Effects of therapeutic percutaneous electrical stimulation of atrophic human quadriceps on muscle composition, protein synthesis and contractile properties

The effects of percutaneous electrical stimulation (70 V, 300 μs pulses at 30 Hz) on muscle composition and rate of protein synthesis were studied in seven patients with quadriceps atrophy secondary to unilateral osteoarthritis of the knee (stimulated group). Quadriceps were stimulated on the affected side for 1 h per day. The results were compared to those from seven patients who did not use a muscle stimulator (control group); in whom muscle biopsy at surgery provided evidence of wasting of tissue protein on the side of osteoarthritis (normal leg 608 ± 266 μg protein μg ‐1 DNA, affected leg 256 ± 100 μg protein μg ‐1 DNA, means ± SD, P <0.05; type I fibre diameters: normal 53.2 ± 6.7 μm, affected 43.8 ± 4.0 μm, P <0.05). In patients who had received stimulation there was no residual difference between the legs in either muscle protein concentration (normal 411 ± 168 μg protein μg ‐1 DNA, affected 373 ± 112 μg protein μg ‐1 DNA) or fibre diameter (type I diameters: normal 56.1 ± 7.8 μm, affected 58.0 ± 10.7 μm). Stimulation did not influence the ratios of muscle force elicited by acute stimulation at 20 and 50 Hz (normal 75 ± 15%, affected 79 ± 15%), or rates of muscle relaxation (percentage losses of tetanic force 10 ms ‐1 : normal 7.66 ± 1.2%, affected 8.67 ± 2.2%). In control (not stimulated) patients there was a higher rate of muscle protein synthesis ( k s ) on the side of knee osteoarthritis (normal 0043 ± 0.028% h ‐1 , affected 0.068 ± 0.044% h ‐1 , P <0.05). In patients stimulated on the affected side k s was certainly maintained (0.052 ± 0.02% h ‐1 normal, 0.056 ± 0.02% h ‐1 affected). The calculated rate of increase in muscle fibre volume induced by stimulation (0.055% h ‐1 ) required to balance the discrepancy in volume between the legs of patients in the control group was similar to the rate of muscle protein synthesis measured in quadriceps after stimulation, suggesting that muscle protein breakdown had fallen to a level approaching zero. The results suggest possible therapeutic benefits of electrical stimulation in patients awaiting knee surgery.