Brandi S. Row

Influence of Ramp Position on Joint Biomechanics During Elliptical Trainer Exercise

Introduction: The elliptical trainer, developed to simulate running while minimizing joint loads, elicits a unique lower extremity biomechanical response. The purpose of this study was to examine the angular kinematics, peak net joint moments, and peak joint powers at the hip, knee and ankle joints while exercising at three different ramp settings on the elliptical trainer exercise machine (Precor EFX). Methods: Twenty-six healthy individuals with no history of lower extremity injury and with previous experience exercis- ing on an elliptical trainer volunteered for this study. Motion was captured with two cameras as subjects performed exer- cise at three ramp conditions. The pedal resistance was kept constant at the lowest setting. The pedals of the elliptical were fitted with three orthogonal load cells. Video and force data were synchronized and used to perform a 2D inverse dynamics analysis. Results: As the ramp inclination increased, subjects demonstrated greater amounts of ankle dorsiflexion, knee flexion, hip flexion and lesser degrees of plantar flexion and hip extension (p <.000). Mean peak moments at the ankle joint were not significantly different across the ramp settings, but peak knee extensor and hip flexor moments increased while knee flexor and hip extensor at the hip decreased (p <.000). As the ramp inclination increased, peak positive power at both the knee and hip significantly decreased and negative power decreased at the knee joint (p <.000), though the effect size for these changes was small. Conclusions: The hip and knee joints were observed as the primary sources of power during exercise on the elliptical trainer at the lowest resistance setting.

Common errors in textbook descriptions of muscle fiber size in nontrained humans.

Exercise science and human anatomy and physiology textbooks commonly report that type IIB muscle fibers have the largest cross-sectional area of the three fiber types. These descriptions of muscle fiber sizes do not match with the research literature examining muscle fibers in young adult nontrained humans. For men, most commonly type IIA fibers were significantly larger than other fiber types (six out of 10 cases across six different muscles). For women, either type I, or both I and IIA muscle fibers were usually significantly the largest (five out of six cases across four different muscles). In none of these reports were type IIB fibers significantly larger than both other fiber types. In 27 studies that did not include statistical comparisons of mean fiber sizes across fiber types, in no cases were type IIB or fast glycolytic fibers larger than both type I and IIA, or slow oxidative and fast oxidative glycolytic fibers. The likely reason for mistakes in textbook descriptions of human muscle fiber sizes is that animal data were presented without being labeled as such, and without any warning that there are interspecies differences in muscle fiber properties. Correct knowledge of muscle fiber sizes may facilitate interpreting training and aging adaptations.

Effect of Inspiratory Muscle Training and Core Exercise Training on Core Functional Tests: 3164

Brilla LB, Kauffman TH. Effect of Inspiratory Muscle Training and Core Exercise Training on Core Functional Tests. JEPonline 2014;17(3):12-20. This study tested the effects of inspiratory muscle training on core function compared to a typical core training program. Subjects consisted of 32 healthy, recreationally active individuals (18-25 yrs of age) who were randomly assigned to one of three groups: Control (C), Inspiratory Muscle Training (IMT), and Core Exercise Class (AbEx). IMT performed inspiratory muscle training for 6 wks at 85% maximal inspiratory pressure (MIP), while AbEx performed standard core training of the same duration. Core function was assessed preand post-training using a side bridge, prone extension and Stabilizer test of transversus abdominis (TrA) function. MIP was also assessed before and after the treatment. Significant interaction effect was observed for MIP (P≤0.05). IMT MIP increased from 1.06 ± 0.37 to 1.71 ± 0.41 cm H2O (P≤0.05) with no significant pre-post changes in C (1.09 ± 0.29 to 1.15 ± 0.36 cm H2O) or AbEx (0.78 ± 0.31 to 0.88 ± 0.33 cm H2O). A significant interaction effect was noted in prone extension (P≤0.05). Time increased in AbEx from 114.0 ± 53.0 to 154.0 ± 77.6 sec (P≤0.05), with no significant changes in C (158.9 ± 75.5 to 152.1 ± 62.6 sec) or IMT (132.0 ± 39.2 to 132.8 ± 40.3 sec). A significant interaction for the Stabilizer test of TrA function was found (P≤0.05). The IMT group improved from -6.9 ± 12.6 to -10.0 ± 11.0 mmHg (P≤0.05), with no significant changes in the Control (-5.0 ± 12.1 to -4.8 ± 13.4 mmHg) or AbEx groups (-15.0 ± 5.8 to -9.7 ± 10.4 mmHg). There were no significant differences (P≥0.05) in the side bridge test. Six weeks of core training and inspiratory muscle training improve core function and target different muscles.