Eccentric Training - Best Practice to Strengthen Your Leg Muscle and Improves Your Running Economy

running down the mountain

Storming up the mountain increases leg muscle strength and improves your running economy, but what about running down the mountain? If you do repetitions on a neighborhood mountain, you'll need to jog down the mountain before you can storm back up the hill. Does this downhill jog get you anything but a good jolt of your knees?

Naturally! As we have already reported earlier, running down the mountain can prevent leg muscle pain, especially in the anterior quadriceps femoris muscle. Pain often occurs when the muscles are engaged in a higher than usual number of eccentric contractions, in which the muscles try to contract while actually stretching them.

The quadriceps notoriously play the role of the "offended liver sausage" mainly because gravity pulls the knee down (i.e., flexing the knee) with every step while running. This flexion stretches the quadriceps muscles just as they are contracting (trying to contract) to avoid excessive knee flexion. The resulting repetitive stretching (which occurs approximately 90 times per minute per leg) can cause significant damage to the quadriceps muscles.

By simply doing your usual level of exercise, your quadriceps will be used to the tension that comes with it and usually don't protest too much. However, if you run more kilometers than you are used to, your quadriceps muscles may protest, which cannot be ignored. If you've ever increased your mileage significantly, or oneRun a marathon , you know the feeling.

The downhill run increasingly eccentric this, "pullout" effect on the quadriceps muscles because the leg at each step a little further "falls" than usual. Thus, the leg acceleration on impact (foot strike) is greater and the forces that lead to knee flexion are correspondingly greater. The quadriceps muscles, of course, keep trying to do their job and resist the knee flexion, but the strain on them is much greater. Microscopic tears in the quadriceps muscle fibers and connective tissue can occur, which can result in significant pain.

But that doesn't mean that going downhill will hurt you. In fact, it's good in the long run because your quadriceps adapt quickly. Obviously, if the quadriceps are exposed to downhill walking, they will hurt, but if you start walking downhill a few weeks later, your quadriceps will be considerably more robust and less prone to pain. Additionally, if you run longer than usual after the downhill workout, your quadriceps muscles won't hurt as quickly. The protection against pain gained by running downhill seems to carry over to regular training.

The 6 week factor

The pain protection through a single mountain run cycle can in fact last up to 6 weeks for reasons still to be clarified. Several years ago, scientists at the University of Massachusetts had 109 people perform 2 sets of 35 maximum eccentric contractions of the biceps muscle in the upper part of an arm. Essentially, these eccentric contractions consisted of lifting a heavy weight, forcing the biceps muscles to stretch as the weight was being lowered at the same time the muscles were trying to contract in order to counter the downward movement of the weight as long as possible. (1)

After this unusual workout, muscle pain and tension peaked about 2-3 days later; the maximum swelling did not appear until a few days later. Biceps strength decreased immediately after the hard workout and stayed below nominal for 10 days.

When the test subjects completed the same biceps program 6 weeks later (without any intervening biceps training), they felt significantly less pain and less muscle strength loss. The biceps muscles were somehow protected from these problems by the previous eccentric training session.

Interestingly, this protection didn't last much longer than 6 weeks. When a second group of test subjects waited 10 weeks after the previous excessive training session before exerting their biceps muscles again, they suffered from uncontrollable pain and lost much of their strength. What happened? Why could the biceps "remember" what happened 6 weeks ago but not what happened 10 weeks ago?

The Massachusetts scientists suspected that a tough session of eccentric training “teaches” the nervous system how to better control and distribute the forces acting on particular muscles. Theoretically, this reduces the stress on the individual muscle fibers when an eccentric activity threatens to “tear them apart” - and thus reduce muscle damage and the resulting pain. Just as the nervous system can learn this process, it can also unlearn it again and this unlearning seems to come after 10 weeks.

Australian rats!

Nice theory, but does it really work that way? To find out, scientists at Monash University in Australia ran 16 laboratory rats on a treadmill over a period of 5 days. 8 of these rats were only allowed to run uphill, while the other 8 only walked downhill. The direct workouts consisted of 5-minute training intervals with 1.5-minute breaks and began on the first training day with 3 training intervals, which increased to 7 intervals on the 5th day. The running speed during the training intervals was a moderate 16 meters per minute. After 5 days, the rats' quadriceps muscles were tested for strength. A biopsy was then performed. (2)

One of the key findings was that the quadriceps muscle cells of the downhill rats contained approximately 10% more sarcomeres per cell compared to the quadriceps muscles of the uphill rodents. To understand what sarcomeres are, you need to remember that a muscle cell is a barrel-shaped structure, and that each “barrel” is filled with a few hundred to a thousand cylindrical, thread-like structures called myofibrils. To illustrate this, just imagine a tubular structure (the muscle cell) crammed with countless small, cylindrical wires (the myofibrils). By the way, when we say a muscle cell is in the shape of a pipe, we are referring to part of a water pipe.

