They've put on their gear and done their warmup, and now it's time for one more routine—stretching.

他已經著裝完畢並做好了熱身，現在要進行一項例行運動了——伸展。

Typically, athletes stretch before physical activity to avoid injuries like muscle strains and tears.

通常，運動員在運動前會進行伸展避免像肌肉拉傷和撕裂這樣的受傷。

But does stretching actually prevent these issues?

但是伸展真的可以預防這些問題嗎？

And if so, how long do the benefits of stretching last?

如果是的話，伸展的效果可以持續多久呢？

To answer these questions, we need to know what's actually happening in the body when we stretch.

為了回答這些問題，我們需要先知道當我們進行伸展運動時體內究竟會發生什麼事。

There are two kinds of stretching our athlete might be doing.

我們的運動員可能會進行兩種不同的伸展運動。

Dynamic stretches, which are controlled movements that engage a range of muscles throughout the motion.

一種是動態伸展運動，這是一種加以控制的運動，可以在運動過程中運用到一系列肌肉。

And static stretches, where the stretcher holds a position to keep specific muscles at a fixed length and tension.

另一種是靜態伸展運動，這種運動是透過將身體姿勢保持在某個特定的位置上，以維持特定肌肉的長度和張力。

Our athlete is currently doing a static hamstring stretch—a 30-second interval where he pulls his hamstring beyond its usual range of motion.

這位運動員目前正在進行靜態的腿後肌伸展運動——他將腿後肌伸展到超出其正常運動的範圍，每次持續 30 秒。

However, while we often think of stretching a muscle like stretching a rubber band, muscles are actually comprised of various tissue types, which interact to make a complex material.

但是，儘管我們通常將伸展肌肉比擬為伸展橡皮筋，肌肉其實是由各種類型的組織組合而成，這些組織相互作用形成了一種複雜的物質。

Rubber is elastic, meaning it resists being stretched and then returns to its original shape.

橡皮具有彈性，代表它會抵抗被伸展，然後恢復到原來的形狀。

But muscle is viscoelastic.

但是肌肉是黏彈性的。

This means that, in addition to those elastic qualities, muscle changes under the stress of being stretched.

表示除了擁有橡皮筋的彈性外，肌肉在承受伸展壓力時也會發生變化。

Let's see this in action.

我們來看看實際情況。

At the large scale, this hamstring stretch is pulling on layers of protective tissue surrounding the muscle fibers, as well as the tendons that connect this muscle to nearby bones.

宏觀來看，這種腿後肌伸展運動會伸展肌纖維周圍的保護性組織層，以及該肌肉與附近骨骼相連的肌腱。

These tissues contain elastic proteins like collagen and elastin, which allow them to slightly elongate over the duration of the stretch.

這些組織中含有彈性蛋白，如膠原蛋白和彈性蛋白，使它們能夠在伸展運動期間內稍微被拉長。

At the smaller scale, these skeletal muscle fibers are comprised of millions of sarcomeres—the smallest contracting unit of muscle tissue.

從微觀來看，這些骨骼肌纖維由數百萬個肌節組成，為肌肉組織中最小的收縮單元。

Sarcomere's long, fibrous proteins can relax to elongate muscle fibers or they can contract to shorten them—pulling on tendons and protective tissue to create the force propelling our athlete's body.

肌節長長的纖維狀蛋白可以放鬆來延長肌纖維，或者可以收縮來縮短，拉動肌腱和保護組織，產生推動我們的運動員身體的力量。

And when those tissues have been stretched out, they retain their strength at longer lengths, allowing our athlete to take full advantage of his improved range of motion.

當這些組織被伸展後，它們就能將强度維持更長的時間，讓運動員充分運用提升後的動作幅度。

Unlike a rubber band, this muscle's resistance to stretching decreases with each 30 second stretch, allowing our athlete to continually elongate his hamstring.

與橡皮筋不同，這種肌肉對伸展的抵抗力在每次 30 秒的伸展運動中都會減少，使得運動員能夠不斷地延長他的腿後肌，

And this improved flexibility likely decreases the chance of incurring certain muscle injuries.

改善的靈活性可能會減少受到某些肌肉損傷的機會。

But due to muscle's elastic properties, this effect will be gone in just 10 minutes without further activity.

但由於肌肉的彈性，如果沒有接著運動，這種效果將在短短的十分鐘內消失。

The exercise from his match should elevate his muscle's temperature and continue elongating the muscle, maintaining his increased flexibility throughout the game.

比賽中的運動應該會提高他的肌肉溫度並繼續伸展肌肉，在整場比賽中保持他增強的彈性。

But once he gives his hamstrings a break, they'll retract back to their previous state.

但一旦讓腿後肌肉休息，它們就會回到之前的狀態。

So if all this is just temporary, how can you permanently improve your flexibility?

如果這些都只是暫時性的，那麼如何才能永久提升身體的柔韌性呢？

For skeletal muscles, improved flexibility comes from additional sarcomeres, which allow you to maintain strength at even greater lengths.

對於骨骼肌而言，改善柔韌性是通過增加肌纖維中的肌節來做到的，甚至可以讓你更久地維持力量。

Sarcomeres are added and subtracted to muscles depending on how frequently they're used, so improving overall flexibility requires a comprehensive stretching regimen.

肌節會根據肌肉的使用頻率增加或減少，因此提高整體柔韌性需要一個全面的伸展計劃。

Plus, you need to stretch often—very often.

此外，你需要經常進行伸展，非常頻繁。

Current research suggests at least 10 minutes a day for roughly two months.

目前的研究表明，每天至少伸展十分鐘，大約需要持續兩個月的時間。

And since it's unsafe to hold any stretch for too long, it's recommended that you break up your stretching within any given session.

而且，由於長時間保持任何一種伸展姿勢都是不安全的，建議在每次伸展中間進行休息。

Frequent stretching also makes lasting changes to your brain.

頻繁的伸展還會對大腦產生持久的改變。

The more you stretch a muscle, the higher your pain threshold becomes, allowing you to stretch further and further.

當你不斷地伸展一個肌肉時，疼痛閾值就會越高，讓你可以進一步地伸展肌肉。

Long-term improvements to your flexibility can provide a better range of motion for your joints, potentially reducing your risk of muscle injury in the short and long-term.

柔韌性的長期改善可以有更好的關節活動度，從短期和長期來看都可以降低肌肉受傷的風險。

But it's also possible to stretch too much, as flexible people can move their joints in potentially dangerous ways.

但是也有可能過度伸展，因為柔韌性強的人可能會以造成危害的方式活動關節。

Stretching also isn't helpful for every kind of movement, especially those where muscle injuries aren't very common.

伸展並不是對於每一種運動都有幫助，尤其是那些不常肌肉受傷的運動。

For example, long distance running only involves a small range of motion for the joints involved, so stretching is unlikely to prevent that sport's most common injuries.

例如長跑等只涉及少量關節活動的運動，進行伸展不太可能預防該運動中常見的肌肉受傷。

When it comes down to it, different lifestyles require different kinds of mobility.

歸根結底，不同的生活方式需要不同的活動量。

And no single stretching regimen is flexible enough to fit every situation.

沒有一種伸展方法適用於所有情況。