Periods Of Physical Inactivity Research Articles

Metformin Blunts Bed Rest-induced Skeletal Muscle Ceramide Accumulation in Older Adults

Skeletal muscle insulin resistance is an undesirable outcome during periods of physical inactivity in older adults, which can lead to a variety of metabolic diseases. Insulin sensitive tissue (e.g., liver, and skeletal muscle) derived ceramides are well known to promote insulin resistance. Evidence suggests that metformin can regulate tissue ceramide accumulation. Therefore, we hypothesized that metformin treatment during a short-term period of bed rest in male and female older adults would reduce skeletal muscle ceramide accumulation and prevent insulin resistance. Our study design consisted of older adults (66 ± 4.5 y/o placebo, n=10; 71.7 ± 5.1 y/o metformin, n=10) who were subjected to 5 days of bed rest. Participants were randomly assigned to placebo or metformin treatment groups. Drug or placebo treatments started two weeks prior to bed rest and continued throughout the 5 days of bed rest. Prior to and after bed rest, participants underwent a euglycemic-hyperinsulinemic clamp. Muscle biopsies (from the vastus lateralis) were taken prior to and after each clamp both before and after bed rest. We found that insulin-stimulated muscle ceramides were increased after bed rest but were blunted in older adults who took metformin. In addition, muscle insulin resistance correlated with the increase in ceramides. We conclude that metformin was effective to reduce ceramide accumulation in muscle during a period of bed rest in older adults. R21AG064576 awarded to M.J.D. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Tibial Bone Co-Morbidities Following Volumetric Muscle Loss Injury and Physical Inactivity

Volumetric muscle loss (VML) injuries are a traumatic loss of muscle, limiting regenerative potential and resulting in chronic loss of function. In isolation the bone adjacent to the VML injury is often overlooked, but known association between the tissues are important to long-term health and function. Recent work suggests decrements in both bones and muscles of VML-injured limbs, as well as a distinct relationship between VML and bone health. The clinically injured VML population is expected to undergo considerable periods of physical inactivity or a long-term sedentary lifestyle, and thus decreased loading, after VML. Our objective was to investigate the concomitant impact of VML on the adjacent bone, with and without the restriction of physical activity (reduced ~50% of daily ambulation). We hypothesized that with restriction of physical activity, the tibia adjacent to the VML would have functional impairments greater than those with normal physical activity (daily ambulation >1km). Adult male C57BI/6J mice (n=41) underwent unilateral VML to the posterior hindlimb compartment or served as uninjured age-matched controls, then were randomized to standard or restricted activity cages for 8-wks. Terminally (age 20-wks), mice underwent in vivo muscle function testing. Adjacent tibia were assessed for strength, mid‐diaphysis cortical geometry, and intrinsic material properties, and the metaphyseal trabecular bone structure was evaluated by microcomputed tomography and three‐point bending. A subset of tibias was saved for histologic staining (H&E, TRAP). Data were evaluated by two-way ANOVA. There were no absolute or normalized functional muscle deficits following 8-wks of inactivity. That said, there were significant VML-functional deficits (~42% of uninjured) that are not exacerbated by inactivity (p<0.001). Cortical geometric changes in the bone were primarily a result of physical inactivity, with thickness and cross-sectional moment of inertia both diminished independent of injury (p≤0.018). However, there were no differences in cortical bone volume, diameter, or cross-sectional area (p≥0.056). Trabecular bone mineral density was lower in all VML-injured tibias compared to uninjured (p=0.003). While there was no difference across groups for trabecular spacing (p>0.397), there was a reduction in bone mineral density across all VML-injured, compared to uninjured tibias (p=0.003). The functional capacity of the tibia to resist fracture (i.e., ultimate load during 3‐point bending) was ~21% lower with inactivity (p=0.018), while there was only a trend for VML injury to impact resistance to fracture. Stiffness was calculated during the onset to ultimate load and ~15% less in the VML injured and inactivity VML tibias (p=0.016). Tibia of VML injured and inactive groups appear to have greater lipid accumulation compared to uninjured tibias. While discordant with muscle function, physical activity restriction with and without VML injury impairs adjacent tibia. Inactivity alone had the greatest impact on the cortical bone properties, while VML with and without physical inactivity impacted trabecular tibia properties. This study demonstrates the impact of VML with and without physical inactivity on the tibia, furthering the complexity of traumatic injury on the musculoskeletal system. W81XWH‐20‐10885 (JAC & SMG); S10OD025177. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Are changes in muscular strength following head‐down bed rest independently associated with improved cognitive function in older adults? A secondary analysis of a randomized controlled trial

