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Context: Research is needed to find ways of improving physical activity after a lateral ankle sprain. Objective: To investigate the effects of a prolonged rest period on lifelong activity after a surgically induced ankle sprain. Design: Controlled laboratory study. Setting: Research laboratory. Patients or Other Participants: A total of 18 male CBA/J mice (age at surgery = 7 weeks). Main Outcome Measure(s): We transected the anterior talofibular ligament and calcaneofibular ligament of the right hindlimb. Each mouse was placed in a separate cage and randomized into 1 of 3 groups of 6 mice each. A running wheel was placed in each cage at 3 days, 7 days, or 14 days after surgery. Physical activity was measured daily. Daily duration (ie, time spent on the wheel), distance, and running speed were examined using analysis of variance (group 3 age) with repeated measures at 15-week periods to approximate the first 3 quartiles of the lifespan. Results: From weeks 3 to 15 after surgery, we observed no differences in duration, distance, or running speed among groups (P<05). From weeks 16 to 30, distance (F2,14 =0.57, P = .041) and running speed (F2,14 = 0.93, P = .01) were greater in the 14-day group than in the 3- and 7-day groups. From weeks 31 to 45, duration (F2,14 =0.74, P =.02), distance (F2,14 = 0.95, P = .009), and running speed (F2,14 = 1.05, P = .007) were greater in the 14-day group than in the 3- and 7-day groups. Conclusions: Our findings suggest that the longer recovery period of 14 days can increase activity levels throughout the lifespan after a severe ankle sprain. Rest after an ankle injury is critical to restoring physical activity levels across the lifespan. Rest and time away from exercise after an ankle sprain may be necessary to restore physical activity to normal, uninjured levels. [ABSTRACT FROM AUTHOR]

Context: Lateral ankle sprains (LASs) result in short- and long-term adaptations in the sensorimotor system that are thought to contribute to the development of chronic ankle instability and posttraumatic ankle osteoarthritis. Debate continues as to the appropriateness of rapid return to sport after LASs given the prevalence of long-term consequences. Objective: To examine the short- and long-term effects of prolonged rest, as a model of immobilization, on dynamic balance and gait outcomes after a severe LAS in a mouse model. Design: Controlled laboratory study. Setting: Research laboratory. Intervention(s): At 7 weeks of age, 18 male mice (CBA/J) had their right anterior talofibular and calcaneofibular ligaments transected. Mice were then randomized to 1 of 3 groups representing when access to a running wheel postsurgery was gained: at 3 days, 1 week, and 2 weeks. Main Outcome Measure(s): Dynamic balance and spatial gait characteristics were quantified before surgery (baseline) and at 3 days and 1, 2, 4, 6, 12, 18, 24, 30, 36, 42, 48, and 54 weeks postinjury. Results: Relative to prolonged rest, resting for only 3 days resulted in worse dynamic balance during the later assessment points (42-54 weeks postinjury, P <01). Mice that underwent a prolonged rest period of 2 weeks crossed the balance beam faster than the group that rested for only 3 days when averaged across all time points (P>012). Spatial gait characteristics did not differ among the groups (P<05). Conclusions: Relative to 3 days of rest, prolonged rest (1 and 2 weeks) after a severe LAS in mice positively affected balance. The apparent benefit of prolonged rest was noted on both dynamic-balance outcomes and performance. Stride length was not altered by the duration of rest after a surgically induced severe LAS in mice. Future research is needed to determine if these results translate to a human model. [ABSTRACT FROM AUTHOR]

