A lower stroke volume, heart rate, and arteriovenous oxygen difference at maximal exercise all contribute to the age-related decline in VO2max. Effects of age and training on VO2max, maximal cardiac output, and stroke volume cannot be fully explained by differences in body composition. In sedentary subjects, however, the sex difference in maximal cardiac output and stroke volume can be accounted for by the greater percentage of body fat in women than in men.

The early addition of NMES effectively attenuated loss of quadriceps muscle strength and improved functional performance following TKA. The effects were most pronounced and clinically meaningful within the first month after surgery, but persisted through 1 year after surgery.

Weight-bearing physical activity has beneficial effects on bone health across the age spectrum. Physical activities that generate relatively highintensity loading forces, such as plyometrics, gymnastics, and high-intensity resistance training, augment bone mineral accrual in children and adolescents. Further, there is some evidence that exercise-induced gains in bone mass in children are maintained into adulthood, suggesting that physical activity habits during childhood may have long-lasting benefits on bone health. It is not yet possible to describe in detail an exercise program for children and adolescents that will optimize peak bone mass, because quantitative dose-response studies are lacking. However, evidence from multiple small randomized, controlled trials suggests that the following exercise prescription will augment bone mineral accrual in children and adolescents: Mode: impact activities, such as gymnastics, plyometrics, and jumping, and moderate intensity resistance training; participation in sports that involve running and jumping (soccer, basketball) is likely to be of benefit, but scientific evidence is lacking Intensity: high, in terms of bone-loading forces; for safety reasons, resistance training should be Ͻ60% of 1-repetition maximum (1RM) Frequency: at least 3 d⅐wk Ϫ1 Duration: 10-20 min (2 times per day or more may be more effective)

IMPORTANCEParkinson disease is a progressive neurologic disorder. Limited evidence suggests endurance exercise modifies disease severity, particularly high-intensity exercise.OBJECTIVES To examine the feasibility and safety of high-intensity treadmill exercise in patients with de novo Parkinson disease who are not taking medication and whether the effect on motor symptoms warrants a phase 3 trial. DESIGN, SETTING, AND PARTICIPANTSThe Study in Parkinson Disease of Exercise (SPARX) was a phase 2, multicenter randomized clinical trial with 3 groups and masked assessors. Individuals from outpatient and community-based clinics were enrolled from May 1, 2012, through November 30, 2015, with the primary end point at 6 months. Individuals with idiopathic Parkinson disease (Hoehn and Yahr stages 1 or 2) aged 40 to 80 years within 5 years of diagnosis who were not exercising at moderate intensity greater than 3 times per week and not expected to need dopaminergic medication within 6 months participated in this study. A total of 384 volunteers were screened by telephone; 128 were randomly assigned to 1 of 3 groups (high-intensity exercise, moderate-intensity exercise, or control). INTERVENTIONS High-intensity treadmill exercise (4 days per week, 80%-85% maximum heart rate [n = 43]), moderate-intensity treadmill exercise (4 days per week, 60%-65% maximum heart rate [n = 45]), or wait-list control (n = 40) for 6 months. MAIN OUTCOMES AND MEASURES Feasibility measures were adherence to prescribed heart rate and exercise frequency of 3 days per week and safety. The clinical outcome was 6-month change in Unified Parkinson's Disease Rating Scale motor score.RESULTS A total of 128 patients were included in the study (mean [SD] age, 64 [9] years; age range, 40-80 years; 73 [57.0%] male; and 108 [84.4%] non-Hispanic white). Exercise rates were 2.8 (95% CI, 2.4-3.2) days per week at 80.2% (95% CI, 78.8%-81.7%) maximum heart rate in the high-intensity group and 3.2 (95% CI, 2.8-3.6; P = .13) days per week at 65.9% (95% CI, 64.2%-67.7%) maximum heart rate in the moderate-intensity group (P < .001). The mean change in Unified Parkinson's Disease Rating Scale motor score in the high-intensity group was 0.3 (95% CI, −1.7 to 2.3) compared with 3.2 (95% CI, 1.4 to 5.1) in the usual care group (P = .03). The high-intensity group, but not the moderate-intensity group, reached the predefined nonfutility threshold compared with the control group. Anticipated adverse musculoskeletal events were not severe.CONCLUSIONS AND RELEVANCE High-intensity treadmill exercise may be feasible and prescribed safely for patients with Parkinson disease. An efficacy trial is warranted to determine whether high-intensity treadmill exercise produces meaningful clinical benefits in de novo Parkinson disease.

