Fitbit Activity Trackers Interrupt Workplace Sedentary Behavior: A New Application.

This study investigated whether Fitbit devices can reduce sedentary behavior among employees in the workplace. Participants were asked to wear Fitbits during 8-hour work shifts, 5 days per week, for 8 weeks. They were instructed to stand at least once every 30 minutes throughout the workday. The goal of the study was to determine whether standing once every 30 minutes was a feasible strategy for reducing sedentary workplace behavior. On average, participants completed 36 of 40 workdays using Fitbits. The number of times participants stood during an 8-hour workday averaged 12 stands per day (maximum 16 stands per day). These results indicate that Fitbit technology is effective for recording and tracking interruptions in sitting time; however, to reduce sitting behavior, alternate approaches are required to motivate larger numbers of workers to participate.

Clinical utility of the 2-minute walk test for older adults living in long-term care.

PURPOSE: This study's purposes were to examine the measurement properties of the 2-minute walk test (2MWT), to illustrate the use of reliability coefficients in clinical practice, and to estimate sample size for a subsequent validity study. METHOD: Sixteen residents of long-term care (LTC; mean age = 87 years) completed two 2MWTs with Rater A and two 2MWTs with Rater B on test days 1 and 2, approximately 1 week apart. On a third test day, subjects completed one trial of the Berg Balance Scale (BBS), timed up-and-go (TUG) test, and 6-minute walk test (6MWT) with Rater A. On 2 other test days, approximately 1 week apart, Rater A administered the 2MWT to five older adults living in a retirement facility. Absolute and relative reliability and concurrent and known-groups validity coefficients were calculated. RESULTS: No main effect for rater, trial, or occasion was found. Test-retest reliability estimates of 0.94 and 0.95 were obtained. The 2MWT demonstrated concurrent validity (r > or = 0.84) with the BBS, TUG, and 6MWT. Comparison of distance walked by LTC and retirement residents showed a difference of 72.9 m (95% CI: 44.2, 101.6). The results suggest that 90% of truly stable older adults will display random fluctuations in 2MWT performance within a boundary of 15 m. CONCLUSION: The 2MWT had sound measurement properties in this sample of LTC residents. Based on our results, 24 subjects would be required for a subsequent hypothesis-testing validity study.

Effects of isokinetic strength training on concentric and eccentric torque development in the ankle dorsiflexors of older adults.

This study quantifies concentric and eccentric dorsiflexor muscle torque at various movement velocities and determines the neuromuscular effects from short-term practice of repeated maximal voluntary contractions using an isokinetic resisted exercise program in older adults. Twenty-eight subjects (76.3+/-4.6 years) trained concentric and eccentric dorsiflexion 3 days per week for 2 weeks at 30 degrees, 90 degrees, and 180 degrees/s through 40 degrees of dorsiflexion range of motion. Peak torque, rate of torque development, surface electromyography, and strength curves at each velocity were compared before and after training. Increases were found for concentric (27%) and eccentric (20%) dorsiflexor peak torque and concentric rate of torque production (20%-53%) across all movement velocities (p < .01). Training also significantly increased dorsiflexor concentric (64%) and eccentric (55%) surface electromyography; taken together, this is evidence of apparent adaptation of neural factors in older adults with short-term training. These findings support that eccentric and concentric strength training enhances the control and production of ankle muscle dorsiflexor torque in older adults, with implications for improving functional mobility of the ankle joint.

Motor skill learning of concentric and eccentric isokinetic movements in older adults.

Neuromuscular adaptation at the onset of resisted exercise can be observed as increases in torque and surface electromyography. The effect of learning the motor task has been hypothesized to contribute to these early increases, especially for older people. Thus, the purpose of this study was to investigate the facilitatory effects of practice on motor performance in older adults during short-term isokinetic training of the ankle dorsiflexors (DF). Twenty-eight men and women (M = 76.3 +/- 4.6 years) volunteered for a 2-week, 3-days/week strength training program. They were tested in a sitting position on a KinCom isokinetic dynamometer at 30, 90, and 180 degrees s-1 through 40 degrees of DF movement (concentric and eccentric contractions). Criterion curves of lever arm angle patterns were cross-correlated with subject-generated angle patterns, showing significantly better correlations on posttest versus baseline. Smoothness and proficiency of muscle contraction improved with practice by fewer hesitations in movement and increased ability to change between concentric and eccentric muscle contractions. Increased agonist electromyography and torque were hypothesized to be secondary to greater neural drive and/or synchronization of motor unit firing rate and/or recruitment during maximal voluntary contraction, improved coordination, and adapted neural control of concentric and eccentric muscle contraction.

