Influence of external ankle support on lower extremity joint mechanics during drop landings.

OBJECTIVE: To investigate the effects of external ankle support (EAS) on lower extremity joint mechanics and vertical ground-reaction forces (VGRF) during drop landings. DESIGN: A 1 x 3 repeated-measures, crossover design. SETTING: Biomechanics research laboratory. PATIENTS: 13 male recreationally active basketball players (age 22.3 +/- 2.2 y, height 177.5 +/- 7.5 cm, mass 72.2 +/- 11.4 kg) free from lower extremity pathology for the 12 mo before the study. INTERVENTIONS: Subjects performed a 1-legged drop landing from a standardized height under 3 different ankle-support conditions. MAIN OUTCOME MEASURES: Hip, knee, and ankle angular displacement along with specific temporal (TGRFz1, TGRFz2; s) and spatial (GRFz1, GRFz2; body-weight units [BW]) characteristics of the VGRF vector were measured during a drop landing. RESULTS: The tape condition (1.08 +/- 0.09 BW) demonstrated less GRFz1 than the control (1.28 +/- 0.16 BW) and semirigid conditions (1.28 +/- 0.21 BW; P < .0001), and GRFz2 was unaffected. For TGRFz1, no-support displayed slower time (0.017 +/- 0.004 s) than the semirigid (0.014 +/- 0.001 s) and tape conditions (0.014 +/- 0.002 s; P < .05). For TGRFz2, no-support displayed slower time (0.054 +/- 0.006 s) than the semirigid (0.050 +/- 0.006 s) and tape conditions (0.045 +/- 0.004 s; P < .05). Semirigid bracing was slower than the tape condition, as well (P < .05). Ankle-joint displacement was less in the tape (34.6 degrees +/- 7.7 degrees) and semirigid (36.8 degrees +/- 9.3 degrees) conditions than in no-support (45.7 degrees +/- 7.3 degrees; P < .05). Knee-joint displacement was larger in the no-support (45.1 degrees +/- 9.0 degrees) than in the semirigid (42.6 degrees +/- 6.8 degrees; P < .05) condition. Tape support (43.8 degrees +/- 8.7 degrees) did not differ from the semirigid condition (P > .05). Hip angular displacement was not affected by EAS (F(2,24) = 1.47, P = .25). CONCLUSIONS: EAS reduces ankle- and knee-joint displacement, which appear to influence the spatial and temporal characteristics of GRFz1 during drop landings.

Effect of transducer velocity on intramuscular temperature during a 1-MHz ultrasound treatment.

STUDY DESIGN: A 3 x 2 repeated-measures design was used. The independent variables were transducer velocity (2-3 cm/s, 4-5 cm/s, and 7-8 cm/s) and time (pretreatment and posttreatment). OBJECTIVE: To determine if transducer velocity of a 1-MHz ultrasound treatment affects intramuscular tissue temperature. BACKGROUND: Most authors advocate ultrasound transducer velocities of 2 to 4 cm/s within an area of 2 to 3 times the effective radiating area or 2 times the size of the transducer head. However, a much faster rate of application (approximately 7-8 cm/s) is often observed in clinical settings. METHODS AND MEASURES: Eleven healthy screened volunteers (9 males, 2 females; mean +/- SD age, 22.6 +/- 1.7 years; mean +/- SD height, 175.7 +/- 13.7 cm; mean +/- SD body mass, 82.5 +/- 19.5 kg) were randomly assigned to a treatment order with all conditions administered during a single testing session. Each transducer velocity condition was administered for 10 minutes, using 1-MHz ultrasound with a 100% continuous duty cycle at an intensity of 1.5 W/cm2 over an area twice the size of the transducer head. After the first treatment, the 2 remaining subsequent velocity conditions were administered after the intramuscular temperature returned to within +/- 0.3 degrees C of the initial pretreatment temperature for 5 minutes. The dependent variable was left triceps surae muscle temperature measured at 3 cm below one half the measured skinfold thickness. RESULTS: Temperature increase across the 3 velocities was within 0.4 degrees C (F2.20 = 0.07, P = .93). Posttreatment values (mean +/- SD) ranged from 42.7 degrees C +/- 2.3 degrees C for the slowest velocity to 43.1 degrees C +/- 1.4 degrees C for the fastest velocity. Temperature increase was significant for time (F1.01 = 155.68, P<.00001), increasing from 37.8 degrees C +/- 0.8 degrees C pretreatment to 42.9 degrees C +/- 1.9 degrees C after treatment. CONCLUSION: Very similar intramuscular temperature increases can be observed among ultrasound treatments (10-minute duration, 1-MHz frequency, 100% continuous duty cycle, 1.5 W/cm2 intensity, within an area twice the size of the transducer head), with transducer velocities of 2 to 3, 4 to 5, and 7 to 8 cm/s.

Exercise and quadriceps muscle cooling time.

