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In recent years, with the rapid development of the marathon industry, trail running events in China have also become increasingly popular. Many road running experts have also joined the ranks of trail running. Just a few days ago, a running friend privately messaged the editor saying, 'Is trail running more damaging to the knees compared to road running?'
Running, in general, is a medium to high-intensity activity. Whenever running is mentioned, someone will jump out and say 'running damages the knees.' Some of these comments are based on personal experiences of injury from running, while many others have never run themselves and are simply repeating hearsay, afraid to start trying.
So, does running really damage the knees? Is trail running more damaging to the knees than road running? How can we run without injuring our knees?To address this issue, Wuyan Zu will explain it to everyone today.
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Why do people often say that running damages the knees?
We all know that any material or equipment will experience wear and tear under long-term stress and use. Therefore, as part of our body, the knees will also experience some wear and tear under long-term use and high-intensity exercise.
The knee is the most complex joint in the human body, connecting the thigh bone and the shin bone through the knee joint, and it bears most of the body's weight. Each time we run, the movement of the joint is driven by muscles and the ligaments stretch and extend. There are two small pads between the thigh bone and the shin bone called menisci that act as shock absorbers, and the joint capsule secretes joint fluid for lubrication.
The knee works like a machine: muscles are the engine, ligaments are the transmission belt, menisci are the shock absorbers, and the joint capsule is the lubrication system.However, the human body is not as simple as a machine. The cushioning of force upon landing is not solely completed by the menisci but is assisted by the instantaneous contraction and relaxation of muscles and ligaments. Therefore, the stronger, more powerful, and more elastic the muscles are, the less likely they are to get injured.
Let's talk about the impact force on the knees during running—each landing impact during running is 2-4 times the body weight, with a stride frequency of 120-160 times per minute. The longer the running time and the greater the mileage, the greater the impact and wear, making injury more likely.
The faster you run, the higher the stride frequency, and the higher the pressure on the knees, making injury more likely. Although the main range of motion of the knee joint is forward and backward, there is also a certain degree of lateral movement, generally 3-5 degrees. This creates lateral impact forces. However, the bones primarily bear impact forces from the front, so incorrect posture can also cause additional impact forces leading to injury.
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Why is trail running more likely to damage the knees than road running?
The biggest difference between outdoor running and marathon running is the uncertainty during the running process.Marathons are generally held in cities, with flat roads and mostly paved tracks, featuring representative cityscapes and buildings along the way. There are markers at appropriate intervals, so getting lost is unlikely.
Trail races are held in mountainous areas, with undulating tracks and elevation changes usually measured in kilometers. Participants have to deal withdense forests and rocks, steep and slippery paths, moss-covered trails, and narrow winding tracks.Sometimes you have to wade through water, and when the slopes are steep, you may even need to climb.Encountering bad weather like strong winds, hail, rain, snow, or fog makes it even worse.
Most importantly, the ascents and descents in trail running are not comparable to the ups and downs in road running.Running downhill puts 3-6 times the usual pressure on the knees, and the lubricating fluid that effectively reduces cartilage wear varies with each runner's age and physical condition. Additionally, improper equipment and downhill techniques can cause significant knee damage.
Moreover, when running downhill, muscles are in eccentric contraction, forcing muscle fibers to stretch, causing micro-tears and minor injuries. This results in slower speeds and post-race leg soreness and pain. Continuous downhill running keeps some muscles in a constant state of tension, which can lead to cramps.
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Whether road running or trail running, running doesn't have to damage the knees
1. Focus on controlling running volume
To avoid knee injuries while running, the first thing to do is to reasonably control the running volume. When the annual increase in running volume is unreasonable, yourlegmuscleswill feel a certain level of fatigue. The more fatigued the muscles are, the greater the impact force on the menisci. When this exceeds their cushioning capacity, it can damage the femoral head. Many injuries to the menisci and femoral head are irreparable.
