Stress response occurs almost immediately, within seconds. But it takes the body much longer to de-stress and calm down.

Notes:

1. Data are for stress hormone induced heart rate increases resulting from sympathetic nervous system arousal. Exercise induced increases do not have the same effect.
2. Stress hormone induced performance and strength increases can achieve 100% of potential maximum within 10 seconds, but only drop 55% after 30 seconds, 35% after 60 seconds, and 31% after 90 seconds.
   It takes a minimum of 3 minutes of rest to “recharge” the system. That means stress response is immediate. But it takes efforts and time for the body to de-stress.
3. Any extended period of relaxation after intense sympathetic nervous system arousal can result in a parasympathetic backlash with significant drops in energy level, heart rate and blood pressure.
   This may show up as shock symptoms - dizziness, nausea and/or vomiting, paleness, clammy skin - and/or profound exhaustion.

Heart beats in beats per minute

Effects of heart rate increases due to stress (not induced by exercise)

Above 175 bpm

• Irrational fighting or fleeing
• Freezing
• Submissive behaviour
• Vasoconstriction (= reduced bleeding from wounds)
• Voiding of bladder and bowels
• Gross motor skills (running, charging, etc.) at highest performance level

175 bpm: Cognitive processing deteriorates

• Loss of peripheral vision (tunnel vision)
• Loss of depth perception
• Loss of near vision
• Auditory exclusion (tunnel hearing)

155 bpm: complex motor skills deteriorate

115-145 bpm: optimal survival and combat performance level for:

• Complex motor skills
• Visual reaction time
• Cognitive reaction time

115 bpm: fine motor skill deteriorates

60-80 bpm: normal resting heart rate Effects of hormone induced heart rate increase