Context: Ankle sprains remain the most common orthopaedic injury. Conducting long-term studies in humans is difficult and costly, so the long-term consequences of an ankle sprain are not entirely known. Objective: To measure knee-joint space after a single surgically induced ankle sprain in mice. Design: Randomized controlled trial. Setting: University research laboratory. Patients or Other Participants: Thirty male mice (CBA/2J) were randomly placed into 1 of 3 surgical groups: the transected calcaneofibular ligament (CFL) group, the transected anterior talofibular ligament/CFL group, or a sham treatment group. The right ankle was operated on in all mice. Main Outcome Measure(s): Three days after surgery, all of the mice were individually housed in cages containing a solidsurface running wheel, and daily running-wheel measurements were recorded. Before surgery and every 6 weeks after surgery, a diagnostic ultrasound was used to measure medial and lateral knee-joint space in both hind limbs. Results: Right medial (P = .003), right lateral (P = .002), left medial (P = .03), and left lateral (P = .002) knee-joint spaces decreased across the life span. The mice in the anterior talofibular ligament/CFL group had decreased right medial (P = .004) joint space compared with the sham and CFL groups starting at 24 weeks of age and continuing throughout the life span. No differences occurred in contralateral knee-joint degeneration among any of the groups. Conclusions: Based on current data, mice that sustained a surgically induced severe ankle sprain developed greater joint degeneration in the ipsilateral knee. Knee degeneration could result from accommodation to the laxity of the ankle or biomechanical alterations secondary to ankle instability. A single surgically induced ankle sprain could significantly affect knee-joint function. [ABSTRACT FROM AUTHOR]

PURPOSE: The purpose of this study was to investigate the age-related changes in diastolic filling parameters in the aging hearts of active C57Bl/6J mice throughout the life span to indicate optimal age periods for improvements in resting diastolic parameters. METHODS: Fourteen C57Bl/6J mice (seven males and seven females) were individually housed at 8 wk of age in cages with a running wheel, magnetic sensor, and digital odometer. Duration, distance, and running velocity were recorded daily. Fourteen additional mice C57Bl/6J mice (seven males and seven females) were placed in individual cages without running wheels at 8 wk of age. Pulsed-wave Doppler transmitral inflow recordings with a SONOS 5500 ultrasound and 15-6L ultrasound probe were used to image the left ventricle every 4 wk throughout the life span. RESULTS: Peak E wave filling velocities were significantly greater by the start of the second quarter of the life span in the mice with access to running wheels (P < 0.0001). Peak E wave velocities improved in both groups during the first half of the life span (P < 0.0001) and declined throughout the second half of the life span (P < 0.0001). Early-to-late (E:A) filling ratio was significantly greater for the physically active mice by the start of the second quarter of the life span (P < 0.0001) and continued throughout most of the remainder of the life span (P < 0.0001). No differences were observed between the two groups of mice with peak A wave filling velocities (P > 0.05). Similar findings were observed when corrected for resting heart rate. CONCLUSIONS: Lifelong physical activity resulted in greater diastolic filling parameters by the second quarter of the life span, highlighting the clinical importance of regular aerobic activity in young adulthood as a mechanism for improved left ventricular performance with aging. [ABSTRACT FROM AUTHOR]

Sedentarism is associated with obesity and other chronic diseases at all ages. Increasing physical activity with in-school interventions, focusing on energy expenditure and bone loading reduces risk of a number of costly chronic diseases. The aim of the current study was to characterise the metabolic and musculoskeletal load intensity of the recent successful CAPO Kids exercise intervention. Pre and early pubertal children (10.4 ± 0.5 years old) from the CAPO Kids trial wore an armband sensor to estimate energy expenditure during a 10-minute CAPO Kids session. Eleven participants performed manoeuvres from the session on a force platform to determine vertical ground reaction forces. In total, 28 boys and 20 girls had armband measures and 11 boys and girls undertook GRF testing. The energy expenditure associated with the 10-minute session was 39.7 ± 9.3 kcal, with an average of 4 kcal∙min-1. The intensity of physical activity was ‘vigorous' to ‘very vigorous' for 34% of the session. Vertical ground reaction forces of the CAPO Kids manoeuvres ranged from 1.3 ± 0.2 BW (cartwheels) to 5.4 ± 2.3 BW (360° jump). CAPO Kids generates adequate load intensity to stimulate positive health adaptations in both metabolic and musculoskeletal systems of pre and early pubertal children. [ABSTRACT FROM AUTHOR]