For experienced runners, during the pre-race period of increasing running volume, first sense whether running the same volume as the previous week feels easier. If it does, stop immediately if you feel unable to control your running posture at any point in the increased volume. If it doesn't feel easier than the previous week, do not increase the running volume.
For beginners, increasing the running volume every two weeks is more reasonable. This means one week of improvement and one week of consolidating results. The increase does not need to be a fixed proportion. Pay attention to your body and stop immediately if you feel your landing becomes heavier or if your knees feel pressured.
2. Reduce speed training
At the same running volume, higher speed means greater impact force and a higher likelihood of knee injury. Additionally, higher speed can deform running posture as you unconsciously extend your legs to increase stride length and speed. This often results in landing with straight legs, losing the muscle cushioning ability provided by joint bending, and directly transmitting the impact force to the knees. This is why many novice runners get injured within the first two months of running, even with low running volumes.
For long-distance and endurance running, even experienced runners generally do not have speed training exceeding 10% of their total training volume. Usually, there is only one interval speed training session per week. Novice runners do not need to schedule speed training at all. Simply accumulating training volume reasonably and arranging rest will steadily improve performance.
3. Adjust running posture
Running posture's impact on the knees is thoroughly described in the documentary 'Marathon Legion.' Properly controlling running posture can reduce knee impact by more than 25% for Patrick Makau (the marathon world record holder) compared to top Japanese marathon runners.
For ordinary runners, the following postures cause the most knee damage. Overcoming these issues can adjust running posture to the most efficient state:
a. First, landing with the foot in front of the knee causes the knee joint to straighten or even lock. At this point, a considerable forward force is transmitted back through the ground, impacting the knee joint.Therefore, when landing, control the ankle position to be as close to directly under the knee as possible or slightly behind it. The bend in the knee will provide excellent cushioning.
b. Try to land on the forefoot, especially with the center of gravity ideally on the forefoot between the big toe and second toe. This gravity position is the force point for the leg's proper alignment. Any force point closer to the outer side, inner side, or rear of the foot will cause lateral impact forces on the knee, leading to injury.
c. Learn to control body stability and avoid swaying from side to side. Lateral swaying changes the center of gravity position laterally, causing lateral impact forces on the knee. The knee's front side bears weight most effectively. Therefore, avoid excessive arm swinging and overstepping during running, as these increase body instability.
4. Strengthen muscle training
Strong leg muscles, especially the thigh muscles, can provide corresponding protection for the knee joint, particularly the quadriceps and tensor fasciae latae. Strong quadriceps can reduce the impact on the patella and menisci during landing, which is a common cause of front knee pain. The tensor fasciae latae is related to the iliotibial band, and many cases of outer knee pain are due to iliotibial band issues.
There are many ways to train thigh muscles, such as lunges, squats, stair climbing, and wall sits. Wall sits are a static exercise with minimal impact on the knee joint, making them an important part of many runners' leg muscle training. However, do not pursue wall sit duration and intensity too quickly during training.
5. Pay attention to stretching and relaxation
Post-run stretching is often overlooked by many runners, especially after high-intensity training when they are exhausted and just want to eat something quickly, take a shower, and rest, often skipping the stretching phase. However, stretching is very beneficial for muscle recovery and growth.After training, fully extend your muscles, ligaments, and even fascia to help them quickly recover from fatigue and become stronger during regeneration.
Pre-run relaxation and warm-up are also essential. Many sports injuries occur at the beginning of training when the body has not fully adapted to the exercise state. The joint capsule in the knee joint has not yet secreted lubricating fluid. Starting intense training at this time is like driving a car at 180 km/h without warming up the engine.Therefore, always have a sufficient warm-up before each run.
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Conclusion
Running doesn't have to damage the knees. To achieve this, no single factor is decisive; the five factors mentioned above are interrelated. Many articles on running training mention 'listening to your body.' This seemingly vague advice is actually a crucial principle for protecting the knees. The better you understand your body, the better you can control it, and the further you can stay from knee injuries.