CONTEXT: Cryotherapy is commonly used for a variety of purposes; however, the body's response to cryotherapy immediately postexercise is unknown. OBJECTIVE: To investigate the effect of prior exercise on crushed-ice-bag treatment of a large muscle group. DESIGN: 2 x 3 repeated-measures design on depth (1 cm and 2 cm below adipose tissue) and treatment (exercise followed by ice, exercise followed by no ice, and no exercise followed by ice). SETTING: Sports Injury Research Laboratory. PATIENTS OR OTHER PARTICIPANTS: Six physically active, uninjured male volunteers. INTERVENTION(S): For the 2 exercise conditions, subjects rode a stationary cycle ergometer at 70% to 80% of their age-predicted maximum heart rate, as calculated by the Karvonen method. For the no-exercise condition, subjects lay supine on a treatment table. The cryotherapy treatment consisted of a 1-kg ice bag applied to the anterior mid thigh. For the no-ice condition, subjects lay supine on a treatment table. MAIN OUTCOME MEASURE(S): Time required for the intramuscular temperatures at the 1-cm and 2-cm depths below adipose tissue to return to pre-exercise baseline and time required to cool the 1-cm and 2-cm depths to 10 degrees C below the pre-exercise temperature. RESULTS: The time to cool the rectus femoris to the pre-exercise temperature using a crushed-ice-bag treatment was reduced by approximately 40 minutes (P < .001). The ice bag cooled the 1-cm and 2-cm depths to the pre-exercise temperature within 7 minutes (P = .38), but the 2-cm tissue depth took nearly 13.5 minutes longer to cool than the 1-cm depth when no ice was applied (P = .001). The 1-cm depth cooled to 10 degrees C below the pre-exercise temperature about 8 minutes sooner than the 2-cm depth, regardless of whether the tissue was exercised or not (P < .001). Exercise shortened the cooling time to 10 degrees C below the pre-exercise temperature by approximately 13 minutes (P = .05). CONCLUSIONS: Exercise before cooling with a crushed-ice bag enhanced the removal of intramuscular heat.

Local ice-bag application and triceps surae muscle temperature during treadmill walking.

CONTEXT: Ice bags "to go" are a common practice in athletic training. OBJECTIVE: To determine the effect of submaximal exercise on tissue temperatures during a common ice-bag application. DESIGN: 2 X 5 fully repeated-measures design with treatment (cooling while resting, cooling while walking) and time (pretreatment, immediately after ice application, and at 10, 20, and 30 minutes during treatment) as the independent variables. SETTING: Laboratory setting. PATIENTS OR OTHER PARTICIPANTS: Sixteen healthy, physically active volunteers (age = 21.63 +/- 2.63 yrs, height = 68.97 +/- 4.00 cm, mass = 80.97 +/- 18.18 kg, calf skinfold = 21.1 +/- 9.3 mm). MAIN OUTCOME MEASURE(S): Left triceps surae intramuscular and skin temperatures, as measured by thermocouples to the nearest 0.1 degrees C, served as dependent measures. INTERVENTION(S): After collecting baseline temperatures, we secured a 1.0-kg ice bag to the calf using plastic wrap before the subject either rested prone or walked on a treadmill at 4.5 km/h for 30 minutes. RESULTS: Treatment did not (P < 0.10) affect the approximately 15 degrees C (P < 0.0001) surface temperature decrease, which remained depressed immediately upon ice-bag application (P < 0.05). Conversely, intramuscular temperature continually cooled (34 to 28 degrees C), while subjects rested (P < 0.0001), whereas no change took place during walking (P = 0.49). Moreover, at the 20- and 30-minute treatment intervals, the resting intramuscular temperatures were, respectively, 3.9 degrees C and 5.4 degrees C cooler than the walking intramuscular temperatures (P < 0.01). CONCLUSIONS: The current trend of wrapping "to go" ice bags to the leg is not likely to achieve deep tissue cooling despite surface temperature decreases.

An 18-day stretching regimen, with or without pulsed, shortwave diathermy, and ankle dorsiflexion after 3 weeks.

CONTEXT: The amount of retained ankle flexibility gains and the effects of diathermy on those gains are unclear. OBJECTIVE: To determine the retention of flexibility 3 weeks after an 18-day stretching regime and the effect of pulsed, shortwave diathermy on that retention. DESIGN: We used a 2x4 factorial with repeated measures on day (1, 19, 24, and 39). The other independent variable was treatment (stretch only versus diathermy and stretch). The dependent variable was ankle-dorsiflexion angular displacement as measured on a digital inclinometer. SETTING: Therapeutic Modality Research Laboratory. PATIENTS OR OTHER PARTICIPANTS: 23 healthy college-aged volunteers (8 males, 15 females; age = 22.7 +/- 2.1 years, height = 171.1 +/- 8.8 cm, mass = 70.4 +/- 13.5 kg). INTERVENTIONS: All subjects performed 3 weeks (not including weekends) of low-load, prolonged, long-duration stretching. One group performed stretching only; the other group also received diathermy. MAIN OUTCOME MEASURE(S): After an 18-day stretching regime and 7-day retention study, subjects returned 14 days later for the 3-week retention measure. The angle of inclination from the posterior Achilles tendon to the sole of the shoe near the heel was measured on each treatment and test day. RESULTS: Regardless of group (F(1,21) = 0.74, P = 0.40), the flexibility gained between days 1 (99.7 +/- 4.0 degrees), 19 (102.9 +/- 5.8 degrees), and 24 (105.0 +/- 6.2 degrees) were maintained at day 39 (104.8+/- 7.2 degrees) (P < .05). CONCLUSIONS: Flexibility gains in normal ankles with 3 weeks of training were retained for at least 3 weeks after training ceased. The application of pulsed, shortwave diathermy during stretching did not appear to influence the chronic retention of flexibility gains in normal subjects.