax. For our hypothetical runner from the last paragraph, this would mean stepping up from 5 X 800 in three minutes each to 6 X 1200 in 4:30 each, with all 1200s completed right at Vmax. That would entail 27 minutes total of Vmax running Red-hot!!

Basically, the runners completed two similar sessions each week, with the rest of their work consisting of "recovery runs". This simple - but very challenging - approach to training produced major gains in performance and fitness. For example, at the end of the four-week period average 3-K time improved from 616.6 to 599.6 seconds. Mean speed in the 3K ascended from 4.9 meters per second to 5.1 meters per second, about a 4-percent upgrade.

To learn more about how BEST TRAINING FOR MAXIMIZING AEROBIC CAPACITY (the full article can be read by purchasing VOL. 23-2 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.

In preparing for events ranging in length from 800 to 100,000 meters, you should always emphasize the quality of your training over mere volume. That is, you should stress speed (and the development of a higher maximal running speed), instead of placing your primary
focus on the accumulation of mileage. Great Workouts

Why is this so? If you had 100 runners standing before you and you wanted to figure out which ones would finish near the front in a race (regardless of whether that race covered 800 meters, 10K, a marathon, or 100K), one of the simplest and most effective forecasting techniques would be to time each runner in a 20-meter dash!

The runners with the fastest 20-meter times would also be the individuals with the quickest clockings for 5K – and for the marathon! On the other hand, if you ranked the runners according to weekly average mileage, you would no relationship at all between training distance per week and performance time!

While this linkage is surprising to runners and coaches, the majority of whom think that the 20-meter sprint is an “anaerobic” event and that running events like the 10K and marathon are purely “aerobic” endeavors, the simple 20-meter test is very accurate.

It has been verified in research carried out by Heikki Rusko, Leena Paavolainen, and Ari Nummela of the KIHU Research Institute for Olympic Sports in Jyvaskyla, Finland with 17 male endurance runners (1). In this Finnish research, the connection between 20-meter and 5000-meter race velocities was extremely strong, even though the average 20-meter speed of 8.15 meters per second was roughly 76-percent faster than 5-K alacrity.

 As it turned out, 20-meter time was a better predictor of 5-K speed than that vaunted “aerobic” variable, VO2max, and 20-meter burning was almost as good as another big-name physiological characteristic – running economy. Great Workouts

Could the 20-meter, 5-K connection detected by the Finns be purely a fluke? If you think so, consider the research carried out at the University of Nebraska at Omaha, in which Aaron Sinnett, Kris Berg, and their colleagues determined that performance times for 10,000 meters can be predicted with a high degree of accuracy using two other attributes of speed and power – 300 meter sprint time and plyometric leaping distance (2). Sinnett, Berg, and co-workers also found significant correlations between 10-K performance and 50-meter sprint time, as well as vertical jumping ability.

Why are researchers finding that “anaerobic” physiological attributes are so important for success in almost purely “aerobic” events? To put it another way, why are exercise scientists discovering that measures of speed and explosiveness are great predictors of performance in races which seem to rely more on endurance than
on power?

To understand this completely, let’s take a close look at the Nebraska-Omaha study carried out by Sinnett, Berg, et al. In this fascinating work, the researchers examined 36 e experienced runners (20 men and 16 women) whose 10-K times varied from 32:36 to 56:24.

The age of these runners ranged from 19 to 35 years, and 27 of the athletes were preparing for a marathon as the research was conducted. The 36 subjects were running about 30 miles per week and had trained five times weekly for at least six months before the study started. Nineteen of the 36 subjects engaged in some form of strength training, and 27 had completed a marathon at some point in their running careers. They were not beginners! Great Workouts

Sinnett and Berg were smart to put all of the runners through a 50-meter sprint test. For one thing, Rusko and the Finns had found predictive success for the 5K with the even-more abbreviated 20-meter sprint.

In addition, essentially none of the power created for 50-meter sprinting from a standing start is derived aerobically; the energy for 50-meter blast-offs comes from the “phosphagen system” within muscle cells, i. e., from existing ATP within muscle cells and from the high-energy phosphates which are donated by creatine phosphate to ADP inside muscles to make ATP (ATP is the energy currency for muscle fibers; its energy is used directly to produce muscle contractions; all other “fuels” for muscle contraction, including carbohydrate, fat, protein, and creatine phosphate, must first be converted to ATP before any muscular action can take place).

