Electrical stimulation cramp threshold frequency correlates well with the occurrence of skeletal muscle cramps

The minimum electrical stimulation frequency (HZ) at which a muscle cramps is termed threshold frequency (TF). TF is theorized to represent one's predisposition to cramping; however, TF and cramp occurrence have never been correlated. We hypothesized that TF would be lower in individuals with a cramp history and lower on the second of two days of testing; genetics may partially explain this lower TF. Cramp TF was measured in 19 subjects with (Group 1), and 12 subjects without (Group 2), a cramp history. Group 1 had a lower TF (14.9 ± 1.3 vs. 25.5 ± 1.6 HZ; P < 0.001) and a higher family history of cramping than Group 2 (89% vs. 27%; P < 0.001). TF was lower on day 2 (18.3 ± 0.26 HZ) than day 1 (19.7 ± 0.25 HZ; P = 0.03). Lower TFs are correlated with cramp history, supporting the inference that lower TFs may represent increased predisposition toward cramping. TF may be used to identify individuals at risk of cramping.