HRV X HRV is higher in summer and lower in winter

 A

1. Environmental temperature directly affects physiology
   Changes in external temperature can significantly influence the body’s resting state, including heart rate variability (HRV), as the body works to regulate core temperature through thermoregulation.

2. Seasonal transitions can temporarily disrupt balance
   Shifts from colder to warmer seasons (or vice versa) may cause short-term physiological stress, leading to temporary drops in HRV, fatigue, or altered sleep, before the body gradually adapts to a new equilibrium.

3. HRV must be interpreted in environmental context
   Heart rate variability is not shaped only by lifestyle factors like exercise or diet—it is also strongly influenced by external conditions such as temperature, sleep quality, and seasonal change. This makes context essential when interpreting HRV trends.