The biophysical effects of ultrasound on median nerve distal latencies.

PURPOSE: Previous studies have documented the lack of ultrasound's non-thermal effects on nerve conduction using frequencies of 1 MHz and 870 kHz. The analyses and conclusions were reached, despite only one study incorporating pulsed ultrasound. The purpose of this study was to determine the biophysical effects of continuous wave (CW) and pulsed wave (PW) ultrasound on median nerve motor and sensory latencies using common frequencies of 1.0 and 3.0 MHz. SUBJECTS: Fifteen healthy subjects (8 males, 7 females, age = 23.5 + 4.44 yrs, height = 171.2 + 10.7 cm, weight = 67.5 + 7.9 kg) without a history of neurological or musculoskeletal injury to their non-dominant arm volunteered for testing. METHODS AND MATERIALS: Subjects were exposed in counterbalanced order to five ultrasound treatment conditions: (1) 1 MHz, 1.0 W/cm2, 8 min., (2) 1 MHz, 1.0 W/cm2, 50% PW, 8 min., (3) 3.0 MHz, 1.0 W/cm2, CW, 8 min., (4) 3.0 MHz, 1.0 W/cm2, 50% PW, 8 min., (5) placebo, 0.0 W/cm2, 8 min. Dependent measures for motor and sensory latencies, and subcutaneous temperatures were taken pretreatment, at 2, 4 and 6 minutes during treatment, and immediately post-treatment. Separate two within repeated measures ANOVA were used for each dependent measure. RESULTS: Analysis revealed significant interactions for motor latencies [F (16,224) = 52.77, p < .001], sensory latencies [F (16,224) = 41.10, p < .001], and subcutaneous temperatures [F (16,224) = 52.77, p < .001]. Tukey's HSD post hoc analyses confirmed that nerve latencies responded similarly to subcutaneous temperature changes during and after ultrasound treatment. CONCLUSIONS: Alterations in nerve latencies from ultrasound on healthy nerves appeared to be related to temperature changes induced by ultrasound's thermal effects, and not by non-thermal or mechanical effects.

Reliability and responsiveness of disablement measures following acute ankle sprains among athletes.

The minimum amount of change which represents clinical improvement following ankle sprains is unknown. This study considers the usefulness of physiological and behavioral measures commonly employed for this purpose in sports rehabilitation settings. Thirteen collegiate athletes of both genders were measured at approximately 3 and 10 days post-grade I or II ankle sprain. Volumetric displacement and sagittal plane ankle range of motion measures were used as impairment indicators. Motor ability scores (activity count) and a perceived athletic ability measure (visual analog scale) were used to indicate functional limitations. Volumetric displacement and both functional limitation measures demonstrated responsiveness to change between two occasions of measurement separated by 1 week. Observed changes in range of motion deficits could not be distinguished from measurement error. The results of this study suggest that behavioral measures of motor activity and perceived athletic ability may be at least as useful as physical measures of organic dysfunction for assessing clinical improvement following acute ankle sprains among athletes.

Application of modalities in overuse syndromes.

Improper techniques are often the cause of overuse syndromes. Unless the technique is corrected, the patient is doomed to recurrence. The same is true of improper posture, especially in the lower extremity and trunk areas. The pitcher or tennis player should have his or her style analyzed for proper form. The runner should have his or her muscular imbalances corrected by exercise and orthotic appliances. As with all other modalities used for treating painful conditions, proper evaluation of the etiology and the rectification of the cause is important. When athletes are underway in their sports seasons, it is often difficult to convince them to accept the ideal healing conditions needed to eliminate the problem. Management of the condition with any modality while maintaining an active lifestyle often brings about ethical scrutiny. However, it is the belief of the authors that noninvasive modalities do not provide the pain relief that would enable the athlete to tolerate activity beyond a significant injurious stress level. The modalities allow the athlete to regain the criteria for return, strength, and range of motion more successfully. Short-term goal setting is imperative to proper return. Several plateaus should be successfully completed before full return to activity is allowed. Tennis elbow, for example, may be allowed an initial period of 5 minutes on alternate days, gradually increasing to full activity every other day. Patients are often so anxious to return to activity that they overdo, leading to a decrease in function with a rapid return to the results of inflammation. The goals of successful rehabilitation of the overuse syndrome are pain-free range of motion, strength, and endurance. The use of cold, heat, electrotherapy, and exercise allow the athlete to reach his or her goal of returning to activity more quickly with a reduced risk of reinjury.