EXERCISE AND YOUR IMMUNE SYSTEM
What Every Physical Therapist (and Client) Should Know
Note: This blog post highlights key findings from a comprehensive review by Nieman & Wentz (2019)
"Pain can change you, but never let it define you."
If you feel like you have been battling the weather, and well, everything else – you are not alone! Colds, flus, and RSVs have been everywhere (and always seem to be) which is why it is important we have tools to defend ourselves with!
The immune system is not separate from the musculoskeletal system. No system is. We so often think in terms of pieces and parts and forget to realize that we are ONE. Typically what helps one system, will help all of them.
A growing body of research in exercise immunology shows that physical activity has a profound and nuanced effect on immune function. Therefore, understanding this relationship helps us think about exercise and movement more intelligently to not only support resilience and recovery but aging, and chronic disease management as well.
The Immune System Is Highly Responsive to Exercise
The immune system responds dynamically to exercise! The magnitude and direction of this response depends on intensity and duration.
For example:
- Moderate-to-vigorous exercise <60 minutes
- Enhances immune surveillance
- Prolonged, vigorous exercise (>90 minutes at high intensity)
- Can cause temporary immune perturbation
If we are considering exercise as a way to enhance immune function, the first thing we have to realize is that it is dose-dependent.
Moderate Exercise Enhances Immune Surveillance
Each bout of moderate aerobic exercise (which can be brisk walking, cycling, or swimming to name a few) stimulates a coordinated immune response.
During and immediately after moderate exercise:
- Increased circulation of:
- Natural killer (NK) cells
- T cells
- Neutrophils
- Immature B cells
- Enhanced macrophage activity and increased anti-inflammatory cytokines
This is a good thing! These immune cells are preferentially mobilized because they are particularly effective at identifying infected or abnormal cells!
Why this matters for us:
Repeated daily exercise bouts create a cumulative effect:
- Enhanced immune surveillance
- Reduced systemic inflammation
- Improved metabolic regulation
Heavy Exertion: Temporary Immune Disruption
In contrast, prolonged high-intensity endurance events (marathon running, ultra-endurance training – if you are into that sort of thing) can produce a different effect.
During and immediately after vigorous exercise lasting >90 minutes:
- Elevated stress hormones (cortisol, epinephrine)
- Increased inflammatory cytokines
- Oxidative stress
- Increased illness risk during the 1–2 weeks post-event
The BIG takeaway (No, marathons are not bad!): Our immune system simply reflects total load, not just mechanical load.
For those of us training intensely or for a big event:
- Monitor sleep
- Monitor stress
- Ensure adequate nutrition
- Avoid aggressive progression during illness
Exercise Reduces Chronic Systemic Inflammation
While intense bouts transiently increase inflammatory markers, habitual moderate exercise lowers resting inflammation.
Physically fit individuals demonstrate:
- Lower C-reactive protein (CRP)
- Lower IL-6
- Lower TNF-alpha and white blood cell counts
Obese individuals, by contrast, show:
- 4x higher CRP
- Chronically elevated inflammatory cytokines
This is an important consideration as low grade inflammation has been linked to multiple diseases including cardiovascular disease, type 2 diabetes and certain cancers.
How does exercise help? Exercise reduces inflammation through:
- Improved adipose tissue function
- Myokine release
- Enhanced antioxidant defense
Exercise and Aging: Combating "Immunosenescence"
Immunosenescence = Immune dysregulation with aging
This has been associated with:
- Reduced T-cell function
- Increased inflammatory cytokines (“inflammaging”)
- Exhausted T cells
- Reduced vaccine response
What helps? You guessed it.
For older adults exercise is one of the most powerful non-pharmacologic interventions to preserve immune function.
Practical Applications for Physical Therapists and Our Clients
1. Dose Matters
- Moderate-intensity aerobic exercise (20–45 minutes, 4–5 days/week) should be recommended for foundational immune system support.
2. Monitor Total Load
For high-level athletes during competition:
- Track psychological stress
- Screen for sleep disruption
- Ensure nutritional adequacy
- Avoid sharp spikes in training
3. Avoid Hard Training During Illness
- It is ok to take a rest day! Training intensely during active infection increases complication risk and prolongs recovery.
4. Exercise = Immune (AND everything else) Care
- It is not all about muscles, tendons and joints – it is about YOU!
Remember: Movement IS Medicine.