Q.Physical activity helps to increase ________________________. a. size of muscle b. size of bone c. size of brain d. size of liver

Imagine you lift a heavy bag of groceries every day. At first, your arm tires quickly. But after a few weeks, the same bag feels lighter, and your arm looks slightly fuller or more defined. That change — the increase in the size of your muscle — is muscle hypertrophy.

At its simplest, muscle hypertrophy is the scientific term for a muscle getting bigger. It happens when the individual muscle cells (called muscle fibres) increase in thickness. Think of it like blowing up a balloon: the rubber itself stretches and expands, but you aren't adding new balloons. Similarly, hypertrophy doesn't create new muscle cells; it makes the existing ones larger.

The process is triggered by stress — specifically, when you work a muscle harder than it is used to. This stress causes tiny, microscopic tears in the muscle fibres. Your body then repairs these tears by fusing the damaged fibres together, which increases their mass and thickness. This repair is why you feel sore after a tough workout, and why you need rest days. The muscle doesn't grow during the exercise; it grows during the recovery.

There are two main types of hypertrophy, and they produce different results:

• Myofibrillar hypertrophy – This increases the number of contractile proteins (the parts that actually pull and shorten the muscle). It makes the muscle denser and stronger, but not necessarily much bigger. Think of a powerlifter who is incredibly strong but doesn't look bulky.
• Sarcoplasmic hypertrophy – This increases the volume of the fluid and energy-storing substances (like glycogen) inside the muscle cell. It makes the muscle look larger and more "pumped," but doesn't add as much raw strength. Think of a bodybuilder's aesthetic, show-ready muscles. …