HIGH-INTENSITY TRAINING AND CANCER: ANALYSIS OF THE SCIENTIFIC EVIDENCE

AXIS I: HIGH-INTENSITY INTERVAL TRAINING (HIIT) AND ONCOLOGY

Based on the body of scientific evidence available to date, the relationship between high-intensity training (HIIT or vigorous exercise) and oncological pathology is structured on three operational levels: prevention, treatment, and survivorship.

1. Impact of high-intensity training on cancer incidence

Epidemiological analysis confirms a probable reduction in risk. Large meta-analyses involving millions of individuals demonstrate that physically active populations present lower cancer mortality and a lower incidence of various types of tumours. Although the benefit occurs with moderate exercise, vigorous exercise provides statistically equivalent or slightly superior risk reductions.

The most robust prophylactic associations are documented for:

• Breast cancer.
• Colorectal cancer.
• Endometrial cancer.
• Oesophageal cancer.
• Kidney cancer.
• Liver cancer.
• Specific variations of lung cancer.

Cohort evidence (N > 85,000) correlates a higher volume of daily physical activity with an approximate 26% reduction in the risk of developing 13 oncological typologies, regardless of exact variations in intensity.

2. Safety of HIIT in patients with an active cancer diagnosis

Recent systematic reviews determine that, subject to prior clinical assessment and technical supervision, HIIT is safe and highly tolerated. Empirical data indicate:

• High adherence rates to exercise programmes.
• Clinically insignificant incidence of adverse events.
• Feasibility of execution in the pre-, peri-, and post-treatment phases.

Prescription requires intensity modulation strictly adapted to the tumour's aetiology, the toxicity of the ongoing treatment, and the patient's biomechanics.

3. Effects on the patient's clinical evolution

Meta-analyses of randomised clinical trials show the following adaptations:

• Cardiorespiratory fitness (VO2 max): This is the most consistent and measurable physiological adaptation.
• Quality of life: Attenuation of fatigue and stabilisation of psychophysiological well-being.
• Haemodynamics and cardiovascular health: A critical factor in mitigating cardiotoxicity induced by antineoplastic therapies.
• Mechanics and motor function: Preservation of the capacity to perform activities of daily living (ADLs).
• Toxicity mitigation: The literature (British Journal of Sports Medicine) validates exercise as a mitigator of the side effects of chemotherapy and radiotherapy regimens.

4. Biological and cellular mechanisms

The postulated physiological pathways include:

• Suppression of chronic inflammation markers.
• Optimisation of insulin signalling and sensitivity.
• Down-regulation of circulating oestrogen levels.
• Up-regulation of NK (Natural Killer) cell activity, vital in antitumour immune surveillance.
• Endocrine secretion of muscle myokines with apoptotic or suppressive properties.
• General enhancement of immune system competence.

In vitro models based on blood samples from breast cancer survivors subjected to an acute HIIT session demonstrated an increase in suppressive markers and a reduction in tumour cell proliferation. In vivo causality, however, remains under investigation.

5. Therapeutic limitations

The premise that HIIT possesses tumour eradication capabilities is categorically false. There is no empirical validation that positions exercise as a substitute for primary intervention protocols (surgical resection, chemotherapy, radiotherapy, or immunotherapy). Its clinical classification is restricted to a modulating variable of prognosis, recurrence risk, and systemic tolerance.

AXIS II: MOBILITY EXERCISES AND ONCOLOGY

Based on published systematic reviews, meta-analyses, and umbrella reviews, mobility work (static and dynamic stretching, joint activation, yoga) has no direct and measurable effect on the incidence or pathophysiological progression of cancer. Its utility is restricted to the functional domain.

1. Mobility as a prevention variable

Causal evidence is null. The reduction of oncological risk in active populations is attributed exclusively to the activation of aerobic metabolic pathways, strength training, and total metabolic volume (METs).

2. Clinical application in oncological populations

In this context, biomechanical utility is validated:

• Physical function: Preservation of range of motion (ROM), locomotor capacity, and mechanical efficiency. Effect sizes are classified as small to moderate.
• Fatigue management: Meta-regressions (42 clinical trials) validate the positive impact on the mitigation of peripheral and central fatigue.
• Attenuation of structural stiffness: Especially relevant in the post-operative period (e.g., resection of breast tumours), in the management of lymphoedema, and during hormone deprivation therapies.

3. Inflammation and cellular biological markers

The isolated intervention of mobility does not trigger the physiological stress threshold necessary to induce changes in inflammatory markers or intervene in the mechanisms of carcinogenesis.

4. Synthesis of Macro Evidence (2025 Umbrella Review)

The analysis of 740 associations derived from meta-analyses establishes a high evidentiary robustness for exercise intervention in reducing fatigue, optimising physical function, and cardiorespiratory fitness. However, these benefits are almost invariably the product of experimental designs that use aerobic exercise and mechanical resistance (strength) as primary axes, operating mobility as a strictly accessory element.