Not even a single molecule of oxygen is required for the phosphagen system to work, and thus the 50-meter sprint is a true “anaerobic” test.

The 300-meter test was another good choice for the Nebraska researchers. Running all-out for 300 meters from a standing start puts little energetic demand on the aerobic system; it instead depletes the phosphagen system in about 10 seconds or so and then relies almost exclusively  on the “glycolytic energy system,” an oxygenindependent, intracellular, energy-producing mechanism which relies on the breakdown of glucose to pyruvate and
lactate for the creation of immediately usable energy (in the form of our friend, ATP).

The 36 athletes also performed two vertical-jump tests, one with a dynamic counter-movement involved and the other from a static, flexed-knee beginning position.

For these tests, each athlete’s vertical reach was first assessed as he/she stood motionless next to a Vertec instrument. Every runner simply reached as high as possible
with his/her dominant arm, without letting the heels rise off the floor. To determine actual jumping height, the loftiest reach in inches from this standing position was subtracted from the highest mark made on the Vertec instrument during the two jumps. Great Workouts

For the jump with counter-movement, the athletes started in a standing position next to the Vertec device, quickly descended into a semi-crouched, flexed-knee position, and then – without the slightest hesitation – jumped straight up with maximum power and attempted to touch the highest-possible point on the Vertec instrument.

For the no-counter-movement vertical jump, the runners started from a static take-off position, with the knees locked at 90 degrees of flexion. Each athlete held this position for three seconds and then jumped as high as possible– straight up.

In the counter-movement jumps, the “snap-back” of muscles which have been quickly stretched provides a significant amount of the force required for vertical leaping without incurring the penalty of direct energetic cost. For the no-counter-movement jumps, the force is provided primarily by energy-costly, active contractions of propulsive muscles which are forced to work “from a standing start.”

As you might guess, athletes whose muscles can generate much work by means of energetically cheap, elastic reactions tend to be able to run quite efficiently, i. e., at relatively low percentages of their maximal rates of energy usage. Such athletes tend to find specific speeds of movement to be easier to sustain, compared with those athletes whose muscles have less-enhanced elastic properties.

These athletes would also be capable of generating greater power (attaining higher maximal speeds), compared with elastically deficient runners, since the enhanced
elastic forces would supplement the normal forces created by the costly breakdown of ATP. In other words, having ample elastic characteristics in the leg muscles is a good thing for a runner! Small wonder that one of the highest compliments an elite Kenyan runner can pay another competitor is to say, “You run as though you have springs for legs.” Great Workouts

Note that muscle elasticity has nothing to do with a runner’s aerobic prowess. A runner with great elasticity might have a high VO2max or a low VO2max; there is simply no direct connection.

The final test of “anaerobic” prowess – the plyometric leap test – was initiated from a standing position, from which the athletes performed three consecutive forward leaps by springing from one foot to the other; for the third and last leap, the athletes landed on both feet. In effect, the plyometric leap test was just like the triple jump performed in track and field, except that the leap exam was carried out from a standing rather than a running start.

Actual plyometric-leap length was measured from the heel which was closer to the starting line after the third leap back to the starting line itself. Sinnett, Berg, and their fellow researchers found that there were significant correlations between 10-K time and (1) 50-meter sprint time, (2) counter-movement jump height, (3) non-counter-movement jump height, and (4) percent body fat.

The two best predictors of 10-K success were plyometric leap distance and 300-meter sprint performance. Great Workouts

Just by itself, plyometric leap distance explained a whopping 74 percent of the variation in 10-K race times for the entire group of 36 runners. Together with 300-meter sprint performance, plyometric leap distance accounted for an incredible 78 percent of the variance!

To summarize, one “anaerobic” attribute – plyometric leap distance – was able to account for nearly three-fourths of the variation in performance times for this relatively large group of distance runners. “Aerobic” variables such as VO2max, lactate threshold, and running
economy have been known to do worse than this in various studies of endurance-running performance (i. e., they have accounted for substantially less of the variation in
performance). Two “anaerobic” attributes – plyometric leap length plus 300-meter run time – accounted for about four-fifths of the 10-K variation.

