We all speak of it and experience it, but what is stress? It is defined as a non-specific response by the body to any demand (stressor) that overcomes, or threatens to overcome, the body’s ability to maintain homeostasis (that state of equilibrium of the body’s internal biological mechanisms) (1 – 2). What this means is that regardless of the nature of the stressor (e.g., exercise, starvation, daily commute, work-related issues), the body perceives stress as a biological event and responds in essentially the same way. What differs is simply the magnitude of our response and this task is assigned to the brain that initiates the appropriate ‘fight-or-flight’ response through our nervous and hormonal systems (3-4). An acute bout of stress and the consequent biological response is quite normal and integral to our survival as a species as long as the body has the opportunity to recover between stressors to restore itself back to baseline (5).
To gain a deeper insight into our biological stress response, using an example of our ancestors may paint a clearer picture. The nature of their stress was very different to what we typically experience today. Their primary stressors involved a fight for survival or to the death against a predator or aggressor and the nature of the stress was an intense, acute physiological response (Figure 1). However, after this brief, but stressful encounter, what followed was ample recovery to return to baseline (state of calm – parasympathetic or PNS dominance). This allowed each physiological system (e.g., immune system) time to restore and regenerate itself after fighting to maintain homeostasis.
By contrast, today’s stress generally involves lower-intensity, sustained psychological stressors that sometimes never go away, but accumulate (Figure 2). For example, you might sleep through your alarm and wake up in a panic late for your meeting, skip breakfast, get delayed by a slow commute, arrive late for a presentation, get reprimanded by your boss, then finally make it to your office whereupon you receive a call that your child is sick and needs to be picked up from school – sound familiar? These sustained stressors, although smaller individually, accumulate and deny the body that needed time to repair, recover and replenish.
Table 1: Stress Response Influence on Physiological Systems