Introduction/Purpose: Most U.S. adults (54%) do not meet minimum exercise recommendations by American College of Sports Medicine (ACSM). Neuromuscular electrical stimulation (NMES) is a novel alternate strategy to induce muscle contraction. However, effectiveness of NMES to improve insulin sensitivity and energy expenditure is unclear. The purpose of this study was to investigate the effects of four weeks of NMES on glucose tolerance in a sedentary overweight or obese population. Methods: Participants (n=10; age: 36.8 ± 3.8 years; BMI=32 ± 1.3 kg/ m2) were randomized into either control or NMES group. All participants received bilateral quadriceps stimulation (12 sessions; 30 minutes/session; 3 times/week at 50 Hz and 300 µs pulse width) altering pulse amplitude to either provide low intensity sensory level (control; tingling sensation) or at high intensity neuromuscular level (NMES; maximum tolerable levels with visible muscle contraction). Glucose tolerance was assessed by three-hour oral glucose tolerance test (OGTT), substrate utilization was measured by indirect calorimetry and body composition via dual X-ray absorptiometry at baseline and after four weeks of NMES intervention. Results: Control and NMES groups had comparable fasting blood glucose, glucose tolerance, substrate utilization, and muscle mass at baseline. Four weeks of NMES resulted in a significant improvement in glucose tolerance measured by OGTT, whereas no change was observed in control group. There was no change in substrate utilization and in muscle mass in both control and NMES groups. Conclusion: NMES is a novel and effective strategy to improve glucose tolerance in an at-risk overweight or obese sedentary population.

Three experiments were designed to determine the level of cooperation or interference observed from the forces generated in one limb on the forces exhibited by the contralateral limb when one or both limbs were producing a constant force (Experiment 1), one limb was producing a dynamic force while the other limb was producing a constant force (Experiment 2), and both limbs were producing dynamic force patterns (Experiment 3). The results for both Experiments 1 and 2 showed relatively strong positive time series cross correlations between the left and right limb forces indicating increases or decreases in the forces generated by one limb resulted in corresponding changes in the forces produced by the homologous muscles of the contralateral limb. Experiment 3 required participants to coordinate 1:1 and 1:2 rhythmical bimanual force production tasks when provided Lissajous feedback. The results indicated very effective performance of both bimanual coordination patterns. However, identifiable influences of right limb forces on the left limb force time series were observed in the 1:2 coordination pattern but not in the 1:1 pattern. The results of all three experiments support the notion that neural crosstalk is partially responsible for the stabilities and instabilities associated with bimanual coordination.

The experiment was designed to determine participants' ability to coordinate a bimanual multifrequency pattern of isometric forces using homologous or non-homologous muscles. Lissajous feedback was provided to reduce perceptual and attentional constraints. The primary purpose was to determine whether the activation of homologous and non-homologous muscles resulted in different patterns of distortions in the left limb forces that are related to the forces produced by the right limb. The task was to rhythmically produce a 1:2 pattern of isometric forces by exerting isometric forces on the left side force transducer with the left arm that was coordinated with the pattern of isometric forces produced on the right side force transducer with the right arm. The results indicated that participants were able to 'tune-in' a 1:2 coordination patterns using homologous (triceps muscles of the left and right limbs) and using non-homologous muscles (biceps left limb and triceps right limb) when provided Lissajous feedback. However, distinct but consistent and identifiable distortions in the left limb force traces were observed for both the homologous and non-homologous tasks. For the homologous task, the interference occurred in the left limb when the right limb was initiating and releasing force. For the non-homologous task, the interference in the left limb force occurred only when the right limb was releasing force. In both conditions, the interference appeared to continue from the point of force initiation and/or release to peak force velocity. The overall results are consistent with the notion that neural crosstalk manifests differently during the coordination of the limbs depending upon whether homologous or non-homologous muscles are activated.

An experiment was designed to determine the effectiveness of auditory and visual models in the learning of a 2:3 bimanual tapping pattern. Participants were randomly assigned to an auditory model, visual model, auditory + visual model, or a control (visual metronome) group. The task for all groups was to tap a left side force transducer with the left hand and a right side force transducer with the right hand in attempt to produce the desired 2:3 bimanual coordination pattern. The auditory model consisted of a series of tones representing the goal pattern played prior to each practice trial. The visual model consisted of a visual display representing the goal tapping pattern. Visual pacing metronomes were provided to the control group. The right and left side metronomes flashed during the trial in a pattern representing the goal tapping pattern. Subjects in all groups performed 14 practice trials consisting of 15 s each devoted to tapping the goal pattern (total practice time = 3.5 min). A retention test without the aid of the models or metronomes was administered following the practice trials. The results for the model groups indicated extremely effective performance of the bimanual coordination patterns for the auditory, visual, and auditory + visual model conditions with not only the relative, but also the absolute characteristics of the models exhibited during retention testing. Retention performance for the visual metronome condition was less accurate and more variable than the three model conditions. In addition, the auditory + visual model condition resulted in retention performance that was more stable than the auditory model condition.

Two recent experiments have demonstrated that young adult participants were able to make faster and more harmonic movements in a typical reciprocal Fitts task (ID = 6) following a practice session of sine wave tracking (Boyle et al. in Exp Brain Res 223:377-387, 2012; J Mot Behav 46:277-285, 2014). The purpose of the present experiment was to replicate these findings with a young adult population (age 18-25) and determine whether sine wave tracking also enhances goal-directed limb movements in an older adult population (age 65-90). To establish a performance baseline, all participants were first pretested on a typical ID = 6 Fitts task. Participants in each age group were then randomly assigned to one of the two training conditions where they practiced (45 trials) on a typical Fitts task (ID = 6) or they were asked to track a sine wave template (45 trials). Following practice, all participants were then posttested under the ID = 6 Fitts conditions. The results demonstrated that both young and older adult participants that practiced under the sine wave conditions enhanced their Fitts task performance compared to participants in their respective age groups who practiced under the Fitts conditions. These enhancements included faster movement times, smaller dwell times, and more harmonic movements, all without decreases in movement accuracy. These results replicate our previous findings with young adults and extend the finding to older adult participants. Interestingly, the performances of the older adults following sine wave practice were as fast and as accurate as the young adults following Fitts task practice.