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Osteoporosis and loss of muscle mass are secondary issues with spinal cord injury. Robotic gait training has provided evidence of increasing bone density and muscle mass, but its effect on bone strength is undetermined. The purpose of this study was to determine the effect of a 6‐week robotic locomotion training program on skeletal muscle mass and bone characteristics. Twelve female Sprague‐Dawley rats received a mid‐thoracic spinal cord transection at 5 days old and at 3 weeks old were assigned to a Control or Trained Group. The Trained Group performed 5‐min sessions on the Rat Stepper 5 days a week for 6 weeks with 90% of body weight supported. At the end of the 6 weeks, body mass was obtained and right femurs and four lower extremity muscles were harvested. Femur bone mineral density was measured with DXA and mechanical characteristics of the femur were determined via 3‐point bending testing. Independent t‐tests, effects sizes and percent differences were computed between the two groups (p < 0.05). The Trained Group had significantly larger normalized femur mass (p = 0.007) and normalized soleus muscle mass (p = 0.033) when compared to the Control Group. There was a medium or large effect size with the Trained Groups' femurs having larger mass, bone mineral density, rupture loads, cortical wall thickness, shaft cross sectional area, soleus mass, normalized gastrocnemius mass, and smaller shaft inner diameters compared to the Control Group. These changes may contribute to decreasing osteoporosis and fracture risk in those with spinal cord injuries. [ABSTRACT FROM AUTHOR]

This article reviews several tools we have developed to improve the understanding of locomotor training following spinal cord injury (SCI), with a view toward implementing locomotor training with robotic devices. We have developed (1) a small-scale robotic device that allows testing of locomotor training techniques in rodent models, (2) an instrumentation system that measures the forces and motions used by experienced human therapists as they manually assist leg movement during locomotor training, (3) a powerful, lightweight leg robot that allows investigation of motor adaptation during stepping in response to force-field perturbations, and (4) computational models for locomotor training. Results from the initial use of these tools suggest that an optimal gait-training robot will minimize disruptive sensory input, facilitate appropriate sensory input and gait mechanics, and intelligently grade and time its assistance. Currently, we are developing a pneumatic robot designed to meet these specifications as it assists leg and pelvic motion of people with SCI.

Prior research has demonstrated that male adults and youth engaged in skateboarding at community skateparks achieve heart rates that meet or exceed recommendations for exercise by the CDC. However, these studies do not adequately evaluate other non-traditional or ethnically diverse users who may differ in how they utilize the skatepark and in their cardiovascular response. The purpose of this experiment was to measure heart rate response and locomotor movement in three lesser studied groups that frequently utilize community skateparks, and to compare these results with those reported previously in male adult and youth skateboarders. Fifty-six skatepark users were analyzed, including thirty female and BIPOC skateboarders, and twenty-six non-skateboard users. All participants were instrumented with a HR monitor with GPS capability and asked to engage in their preferred activity with no duration specified. Average heart rate and time spent at high and moderate levels of heart rate intensity were not statistically different among the groups studied here, nor were they different from those reported previously for male adult and youth skateboarders. Distances traveled, average, and peak velocities were also not statistically different among the groups studied here, but all were significantly lower than values previously reported for adult male skateboarders. While some differences in distances traveled and velocity were noted, all groups met or exceeded CDC guidelines for cardiovascular fitness. These data suggest that skateparks can help a community achieve health outcomes, particularly among diverse users. [ABSTRACT FROM AUTHOR]

We have developed a robotic device (the "rat stepper") for evaluating and training locomotor function of spinal cord injured rodents. This paper provides a detailed description of the device design and a characterization of its robotic performance capabilities.