AbstractBackgroundPhysical inactivity is common among older adults and is a risk factor for cognitive decline. Even a brief period of physical inactivity, such as bed rest due to hospitalization, in older adults has significant negative impacts. Exercise is strategy to counter the negative effects of physical inactivity. Exercise‐induced improvements in cardiorespiratory fitness is associated with improved cognitive function. Less is known regarding the contribution of exercise‐induced changes in muscle strength to changes in cognitive function. Thus, we aimed to examine the independent contribution of: 1) change in cardiorespiratory fitness; and 2) change in peak muscle torque of the lower extremity to changes in cognitive function in a randomized controlled trial (RCT) of head‐down bed rest (HDBR) vs. HDBR with exercise in healthy older adults.MethodAn analysis of a non‐blinded, parallel‐group, RCT of 22 healthy older adults (11 males and 11 females) aged 55‐65 years. Participants were randomized to: 1) 14 days of 6° HDBR (CON); or 2) HDBR with daily resistance and aerobic exercise training (EX). Outcome measures were taken at baseline and HDBR completion. The Flanker Inhibitory Control and Attention Task measured executive function. Physical fitness measures included: 1) maximal aerobic capacity (VO2max) using a bicycle ergometry test; and 2) knee extension isokinetic muscular strength (KE) using a Biodex dynamometer. We performed two separate multiple linear regressions to determine whether following 14 days of HDBR: 1) VO2max was associated with Flanker score, after accounting for ΔKE; and 2) KE was associated with Flanker score, after accounting for ΔVO2max. Each model was also adjusted for baseline Flanker score and the baseline physical fitness measure of interest.ResultAt baseline, average Flanker t‐score was 48.33, mean VO2max was 32.527 ml/kg/min, and knee extension strength was 64.472 Nm. VO2max at follow‐up was not significantly associated with Flanker performance (b = 0.232 ± 0.716; p = 0.635; R2 adj. = 0.285). However, greater KE strength was significantly associated with better Flanker performance (b = 2.023 ± 0.389; p = 0.043; R2 adj. = 0.633) at HDBR completion.ConclusionThe maintenance of muscle strength even during brief periods of physical inactivity appears to be critical for cognitive health in older adults.

Relation between mortality and physical activity levels or sedentary behavior: Proof cohort

Abstract Although moderate-to-vigorous physical activity has been proven to be effective in preventing major chronic diseases, the most recent epidemiological studies now focus on low-intensity physical activity, due to the need to promote all activities. However, the evidence currently remains weak. The objective of the study is to clarify the effects of different levels of physical activity and sedentary behavior on mortality. The different levels of physical activity were assessed by a validated self-administered questionnaire (POPAQ) covering different types of physical activity in the previous 7 days. Medical history and examinations were taken during each clinical visit to determine clinical events. The relationships between the intensity of physical activity (light, moderate to vigorous) as well as periods of physical inactivity in relation to mortality or cardiovascular events were analyzed by splines and COX models. Of the 1011 65-year-old subjects initially included in 2001 (60% women), the last 18-year follow-up is now completed since 2019. A total of 197 deaths (19.2% including 77 cardiovascular deaths) and 195 cardiovascular events (19.3%) have been reported. The means (standard deviation) of moderate or intense activity, light or sedentary activity were respectively 1.2 h/d (0.3), 5.8 h/d (1.1) and 6.6 h/d (2.3). For all-cause deaths, as well as cardiovascular deaths, splines were significant for light (p = 0.04 and p = 0.01) and moderate to vigorous (p < 0.001 and p < 0.001) activities, but not for sedentary lifestyle (p = 0.24 and p = 0.90). However, there is a significant reduction in cardiovascular events when the sedentary time decreased from 10.9 to 3.3 h/d. The PROOF cohort study shows a clear dose-response relationship between the dose of light, moderate to vigorous and sedentary behavior with mortality and cardiovascular events. These results provide evidence to support the inclusion of light physical activity in future activity guidelines physical. Key messages • Relationship between the dose of light, moderate to vigorous and sedentary lifestyle with mortality and cardiovascular events. • Importance of inclusion of light physical activity in future activity guidelines physical.