Background The effects of progressive resistance exercise (PRE) on the motor signs of Parkinson’s disease have not been studied in controlled trials. Our aim was to compare 6, 12, 18, and 24 month outcomes of patients with Parkinson’s disease who received PRE to a stretching, balance, and strengthening exercise program. Methods We conducted a randomized controlled trial between September 2007 and July 2011. Pairs of patients, matched by sex and off-medication Unified Parkinson’s Disease Rating Scale, motor subscale (UPDRS-III), were randomly assigned to the interventions with a 1:1 allocation ratio. The PRE group performed a weight lifting program. The Modified Fitness Counts (mFC) group performed a stretching, balance, and strengthening exercise program. Patients exercised two days per week for 24 months at a gym. A personal trainer directed both weekly sessions for the first six months and one weekly session after six months. The primary outcome was the off-medication UPDRS-III score. Patients were followed for 24 months at six-month intervals. Results Of 51 patients, 20 in PRE and 18 in mFC completed the trial. At 24 months, the mean off-medication UPDRS-III score decreased more with PRE than with mFC (mean difference: - 7·3 points; 95% CI: -11·3 to -3·6; P < 0·001). The PRE group had ten adverse events. The mFC group had seven adverse events. Conclusions PRE demonstrated a statistically and clinically significant reduction in UPDRS-III scores compared to mFC and is recommended as a useful adjunct therapy to improve Parkinsonian motor signs.

STUDY DESIGN Prospective cohort study. OBJECTIVES To measure changes in muscle strength, range of motion, and function from 2 weeks before to 6 months after total knee arthroplasty (TKA) and compare outcomes with data from a control group consisting of healthy adults. BACKGROUND Total knee arthroplasty successfully alleviates pain from knee osteoarthritis, but deficits in function can persist long term. How impairments and functional limitations change over the first 6 months after TKA, compared to data from healthy adults, has not been well reported in the literature. METHODS Twenty-four patients who underwent a primary unilateral TKA were compared to healthy adults (n = 17). All patients participated in a standardized rehabilitation program following surgery. Isometric quadriceps torque was assessed using an electromechanical dynamometer. Range of motion was measured actively and passively. Functional performance was assessed using the stair-climbing test, timed up-and-go test, 6-minute walk test, and single-limb stance time. Patients underwent testing at 2 weeks preoperatively and at 1, 3, and 6 months postoperatively. RESULTS Compared to healthy older adults, patients performed significantly worse at all times for all measures (P<.05), except for single-limb stance time at 6 months (P>.05). One month postoperatively, patients experienced significant losses from preoperative levels in all outcomes. Patients recovered to preoperative levels by 6 months postoperatively on all measures, except knee flexion range of motion, but still exhibited the same extent of limitation they did prior to surgery. CONCLUSION The persistent impairments and functional limitations 6 months after TKA with standard rehabilitation suggest that more intensive therapeutic approaches may be necessary to restore function of patients following TKA to the levels of healthy adults.

Background. The relative importance and association of factors contributing to physical frailty in elderly persons are unclear.

The beneficial effects of physical activity (PA) are well documented, yet the mechanisms by which PA prevents disease and improves health outcomes are poorly understood. To identify major gaps in knowledge and potential strategies for catalyzing progress in the field, the NIH convened a workshop in late October 2014 entitled "Understanding the Cellular and Molecular Mechanisms of Physical Activity-Induced Health Benefits." Presentations and discussions emphasized the challenges imposed by the integrative and intermittent nature of PA, the tremendous discovery potential of applying "-omics" technologies to understand interorgan crosstalk and biological networking systems during PA, and the need to establish an infrastructure of clinical trial sites with sufficient expertise to incorporate mechanistic outcome measures into adequately sized human PA trials. Identification of the mechanisms that underlie the link between PA and improved health holds extraordinary promise for discovery of novel therapeutic targets and development of personalized exercise medicine.