Should you begin carrying out daily three-jump plyometric training in order to improve your racing performances? No, not at all (although such effort can be profitably included in your overall program): What this Nebraska study simply means is that the power and elastic
characteristics of your leg muscles will play a large role in determining how well you will perform in your races.

Thus, you need to carry out the kind of training which will optimize such characteristics – the kind of effort described in detail in this book. Great Workouts

If you are somewhat shocked about the ability of “anaerobic” factors such as plyometric leaping distance, counter-movement jump height, 300-meter sprint time, 50-meter sprint performance, and 20-meter clocking to predict distance running performances, you shouldn’t be.

For one thing, it is readily apparent that the fundamental attributes which promote better sprint times, notably the ability to apply more force to the ground during foot strike and the ability to apply that greater force more quickly, can also be great for middle- and long-distance running, provided a runner can develop the ability to sustain such enhanced power outputs for the necessary amount of time.

Greater force will translate to longer strides, and quicker force production will mean faster strides; the combination taken together can lead to major improvements in running velocity – and the ability to run faster in your chosen competitive distance. There are other fundamental reasons for this linkage between “anaerobic” and “aerobic” factors, which I will explain in a moment, and several other research studies also connect such apparent “opposites.” Great Workouts

For example, in Heikki Rusko’s 5,000-meter research, 5-K fortune was well predicted by 20-meter time, but it was also forecast by another high-speed attribute which Rusko called VMART – the maximal speed a runner could attain during a series of progressively more difficult, increasingly anaerobic, short-duration sprints.

During Rusko’s strenuous VMART tests, his runners initially jumped on a treadmill and cruised along for 20 seconds at a pace of 3.71 meters per second (7:14 per mile) with a treadmill grade of four degrees. 100 seconds of recovery followed, and then the runners burst along for 20 seconds at 4.06 meters per second (6:36 per mile).

This pattern (20 seconds of fast running alternating with 100 seconds of recovering) continued for as long as possible, with each successive 20-second jaunt taking place at a speed which was .35 meters per second faster than the previous work interval.

The runners kept going until they collapsed or began to fall off the treadmill during one of the 20-second explosions (fortunately, all of the Finns were “in harness,” with their special, light-weight, leather “straightjackets” connected to both an automatic treadmill brake and an overhead support arm which held them Tinkerbelle-style whenever their leg muscles ceased producing adequate power).

The average speed at the collapse point was 6.57 meters per second (4:05 per mile), so you can see that the Finnish harriers did quite well on the four-degree treadmill grade. Naturally, the speed attained wasn’t as great as during the 20-meter races (wherein 8.15 meters per second turned out to be the average velocity), since the 20-meter pacing occurred on flat ground with “fresh legs” and the VMART test took place in the face of considerable built-up fatigue (the 20-meter sprints were helped along, too, by their short duration of approximately 2.5 seconds, while VMART had to be sustained for 20 seconds).

As we have indicated, VMART was a terrific predictor of 5-K prowess. In fact, just like 20-meter sprint time, VMART was better than the venerable VO2max in predicting 5-K race time. In fact, VMART was even superior to running economy at foretelling what would happen in a 5-K race!

The question you have to be asking right now (especially if you are a 5-K runner) is: How can I optimize my VMART? That is the right question to ask, especially since it is certain that the optimization of VMART will improve your performances significantly, even if you are an
800-meter runner – and even if you are a 100-K competitor. Great Workouts

Rusko’s outstanding body of research reveals that hikes in mileage do not maximize VMART, nor should they be expected to do so. To have a great VMART and to reach
your highest-possible VMART, you have to be able to run fast – faster than you do now.

Running tons of miles at moderate paces will not get this done; in fact, there is a good chance it will reduce the power and explosiveness of your leg muscles (not to mention the spiked risk of injury which goes hand in hand with high-mileage training).

The route to an optimal VMART travels through regions of highintensity, high-quality, explosive training, not through phases of vast volumes of moderate-speed miles. Despite what any coach may tell you, you do not get faster by focusing on running lots of miles at slow and moderate velocities – and then hoping for the best. VMART moves upward optimally in response to high-quality, not highvolume, running.