Follow-up of health-related quality of life and pain in a cohort of patients with rheumatoid arthritis before and after COVID-19

BackgroundThe foot is one of the anatomical structures of the body most affected in rheumatoid arthritis (RA), associated with the disability of patients, even more during COVID-19. The aim of this study was to analyse whether the period of physical inactivity during COVID-19 is an influential factor on health-related quality of life and foot pain in patients with RA. Methods162 patients with foot pain and RA, recruited from the Hospital Virgen de las Nieves, Granada (Spain) were included. Data was collected during two different periods: January - December 2018 in person and June - September 2021 by phone. Patients were asked to complete the Spanish adapted version of the 12-Item Short Form Survey (SF-12) and the Visual Analogue Scale (VAS). ResultsThe results from the SF-12 questionnaires were divided between its two subscales (i.e., mental, and physical component). The physical component shows an improvement between 2018 and 2021, from 32.05 in 2018–35.18 in 2021 (p < 0.05). The opposite happened with the mental component, showing a deterioration, from 39.69 in 2018–34.48 in 2021 (p < 0.05). Regarding pain, VAS shows higher levels of pain with statistically significant differences, both in general pain (from 6 in 2018–7 in 2012) and in foot pain (from 5 to 7), (p < 0.05). ConclusionMental quality of life and pain, both general and foot pain, are influenced by the period of physical inactivity during COVID-19. Level of evidenceLevel II.

Changes in muscle strength and muscle mass after transcatheter aortic valve implantation (TAVI)

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Amsterdam UMC. Background Maintenance of muscle strength and muscle mass is important for long-term health. Periods of physical inactivity and poor dietary intake (e.g. waiting for a medical procedure) can provoke loss of muscle strength and muscle mass. Purpose We aim to determine the course of muscle strength and muscle mass in patients with severe aortic stenosis from before until six months after an elective transcatheter aortic valve implantation (TAVI). Moreover, we aim to explore baseline characteristics associated with change. Methods All patients undergoing an elective TAVI in our high-volume tertiary center were asked to participate. Included patients received three home visits (pre-procedural and 30 days and 6 months post-procedural). During these home visits, handgrip strength was measured with a handheld dynamometer. Muscle mass was determined as skeletal muscle index with a bioelectrical impedance (BIA) measurement. Multivariate mixed linear models were used to determine changes over time. A linear model adjusted for age and sex was performed to explore baseline characteristics associated with changes in muscle strength or muscle mass. Results In total 112 patients were included, mean age of the participants was 81 ± 5 years and 58% were male. The preprocedural measurement took place on a median of 48 [IQR: 19 – 79] days before the TAVI. Preprocedural handgrip strength was on average 36 kg for male and 24 kg for female patients and decreased after the TAVI (-0.12 [95% CI: -0.21, -0.02] kg/month, p=0.02). Living alone and lower hemoglobin level were predictive for a higher decrease in strength (β -2.20 [95% CI: -3.98, -0.42], p=0.02 and β 0.14 [95% CI: 0.02, 0.27] per mmol/l, p=0.03, respectively). Appendicular skeletal muscle index was 7.2 kg/m2 for males and 6.1 kg/m2 for females and did not change after TAVI (0.00 [95%CI: -0.01, 0.01] kg/m2/month, p=0.95). No baseline characteristics were associated with a change in muscle mass. Conclusion Muscle strength significantly declines and muscle mass remains the same from before until six months after the TAVI procedure. Patients living alone or patients with low hemoglobin levels are at increased risk to lose muscle strength. Future studies should focus on the prevention of strength loss, for instance with interventions focusing on nutrition and exercise around the TAVI procedure.

