A single HIIT session transiently mobilized NK cells and cILCs in advanced cancer patients undergoing chemotherapy, indicating that acute HIIT is feasible in this population and providing hypothesis-generating evidence on exercise-induced changes in immune cell counts.
Key Findings
Results
A single 20-minute HIIT session significantly increased circulating total NK cell counts immediately after exercise in both advanced cancer patients and healthy controls.
Patient group (PG) showed a median within-subject increase of 50% in NK cells immediately post-exercise (p = 0.001)
Healthy group (HG) showed a median within-subject increase of 38% in NK cells immediately post-exercise (p = 0.045)
PG consisted of n = 20 participants, mean age 59.8 ± 10.3 years, 70% with pancreatic cancer, all undergoing chemotherapy
HG consisted of n = 19 age-matched healthy controls, mean age 60.7 ± 10.6 years
Blood samples were collected before (T0), immediately after (T1), and 1 hour post-exercise (T2)
Results
NK cell counts significantly decreased during the 1-hour recovery period following HIIT in both groups.
The decrease from T1 to T2 was significant in both groups (PG/HG: p < 0.001)
The median within-subject decrease was 43% in the patient group (PG)
The median within-subject decrease was 69% in the healthy group (HG)
This recovery-period decrease was larger in magnitude in healthy controls than in cancer patients
Results
Circulating innate lymphoid cells (cILCs) significantly increased during the exercise period in both groups but did not show significant changes during recovery.
cILC increases were statistically significant in PG (p = 0.005) and HG (p = 0.001) immediately post-exercise
Median within-subject increase of 21% in the patient group (PG)
Median within-subject increase of 55% in the healthy group (HG)
cILC changes were observed only during the exercise period, not during the recovery period, in both groups
Results
NK cell and cILC immune responses positively correlated with higher training heart rate in both groups.
The positive correlation between NK response and training heart rate was observed in both the patient group and healthy controls
Additional correlations were found between cILC2 and BMI in the healthy group (HG)
Additional correlations were found between CD56bright NK cells and age in the patient group (PG)
Differences were observed between groups and across individual immune cell subpopulations
Methods
The study compared advanced cancer patients (70% pancreatic cancer) undergoing chemotherapy to age-matched healthy controls using a standardized 20-minute HIIT protocol.
HIIT session duration was 20 minutes for both groups
NK cells, cILCs, and subsets were analyzed via flow cytometry
Patient-reported outcomes including quality of life, fatigue, and nutrition were assessed with validated questionnaires
The study was registered on 13.11.2022 with registration number NCT05656651
The design was a within-subject repeated measures study with three time points (T0, T1, T2)
Conclusions
Acute HIIT was found to be feasible in advanced cancer patients undergoing chemotherapy.
Both groups completed the 20-minute HIIT session
The study provides 'hypothesis-generating evidence on exercise-induced changes in immune cell counts' in this population
The authors note that acute immune responses to exercise in advanced cancer patients are underexplored
Regular exercise is noted to improve quality of life and reduce fatigue in advanced cancer patients
What This Means
This research suggests that a single session of high-intensity interval training (HIIT) can temporarily boost the number of immune cells — specifically natural killer (NK) cells and innate lymphoid cells — circulating in the blood of both cancer patients receiving chemotherapy and healthy people of similar age. In cancer patients, NK cells increased by about 50% immediately after a 20-minute workout, and innate lymphoid cells rose by about 21%. These immune cells are important because NK cells are known to help the body fight cancer and infections. However, the boost was temporary: within one hour of finishing the exercise, cell counts dropped back down, and in some cases fell below pre-exercise levels.
Importantly, this study found that cancer patients undergoing active chemotherapy were able to complete the HIIT session, suggesting this type of exercise is physically feasible even in people with advanced cancer. The immune responses were stronger when participants exercised at a higher heart rate, hinting that exercise intensity may matter for triggering these effects. The patient group in this study was predominantly made up of people with pancreatic cancer, which is one of the harder-to-treat cancers, making the feasibility finding particularly noteworthy.
This research suggests that exercise — even a single intense session — may have meaningful short-term effects on immune function in cancer patients, though the long-term significance of these temporary immune changes is not yet known. The authors describe the findings as 'hypothesis-generating,' meaning more research is needed to determine whether these transient immune boosts have any real impact on cancer outcomes or treatment effectiveness. The study adds to growing evidence that physical activity is not only safe but may have biological benefits for people undergoing cancer treatment.
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Kiehl F, De Lazzari N, Beller R, Deppe I, Bennstein S, Botzenhardt S, et al.. (2026). High-Intensity Interval Training Boosts Immune Cells in Advanced Cancer Patients and Healthy Controls: Implications for Cancer Care.. Cancer medicine. https://doi.org/10.1002/cam4.71977