The physical experience of stress produces sensations that people frequently interpret as illness, and each has a straightforward explanation.
Racing heart
Adrenaline acting on the heart increases rate and force of contraction.
Which is preparing to deliver more blood to muscles, and it is exactly what happens during exercise.
The sensation feels different because it occurs without exertion, which is what makes it alarming rather than the rate itself.
Breathlessness
Airways dilate and breathing rate increases.
Which increases oxygen availability, and the increase generally exceeds requirement since no physical activity follows.
The resulting reduction in carbon dioxide produces lightheadedness, tingling in extremities and a sense of not getting enough air, which paradoxically follows from breathing too much.
Digestive symptoms
Blood is redirected away from the digestive system, and gut motility changes.
Which produces nausea, altered bowel habit and the sensation frequently described as butterflies.
The gut has extensive nerve supply and responds to stress signalling directly.
Muscle tension
Muscles prepare for action, and sustained tension without movement produces aching, particularly in the neck, shoulders and jaw.
Which accounts for a substantial proportion of tension headaches and jaw pain.
Sweating and temperature
Sweating increases in anticipation of exertion and blood is redirected from skin to muscle.
Which produces the combination of feeling cold and clammy that people find distinctive.
Vision and hearing
Pupils dilate, and attention narrows toward what is perceived as threatening.
Which produces the tunnel vision reported during acute stress, and it is an attentional effect as much as an optical one.
Why knowing this helps
Panic frequently escalates because the physical sensations are interpreted as evidence of a medical emergency.
Which generates more alarm, which produces more of the response, which produces stronger sensations.
Understanding that a racing heart during anxiety is the same physiological event as a racing heart during exercise interrupts that cycle.
This is a central component of psychological treatment for panic, and it works.
The important caveat
Symptoms that resemble anxiety can have medical causes.
Thyroid conditions, cardiac arrhythmias, anaemia, and several others produce overlapping symptoms.
Which means a first presentation should be assessed medically rather than assumed to be anxiety, and this is standard clinical practice for good reason.
Chest pain, particularly with exertion, spreading to arm or jaw, or with breathlessness, requires emergency assessment.
What reduces it
Extended exhalation, which engages the parasympathetic system directly.
Physical activity, which uses the mobilised energy for its intended purpose.
And addressing the situation producing it, where that is possible.
Persistent anxiety interfering with daily life warrants seeing a doctor, since effective treatments exist and it rarely resolves alone.
The recovery phase
After the acute response, the parasympathetic system restores baseline.
Which takes time, and repeated activation without full recovery is what produces the chronic pattern.
Deliberately triggering recovery — slow breathing, physical activity, rest — shortens the period of elevated arousal.
Chronic activation
Sustained stress produces different effects from acute stress.
Sleep disruption, digestive symptoms, muscle pain, reduced immune function and mood effects all appear in the research on prolonged stress.
Which is why the duration matters more than the intensity for health outcomes.
Individual variation
People differ substantially in reactivity and in recovery speed.
Which is partly genetic, partly developmental and partly a matter of current circumstances including sleep and fitness.
Physical fitness is associated with reduced physiological reactivity to psychological stressors, which is one of the more interesting findings in this area.
What to do in the moment
Extended exhalation, which acts within seconds.
Moving, which uses the mobilised energy.
Naming what is happening, which some evidence suggests reduces intensity.
And accepting the sensations rather than fighting them, which prevents the escalation that resistance produces.
Stress and performance
Moderate arousal improves performance on many tasks while high arousal impairs it, which is a long-standing finding.
Which means some stress before a demanding task is functional, and the aim is not eliminating it.
The optimal level differs by task complexity, with simple tasks tolerating higher arousal than complex ones.
Physical activity as the outlet
The stress response mobilises energy for physical action that generally does not follow.
Which is the clearest rationale for exercise as a stress intervention, and the evidence for effects on mood and anxiety is substantial.
Even short bouts produce measurable effects on state anxiety.
Social contact
Has independent effects on physiological stress markers in experimental studies.
Which means talking to someone is not only emotionally useful, and the effect appears in measurements as well as reports.
Control and predictability
The same objective stressor produces different physiological effects depending on whether it is controllable and predictable.
Which is one of the more robust findings in this area, and it explains why the same workload feels different under different management.
Where control cannot be increased, increasing predictability sometimes can be, and it has measurable effects.