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Eadric Bressel and Gary D. Heise

The purpose of this study was to compare muscle activity, kinematic, and oxygen consumption characteristics between forward and reverse arm cranking. Twenty able-bodied men performed 5-min exercise bouts of forward and reverse arm cranking while electromyographic (EMG), kinematic, and oxygen consumption data were collected. EMG activity of biceps brachii, triceps brachii, deltoid, and infraspinatus muscles were recorded and analyzed to reflect on-time durations and amplitudes for each half-cycle (first 180° and second 180° of crank cycle). Kinematic data were quantified from digitization of video images, and oxygen consumption was calculated from expired gases. Dependent measures were analyzed with a MANOVA and follow-up univariate procedures; alpha was set at .01. The biceps brachii, deltoid, and infraspinatus muscles displayed greater on-time durations and amplitudes for select half-cycles of reverse arm cranking compared to forward arm cranking (p < 0.01). Peak wrist flexion was 9% less in reverse arm cranking (p < 0.01), and oxygen consumption values did not differ between conditions (p = 0.25). Although there were no differences in oxygen consumption and only minor differences kinematically, reverse arm cranking requires greater muscle activity from the biceps brachii, deltoid, and infraspinatus muscles. These results may allow clinicians to more effectively choose an arm cranking direction that either minimizes or maximizes upper extremity muscle activity depending on the treatment objectives.

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Eadric Bressel, Gary D. Heise and Greg Bachman

The purpose of this study was to determine how muscle activity and oxygen consumption are influenced by reverse pedaling (RP) compared to forward pedaling (FP). Seventeen physically active males performed FP and RP at an external workrate of 157 W (80 rpm) while EMG data were collected from five muscles: rectus femoris (RF), biceps femoris (BF), gastrocnemius (GN), tibialis anterior (TA), and vastus medialis (VM). Oxygen consumption (V̇O2 L·min-1) data were collected. On-time durations and EMG amplitudes were quantified for each half-cycle (first 180° and second 180° of crank angle). V̇O2 was similar between pedaling conditions while muscles RF and BF exhibited phasic shifts in response to RP with no amplitude change. VM showed an increase and GN displayed a decrease in EMG amplitude from FP to RP. The phasic shifts in muscle activation seen in RP, particularly in RF and BF, may alter the sequence of the knee extensor–hip extensor joint moments during the first half-cycle of pedaling.

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John B. Cronin, Eadric Bressel and Loren Finn

Context:

Frequency and magnitude of ground reaction forces (GRF) have been implicated in causing injuries such as “jumpers knee.”

Objective:

To investigate whether a single session of augmented feedback concerning landing technique would decrease GRF.

Design:

Pretest posttest experimental design.

Setting:

University biomechanics laboratory.

Participants:

Fifteen female Division 1 intercollegiate volleyball players.

Intervention:

Participants were required to land on a force platform after spiking a volleyball from a four-step approach before and after an intervention involving visual and aural augmented feedback on correct jumping and landing technique.

Main Outcome Measures:

Mediolateral (ML), anterioposterior (AP), and vertical (V) GRF normalized to body weight (BW).

Results:

Augmented feedback was found to significantly (P = 0.01) decrease VGRF by 23.6% but not ML (25%, P = 0.16) and AP (4.9%, P = 0.40) peak GRF.

Conclusions:

A single session of augmented feedback may be effective in reducing VGRF in collegiate athletes.

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Talin Louder, Dennis Dolny and Eadric Bressel

Context: The aquatic environment provides a low-impact alternative to land-based exercise and rehabilitation in older adults. Objective: Evaluate the biomechanics of older adults and young adults performing jumping movements on land and in water. Design and Setting: Cross-sectional, mixed-factorial experiment; adjustable-depth pool at sports medicine research facility. Participants: Fifty-six young adults (age = 22.0 [3.9] y) and 12 healthy older adults (age = 57.3 [4.4] y). Interventions: Each participant performed 6 maximal effort countermovement jumps: 3 jumps were performed on land, and 3 other jumps were performed with participants immersed in chest-deep water. Main Outcome Measures: Using data from the amortization and propulsive phases of jumping, the authors computed the following kinetic and kinematic measures: peak and mean mechanical power, peak force, amortization time and rate, unweighting and propulsive times, and lower-extremity segment kinematics. Results: Mechanical power outputs were greater in younger adults (peak: 7322 [4035] W) versus older adults (peak: 5661.65 [2639.86] W) and for jumps performed in water (peak: 9387 [3981] W) versus on land (peak: 4545.84 [1356.53] W). Peak dorsiflexion velocities were greater for jumps performed in water (66 [34] deg/s) versus on land (4 [7] deg/s). The amortization rate was 26% greater in water versus on land. The amortization time was 20% longer in older adults versus young adults. Conclusions: Countermovement jumps performed in water are mechanically specific from those performed on land. Older adults jumped with longer unweighting times and increased mechanical power in water. These results suggest that aquatic-based exercise and rehabilitation programs that feature jumping movements may benefit older adults.

