Abstract
Introduction
Delayed onset muscle soreness (DOMS) in the quadriceps is frequent in runners finishing a marathon race, and may result in several days of discomfort and pain. There is an increasing clinical evidence that noninvasive, pulsed electromagnetic field therapy (PEMF) can have physiological effect on inflammation and tissue repair. The purpose of this pilot study was to investigate the effect of PEMF on quadriceps muscle soreness in marathon runners and to use the data to calculate an appropriate sample size for a subsequent study.
Material and methods
The design was a randomized double-blind prospective study covering a 5 days period after completion of a beach marathon. After the marathon all 74 runners that completed the 42.195 km were asked to participate in the study. Forty-six agreed to enter the study and were block randomized into an intervention group or a control group. The intervention group received an active pulsed electromagnetic field device, and the control group received a sham device. The sham devices were used in exactly the same manner but produced no electromagnetic field. The active PEMF device does not produce heat or cause any sensation in the tissue allowing participants to be blinded to treatment. The pulsed electromagnetic field signals of a 2-msec burst of 27.12-MHz sinusoidal waves were repeated at two bursts per second. Peak magnetic field was 0.05 G, which induced an average electric field of 10 mV/cm in the tissue with an effect of 7.3 mW/cm3. All subjects were instructed to place the device on the most painful area of the quadriceps for 20 minutes four times a day. Pain intensity was measured three times a day with the Visual Analogue Scale (VAS) during a 90o squat with a self-administered questionnaire. Data were non-parametric and compared with a two-sample Wilcoxon rank-sum test.
Results
39 of the 46 runners returned the questionnaire. There was no difference in characteristiscs between the groups. There was a clear trend towards a smaller amount of pain in the intervention group compared to the control group at day one and two. Subjects in the intervention group reported on average 20mm (40 %) less pain on day one and approximately 10mm (40 %) less pain on day two(p=0.17−0.27). At day three, four and five, there were no clear differences in pain intensity reported in the two groups. Using the data from the current pilot study a sample size of 41 subjects in each group are needed to show a statistically significant difference between groups((power 0.90, alpha 0.05 one-sided test))
Conclusion
This pilot study indicate that PEMF can reduce quadriceps DOMS following a marathon race. However a study with a larger sample-size is needed before any firm conclusions on the pain reducing effect of PEMF can be drawn.
