Beyond relaxation: Improving the validity of PMR studies in chronic disease research

Sir,

The article by Arunraj et al¹ published in the January 2025 issue of Indian Journal of Medical Research attracted our attention. The research offers meaningful findings about how progressive muscle relaxation (PMR) therapy helps reduce psychological distress and enhances glycaemic control for people with type 2 diabetes mellitus (T2DM). As mental health becomes more acknowledged in chronic disease treatment this research proves to be both timely and relevant.

However, the study contains several limitations that require attention. The authors justify as to why the sample size of this study is adequate, however, there is lack of clarity in context of participant retention due to its assumption of a 20 per cent dropout rate. Providing a thorough explanation about how this estimate was calculated could have strengthened the reasoning behind it. The study lacked blinding procedures, and it remains uncertain whether participants, researchers, or outcome assessors received blinding. Without blinding, there is a risk of performance and detection bias, potentially influencing the study’s outcomes².

Furthermore, while the study accounts for diabetes medication, it does not account for other potential confounding variables such as changes in diet, levels of physical activities aside from self-reported walking, or other stress-coping activities used by the participants. This neglect of consideration reduces the accuracy of the isolation of effects for PMR therapy³.

Additionally, the self-reported compliance through WhatsApp, despite being innovative, is prone to reporting bias⁴. More objective data could be collected using methods like digital tracking⁵ or biochemical markers linked with stress relief⁶. Another limitation includes the study duration, as three months is likely insufficient for understanding the long-term effects of PMR on diabetes. Longer follow up could provide more information on the tenability of the intervention’s effect⁷.

To summarise, the study appears to be well designed and has all the critical elements required for a thorough investigation. Nonetheless, the study’s validity is likely to be increased in the future through enhanced blinding, control of confounding variables, and more objective indicators of compliance. Reducing the reliance on self-reported adherence and increasing the follow up time would also contribute to the improvements in the strength and generalisability of the results.