References Cramp et al. Arch Phys Med Rehabil 2002;83:5-9

1. The Effects of Muscle Contractions Induced by Transcutaneous Electrical Nerve Stimulation (TENS) on Skin Blood Flow Allen Dickie, Osama Tashani, Mark I Johnson Faculty of Health, Leeds Metropolitan University and Leeds Pallium Research Group, UK Results There was a significant decrease in skin blood flow (flux) following 30 minutes TENS intervention, both in the presence and absence of muscle contractions (Table 1, Fig 4). Introduction Transcutaneous Electrical Nerve Stimulation (TENS) is predominantly used for pain relief. TENS is claimed to alter blood flow which may be beneficial for wound healing and for circulatory disorders such as Reynaud's disease. It has been proposed that circulatory effects could result from TENS induced muscle contractions, although existing the evidence is inconclusive1,2. Aim The aim of this cross-over study was to investigate the effect of strong but comfortable rhythmic muscle contractions generated by low frequency burst mode TENS on skin blood flow. There were no significant difference in the magnitude of the change in blood flow from baseline during VMC when compared to NMC (VMC mean±SD decrease in flux = 112.9±52.9, NMC = 90.29±64.4, mean difference (Md) = -22.6, p=0.48; paired t-test). Methods Six healthy female volunteers (mean age = 21.17 years, range 20 to 23) completed two experimental sessions separated by 24 hours (Fig 1). Each experimental session was identical except participants adjusted TENS amplitude to produce strong visible muscle contractions (VMC) (TENS amplitude mean±SD = 17.7±4.8mA) during one TENS intervention (visit) and to produce a TENS sensation without visible muscle contractions (NMC) (12.5±1.1mA) in the other intervention (visit). The order of interventions was randomised in a cross-over manner (i.e. visit 1 or 2). TENS was administered for 30 minutes using 1 self-adhering electrode (5cmx5cm) attached to the skin of the dorsal web of the hand between the 1st and 2nd metacarpal bones and 1 electrode on the ulnar edge of the hand (Fig 2). Parameters were burst mode TENS at 2 bursts per second, 9 pulses per burst and 100Hz pulse stream. Skin blood flow was measured on the dorsal side of the fingers (excluding the thumb) using laser Doppler imaging (LDI) before and nine minutes after TENS had been switched off (Fig 3). Room temperature was maintained within ±1oC. Discussion Skin blood flow decreased during low frequency burst-mode TENS in the presence and absence of strong but comfortable muscle contractions. Previous studies have found increased, rather than decreased skin blood flow following phasic muscle contractions induced by low frequency TENS1,2. It has been suggested that the rise in blood flow results from a muscle pumping action, however our findings do not support this. One possible explanation for the reduction in blood flow reported in this present study is that TENS may have activated sympathetic vasoconstrictor nerves. Conclusion: The presence or absence of muscle contractions had no measurable affect on the circulatory response to TENS. • References • Cramp et al. Arch Phys Med Rehabil 2002;83:5-9 • Sherry et al. Physical Therapy 2001;81:1183-1191