Passive heat therapy is feasible but does not affect cardiometabolic health outcomes in persons with spinal cord injury – a pilot study

Passive heat therapy can improve cardiometabolic health outcomes in some clinical populations, making it a potential therapeutic tool for individuals with spinal cord injury (SCI), who exhibit elevated cardiometabolic disease risk and face barriers to physical activity. Following a no-intervention run-in of 8 weeks (Control), 10 adults with chronic SCI (age: 48 ± 14 years; lesion level: C4-T12, body mass index: 29 ± 2) attended thrice weekly sessions over 8 weeks (Intervention), during which sublingual temperature was raised by 1°C using a water-perfused suit and heated blankets. An oral glucose tolerance test, resting plasma interleukin 6, C-reactive protein and tumour necrosis factor α concentration, as well as the skin hyperaemic response to local heating of 39°C and 45°C were assessed at baseline, after Control and Intervention. Adherence, safety and tolerability was monitored throughout the intervention. While one participant dropped-out after 18 intervention sessions due to a medical issue unrelated to the intervention, adherence was 100% in the remaining nine participants and tolerated well. Glucose tolerance did not differ between Control and Intervention (glucose area under the curve Control: 7410 ± 6088 mg/dl*180min, Intervention: 8253 ± 2139 mg/dl*180min; P = 0.857). Similarly, neither inflammatory markers (P > 0.055) nor hyperaemic responses to local skin heating (P > 0.829) changed after intervention. In summary, passive heat therapy that raised sublingual temperature by 1°C was well tolerated, but did not change outcomes associated with cardiometabolic health and inflammation in persons with chronic SCI.