Functional electrical stimulation improves muscle strength and endurance in patients after cardiac surgery: a randomized controlled trial

Highlights • FES is widely used in patients with chronic heart failure. • FES increased quadriceps muscle strength after eight weeks of training. • FES increased lower limb muscle endurance after eight weeks of training. • FES was unable to modify functional capacity after eight weeks of training.
Background Functional electrical stimulation (FES) has shown benefits in patients with chronic heart failure. Therefore, it is possible that FES can benefit patients similarly after cardiac surgery. Objective This randomized placebo-controlled trial aimed to evaluate the effects of FES on lower limb functional capacity, strength, endurance, and muscle mass after discharge from cardiac surgery. Methods Twenty patients were allocated (1:1) to the group receiving FES to the quadriceps (FESG) or FES placebo (FESPG). FES was applied at a frequency of 15 Hz, with 0.5 ms pulse width, 5 s contraction time, and 10 s resting time, twice a week for 40 min over a period of eight weeks. Functional capacity was assessed using the six-minute walk test (6MWT), lower limb muscle strength using the one repetition maximum test (1RM), endurance using the sit-and-stand test (SST), and muscle using the perimeter of the thighs. Results Both groups increased the distance covered in the 6MWT (FESG: 49.6 m, 95% CI 15.9–83.3; FESPG: 41.5 m, 95% CI 7.8–75.2), but without a difference between groups. There were significant between-group differences for quadriceps muscle strength (7.2 kg, 95% CI 0.2–14.2) and muscle endurance (2.2 repetitions, 95% CI 1.0–3.4) in favor of the FESG. Conclusion FES improves lower limb muscle strength and endurance in patients after cardiac surgery. Larger trials are needed to confirm our findings.