Bone adaptation and osteoporosis prevention in hibernating mammals

Hibernating bears and rodents have evolved mechanisms to prevent disuse osteoporosis during the prolonged physical inactivity that occurs during hibernation. Serum markers and histological indices of bone remodeling in bears indicate reduced bone turnover during hibernation, which is consistent with organismal energy conservation. Calcium homeostasis is maintained by balanced bone resorption and formation since hibernating bears do not eat, drink, urinate, or defecate. Reduced and balanced bone remodeling protect bear bone structure and strength during hibernation, unlike the disuse osteoporosis that occurs in humans and other animals during prolonged physical inactivity. Conversely, some hibernating rodents show varying degrees of bone loss such as osteocytic osteolysis, trabecular loss, and cortical thinning. However, no negative effects of hibernation on bone strength in rodents have been found. More than 5000 genes in bear bone tissue are differentially expressed during hibernation, highlighting the complexity of hibernation induced changes in bone. A complete picture of the mechanisms that regulate bone metabolism in hibernators still alludes us, but existing data suggest a role for endocrine and paracrine factors such as cocaine- and amphetamine-regulated transcript (CART) and endocannabinoid ligands like 2-arachidonoyl glycerol (2-AG) in decreasing bone remodeling during hibernation. Hibernating bears and rodents evolved the capacity to preserve bone strength during long periods of physical inactivity, which contributes to their survival and propagation by allowing physically activity (foraging, escaping predators, and mating) without risk of bone fracture following hibernation. Understanding the biological mechanisms regulating bone metabolism in hibernators may inform novel treatment strategies for osteoporosis in humans.

The mediating role of inhibitory control in the relationship between prefrontal cortex hemodynamics and exercise performance in adults with overweight or obesity

Physical inactivity has been suggested to impair physical performance, cognitive functions and facilitate weight gain. One hypothesis is that long periods of physical inactivity could impair oxygen delivery to the prefrontal cortex (PFC), impairing one's cognitive ability to inhibit unhealthy automated behaviors and, therefore, reduce exercise tolerance. The present study sought to further understand the relationship among PFC hemodynamics, inhibitory control, and exercise tolerance in individuals with low physical fitness levels who are overweight or obese. Thirty-four participants were asked to perform a series of inhibitory control tests (i.e., Stroop task) in one testing session and complete an incremental cycling exercise test with hemodynamic fluctuations of the PFC measured with functional near-infrared spectroscopy in another session. Our results indicate that exercise performance varied with PFC oxygenation. We also found that inhibitory control played a key role mediating the relationship between PFC oxygenation and exercise performance, suggesting that the cognitive ability to inhibit automated responses has an impact on exercise behavior in adults with overweight and obesity.

MOTS‐c protein expression increases following aerobic exercise training and remains elevated during detraining

Mitochondrial open reading frame of the 12S rRNA‐c (MOTS‐c) is a mitochondrial‐derived peptide that is released into the circulation following intense physical activity and, purportedly, has systemic impacts on energy metabolism and insulin sensitivity. Exogenous administration of MOTS‐c in rodent models enhances physical activity / endurance and reduces fat mass in aged mice through the regulation of, in part, the glycolysis / pentose phosphate pathway and amino acid metabolism. Considering that mitochondrial volume and mitochondrial DNA copy number increase following chronic aerobic exercise training, we hypothesized that MOTS‐c expression also would be elevated in exercise‐trained skeletal muscle. MOTS‐c protein expression from phenotypically mixed plantaris muscles of adult female Sprague Dawley rats were compared from six conditions: sedentary (SED; n=11), voluntary exercise training for four (EX4; n=9), six (EX6; n=6), or eight weeks (EX8; n=8), and detraining after four (DETR4) or six (DETR6) weeks, which followed four or six weeks of exercise training, respectively. Total running distances were ~551±61, 371±94, 560±71, 321±44, and 519±27 km for EX4, EX6, EX8, DETR4 and DETR6, respectively. DETR4 rat running distance was significantly lower than EX4, EX8, and DETR6 rats (p&lt;0.01). Total muscle protein homogenate was isolated from mid‐belly muscle chunks and separated using 15% SDS‐PAGE gels (10 μg/sample). Following transfer, membranes were incubated with a custom rabbit anti‐rat MOTS‐c polyclonal antibody, developed, scanned, stripped and re‐probed for GAPDH as a loading control. MOTS‐c protein was significantly elevated from SED (set at 100%) to 188±61, 158±37, 212±27, 168±29, 223±36% in EX4, EX6, EX8, DETR4 and DETR6, respectively (p&lt;0.05). Furthermore, preliminary findings indicate that MOTS‐c is present exclusively within the cytoplasm of skeletal muscle and not compartmentalized within the nuclei or mitochondria. Given that long‐term aerobic exercise augments mitochondrial volume within skeletal muscle, our data suggest that the observed increase in MOTS‐c protein in the present study parallels this mitochondrial adaptation to aerobic physical activity. Taken together, these findings indicate that a more aerobically‐trained individual would have an enhanced MOTS‐c presence within skeletal muscle and, therefore, a greater potential to regulate energy and insulin sensitivity when MOTS‐c is released systemically; additionally, the potential benefits of MOTS‐c are sustained during a period of physical inactivity (e.g., detraining) following exercise training.

