Associations between sedentary time, physical activity and bone health among older people using compositional data analysis

Introduction : Aging is associated with a progressive decrease in bone mass (BM), and being physical active is one of the main strategies to combat this continuous loss. Nonetheless, because daily time is limited, time spent on each movement behavior is co-dependent. The aim of this study was to determine the relationship between BM and movement behaviors in elderly people using compositional data analysis. Methods : We analyzed 871 older people [395 men (76.9 +/- 5.3y) and 476 women (76.7 +/- 4.7y)]. Time spent in sedentary behavior (SB), light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA), was assessed using accelerometry. BM was determined by bone densitometry (DXA). The sample was divided according to sex and bone health indicators. Results : The combined effect of all movement behaviors (PA and SB) was significantly associated with whole body, leg and femoral region BM in the whole sample (p<0.05), with leg and pelvic BM (p<0.05) in men and, with whole body, arm and leg BM (p<0.05) in women. In men, arm and pelvic BM were negatively associated with SB and whole body, pelvic and leg BM were positively associated with MVPA (p<0.05). In women, whole body and leg BM were positively associated with SB. Arm and whole body BM were positively associated and leg BM was negatively associated with LPA and arm BM was negatively associated with MVPA (p<0.05). Women without bone fractures spent less time in SB and more in LPA and MVPA than the subgroup with bone fractures. Conclusion : We identified that the positive effect of MVPA relative to the other behaviors on bone mass is the strongest overall effect in men. Furthermore, women might decrease bone fracture risk through PA increase and SB reduction, despite the fact that no clear benefits of PA for bone mass were found

Task Failure during Exercise to Exhaustion in Normoxia and Hypoxia Is Due to Reduced Muscle Activation Caused by Central Mechanisms While Muscle Metaboreflex Does Not Limit Performance

To determine whether task failure during incremental exercise to exhaustion (IE) is principally due to reduced neural drive and increased metaboreflex activation eleven men (22±2 years) performed a 10s control isokinetic sprint (IS; 80 rpm) after a short warm-up. This was immediately followed by an IE in normoxia (Nx, PIO2:143 mmHg) and hypoxia (Hyp, PIO2:73 mmHg) in random order, separated by a 120 min resting period. At exhaustion, the circulation of both legs was occluded instantaneously (300 mmHg) during 10 or 60s to impede recovery and increase metaboreflex activation. This was immediately followed by an IS with open circulation. Electromyographic recordings were obtained from the vastus medialis and lateralis. Muscle biopsies and blood gases were obtained in separate experiments. During the last 10s of the IE, pulmonary ventilation, VO2, power output and muscle activation were lower in hypoxia than in normoxia, while pedaling rate was similar. Compared to the control sprint, performance (IS-Wpeak) was reduced to a greater extent after the IE-Nx (11% lower P<0.05) than IE-Hyp. The root mean square (EMGRMS) was reduced by 38 and 27% during IS performed after IE-Nx and IE-Hyp, respectively (Nx vs. Hyp: P<0.05). Post-ischemia IS-EMGRMS values were higher than during the last 10s of IE. Sprint exercise mean (IS-MPF) and median (IS-MdPF) power frequencies, and burst duration, were more reduced after IE-Nx than IE-Hyp (P<0.05). Despite increased muscle lactate accumulation, acidification, and metaboreflex activation from 10 to 60s of ischemia, IS-Wmean (+23%) and burst duration (+10%) increased, while IS-EMGRMS decreased (-24%, P<0.05), with IS-MPF and IS-MdPF remaining unchanged. In conclusion, close to task failure, muscle activation is lower in hypoxia than in normoxia. Task failure is predominantly caused by central mechanisms, which recover to great extent within one minute even when the legs remain ischemic. There is dissociation between the recovery of EMGRMS and performance. The reduction of surface electromyogram MPF, MdPF and burst duration due to fatigue is associated but not caused by muscle acidification and lactate accumulation. Despite metaboreflex stimulation, muscle activation and power output recovers partly in ischemia indicating metaboreflex activation has a minor impact on sprint performance

The impact of movement behaviors on bone health in elderly with adequate nutritional status: compositional data analysis depending on the frailty status

The aim of this study was to determine the relationship between bone mass (BM) and physical activity (PA) and sedentary behavior (SB) according to frailty status and sex using compositional data analysis. We analyzed 871 older people with an adequate nutritional status. Fried criteria were used to classify by frailty status. Time spent in SB, light intensity PA (LPA) and moderate-to-vigorous intensity PA (MVPA) was assessed from accelerometry for 7 days. BM was determined by dual-energy X-ray absorptiometry (DXA). The combined effect of PA and SB was significantly associated with BM in robust men and women (p ≤ 0.05). In relation to the other behaviors, SB was negatively associated with BM in robust men while BM was positively associated with SB and negatively with LPA and MVPA in robust women. Moreover, LPA also was positively associated with arm BM (p ≤ 0.01). Finally, in pre-frail women, BM was positively associated with MVPA. In our sample, to decrease SB could be a good strategy to improve BM in robust men. In contrast, in pre-frail women, MVPA may be an important factor to consider regarding bone health

Androgen receptor gene polymorphism influence fat accumulation: a longitudinal study from adolescence to adult age.

