For many of us, exercise is more than movement, it’s medicine. A long ride, gym session, or steady run can clear the mind and soften stress. These benefits extend beneath the surface; emerging research continues to reveal how deeply exercise influences immune resilience. And if you’ve ever returned from working out feeling like a slightly sweatier, slightly more optimistic version of yourself, you’ve already felt this in action.
A recent study offers compelling evidence: older adults with a long history of endurance training such as running, cycling, or other sustained aerobic work showed enhanced metabolic flexibility and adaptability in their natural killer immunity cells compared to sedentary peers, suggesting that regular aerobic training may preserve immune-cell function well into older age. This aligns with findings showing that regular resistance training also leads to beneficial immune adaptations, helping to enhance immune function that normally declines with age.
But as with many things in life, more isn’t always better, and when it comes to immune health, finding the sweet spot of training is essential.
Finding the immune-friendly endurance zone
Research suggests that the immune system responds in a dose-dependent way to exercise. Moderate activity tends to support immune function, while overly intense or prolonged exertion, especially without adequate rest, may temporarily suppress it.
This does not mean training is harmful. Instead, it highlights the importance of progression and recovery, particularly in older athletes or those training at high volumes. In other words: train like you’re trying to improve, not like you’re trying to impress your GPS watch.
Sports medicine doctor Nolan Rau underscores the importance of a balanced approach, stating, “I will often recommend using measurements such as heart rate variability and monitoring how an athlete subjectively feels … as a marker for how adequate their recovery between workouts is.”
The science of full recovery
But monitoring recovery is only part of the equation. If recovery is the construction crew, sleep is your master carpenter. Immune regulation, inflammatory control, and cellular repair all intensify during sleep. Studies confirm sleep is key in regulating immune-cell function and may also influence processes associated with immune aging. Rau emphasizes, “I am a huge advocate for the importance of good sleep … I’ll often ask whether an athlete feels rested in the morning.”
Modern trials show that inadequate energy intake and vitamin or mineral deficiencies also influence immune function, weakening the body’s ability to defend against infections. Chronic stress elevates cortisol, stymies immune responsiveness, and magnifies inflammation. Research consistently demonstrates that psychological stress and physical overtraining share overlapping pathways, which can overwhelm recovery systems and negatively affect health and performance. Rau notes that “The combination of high-intensity exercise with unmanageable stress … can be quite detrimental.”
Mindfulness, yoga, breathwork, and consistent routines can help athletes stay adaptive. Planning rest days and periodized training may help reduce overtraining and maintain a strong immune system. But Rau reinforces the individual nature of this: “No two athletes are ever the same … I recommend athletes work with their coaches and experiment to find what works best.” Essentially, you are your own science experiment, so get curious!
Thoughtful nutrition and supplementation can play a strong role in supporting your immune system!
Rau adds, “Ensuring athletes are getting adequate nutrition is vital … vitamins A, C, D, E, B6, B12, zinc, and iron are all implicated in immunity.”
Signs you’re overdoing it
Key indicators of overtraining include several warning signs:
- frequent illnesses
- feeling tired, drained, or struggling to stay motivated
- recurring injuries and aches
- dips in mood, energy, and focus
Exercise during cancer therapy
When undergoing cancer treatment, many people assume rest, rather than exercise, is the safest path. But increasingly, research shows that carefully adapted endurance and strength training can be both safe and beneficial even during active therapy.
A 2024 study found that resistance training during chemotherapy significantly improved lower-body strength, a crucial improvement when treatment can sap muscle mass and functional capacity. A broader review of mixed aerobic and resistance programs delivered during ongoing cancer treatment also demonstrated improvements in cardiorespiratory fitness, muscle strength, body composition, and quality of life.
As always, exercise during cancer therapy should be personalized, carefully monitored, and adjusted in collaboration with medical and support teams.
This article was originally published in the April 2026 issue of alive magazine.