Ankle sprains are the most common orthopedic pathology experienced during sport and physical activity and often result in chronic ankle instability (CAI). Understanding how to prevent CAI is difficult because of the costs and logistics associated with clinical trials aimed at preventing the heterogeneous symptoms associated with CAI. Thus, a need exists to develop an animal model that presents similar long-term consequences as CAI to assess preclinical data. Thus, the purpose was to determine whether surgically transecting the lateral ligaments of a mouse hind limb results in the development of CAI-like symptoms 12 months after injury. Methods: Thirty male mice (CBA/J) were randomly placed into a SHAM (control), CFL (calcaneofibular ligament; mild ankle sprain), or ATFL/CFL (anterior talofibular ligament/ CFL; severe) ankle sprain group and housed individually. Three days after surgically transecting the respective lateral ligaments, mice were given a solid surface running wheel and daily running wheel measurements were recorded. Outcome measures of balance and gait were obtained before and at 4, 48, 54, and 60 wk after injury. Results: The ATFL/CFL group had significantly more hind foot slips than the CFL and SHAM groups (P < 0.05). The CFL also had more hind foot slips relative to the SHAM group (P < 0.05). The ATFL/CFL group was significantly less physically active relative to the SHAM and CFL groups (P < 0.05). A cut score of 4.75 foot slips had a sensitivity of 0.68 and specificity of 1.00 and indicates that 70% (14/20) of mice with an ankle sprain had developed CAI. Conclusions: The results of this study indicate that an acute ankle sprain in mice can result in the development of CAI-like symptoms 12 months after injury. [ABSTRACT FROM AUTHOR]

A baroreflex equilibrium diagram describes the relation between input pressure and sympathetic nerve activity (SNA) and that between SNA and arterial pressure (AP). To calibrate the SNA axis (abscissa) of the baroreflex equilibrium diagram, the AP response to intravenous bolus injections of phenylephrine (0.2-50 µg/kg) or norepinephrine (NE, 0.02-5 µg/kg) was examined in normal control rats (NC, n = 9) and rats with chronic heart failure (CHF, n = 6). The maximum slope of the dose-effect curve was significantly smaller in the CHF group than in the NC group (57.3 ± 5.2 vs 80.9 ±6.3 mmHg/decade for phenylephrine, 60.2 ± 7.8 vs 80.4 ± 5.9 mmHg/decade for NE; P, 0.01). The CHF/NC ratio of the maximum slope was used to calibrate SNA. While the calibrated baroreflex equilibrium diagram showed increased maximum SNA and operating-point SNA in CHF rats compared with NC rats, the magnitude of increase was smaller than that expected from the excess plasma NE concentration in CHF rats. Plasma NE concentration in the CHF group could be disproportionally high relative to SNA. [ABSTRACT FROM AUTHOR]

Introduction: Ankle sprains remain the most common orthopedic pathology. Conducting long-term studies in humans is difficult and costly, so the long-term consequences of an ankle sprain are not entirely known. Purpose: The objective of this study is to develop and test a mechanical ankle instability model in mice. Methods: Thirty male mice (CBA/2J) were randomly placed into one of three groups: the transected calcaneal fibular ligament (CFL) group, the transected anterior talofibular ligament (ATFL)/CFL group, and a SHAM group. Three days after surgery, all of the mice were individually housed in a cage containing a solid surface running wheel, and daily running wheel measurements were recorded. Before and after surgery, measures of balance and gait were measured on all mice for 4 wk. Results: The mice in the ATFL/CFL group had significantly decreased duration (P = 0.0239), distance (P = 0.013), and speed (P = 0.003) compared with the SHAM group during week 1. During weeks 2 and 3, the ATFL/CFL group had significantly less distance (P = 0.0001) and duration (P = 0.002) compared with the SHAM and CFL-only group. The transection of the lateral ankle ligaments did affect the number of slips experienced during the balance test. The ATFL/CFL group had greater slips at 1 and 4 wk postsurgery (P = 0.05), whereas the CFL-only group had greater slips at 3 d and 1 wk postsurgery (P = 0.05). Relative to the SHAM group, the ATFL/CFL group and CFL-only group had smaller right-stride lengths (involved limb) at 3 d postsurgery (P = 0.05). The ATFL/CFL group also had smaller right-side stride lengths at 1 and 4 wk postsurgery (P = 0.05). Conclusions: The results of this study indicate that a mouse model can be used to induce mechanical instability in the ankle. [ABSTRACT FROM AUTHOR]