The findings of Rusko and Berg are supported by those of the great South-African researcher Tim Noakes, who may have gotten this whole “paradigm shift” rolling with an elegant study published in 1988 (3). In Noakes’ investigation, endurance performance was well predicted by the top speeds which athletes could attain on a treadmill; those runners with the highest peak running speeds also had the best endurance race times in their portfolios.

As was the case with Rusko’s research, peak running velocity was a better predictor of performance than VO2max; it was also far superior to running economy.
As if that were not enough, a completely separate investigation has also found that 50-meter sprint time was well correlated with 10-K performance (4). In addition, Ronald Bulbulian and his co-workers determined that 58 percent of the variation in five-mile run times in welltrained college athletes was accounted for by the capacity to perform high-intensity (“anaerobic”) running (5). Great Workouts

In yet another study, famed exercise physiologist Dave Costill and his associate Joe Houmard took a close look at the physiological qualifications of 10 runners who trained about 50 miles per week and averaged a not-tooshabby 16:43 for the 5K (6).

Although oxygen-dependent chemical reactions provide about 93 percent of the energy needed to run a 5K, maximal aerobic capacity VO2max was again a poor predictor of performance. The two best prognosticators of 5-K finishing time were anaerobic power (the ability to sprint at high speed) and a variable called time to exhaustion (TTE).

You heard it right: Even though anaerobic energy creation accounts for only 7 percent of the energy required for a feverish 5-K race, raw anaerobic power is a superior predictor of 5-K success, compared with aerobic capacity (VO2max).

In Costill’s 5-K runners, anaerobic power was measured during short sprints and vertical jumps. TTE was calculated in this way: A stopwatch started as an athlete began running on a flat treadmill at an intensity of 85 percent of VO2max (which normally translates into around 90-92 percent of max heart rate). The treadmill grade was then increased by 3 percent every two minutes, and the clock stopped when the runner could no longer continue at the appropriate pace. Great Workouts

TTE was simply the total time an athlete could hold out on the treadmill and represented a runner’s ability to sustain very high-intensity, significantly anaerobic running. Thus, the Costill-Houmard study parallels the other investigations we have described: Attributes of power, often called anaerobic factors, outweigh aerobic factors such as VO2max and economy in determining overall race performance.

The fundamental mechanisms underlying the connection between outstanding anaerobic capacities and exceptional endurance performances are not really difficult to grasp. As we have already mentioned, the factors which promote very high sprint speeds (more force applied to the ground, force applied more quickly) will also foster considerably faster distance running.

In addition, middle- and long-distance runners with very high maximal running speeds will always tend to out-compete harriers with more-modest maximal velocities, since any specific race pace will represent a higher percentage of maximal
and will therefore be more difficult to sustain in the latter case.

To put it another way, if endurance-runner A has a peak running velocity of 8 meters per second, and endurance-runner B has a max of just 6.8 meters per second, runner A has a much better chance of running a 5K in 15 minutes flat (i. e., at 5.56 meters per second). For runner A, 15-flat pace would be just 70 percent of maximal speed; for B, it would be way up there at 82 percent ofmax.

There is one simple fact about competitive running which you can definitely “put in the bank:” The closer you are to your maximum running speed, the shorter will be the time during which you can sustain your effort.

To put some more numbers on this kind of thinking, if you have a max speed of 8.15 meters per second, a 5-K alacrity of 4.63 meters per second (for an 18-minute 5-K finishing time) would be only 57 percent of your running-speed max, whereas if you’re a poor soul with a
maximum of just 7 meters per second, you would have to settle in at 66 percent of your max during an 18-minute 5K, and the pace would feel (to your mind, muscles, and lungs) quite a bit tougher.

Having a high max velocity makes it more likely that you will be able to handle the higher end of possible race speeds in all of your races. If you have a high max speed, you already have the ability to run fast, and your key additional task is to train in a manner which optimally extends the time over which you can run at your sizzling paces. Running long and slow does not help in this regard, because it simply does not prepare your body for high-velocity effort. Great Workouts

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.

To learn more about how to Is Running Bad For Mtor & Raptor?  (the full article can be read by purchasing Vol. 22 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. A subscription to Running Research News is another way to receive valuable information about running. SIGN-UP NOW!

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

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