To determine the influence of androgen receptor CAG and GGN repeat polymorphisms on fat mass and maximal fat oxidation (MFO), CAG and GGN repeat lengths were measured in 128 young boys, from which longitudinal data were obtained in 45 of them [mean?±?SD: 12.8?±?3.6 years old at recruitment, and 27.0?±?4.8 years old at adult age]. Subjects were grouped as CAG short (CAGS ) if harboring repeat lengths ?21, the rest as CAG long (CAGL ); and GGN short (GGNS ) if GGN repeat lengths ?23, or long if >?23 (GGNL ). CAGS and GGNS were associated with lower adiposity than CAGL or GGNL (P?<?0.05). There was an association between the logarithm of CAG repeats polymorphism and the changes of body mass (r?=?0.34, P?=?0.03). At adult age, CAGS men showed lower accumulation of total body and trunk fat mass, and lower resting metabolic rate (RMR) and MFO per kg of total lean mass compared with CAGL (P?<?0.05). GGNS men also showed lower percentage of body fat (P?<?0.05). In summary, androgen receptor CAG and GGN repeat polymorphisms are associated with RMR, MFO, fat mass, and its regional distribution in healthy male adolescents, influencing fat accumulation from adolescence to adult age

Low relative mechanical power in older adults: An operational definition and algorithm for its application in the clinical setting

The assessment and treatment of low relative muscle power in older people has received little attention in the clinical setting when compared to sarcopenia. Our main goal was to assess the associations of low relative power and sarcopenia with other negative outcomes in older people. Methods: The participants were 1189 subjects (54% women; 65–101 years old) from the Toledo Study for Healthy Aging. Probable sarcopenia was defined as having low handgrip strength, while confirmed sarcopenia also included low appendicular skeletal muscle index (assessed by dual energy X-ray absorptiometry) (EWGSOP2’s definition). Low relative (i.e. normalized to body mass) muscle power was assessed with the 5-repetition sit-tostand power test (which uses an equation that converts sit-to-stand performance into mechanical power) and diagnosed in those subjects in the lowest sex-specific tertile. Low usual gait speed (UGS), frailty (according to Fried’s criteria and the Frailty Trait Scale), limitations in basic (BADL) and instrumental activities of daily living (IADL) and poor quality of life were also recorded. Results: Age-adjusted logistic regression analyses demonstrated that low relative muscle power was associated with low UGS (odds ratio (OR) = 1.9 and 2.5), frailty (OR = 3.9 and 4.7) and poor quality of life (OR = 1.8 and 1.9) in older men and women, respectively, and with limitations in BADL (OR = 1.6) and IADL (OR = 3.8) in older women (all p < 0.05). Confirmed sarcopenia was only associated with low UGS (OR = 2.5) and frailty (OR = 5.0) in older men, and with limitations in IADL in older women (OR = 4.3) (all p < 0.05). Conclusions: Low relative muscle power had a greater clinical relevance than low handgrip strength and confirmed sarcopenia among older people. An operational definition and algorithm for low relative muscle power case finding in daily clinical practice was presented

Relationship between physical performance and frailty syndrome in older adults: the mediating role of physical activity, sedentary time and body composition

The objectives were to clarify whether the relationship between physical performance and frailty was independently and jointly mediated by movement behaviors and body composition. We analyzed 871 older adults (476 women) from The Toledo Study for Healthy Aging. Skeletal muscle index (SMI) and fat index (FI) were determined using bone densitometry. Sedentary time (ST) and moderate-to-vigorous physical activity (MVPA) were assessed using accelerometry. The Frailty Trait Scale and The Short Physical Performance Battery (SPPB) were used to evaluate frailty and physical performance, respectively. Simple and multiple mediation analyses were carried out to determine the role of movement behaviors and body composition, adjusted for potential confounders. ST and MVPA acted independently as mediators in the relationship between SPPB and frailty (0.06% for ST and 16.89% for MVPA). FI also acted as an independent mediator in the same relationship (36.47%), while the mediation role of SMI was not significant. MVPA and FI both acted jointly as mediators in this previous relationship explaining 58.15% of the model. Our data support the fact that interventions should simultaneously encourage the promotion of MVPA and strategies to decrease the FI in order to prevent or treat frailty through physical performance improvement

Increased PIO2 at exhaustion in hypoxia enhaces muscle activation and swifty relieves fatigue: a placebo or a PIO2 dependent effect?

