Muscles During Exercise
When you EXERCISE, your muscles do MUCH more work than usual. They contract and relax repeatedly. To do this, they need more ENERGY (from food) and more OXYGEN (from breathing). That's why your heart rate goes up — to deliver oxygen-rich blood to working muscles faster.
What happens. (1) BLOOD FLOW increases to muscles — they get warmer. (2) ATP, the cell's energy currency, gets used and replenished rapidly. (3) During hard exercise, muscles produce LACTIC ACID — that burning feeling. (4) Tiny TEARS occur in muscle fibers (microtrauma). (5) Afterward, the body REPAIRS those tears stronger than before — that's how muscles grow with practice.
You feel sore the day after a hard workout. What's happening?
Why warm up and cool down. WARM-UP gradually increases blood flow and joint lubrication, reducing injury risk. COOL-DOWN helps your heart rate gradually return to normal and may reduce stiffness. STRETCHING after exercise (when muscles are warm) helps maintain flexibility. SKIP these and you're more likely to get injured or extra-sore.
Notice Your Muscles
Do 20 jumping jacks. Notice: which muscles feel it? How does your breathing change? Your heart rate? After resting 5 minutes, are you back to normal? You just observed your body's exercise response in real time.
Your muscles are remarkable adaptive tissue. They strengthen when challenged and weaken when unused. Move your body regularly — and they'll keep you going for life.
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