Balance performance analysis after the COVID-19 quarantine in children aged between 8 and 12 years old: Longitudinal study

BackgroundCorona Virus Disease 2019 (COVID-19) has caused great changes in daily activities, especially in children. In Spain, to avoid infections, a home quarantine was declared, which caused a drastic reduction in daily or weekly physical activity in children. Objectiveto analyse the balance performance after the COVID-19-induced quarantine on children’s balance, through the use of balance tests, considering the type of sport practiced. Methodsan observational and longitudinal study was carried out with a sample size of 150 healthy children (69 boys and 81 girls) with a mean age of 10.02 ± 1.15 years. Postural control was evaluated under different equilibrium conditions before and after the quarantine period. Two data collections using the Gyko system were compared, with a difference of 8 months between them. In addition, the influence of foot type and physical activity was analysed. ResultsAfter the quarantine, statistically significant differences were found in terms of balance results, which were worse than before (p < 0.05). Postural control was not influenced by the type of sport practiced (i.e., individual, collective and / or not practicing sport), nor by the surface which the test was performed (p > 0.05). Physically active children (i.e., individual and / or collective sport) presented worse results than physically inactive children. A statistically significant impairment in terms of balance was demonstrated in children who performed high and moderate physical activity (p < 0.05). ConclusionsAfter the quarantine period, a significant reduction in balance performance was found in children. The findings suggest that regular physical activity benefits postural control. Loss of balance does not differ in postural stability by the type of sport practised. Postural stability is not influenced by the type of footprint after the period of physical inactivity. Postural control is influenced in children with a great level of physical activity.

FACTORS OF DIABETES MELLITUS

Diabetes mellitus (DM) is one of the most common non-communicable diseases (NCDs) globally. Diabetes mellitus is also known as prameha or madhumeha. It is most commonly found in many economically developing and newly industrialized countries. Diabetes mellitus is a disorder that affects the body’s ability to make or use insulin. Insulin is a hormone produced in the pancreas that helps transport glucose (blood sugar) from the bloodstream into the cells so they can break it down and use it for fuel. It has been narrated in Ayurveda that the long periods of physical inactivity, laziness, sleeping for long hours, excess use of food which is heavy to digest like dairy products, aquatic and marshy animals, sugar/jaggery preparations, fresh grains, etc., and similar foods that increase kapha are generalized causes of prameha/diabetes mellitus. Diabetes is a metabolic disease that occurs when your blood sugar also known as blood glucose level is too high. The term high blood glucose is also known a HYPERGLYCEMIA. Keywords: Diabetes, diabetes mellitus, factors of diabetes, hyperglycemia, insulin Cite this Article Manisha. Factors of Diabetes Mellitus. Research &amp; Reviews: Journal of Medicine . 2020; 10(2): 19–25p.

Programa de Revitalización Geriátrica: efectos sobre la cognición en adultos mayores de 60 años

Background and aimClinical evidence shows that elder individuals display with greater frequency diverse cognitive changes, minor and slightly incapacitating, related to mnesic functions and speed of thought and reasoning. Much scientific evidence supports the role that aerobic physical activity plays as fundamental to prevent or delay the onset of minor cognitive damage or dementia.The aim of this paper is to determine the lasting effect of improved cognitive status in healthy older adults six months after completing a geriatric revitalization programme (GRP). Material and methodsThe study population was recruited among participants in the Universidad de Salamanca GRP. Following the guidelines of the World Health Organization, subjects performed 3 weekly sessions of moderate physical exercise during the intervention period. The sample consisted of 35 subjects of both genders, all of them over 60 years old. For the selection of the sample, random sampling was carried out by conglomerates, where 3 associations of the total number of associations in the city were chosen at random, and in each of the group of people who were willing to follow the GRP. In order to assess the subjects’ neuropsychological capacities, a series of validated neuropsychological tests were included: Mini-Mental State Examination; Benton Visual Retention Test; Rey Auditory Verbal Learning Test; Stroop Test; Trail Making Test. ResultsThe results show significant differences between the three assessments put into effect: after the intervention, performance improved in all variables assessed, and it returned to the initial scores after a period of physical inactivity. ConclusionsWe must find strategies to limit spans of physical inactivity or sedentary lifestyles in people over 65 by looking for ways to encourage participation in physical activity programmes.

