A new randomized crossover trial has found that passive lower-limb heating could improve exercise endurance in patients with heart failure with reduced ejection fraction.
In the study, published in European Journal of Heart Failure and conducted at Griffith University and The Prince Charles Hospital in Australia, researchers showed that participants who immersed their legs in 42°C water for 45 minutes walked an average of 201 m farther in an endurance shuttle walk test (ESWT) compared with those in the 30°C control condition (P < .001).
The researchers enrolled 22 medically stable patients aged 50 to 80 years with heart failure with reduced ejection fraction (HFrEF). Each participant completed two randomized sessions of lower-limb water immersion—one at 42°C and one at 30°C—prior to performing an ESWT. The primary outcome was the difference in walking distance between conditions.
The results showed a substantial increase in femoral artery blood flow following heating (547 mL/min vs 208 mL/min, P = .02), suggesting enhanced oxygen delivery to muscles. Tissue oxygenation was also higher at the start of the ESWT in the heated condition (60.3% vs 53.5%, P < .001), though levels equalized by the test’s end (P = .16). Despite these improvements, no statistically significant differences were observed in mean arterial pressure, heart rate, pulse oximetry, or perceived exertion scores.
“Femoral artery blood flow was higher following lower-limb heating,” said lead study author Fergus K. O'Connor, of the School of Health Sciences and Social Work at Griffith University in Australia, and colleagues. It indicated that passive heat therapy may serve as a nonpharmacologic intervention to enhance exercise capacity in patients with HFrEF.
The study built on prior research showing that warm water immersion increased cardiac output and stroke volume in patients with chronic heart failure. However, whether these acute benefits translate into long-term rehabilitation improvements remains untested.
By improving blood flow and muscle oxygenation, lower-limb heating may help patients sustain higher exercise volumes in rehabilitation programs. Future studies will need to determine if repeated heating sessions lead to greater adaptive responses over time.