Comment on “Effectiveness of Remote High-Intensity Aerobic Interval Training on Quality of Life and Physical Health in Breast Cancer Survivors: Two Years Follow-Up”

Dear Editor,

We read with great interest the study by Klavina et al ¹ examining the long-term effects of remotely supervised high-intensity interval training (HIIT) during neoadjuvant chemotherapy (NACT) on physical fitness and quality of life in breast cancer survivors. The authors have addressed a clinically relevant question within a longitudinal framework. The integration of objective cardiopulmonary assessments and validated quality of life instruments strengthens the methodological rigor of this study and provides valuable insights into survivorship care models that can be adapted to remote settings. However, we wish to raise several concerns regarding the clinical interpretation of these findings.

First, although the authors reported statistically significant improvements in VO₂peak and time to exhaustion at 18 to 24 months post-intervention, the observed effect sizes (ES = 0.169 and 0.211, respectively) fell below the commonly accepted thresholds for clinically meaningful changes. In patients recovering from breast cancer treatment, absolute changes in VO₂peak are only clinically actionable when linked to reductions in cardiovascular risk or functional independence. ² Without contextualizing these physiological improvements alongside patient-reported limitations or functional benchmarks, their clinical applicability remains unclear.

Second, although the study employed repeated-measures analysis to evaluate longitudinal effects, the absence of adjustment for confounding factors such as adjuvant therapy, age, or baseline fitness limits internal validity. For instance, the control group was older on average (P = .096), and age is known to inversely affect 6-minute walk distance. ³ The reported between-group difference of 36 m at follow-up, while statistically significant, may reflect age-related variation rather than an isolated intervention effect. This distinction is critical, as clinicians must determine whether observed gains exceed the minimal clinically important difference specific to this population, a value that remains undefined for breast cancer survivors.

Furthermore, the reported moderate negative associations between improvements in the 6 MWT and self-reported physical and emotional functioning (r = –0.674 and −0.567, respectively) in the HIIT group warrant caution. These findings suggest that physiological gains may not align with subjective recovery, raising concerns over the assumption that exercise-based improvements in fitness directly translate to enhanced quality of life. In the absence of qualitative data or structured follow-up on psychosocial outcomes, the clinical benefits of the intervention remain unclear.

Finally, this study did not quantify or monitor physical activity levels during the follow-up period. This omission introduces uncertainty regarding the extent to which post-intervention behavior contributes to the durability of the reported effects. Without objective monitoring (eg, accelerometry), attributing long-term improvements solely to the HIIT intervention is speculative. ⁴

In conclusion, this study makes a valuable contribution by extending our understanding of remote exercise interventions during active cancer treatment. However, for HIIT to be routinely recommended in clinical practice, future trials must link physiological improvements to tangible, patient-centered outcomes and consider confounding variables. Constructive discourse in this domain is vital for refining survivorship protocols grounded in both efficacy and clinical relevance.

Prajnasini Satapathy, MDCenter for Global Health Research, Saveetha Medical College and Hospital, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, India Rachana Mehta, MScSR Sanjeevani Hospital, Kalyanpur, Siraha, Nepal Ranjana Sah, MDDr. D. Y. Patil Medical College Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth (Deemed-to-be-University), Pune, Maharashtra, India