The quadriceps muscle brings your knee into full extension.

四头肌肌肉让你的膝进入完全的延长。

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Without lifting your heel up in the air, tighten your quadriceps muscle as hard as you can for ten seconds.

向上举起你的脚后跟，绷紧你的四头肌肌肉坚持10秒。

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It doesn't mean you can't climb mountain but first you need to strengthen up the quadriceps muscle in terms of strength and muscular endurance so that your knee is stable when you are climbing.

这并不表示您不能爬山，但首先您需要用强化肌肉力量和肌肉耐力的方式来强化四头肌，这样在您爬山的时候膝盖就能稳定。

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His condition, patellar tendinitis, can be described as inflammation of the tendon that attaches the quadriceps (thigh muscle) to the tibia (shin bone).

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Muscle activation: This phase involves four-second contractions of major muscle groups in the lower body, including calves, quadriceps, hamstrings, hip flexors, groin, and hip and lower back muscles to help athletes increase awareness of individual muscle groups.

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