Hibbert, JE, Klawiter, DP, Schubert, MM, Nessler, JA, and Asakawa, DS. Strength, cardiovascular fitness, and blood lipid measures in law enforcement personnel after a 12-week health promotion program. J Strength Cond Res 36(11): 3105–3112, 2022—Law enforcement personnel often have high rates of cardiovascular disease and injury. Health promotion programs have been found to successfully encourage behavior change among law enforcement personnel, but these programs can often be intensive and expensive. Thus, the purpose of this study was to examine the efficacy of a health promotion program on body composition, metabolic health, muscle strength, and cardiovascular endurance in law enforcement personnel. Active duty officers from a local law enforcement agency were invited to participate in a 12-week health promotion program that included activity tracking and exercise and nutrition education. Eighteen subjects underwent measurements of body composition, V̇ o 2max through treadmill test, knee extensor strength, and blood lipids. An a priori alpha level for significance was set at 0.05, and comparisons were assessed using paired t -tests. Overall, subjects improved blood lipid levels evidenced by movement of mean values toward established healthy ranges. Although 8 subjects improved their V̇ o 2max (range: 1.3–30% change), there was large variability and no statistically significant differences in measures of V̇ o 2max (pre: 38.48 ± 5.86 ml·kg·min−1; post: 39.27 ± 5.26 ml·kg·min−1), body composition (pre: 26.52 ± 8.02% body fat; post: 26.44 ± 7.45% body fat), and strength normalized to body mass (isometric pre: 1.45 ± 0.45; post: 1.08 ± 0.36). Although no significant changes were noted, promising trends in these data suggest that health promotion programs with a modified focus may lead to positive changes in overall health. [ABSTRACT FROM AUTHOR]

Low back pain is a commonly reported problem among recreational surfers. Some individuals report that wearing a vest with an inflatable bladder that alters trunk angle may help to alleviate pain. The purpose of this study was to determine whether such a vest has an effect on muscle activation and extension of the lower back. Twelve recreational surfers completed 12 paddling trials at 1.1 m/s in a swim flume on both a shortboard and a longboard on 2 separate days. Three conditions of no vest, vest uninflated, and vest inflated were presented to participants in random order. Surface EMG and trunk angle were acquired via wireless sensors placed over the right erector spinae, mid-trapezius, upper trapezius, and latissimus dorsi. Wearing the inflated vest affected muscle activation: erector spinae and mid-trapezius demonstrated a significant decrease in activation relative to wearing no vest (12% and 18% respectively, p < .05). Trunk extension was also significantly reduced when the vest was inflated (18% reduction, p < .05). Results were similar for both the short and longboard, though this effect was greater while paddling the larger board. These results suggest that a properly inflated vest can alter trunk extension and muscle activity while paddling a surfboard in water. [ABSTRACT FROM AUTHOR]

Participation in surfing has evolved to include all age groups. Therefore, the purpose of this study was to determine whether activity levels and cardiovascular responses to surfing change with age. Surfing time and heart rate (HR) were measured for the total surfing session and within each activity of surfing (paddling, sitting, wave riding, and miscellaneous). Peak oxygen consumption (VO2peak) was also measured during laboratory-based simulated surfboard paddling on a modified swim bench ergometer. VO2peak decreased with age during simulated paddling (r = –.455, p < .001, n = 68). Total time surfing (p = .837) and time spent within each activity of surfing did not differ with age (n = 160). Mean HR during surfing significantly decreased with age (r = –.231, p = .004). However, surfing HR expressed as a percent of age-predicted maximum increased significantly with age. Therefore, recreational surfers across the age spectrum are achieving intensities and durations that are consistent with guidelines for cardiovascular health. [ABSTRACT FROM AUTHOR]

Law enforcement personnel often carry gear loads, which have a history of causing low back pain. The aim of this study was to evaluate the differences in gait and trunk posture for gear load carried on a gear belt and a gear vest. Twenty-nine participants performed load carriage in three conditions: a no load control trial (C), a symmetrically loaded gear belt (GB), and an anteriorloaded gear vest (ALV). Gear conditions had 9.07 kg of additional mass. Motion capture and insole force sensors were used to collect data while participants walked on a treadmill for three minutes per condition. Mean insole reaction force was significantly greater in both GB and ALV conditions as compared to C (p < 0.001). Mean gait cadence in the GB or ALV condition were not significantly different from the C condition. However, double support time in the ALV condition was significantly longer compared to C condition (p = 0.023). Stance duration on the left foot was significantly longer with the GB (p = 0.001) and ALV (p = 0.028) when compared to C. Results showed trunk flexion/extension excursion was significantly less in the GB condition when compared to the C condition (p = 0.002). These findings demonstrate that law enforcement and other personnel who walk while carrying gear loads may experience altered biomechanics compared to unloaded walking. Altered biomechanics and increased forces on the feet could potentially increase risk of musculoskeletal injury while carrying gear loads. [ABSTRACT FROM AUTHOR]