Metabolic Perturbations from Step Reduction in Older Persons at Risk for Sarcopenia: Plasma Biomarkers of Abrupt Changes in Physical Activity

Sarcopenia is the age-related loss of skeletal muscle mass, strength and function, which may be accelerated during periods of physical inactivity. Declines in skeletal muscle and functionality not only impacts mobility but also increases chronic disease risk, such as type 2 diabetes. The aim of this study was to measure adaptive metabolic responses to acute changes in habitual activity in a cohort of overweight, pre-diabetic older adults (age = 69 ± 4 years; BMI = 27 ± 4 kg/m2, n = 17) when using non-targeted metabolite profiling by multisegment injection-capillary electrophoresis-mass spectrometry. Participants completed two weeks of step reduction (<1000 steps/day) followed by a two week recovery period, where fasting plasma samples were collected at three time intervals at baseline, after step reduction and following recovery. Two weeks of step reduction elicited increases in circulatory metabolites associated with a decline in muscle energy metabolism and protein degradation, including glutamine, carnitine and creatine (q < 0.05; effect size > 0.30), as well as methionine and deoxycarnitine (p < 0.05; effect size ≈ 0.20) as compared to baseline. Similarly, decreases in uremic toxins in plasma that promote muscle inflammation, indoxyl sulfate and hippuric acid, as well as oxoproline, a precursor used for intramuscular glutathione recycling, were also associated with physical inactivity (p < 0.05; effect size > 0.20). Our results indicate that older persons are susceptible to metabolic perturbations due to short-term step reduction that were not fully reversible with resumption of normal ambulatory activity over the same time period. These plasma biomarkers may enable early detection of inactivity-induced metabolic dysregulation in older persons at risk for sarcopenia not readily measured by current imaging techniques or muscle function tests, which is required for the design of therapeutic interventions to counter these deleterious changes in support of healthy ageing.

WHAT CAN L2 WRITERS’ PAUSING BEHAVIOR TELL US ABOUT THEIR L2 WRITING PROCESSES?

AbstractWhen responding to a writing task, writers spend a significant amount of their time not writing. These periods of physical inactivity, or pauses, during writing provide observable and measurable cues as to when, where, and how long writers halt to plan and/or revise their texts. Consequently, examining writers’ pausing patterns can provide important insights into the cognitive processes that writers employ when composing and the impact of various individual, task, and contextual factors on those processes. This article discusses theory and research on writers’ pausing behavior; how pause analysis can be used to investigate second language (L2) learners’ writing processes; challenges in researching writers’ pausing behavior (e.g., defining pauses); and some strategies to address these challenges. Next, the article illustrates how L2 writers’ pause data can be collected, analyzed, and interpreted, using keystroke logging data from a research project that aimed to examine the effects of task type, L2 proficiency, and keyboarding skills on L2 learners’ writing processes when writing on the computer. The article concludes with a call for more research on L2 writers’ pausing behavior, particularly how L2 writers’ pausing behavior relates to L2 writing outcomes and development across learners, contexts, and time.

There is no mystery to sleep.

The reasons why we sleep have been debated endlessly and the arguments have tended to focus upon one key biological function that applies to the human species. Such explanations cannot account for the ubiquity of sleep across all animal life. This Opinion Paper explores the logic which enables all animal sleep to be defined as follows: Sleep is a period of physical inactivity during which time an individual of a particular species avoids movement within an environment to which it is poorly adapted, whilst using this time to undertake a range of essential biological activities that allow optimum performance during the period of activity.

