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.

Study Design: A time series design was used, with the dependent variable being gastrocnemius muscle temperature at a depth of 3 cm. Objectives: To determine the rate of temperature rise and the rate of post-treatment temperature decline in skeletal muscle following the application of pulsed short-wave diathermy (PSWD). Background: Data on PSWD rate and longevity of heating are 20 years old and outdated. With the recent introduction of advanced diathermy equipment, results of our study would provide clinicians with much needed information regarding treatment duration. Methods and Measures: A 23-gauge thermistor was inserted into the center of the medial head of the anesthetized gastrocnemius muscle, 3 cm below the skin's surface of 20 subjects. The PSWD (27.12 MHz frequency) was applied using the following parameters: 800 bursts per second; 400 psecond burst duration; 850 pecond interbunt interval; with a peak root mean square (RMS) amplitude of 150 W per burst and an average RMS output of 48 W. Temperature changes were documented every 5 minutes during the treatment and additionally at 5 and 10 minutes following treatment.Results: The average baseline and peak temperatures were 35.84 2 0.93OC and 39.80 + 0.83"C, respectively. Mean temperature increases were: 1.36 + 0.90°C (5 min); 2.87 2 1.44"C (10 min); 3.78 2 1 .lg°C (1 5 min); 3.49 + 1.13"C (20 min). After the treatment terminated, intramuscular temperature dropped 0.97 + 0.68"C in 5 minutes and 1.78 + 0.69" in 10 minutes. Conclusions: PSWD is an effective modality if temperature elevation of deep tissue over a large area is the clinical objective. ) Orthop Sports Phys 7her 1999;29:13-22.

Our observations suggest that passive warm-up performed before eccentric exercise may be more beneficial than active warm-up or no warm-up in attenuating swelling but does not prevent, attenuate, or resolve more quickly the other clinical symptoms of eccentric muscle damage as produced in this study.

Pickle juice, and not deionized water, inhibits electrically induced muscle cramps in hypohydrated humans. This effect could not be explained by rapid restoration of body fluids or electrolytes. We suspect that the rapid inhibition of the electrically induced cramps reflects a neurally mediated reflex that originates in the oropharyngeal region and acts to inhibit the firing of alpha motor neurons of the cramping muscle.

Mild hypohydration with minimal neuromuscular fatigue does not seem to predispose individuals to cramping. Thus, cramps may be more associated with neuromuscular fatigue than dehydration/electrolyte losses. Health care professionals may have more success preventing exercise-associated muscle cramp by focusing on strategies that minimize neuromuscular fatigue rather than dehydration. However, the effect of greater fluid losses on cramp threshold frequency is unknown and merits further research.