What are stress markers?

Stress markers are various indicators used to measure levels of stress in the body, whether psychological or physical. These markers can include:

• Subjective reports: How stressed individuals feel they are.
• Heart Rate (HR): Observing changes in heart rate.
• Heart Rate Variability (HRV): Measures the variation in time between each heartbeat, which is an indicator of the body's response to stress.
• Cortisol levels: Sometimes referred to as the stress hormone, changes in its levels can indicate stress.
• Free cortisol: Free cortisol, which is not bound to proteins, can also indicate stress levels.

These aspects are relevant not only in the study of psychological stress but also in examining physical stress related to exercise adaptation and recovery. Additionally, the concept of allostatic load or homeostasis is used to describe how various systems in the body respond to overall stress, indicating that stress affects the body globally, impacting various physiological aspects like muscle function, sleep, mood, and behavior. Resting heart rate is also mentioned as a stress marker; however, it's noted to be less sensitive to smaller stressors. In contrast, HRV is considered a more sensitive indicator of stress levels 1.