When you lift weights, something cool happens to energy. It shows us a rule called the Law of Conservation of Energy. This rule says energy can't be created or destroyed. It can only change from one type to another.

Different Types of Energy Involved

1. Chemical Energy:

   • Your body gets energy mainly from chemical energy. This energy comes from things you eat, like carbohydrates, fats, and proteins.
   • On average, a person uses about 2,000-2,500 calories each day. This is around 8,400-10,500 kilojoules of chemical energy.

2. Mechanical Energy:

   • When you lift weights, your body changes chemical energy into mechanical energy. This is the energy your muscles use to move.
   • For example, when you lift a barbell, the energy shifts into kinetic and potential energy. If you lift a barbell that weighs about 80 kg from a height of 1 meter, you can figure out how much energy you gain from gravity using this formula:

   Potential Energy (PE) = mass (m) × gravity (g) × height (h)

   Here’s what the letters mean:

   • PE = potential energy
   • m = mass (80 kg)
   • g = gravity (about 9.81 m/s²)
   • h = height (1 m)

   If we plug in the numbers, it looks like this:

   PE = 80 kg × 9.81 m/s² × 1 m ≈ 785 Joules

3. Thermal Energy:

   • Not all the energy goes into lifting weights. Some energy is lost as heat. This happens because of how our bodies work and the hard effort our muscles put in. This is why you might feel warm after working out.

Energy Transformation Summary

• Starting Energy: Chemical energy from food (about 8,400-10,500 kJ)
• Energy Used: While lifting, this energy changes into:
  • Mechanical energy (like about 785 Joules for lifting 80 kg)
  • Thermal energy (some energy is lost as heat)

So, when you lift weights, the energy changes from chemical to mechanical and thermal forms. This follows the Law of Conservation of Energy. Knowing how this works can help athletes and coaches improve their training methods!