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Erin Coppin, Edward M. Heath, Eadric Bressel and Dale R. Wagner

Purpose:

The aim of this study was to develop reference values for the Wingate Anaerobic Test (WAnT) for peak power (PP), mean power (MP), and fatigue index (FI) in NCAA Division IA male athletes.

Methods:

Seventy-seven athletes (age 20.8 ± 1.8 y, mass 84.4 ± 9.4 kg, height 183.9 ± 6.2 cm) participating in American football (n = 52) and track and field (n = 25) performed a 30-s WAnT resisted at 0.085 kp/kg body mass (BM).

Results:

Absolute mean (± SD) values for PP and MP were 1084.2 ± 137.0 and 777.1 ± 80.9 W, respectively, whereas values normalized to BM were 12.9 ± 1.5 and 9.3 ± 0.9 W/kg BM, respectively. Mean FI values were 49.1% ± 8.4%. PP outputs >13.6, 12.4–13.6, and <12.4 W/kg BM were classified as high, medium, and low, respectively. MP outputs >9.8, 9.0–9.8, and <9.0 W/kg BM were classified as high, medium, and low, respectively.

Conclusions:

The reference values developed in this study can be used in various athletic training and research programs to more accurately assess athletes’ anaerobic fitness and to monitor changes resulting from anaerobic training.

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Jeffrey M. Willardson, Fabio E. Fontana and Eadric Bressel

Purpose:

To compare core muscle activity during resistance exercises performed on stable ground vs. the BOSU Balance Trainer.

Methods:

Twelve trained men performed the back squat, dead lift, overhead press, and curl lifts. The activity of the rectus abdominis, external oblique abdominis, transversus abdominis/internal oblique abdominis, and erector spinae muscles was assessed. Subjects performed each lift under three separate conditions including standing on stable ground with 50% of a 1-RM, standing on a BOSU Balance Trainer with 50% of a 1-RM, and standing on stable ground with 75% of a 1-RM.

Results:

Significant differences were noted between the stable 75% of 1-RM and BOSU 50% of 1-RM conditions for the rectus abdominis during the overhead press and transversus abdominis/internal oblique abdominis during the overhead press and curl (P < .05). Conversely, there were no significant differences between the stable 75% of 1-RM and BOSU 50% of 1-RM conditions for the external obliques and erector spinae across all lifts examined. Furthermore, there were no significant differences between the BOSU 50% of 1-RM and stable 50% of 1-RM conditions across all muscles and lifts examined.

Conclusions:

The current study did not demonstrate any advantage in utilizing the BOSU Balance Trainer. Therefore, fitness trainers should be advised that each of the aforementioned lifts can be performed while standing on stable ground without losing the potential core muscle training benefits.

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Jeffrey M. Willardson, John Emmett, Jon A. Oliver and Eadric Bressel

Purpose:

This study compared failure versus nonfailure training with equated intensity and volume on lower body muscular endurance in trained men.

Methods:

Each subject performed one lower body workout per week for 6 weeks; the Failure group performed 3 sets of the squat, leg curl, and leg extension exercises to the point of voluntary exhaustion, while the Nonfailure group performed 4 sets for each of these exercises, but with a submaximal number of repetitions that did not allow failure to occur on any set. All subjects performed a pre- and postintervention muscular endurance test that involved 3 sets each for the squat, leg curl, and leg extension exercises. Blood lactate concentration (BL) was assessed before, and at 5 and 10 minutes following the test. Heart rate (HR) was assessed before the test, following the last set of each exercise, and for 10 minutes following the test.

Results:

Both groups demonstrated significant increases in total work (P < .0001) for the postintervention test, with no significant differences between the groups (P = .882). When comparing the pre- and postintervention tests, BL and HR were not significantly different at any time point (P > .05).