Surfing is a worldwide sport that often requires participants to wear a wetsuit to assist in thermoregulation. In a recent study, forearm skin temperature decreased by approximately 3 °C while wearing a wetsuit during recreational surfing. The purpose of this study was to test the hypothesis that reducing water flow in and out of the wetsuit by cuffing the wetsuit at the wrist, with a novel cuff closure system (Velcro cuff), would result in greater forearm skin temperature while surfing. One hundred and twelve (94 male, 18 female) recreational surfers between the ages of 18-50 participated in this study. Forearm skin temperature was measured at 1-minute intervals across the surf session in both arms with four wireless iButton thermal sensors located two inches from the styloid process (wrist) and olecranon process (elbow). Following instrumentation, all subjects had one of their wrists randomly cuffed with a one-inch wide Velcro cuff that was tightened to 2 cm less than the circumference of the wrist plus wetsuit. Subjects were then instructed to engage in regular recreational surfing activities for a minimum of 30 minutes at seven beaches in North San Diego County from October to April. No significant differences were found between the average cuffed wrist skin temperature and the average uncuffed wrist skin temperature (p = 0.06). However, average cuffed forearm skin temperature was significantly higher than average uncuffed forearm skin temperature (p = 0.01). Results from this study suggest that cuffing the wrist of wetsuits is a simple technique that can be utilized by surfers to significantly improve forearm skin temperature during surfing. These findings may also have an implication on future wetsuit designs. [ABSTRACT FROM AUTHOR]

Youth participating in recreational skating at community skate parks attain exercise intensities and durations that are comparable with the CDC's exercise recommendations for cardiovascular fitness for their age group. However, it is currently unclear if adults who skateboard in the same environment also achieve the recommended intensities and durations for cardiovascular fitness. Therefore, the purpose of this study was to test the hypothesis that skateboarding would elicit heart rates and durations consistent with the CDC's recommendations for cardiovascular fitness in adults. Fifty-five subjects between ages 18-55 were recruited from six community skateparks for this study. Subjects completed a questionnaire and were instrumented with a Polar V800 heart rate receiver on the left wrist and an H7 Bluetooth heart rate transmitter around the chest below the pectoralis major. Participants were instructed to engage in a typical skateboarding session on their own board with the duration and intensity of activity to be determined by the participant. The mean age of the participants was 27.4 ± 8.5 years, and participants reported skateboarding at a community skate park a mean of 3.1 ± 1.8 days/week. Participants had a mean heart rate of 138.2 ± 21.9 beats per minute (71.7% of age predicted maximum), skated for 65.5 ± 36.2 minutes, and traveled 4.56 ± 4.5 kilometers. Subjects spent 70% of their total duration at moderate-intensity or above and 30% within the low, and below lowintensity range. Results from this study suggest that adults participating in recreational skateboarding in community skateparks achieve the CDC's exercise recommendations for cardiovascular fitness. These findings may have implications for community skatepark design and professional training programs for adult skateboarding athletes. [ABSTRACT FROM AUTHOR]

Studying spontaneous synchronization of stepping as two individuals walk on side-by-side treadmills may be useful for understanding the control of bipedal locomotion and may have implications for gait rehabilitation. Existing data suggest that this behavior is related to differences in leg length, walkway slope, and overground speed between partners, and might be promoted by altering these variables. This idea was evaluated here as 24 pairs of subjects stepped on side-by-side treadmills under several conditions of relative speed and slope. Overall, pairings that demonstrated very little spontaneous synchronization with the same treadmill speed and slope exhibited significant increases in this behavior when one treadmill was manipulated. Conversely, pairings that demonstrated a tendency to synchronize under normal conditions exhibited significant decreases in this behavior when either treadmill was altered. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the effects of interpersonal synchronization of stepping on stride interval dynamics during over-ground walking. Twenty-seven footswitch instrumented subjects walked under three conditions: independent (SOLO), alongside a partner (PAIRED), and side by side with intentional synchronization (FORCED). A subset of subjects also synchronized stepping to a metronome (MET). Stride time power spectral density and detrended fluctuation analysis revealed that the rate of autocorrelation decay in stride time was similar for both the SOLO and PAIRED conditions, but was significantly reduced during the FORCED and MET conditions (p=0.03 & 0.002). Stride time variability was also significantly increased for the FORCED and MET conditions (p<0.001). These data suggest that forced synchronization of stepping results in altered stride interval dynamics, likely through increased active control by the CNS. Passive side by side stepping, where synchronization is subconscious, does not appreciably alter stepping in this manner. [ABSTRACT FROM AUTHOR]