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

The minimum electrical stimulation frequency (H Z ) 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 H Z ; 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 H Z ) than day 1 (19.7 ± 0.25 H Z ; 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. Muscle Nerve 39: 364–368, 2009