Conclusions:

These results indicate that when intensity and volume are equated, failure or nonfailure training results in similar gains in lower body muscular endurance. Therefore, when assessed over relatively short training cycles, the total volume of training might be more important versus whether sets are performed to failure for muscular endurance-related adaptations.

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Eadric Bressel, Gerald Smith, Andrew Miller and Dennis Dolny

Context: Quantification of the magnitudes of fluid resistance provided by water jets (currents) and their effect on energy expenditure during aquatic-treadmill walking is lacking in the scientific literature. Objective: To quantify the effect of water-jet intensity on jet velocity, drag force, and oxygen uptake (VO2) during aquatic-treadmill walking. Design: Descriptive and repeated measures. Setting: Athletic training facility. Participants, Interventions, and Measures: Water-jet velocities were measured using an electromagnetic flow meter at 9 different jet intensities (0-80% maximum). Drag forces on 3 healthy subjects with a range of frontal areas (600, 880, and 1250 cm2) were measured at each jet intensity with a force transducer and line attached to the subject, who was suspended in water. Five healthy participants (age 37.2 ± 11.3 y, weight 611 ± 96 N) subsequently walked (~1.03 m/s or 2.3 miles/h) on an aquatic treadmill at the 9 different jet intensities while expired gases were collected to estimate VO2. Results: For the range of jet intensities, water-jet velocities and drag forces were 0-1.2 m/s and 0-47 N, respectively. VO2 increased nonlinearly, with values ranging from 11.4 ± 1.0 to 22.2 ± 3.8 mL × kg-1 × min-1 for 0-80% of jet maximum, respectively. Conclusions: This study presented methodology for quantifying water-jet flow velocities and drag forces in an aquatic-treadmill environment and examined how different jet intensities influenced VO2 during walking. Quantification of these variables provides a fundamental understanding of aquatic-jet use and its effect on VO2. In practice, these results indicate that VO2 may be substantially increased on an aquatic treadmill while maintaining a relatively slow walking speed.

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W. Matthew Silvers, Eadric Bressel, D. Clark Dickin, Garry Killgore and Dennis G. Dolny

Context:

Muscle activation during aquatic treadmill (ATM) running has not been examined, despite similar investigations for other modes of aquatic locomotion and increased interest in ATM running.

Objectives:

The objectives of this study were to compare normalized (percentage of maximal voluntary contraction; %MVC), absolute duration (aDUR), and total (tACT) lower-extremity muscle activity during land treadmill (TM) and ATM running at the same speeds.

Design:

Exploratory, quasi-experimental, crossover design.

Setting:

Athletic training facility.

Participants:

12 healthy recreational runners (age = 25.8 ± 5 y, height = 178.4 ± 8.2 cm, mass = 71.5 ± 11.5 kg, running experience = 8.2 ± 5.3 y) volunteered for participation.

Intervention:

All participants performed TM and ATM running at 174.4, 201.2, and 228.0 m/min while surface electromyographic data were collected from the vastus medialis, rectus femoris, gastrocnemius, tibialis anterior, and biceps femoris.

Main Outcome Measures:

For each muscle, a 2 × 3 repeated-measures ANOVA was used to analyze the main effects and environment–speed interaction (P ≤ .05) of each dependent variable: %MVC, aDUR, and tACT.

Results:

Compared with TM, ATM elicited significantly reduced %MVC (−44.0%) but increased aDUR (+213.1%) and tACT (+41.9%) in the vastus medialis, increased %MVC (+48.7%) and aDUR (+128.1%) in the rectus femoris during swing phase, reduced %MVC (−26.9%) and tACT (−40.1%) in the gastrocnemius, increased aDUR (+33.1%) and tACT (+35.7%) in the tibialis anterior, and increased aDUR (+41.3%) and tACT (+29.2%) in the biceps femoris. At faster running speeds, there were significant increases in tibialis anterior %MVC (+8.6−15.2%) and tACT (+12.7−17.0%) and rectus femoris %MVC (12.1−26.6%; swing phase).

Conclusion:

No significant environment–speed interaction effects suggested that observed muscle-activity differences between ATM and TM were due to environmental variation, ie, buoyancy (presumed to decrease %MVC) and drag forces (presumed to increase aDUR and tACT) in the water.