Hibernating Little Pocket Mice Show Few Seasonal Changes in Bone Properties

Periods of disuse or physical inactivity increases bone porosity and decreases bone mineral density, resulting in a loss of bone mechanical competence in many animals. Although large hibernators like bears and marmots prevent bone loss during hibernation, despite long periods of physical inactivity, some small hibernators do lose bone during hibernation. Little pocket mice (Perognathus longimembris) remain underground during winter hibernation and undergo bouts of torpor and interbout arousals, but the torpor bout duration is shorter than other rodent hibernators. Additionally, little pocket mice may enter torpor during summer estivation. In this study, cortical and trabecular bone architectural, mineral, and mechanical properties were analyzed for femurs from little pocket mice captured during 8 different months (March to October) to determine seasonal effects on bone. There were no differences in any bone properties between the pre-hibernation month of October and the post-hibernation month of March, suggesting winter hibernation did not adversely affect bone properties. However, cortical area was higher in March than April, May, and June. Bone mechanical and osteocyte lacunar properties were not different between any months. Trabecular bone in the distal femoral epiphysis showed no changes between months. The distal femoral metaphyseal region showed higher trabecular spacing and lower trabecular number in May than August, otherwise, there were no differences in trabecular parameters. The few monthly differences in bone properties may be due to physical inactivity from periodic summer estivation or from the timing of birth and growth in spring and summer months. Anat Rec, 300:2175-2183, 2017. © 2017 Wiley Periodicals, Inc.

Aging-related effects of bed rest followed by eccentric exercise rehabilitation on skeletal muscle macrophages and insulin sensitivity

The pro- and anti-inflammatory macrophages are associated with insulin sensitivity and skeletal muscle regeneration. Infiltrating macrophages in skeletal muscle during a period of physical inactivity and subsequent reloading/rehabilitation in older adults is unknown, but may provide insight into mechanisms related to the development of metabolic disease and changes in muscle cell size. The purpose of this study was to determine if skeletal muscle macrophage infiltration is modulated differently between young and older adults after bed rest and exercise rehabilitation and if these responses are related to muscle and insulin sensitivity changes. 14 young and 9 older adults underwent 5-days of bed rest followed by 8-weeks of lower limb eccentric exercise rehabilitation (REHAB). Dual-energy X-ray absorptiometry, magnetic resonance imaging and myofiber analysis were used to identify muscle morphology and CLIX-IR and CLIX-β were used to assess insulin sensitivity. Skeletal muscle macrophages, CD68 (pan), CD11b (M1), CD163 (M2), CD206 (M2), were characterized using immunohistochemistry and gene expression. Insulin sensitivity, independent of age, decreased ~38% following bed rest and was restored following REHAB. We found robust age-related differences in muscle atrophy during bed rest, yet older and younger adults equally hypertrophied during REHAB. Interestingly, there were age-related differences in macrophage content (CD68+CD11b+ and CD68+CD11b− cells) but both young and old similarly increased macrophages with REHAB. Satellite cell changes during rehab corresponded to macrophage content changes. Muscle tissue resident macrophages and gene expression, were not associated with changes in insulin sensitivity following bed rest and REHAB. These data suggest that muscle macrophages are modulated as a result of exercise rehabilitation following bed rest and may more associated with muscle regrowth/hypertrophy rather than insulin sensitivity in young or older adults.This trial was registered at clinicaltrials.gov as NCT01669590.

Only Two Weeks of Physical Inactivity Induces Insulin Resistance and Impairs Glycemic Control in Older Adults

Periods of physical inactivity are known to result in deleterious consequences for skeletal muscle mass, strength, and insulin sensitivity. We propose that even transient periods of reduced activity likely have a greater impact in older individuals who often fail to fully recover. We aimed to examine the impact of two weeks of step reduction (SR), as a model of physical inactivity akin to that occurring during illness, on indices of glycemic control and muscle strength in thirteen healthy older adults (7 men, 6 women, 68 ± 3yr [all data mean±SD]). Participants underwent 7 d of monitored normal activity (pre‐SR) immediately before reducing their daily step‐count from 7379 ± 3809 to 967 ± 79 steps.d−1 for 14 d (SR), and then returning to their habitual step count for a period of 14 d (post‐SR). The HOMA‐IR and MATSUDA models of insulin resistance, and insulin sensitivity as well as glucose and insulin area under the curve GAUC and IAUC in response to an oral glucose tolerance test were assessed pre‐SR, SR, and post‐SR. Peak isometric maximal voluntary contraction (ISO‐MVCpeak), peak rate of torque development (RTDpeak) number of sit‐to‐stand cycles in 30 s, and total distance walked in 6 min were also assessed at these time points. HOMA‐IR increased from pre‐SR to SR (2.8 ± 0.3 to 3.6 ± 0.6, p&lt;0.05) and MATSUDA decreased (3.7 ± 0.5 to 3.0 ± 0.1, p &lt; 0.05), neither recovered at post‐SR. GAUC was not significantly different between pre‐SR (435 ± 121) and SR (467 ± 136) but was marginally lower at post‐SR (386 ± 140, p=0.05). IAUC increased from pre‐SR to SR (3796 ± 579 to 4329 ± 833, p&lt;0.05) and, was still elevated at post‐SR (4051 ± 768, p&lt;0.05). There was no change from pre‐SR to SR in either ISO‐MVCpeak (146 ± 34 to 148 ± 41 N.m, p&gt;0.05), RTDpeak (2142 ± 1527 to 1956 ± 894 N.m.s−1, p&gt;0.05), sit‐to‐stand cycles in 30 s (17 ± 5 to 16 ± 5, p&gt;0.05) or total distance walked in 6 min (561 ± 108 to 563 ± 110 m, p&gt;0.05). These data indicate that two weeks of SR negatively impacts indices of glycemic control in older adults that are not fully recovered after 14 d of return to habitual step count. However, indices of muscle function remained unaltered.Support or Funding InformationSupported by the Canadian Diabetes Association