Motor unit firing rates and contractile properties in tibialis anterior of young and old men.

The effects of aging on motoneuron firing rates and muscle contractile properties were studied in tibialis anterior muscle by comparing results from six young (20.8 +/- 0.8 yr) and six old men (82.0 +/- 1.7 yr). For each subject, data were collected from repeated tests over a 2-wk period. Contractile tests included maximal voluntary contraction (MVC) with twitch interpolation and stimulated twitch contractions. The old men had 26% lower MVC torque (P < 0.01) than did the young men, but percent activation was not different (99.1 and 99.3%, respectively). Twitch contraction durations were 23% longer (P < 0.01) in the old compared with the young men. During a series of repeated brief steady-state contractions at 10, 25, 50, 75, and 100% MVC, motor unit firing rates were recorded. Results from approximately 950 motor unit trains in each subject group indicated that at all relative torque levels mean firing rates were 30-35% lower (P < 0.01) in the old subjects. Comparisons between young and old subjects' mean firing rates at each of 10%, 50%, and MVC torques and their corresponding mean twitch contraction duration yielded a range of moderate-to-high correlations (r = -0.67 to -0.84). That lower firing rates were matched to longer twitch contraction durations in the muscle of old men, and relatively higher firing rates were matched with shorter contraction times from the young men, indirectly supports the neuromuscular age-related remodeling principle.

Quadriceps muscle strength, contractile properties, and motor unit firing rates in young and old men.

Changes with age in the voluntary static and dynamic strength of the quadriceps muscle group have been well characterized, and the importance of the muscle group for locomotion and independent living have been highlighted in both normal human aging and in clinical studies. Surprisingly few studies of this muscle group have described age-related changes in voluntary activation ability using twitch interpolation and changes in stimulated contractile properties, and none have assessed the influence of old age on motor unit firing rates. We compared in 13 young (mean age 26 years) and 12 old (mean age 80 years) men the voluntary isometric strength, stimulated contractile properties, and average steady state motor unit firing rates in the quadriceps muscle. Maximum voluntary contraction (MVC) force and twitch tension were approximately 50% lower in the old men, but contractile speed was only approximately 10% slower than in the young men. There was no difference in the ability of either group to activate the quadriceps to a high degree (94-96%). At all isometric force levels tested (10%, 25%, 50%, 75%, and 100% MVC), there were no differences in mean motor unit firing rates. In both groups, the range of firing rates was similar and not large ( approximately 8 Hz at 10% MVC and 26 Hz at MVC). Thus, the substantial age-related weakness in this muscle does not seem to be related to changes in neural drive.

Effects of detraining on knee extensor strength and functional mobility in a group of elderly women.

Long-term detraining results for individuals 75 years and older are needed. The purpose of this study was to assess long-term detraining effects on quadriceps strength and functional mobility in nursing home residents. Ten women (X = 82.8 years) who completed a strength training program were reassessed 1 year later. Clinical methods were used to remeasure dynamic and isometric quadriceps strength and functional mobility. One repetition maximum quadriceps strength declined 68.3% (p < 0.05) from trained values. Isometric strength losses were 29.8% at 90 degrees (p < 0.05), 28.7% at 60 degrees (p < 0.05), and 24.4% at 20 degrees (p < 0.05) of knee flexion 1 year postexercise. Fast-paced walking, self-selected paced walking, and timed up and go speed decreased 28.6% (p < 0.05), 19.5% (p < 0.05), and 54.1% (not significant), respectively, from posttraining. One year vs. baseline, isometric strength decreased 0-14.3%, dynamic strength decreased 48.9%, and functional mobility declined 16.5-20.7% despite an intervening training program. An increased strength loss rate beyond the age of 80 years may be a major factor influencing functional independence.

Reduced insulin binding to liver plasma membranes in inherently obese diabetic CBA/Ca mice.

Insulin binding to isolated liver plasma membranes was measured in mice from C57BL and LACG strains, and in normal and obese diabetic mice from the Bristol CBA/Ca colony. A simple and rapid three-step method for the preparation and purification of liver plasma membranes, using Percoll density gradient centrifugation was used. Both high and low affinity binding was detected in membranes from all four groups of mice. The Kd values for binding were similar in all groups, but the insulin binding capacity (Bmax) at low and high affinity was significantly reduced in obese CBA mice compared to age-matched lean controls. It is proposed that insulin receptor down-regulation may account for the insulin resistance observed in spontaneously obese diabetic CBA mice.