To determine the level of hypoxia from which muscle activation (MA) is reduced during incremental exercise to exhaustion (IE), and the role played by PIO2 in this process, ten volunteers (21 ± 2 years) performed four IE in severe acute hypoxia (SAH) (PIO2 = 73 mmHg). Upon exhaustion, subjects were asked to continue exercising while the breathing gas mixture was swiftly changed to a placebo (73 mmHg) or to a higher PIO2 (82, 92, 99, and 142 mmHg), and the IE continued until a new exhaustion. At the second exhaustion, the breathing gas was changed to room air (normoxia) and the IE continued until the final exhaustion. MA, as reflected by the vastus medialis (VM) and lateralis (VL) EMG raw and normalized root mean square (RMSraw, and RMSNz, respectively), normalized total activation index (TAINz), and burst duration were 8–20% lower at exhaustion in SAH than in normoxia (P < 0.05). The switch to a placebo or higher PIO2 allowed for the continuation of exercise in all instances. RMSraw, RMSNz, and TAINz were increased by 5–11% when the PIO2 was raised from 73 to 92, or 99 mmHg, and VL and VM averaged RMSraw by 7% when the PIO2 was elevated from 73 to 142 mmHg (P < 0.05). The increase of VM-VL average RMSraw was linearly related to the increase in PIO2, during the transition from SAH to higher PIO2 (R2 = 0.915, P < 0.05). In conclusion, increased PIO2 at exhaustion reduces fatigue and allows for the continuation of exercise in moderate and SAH, regardless of the effects of PIO2 on MA. At task failure, MA is increased during the first 10 s of increased PIO2 when the IE is performed at a PIO2 close to 73 mmHg and the PIO2 is increased to 92 mmHg or higher. Overall, these findings indicate that one of the central mechanisms by which severe hypoxia may cause central fatigue and task failure is by reducing the capacity for reaching the appropriate level of MA to sustain the task. The fact that at exhaustion in severe hypoxia the exercise was continued with the placebo-gas mixture demonstrates that this central mechanism has a cognitive component.This study was supported by a grant from the Ministerio de Educación y Ciencia of Spain (DEP2009-11638 and FEDER)

Effects of Power-Oriented Resistance Training With Heavy vs. Light Loads on Muscle-Tendon Function in Older Adults: A Study Protocol for a Randomized Controlled Trial

Background: Power-oriented resistance training (PRT) is one of the most effective exercise programs to counteract neuromuscular and physical function age-related declines. However, the optimal load that maximizes these outcomes or the load-specific adaptations induced on muscle power determinants remain to be better understood. Furthermore, to investigate whether these adaptations are potentially transferred to an untrained limb (i.e., cross-education phenomenon) could be especially relevant during limb-immobilization frequently observed in older people (e.g., after hip fracture). Methods: At least 30 well-functioning older participants (>65 years) will participate in a within-person randomized controlled trial. After an 8-week control period, the effects of two 12-week PRT programs using light vs. heavy loads will be compared using an unilateral exercise model through three study arms (light-load PRT vs. non-exercise; heavy-load PRT vs. non-exercise; and light- vs. heavy- load PRT). Muscle-tendon function, muscle excitation and morphology and physical function will be evaluated to analyze the load-specific effects of PRT in older people. Additionally, the effects of PRT will be examined on a non-exercised contralateral limb. Discussion: Tailored exercise programs are largely demanded given their potentially greater efficiency preventing age-related negative consequences, especially during limb immobilization. This trial will provide evidence supporting the use of light- or heavy-load PRT on older adults depending on individual needs, improving decision making and exercise program efficacy. Clinical Trial Registration: NCT03724461 registration data: October 30, 2018

The effect of the stretch-shortening cycle in the force–velocity relationship and its association with physical function in older adults with COPD

This study aimed to evaluate the effect of the stretch-shortening cycle (SSC) on different portions of the force–velocity (F–V) relationship in older adults with and without chronic obstructive pulmonary disease (COPD), and to assess its association with physical function. The participants were 26 older adults with COPD (79 ± 7 years old; FEV1 = 53 ± 36% of predicted) and 10 physically active non-COPD (77 ± 4 years old) older adults. The F–V relationship was evaluated in the leg press exercise during a purely concentric muscle action and compared with that following an eccentric muscle action at 10% intervals of maximal unloaded shortening velocity (V0). Vastus lateralis (VL) muscle thickness, pennation angle (PA), and fascicle length (FL) were assessed by ultrasound. Habitual gait speed was measured over a 4-m distance. COPD subjects exhibited lower physical function and concentric maximal muscle power (Pmax) values compared with the non-COPD group (both p 0.05). The SSC-induced potentiation at 50–100% of V0 was negatively associated with physical function (r = -0.40–0.50), while that observed at 80–100% of V0 was negatively associated with VL muscle thickness and PA (r = -0.43–0.52