Leucine partially protects muscle mass and function during bed rest in middle-aged adults

Physical inactivity triggers a rapid loss of muscle mass and function in older adults. Middle-aged adults show few phenotypic signs of aging yet may be more susceptible to inactivity than younger adults. The aim was to determine whether leucine, a stimulator of translation initiation and skeletal muscle protein synthesis (MPS), can protect skeletal muscle health during bed rest. We used a randomized, double-blind, placebo-controlled trial to assess changes in skeletal MPS, cellular signaling, body composition, and skeletal muscle function in middle-aged adults (n = 19; age ± SEM: 52 ± 1 y) in response to leucine supplementation (LEU group: 0.06 g ∙ kg(-1) ∙ meal(-1)) or an alanine control (CON group) during 14 d of bed rest. Bed rest decreased postabsorptive MPS by 30% ± 9% (CON group) and by 10% ± 10% (LEU group) (main effect for time, P < 0.05), but no differences between groups with respect to pre-post changes (group × time interactions) were detected for MPS or cell signaling. Leucine protected knee extensor peak torque (CON compared with LEU group: -15% ± 2% and -7% ± 3%; group × time interaction, P < 0.05) and endurance (CON compared with LEU: -14% ± 3% and -2% ± 4%; group × time interaction, P < 0.05), prevented an increase in body fat percentage (group × time interaction, P < 0.05), and reduced whole-body lean mass loss after 7 d (CON compared with LEU: -1.5 ± 0.3 and -0.8 ± 0.3 kg; group × time interaction, P < 0.05) but not 14 d (CON compared with LEU: -1.5 ± 0.3 and -1.0 ± 0.3 kg) of bed rest. Leucine also maintained muscle quality (peak torque/kg leg lean mass) after 14 d of bed-rest inactivity (CON compared with LEU: -9% ± 2% and +1% ± 3%; group × time interaction, P < 0.05). Bed rest has a profoundly negative effect on muscle metabolism, mass, and function in middle-aged adults. Leucine supplementation may partially protect muscle health during relatively brief periods of physical inactivity. This trial was registered at clinicaltrials.gov as NCT00968344.

Effects of physical activity on sclerostin concentrations.

The study included 50 women of the Regional Menopause and Osteoporosis Centre of the WAM Teaching Hospital, at the age of 50-75 years with the diagnosis of osteopenia, obtained on the basis of hip and/or lumbar spine densitometry (T-score from -1.0 to -2.5 SD). During the initial 12 weeks (between point 1 and 2), the patients maintained their previous, normal level of physical activity. During subsequent 12 weeks (between point 2 and 3), a programme of exercise was implemented. The programme included the interval training on a bicycle ergometer, three times a week for 36 minutes. During the entire study duration, all the patients received a supplementation of calcium (500 mg) and vit. D3 (1800 IU) once daily. Serum levels of OC, alkaline phosphatase (ALP), β-CTX and sclerostin were assayed at 3 time points. After the course of the exercise cycle, the OC concentration was increased, sclerostin levels decreased, while no statistical differences were observed in β-CTX levels vs. the period of physical inactivity. No correlations were found between sclerostin level changes and osteocalcin level changes during the training time, because of too small groups. Neither statistically significant were the differences in alkaline phosphatase, calcium and phosphorus levels. The obtained results emphasise the role of physical training as an effective stimulation method of bone formation processes in women with osteopenia. Sclerostin can be a marker of physical activity. < /p > < p >.