Characterization of the spontaneous diabetes obesity syndrome in mature male CBA/Ca mice.

A spontaneous maturity onset diabetes obesity syndrome occurs in a small proportion (10-20%) of male CBA/Ca mice. Inbreeding can increase the incidence to 80%. It occurs at 12-16 weeks of age, and is characterized by hyperphagia, obesity, hyperglycaemia, hypertriglyceridaemia, hyperinsulinaemia, and an impaired glucose tolerance. The mice are also resistant to exogenous insulin. Female mice remain normal except for a slight increase in serum insulin. The male obese diabetic mice have a normal life expectancy. It is proposed that CBA/Ca mice can provide examples of a useful model for investigating the aetiology of type 2 diabetes and obesity, and the effectiveness of antidiabetic and antiobesity drugs.

Relief of experimentally induced pruritus with a novel eutectic mixture of local anaesthetic agents.

The effectiveness of a eutectic mixture of the local anaesthetics lignocaine and prilocaine (EMLA cream) in relieving artificially induced pruritus was examined in 20 volunteers. The study was conducted in two parts. In part one, the effect of EMLA on the threshold concentration of histamine necessary to induce pruritus was assessed by a double-blind placebo controlled method. In part two, the effect of EMLA on the perception of pruritus induced by the artificial pruritogens cowhage and papain was assessed by a single blind method. Some subjects were less sensitive to histamine after placebo cream treatment, but all subjects showed a marked reduction in sensitivity to histamine after EMLA treatment. The difference between EMLA and the placebo treatment was statistically significant. The EMLA preparation was found to be effective in alleviating pruritus induced by cowhage and papain and this effect was also statistically significant. Thus, EMLA cream was found to be effective in reducing experimentally induced pruritus and, therefore, may be useful in some clinical circumstances where persistent itch is a distressing symptom.

Effects of chronic ethanol treatment on glucose uptake into tissues of normal and diabetic mice.

Blood glucose levels and glucose uptake into cerebral cortex and diaphragm in vitro and into cerebral cortex and adipose tissue in vivo have been measured in LACG (normal) and C57Bl and CBA (diabetic) mice during chronic ethanol drinking and withdrawal. Chronic ethanol produced hypoglycaemia in diabetic mice but prevented insulin-provoked hypoglycaemia in normal mice. Insulin and ethanol had additive effects in diabetic mice. The hypoglycaemic effect of CET is not dependent upon insulin and can be explained by an increase in insulin-independent brain glucose uptake. Ethanol-induced hypoglycaemia and the changes in glucose uptake occur at relatively low blood levels of ethanol (4-20mM, 18-90mg%) and are rapidly reversible on withdrawal. Diabetic mice appear to be more sensitive to the effects of ethanol on glucoregulation.

Differential effects of ethanol on the plasma glucose of non-alcoholic light and heavy social drinkers.

Plasma glucose levels (PGL) in healthy non-alcoholic heavy drinkers of both sexes were significantly higher than in light drinkers following feeding or fasting. Female heavy drinkers showed significant glucose intolerance following a standard (75 g) glucose tolerance test. Acute alcohol consumption (0.4 g/kg orally) produced a larger fall in the PGL of heavy, compared with light, drinkers, although the rate of clearance of alcohol was similar in both groups. It is concluded that mild hyperglycaemia and glucose intolerance can occur in regular heavy drinkers who are otherwise clinically normal. It is suggested that previous drinking history is an important factor to be considered in assessing the metabolic response of non-alcoholics to acute alcohol consumption.

The role of the blood glucose level in determining voluntary ethanol consumption in the LACG and diabetogenic C57BL strains of mice.

The influence of the blood glucose level (BGL) on the voluntary consumption of ethanol by two strains of mice has been investigated. LACG mice show an aversion towards ethanol whereas C57BL mice which are mildly hyperglycaemic show a preference for ethanol. Chronic compulsory ethanol drinking produced hypoglycaemia only in C57BL mice. The oral antidiabetic drugs phenformin and glibenclamide lowered the BGL of C57BL mice which then showed an aversion to ethanol. Raising the BGL of LACG mice by acute alloxan or streptozotocin treatment did not reduce ethanol aversion significantly, but alloxan significantly increased total fluid intake. Diazoxide chronically increased the BGL and slightly increased ethanol consumption in LACG mice. It is concluded that the BGL in C57BL mice may be a factor in determining their innate preference for alcohol. The relationship between alcoholism and diabetes is discussed.