**How does the body react to sudden changes in physical activity?**
The body responds to sudden changes in physical activity by undergoing physiological adaptations. Initially, increased activity can lead to an elevated heart rate, increased blood flow, and heightened energy expenditure to meet the demands of exercise. However, abrupt increases may also result in muscle soreness, fatigue, or even injuries if adequate recovery is not managed. Over time, consistent adjustments to a new exercise routine can lead to improved strength, endurance, and overall fitness levels as the body adapts and becomes more efficient.