The myofibrils themselves are made up of microscopic, cylindrical chambers that butt together (imagine small cylinders or coils glued at their ends to form a long cylinder). These chambers are called sarcomeres, and it is in the sarcomeres that the proteins (fibers) that allow muscles to contract and expand are found. As special fibers slide inward (toward the center of the sarcomeres), the myofibrils and the whole muscle cell contract, but when the fibers slide outward, the muscle stretches.

As mentioned earlier, walking downhill causes muscle cells to enrich the myofibrils with more sarcomeres. Why is this increase in sarcomeres beneficial and how can it prevent muscle damage and muscle pain? Because the length of the muscle cells does not change significantly with running downhill, the fact that there are more sarcomeres per muscle cell means that each sarcomere will stretch less in a muscle that has been trained by mountain runs during eccentric contractions, in which the whole muscle cell stretches must and is therefore less prone to internal damage.

More sarcomeres, less tension

To illustrate this, let's assume that we have 2 muscle cells that are both 2.54 cm long, but need to stretch to two inches during an eccentric activity. If one of these muscle cells had 10 sarcomeres but the other (the mountain-trained fiber) had 20, it is easy to see that the 10 sarcomeres would each have to stretch 1/10 of an inch to grow the cell to two inches while the 20 sarcomeres in the other cell would only have to stretch 1/20 of an inch to make the cell long enough. As you can see, the sarcomeres are less subject to tension during an eccentric contraction when there are more sarcomeres per myofibril. A pretty clever adaptation!

When you run downhill, you cause your muscle cells to assemble more sarcomeres. An increased sarcomere density reduces the stress on the myofibrils and protects you against pain and damage that may result from future mountain runs and very hard and long workouts and races. The fact that the damage is reduced also means that you will recover more quickly from very hard training sessions and competitions - and be ready for a subsequent qualitative training faster than the poor drip with fewer sarcomeres.

It is no coincidence that elite Kenyan runners train incessantly downhill and uphill - and can do more quality training than any other runnerthis world (4-time off-road world champion Paul Tergat is rumored to do 4 to 6 extremely hard workouts per week when training hard; and the Kenyan runners who took part in the Kenyan off-road race prior to the World Cup routinely did 6 hard Workouts per week and 19 weekly workouts in total). The muscles of the Kenyans trained by the hard mountain runs in the western part of the Rift Valley (or on the rugged slopes of the Aberdares, if the runners come from central Kenya) are oversaturated with sarcomeres and therefore more resistant to wear and tear, both with very fast and with very long running.

It should also be remembered that the higher number of sarcomeres means that muscle contractions can occur more quickly, as each sarcomere has to contract less to compress the whole muscle cell (it takes time for the fibers in the sarcomere to slide into one another; the further they slide, the more it takes longer to compress a muscle). If we revisit our example of one inch muscle cells, but this time assume that they need to contract to a length of 1.26 cm, we can quickly see that the 10 sarcomere cell increases by 1.26 cm per sarcomere needs to contract, while the 20 sarcomere fiber only needs to contract 0.63 cm per sarcomere. The combination of fast-twitch, injury-resistant muscles is a hallmark of Kenyan runners.

All of this speaks all the more in favor of completing a larger part of our training in mountainous terrain. However, there are a few things to keep in mind when walking downhill. When walking down a mountain, bend forward naturally and comfortably; do not try to lean your torso back. Keep yourself under control, but don't stiffen or resist the mountain too much; learn to stay coordinated and balanced as gravity does the work for you. During a race you can run faster than you normally run downhill without exertion, increasing oxygen consumption or increasing your heart rate.

And if you on the mountain train , you should remember that your uphill running exercise while improves your running economy, but that even your mountain operations have a very positive impact on your running. As you run downhill, the sarcomeres of your leg muscle cells multiply. These extra sarcomeres will speed up your steps and help you stay pain and injury free in the future. This will allow you to exercise more regularly and become a better athlete.

References:

-"Muscle Function after Exercise-Induced Muscle Damage and Rapid Adaptation", Medicine and Science in Sports and Exercise, 1992, Vol. 24 (5), pp. 512-520

- "Differences in Rat Skeletal Muscles after Incline and Decline Running", Journal of Applied Physiology, 1998, Vol. 85 (1), pp. 98-104