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Michael G. Miller, David C. Berry, Susan Bullard, and Roger Gilders

Context:

Land and aquatic plyometrics have clinical relevance for exercise, sport performance, and rehabilitation, yet study is limited comparing both.

Objective:

To compare the effects of land-based and aquatic-based plyometric-training programs on performance variables, muscle soreness, and range of motion (ROM).

Setting:

Aquatic facility and biomechanics laboratory.

Subjects:

Forty subjects randomly assigned to 3 groups: land (n = 13), water (n = 13), and control (n = 14).

Main Outcome Measures:

Performance variables, muscle soreness, and ROM were measured before and after an 8-week training period. An analysis of covariance (ANCOVA) and a Bonferroni post hoc test determined significance.

Results:

ANCOVA revealed significant differences between groups with respect to plantar-flexion ROM (P < .05). Paired t test determined that the aquatic group significantly increased muscle power pretest to posttest (P < .05).

Conclusions:

Results indicate that aquatic plyometric training can be an alternative approach to enhancing performance.

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David C. Berry and Michael G. Miller

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Thomas G. Ribble, Michael H. Santare, and Freeman Miller

Finite element models of the proximal femur at birth, 2 years of age, and at 8 years of age were constructed to investigate stress patterns under different loading conditions. These loading conditions represent typical activities of a normal developing child and abnormal activity associated with muscle spasticity. The hypothesis is that the shear stresses in the growth plate correlate with the neckshaft angle as associated with valgus and normal development. Loads for the finite element models were derived from a separate muscle model used to calculate the forces across the hip joint for an arbitrary subject and activity. Results show there is an inverse relationship between the relative magnitude of the shear stress in the growth plate and the developing neck-shaft angle. The relatively high shear stresses generated by normal activity in the 2-year-old’s growth plate correlate with the decrease in neck-shaft angle that accompanies normal development. Alternatively, lower shear stresses are generated in the growth plate by loading conditions representing spasticity. These lower magnitude shear stresses correlate with a valgus deformity, which is often observed clinically.

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David C. Berry and Michael G. Miller

Column-editor : Scott R. Sailor

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William R. Holcomb, Mack D. Rubley, Michael G. Miller, and Tedd J. Girouard

Context:

Previous studies using neuromuscular electrical stimulation (NMES) have suggested that 30-second rest intervals are too short for sufficient recovery.

Objective:

To compare the effect of rest interval on knee-extension torque production.

Design:

Counterbalanced mixed design to test independent variable, rest interval; ANOVA to analyze dependent variable, percentage decline.

Setting:

Athletic training research laboratory.

Participants:

24 healthy men and women.

Intervention:

Participants performed knee extension under 2 contraction conditions, maximum voluntary isometric contraction (MVIC) and NMES with either 30- or 120-second rest between repetitions.

Main Outcome Measure:

Peak torque produced during each repetition of a 5-repetition set.

Results:

The main effect for rest interval was significant (F 1,23 = 30.30, P = .001), as was the main effect for condition (F 1,23 = 11.18, P = .003).

Conclusions:

A 120-second rest between repetitions is recommended when using NMES in early rehabilitation because force decline across repetitions with 30-second rest during NMES is greater than with MVIC.

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David C. Berry and Michael G. Miller

Column-editor : Scott R. Sailor

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David C. Berry and Michael G. Miller

Edited by Malissa Martin

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Michael G. Miller and David C. Berry

Column-editor : Patrick Sexton

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Daniel Krasinski, Ashley B. Thrasher, Michael G. Miller, and William R. Holcomb

Context:

A potential variable that could affect rate of temperature elevation with ultrasound is the pressure (mass) that is applied to the transducer head during application. Added pressure could compress the tissue, affecting density and the transmission of ultrasound energy. Little research has been completed to determine the effects of the amount of pressure applied during therapeutic ultrasound in vivo.

Objective:

To determine the effects of different applied transducer mass on intramuscular temperature during an ultrasound treatment within the left triceps surae.

Design:

Crossover clinical trial.

Setting:

Human performance research laboratory.

Participants:

Convenience sample of thirteen healthy, college-age students.

Interventions:

Three separate MHz, 1.0-W/cm2 ultrasound treatments were administered 1.5 cm within the triceps surae. The independent variables were the linear temperature standards (0.5°C, 1.0°C, 1.5°C, and 2.0°C above baseline) and the 3 different applied pressures measured in grams (200 g, 600 g, and 800 g).

Main Outcome Measures:

A thermocouple probe was used to measure triceps surae temperature, and time to reach the temperature standards was recorded during the ultrasound treatments. A 4 × 3 repeated-measures analysis of variance (RM-ANOVA) was used to analyze the differences for temperature points (0.5°C, 1.0°C, 1.5°C, and 2.0°C) and transducer mass (200 g, 600 g, and 800 g) and with respect to time.

Results:

The results of the RM-ANOVA showed no temperature-point and transducer-mass interaction (F 6,72 = 1.69, P = .137) or main effect for mass (F 2,24 = 1.23, P = .309). The time required to raise temperature 2°C was 209.1 ± 68.10 s at 200 g, 181.5 ± 61.50 s at 600 g, and 194.9 ± 75.54 s at 800 g.

Conclusions:

Under the conditions of this study, the amount of mass applied with the transducer during an ultrasound treatment does not ultimately affect the rate of tissue heating.

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Nicholas J. Hanson, Sarah C. Martinez, Erik N. Byl, Rachel M. Maceri, and Michael G. Miller

Purpose: Although the effect of caffeine in thermoneutral or cool environmental conditions has generally shown performance benefits, its efficacy in hot, humid conditions is not as well known. The purpose of this study was to further examine the effect of caffeine ingestion on endurance running performance in the heat. Methods: Ten trained endurance runners (6 males; mean [SD] age = 26 [9] y, height = 176.7 [5.1] cm, and mass = 72.1 [8.7] kg) came to the lab for 4 visits. The first was a VO2max test to determine cardiorespiratory fitness; the final 3 visits were 10-km runs in an environmental chamber at 30.6°C and 50% relative humidity under different conditions: 3 mg·kg−1 body mass (low caffeine dosage), 6 mg·kg−1 (moderate caffeine dosage), and a placebo. Repeated-measures analyses of variance were used to determine the effect of condition on the 10-km time, heart rate, core temperature, rating of perceived exertion, and thermal sensation. Results: There was no difference in the 10-km time between the placebo (53.2 [8.0] min), 3-mg·kg−1 (53.4 [8.4]), and 6-mg·kg−1 (52.7 [8.2]) conditions (P = .575, ηp2=.060). There was not a main effect of average heart rate (P = .406, ηp2=.107), rating of perceived exertion (P = .151, ηp2=.189), or thermal sensation (P = .286, ηp2=.130). There was a significant interaction for core temperature (P = .025, ηp2=.170); the moderate-dosage caffeine condition showed a higher rate of rise in core temperature (0.26 [0.08] °C·km−1 vs 0.20 [0.06] and 0.19 [0.10] °C·km−1 in the low-caffeine and placebo conditions, respectively). Conclusion: The results support previous research showing a thermogenic effect of caffeine, as the moderate-dosage condition led to a greater rate of heat storage and no performance benefits.