Combined effects of aging and obesity on postural control, muscle activity and maximal voluntary force of muscles mobilizing ankle joint

Quantifying Plantar Flexor Muscles Stiffness During Passive and Active Force Generation Using Shear Wave Elastography in Individuals With Chronic Stroke

OBJECTIVES

This study aims to investigate the mechanical properties of paretic and healthy plantar flexor muscles and assesses the spatial distribution of stiffness between the gastrocnemius medialis (GM) and lateralis (GL) during active force generation.

METHODS

Shear wave elastography measurements were conducted on a control group (CNT, n=14; age=59.9±10.6 years; BMI=24.5±2.5 kg/m2) and a stroke survivor group (SSG, n=14; age=63.2±9.6 years; BMI=23.2±2.8 kg/m2). Shear modulus within the GM and GL was obtained during passive ankle mobilization at various angles of dorsiflexion (P0 =0°; P1=10°; P2=20°; P3=-20° and P4=-30°) and during different levels (30%, 50%, 70%, 100%) of maximal voluntary contraction (MVC). Muscle activations of GM, GL, soleus and tibialis anterior were also evaluated.

RESULTS

The results revealed a significant increase in passive stiffness within the paretic plantar flexor muscles under high tension during passive mobilization (p<0.05). Yet, during submaximal and maximal MVC, the paretic plantar flexors exhibited decreased active stiffness levels (p<0.05). A notable discrepancy was found between the stiffness of the GM and GL, with the GM demonstrating greater stiffness from 0° of dorsiflexion in the SSG (p<0.05), and from 10° of dorsiflexion in the CNT (p<0.05). No significant difference in stiffness was observed between the GM and GL muscles during active condition.

CONCLUSION

Stroke affects the mechanical properties differently depending on the state of muscle activation. Notably, the distribution of stiffness among synergistic plantar flexor muscles varied in passive condition, while remaining consistent in active condition.

Comparative analysis of postural stability and risk of falling and developing disability among overweight and obese women over 40 years

BACKGROUND

Increased body mass index (BMI) adversely affects the mechanics of the musculoskeletal system. It is known that obese people have poorer postural stability and mobility-related outcomes compared to normal weight people, but there is limited research comparing overweight and class 1 obese people, two consecutive and prevalent BMI categories.

AIMS

To compare postural stability, functional mobility, and risk of falling and developing disability between overweight and obese women, and to investigate the relationship of BMI and body weight with the outcomes.

METHODS

Thirty women with class 1 obesity and 30 overweight women were included. Standing postural stability with eyes-open and eyes-closed and stability limits were assessed using the Prokin system. The Timed Up and Go Test (TUG) was used to assess functional mobility and risk of falling (≥11 s) and developing disability (≥9 s).

RESULTS

The average center of pressure displacements on the y-axis (COPY) obtained during quiet standing with both eyes-open and eyes-closed were higher in obese women than overweight women (p < 0.05) and the effect sizes were moderate for the results. The COPY values in the eyes-open and eyes-closed conditions were correlated with BMI (r = 0.295 and r = 0.285, p < 0.05). Furthermore, the COPX value in the eyes-open condition and the TUG score were correlated with body weight (r = 0.274 and r = 0.257, p < 0.05).

CONCLUSIONS

Obese women had poorer static standing stability in the anteroposterior direction than overweight women, while functional mobility and risk of falling and developing disability did not differ. Furthermore, BMI and body weight were related to poorer static standing stability.

Dataset of Inter and intramuscular variability of stiffness in paretic individuals during prone and standing positions

Several studies have investigated muscle rigidity using SWE. However, the assessments may not consider the most affected regions within the same muscle tissue nor the intramuscular variability of rigidity between muscles of the same muscle group, e.g., plantar flexors. The data presented in this article aimed to explore the inter-and intramuscular variability of plantar flexors stiffness during prone and standing positions at different muscle lengths in healthy and paretic individuals. Shear wave ultrasound images were acquired for the three plantar flexor muscles (gastrocnemius medialis [GM], gastrocnemius lateralis [GL], and soleus [SOL]) in two positions: prone and standing. The imaging was conducted at various dorsiflexion angles (0°, 10°, and 20°), and measurements were taken at different proximo-distal regions within each muscle. This data set allowed us to highlight the impact of stroke on mechanical properties that varies depending on whether ankle muscles are in an active or passive state during dorsiflexion. Additionally, the modification of the ankle muscle state influences the distribution of stiffness both within and between the plantar flexors.

Does Obesity Affect the Rate of Force Development in Plantar Flexor Muscles among Older Adults?

The literature offers limited information on the effect of obesity on the rate of force development (RFD), a critical parameter for mobility in older adults. The objectives of this study were to explore the influence of obesity on the RFD in older adults and to examine the association between this neuromuscular parameter and walking speed. The participants (42 older adults) were classified into two groups: the control group (CG, n = 22; mean age = 81.13 ± 4.02 years; body mass index (BMI) = 25.13 ± 3.35 kg/m2), and the obese group (OG, n = 20; mean age = 77.71 ± 2.95 years; BMI = 34.46 ± 3.25 kg/m2). Walking speed (m/s) was measured using the 10 m walking test. Neuromuscular parameters of the plantar flexors were evaluated during a maximal voluntary contraction test using a dynamometer. The RFD was calculated from the linear slop of the force-time curve in the following two phases: from the onset of the contraction to 50 ms (RFD0-50) and from 100 to 200 ms (RFD100-200). The gait speed was lower in the OG compared to the CG (p < 0.001). The RFD50/100 and RFD100/200 were lower in the OG compared to the CG (p < 0.001). The RFD50/100 was found to be the predominant influencer on gait speed in the OG. In conclusion, obesity negatively impacts the RFD in older adults and RFD stands out as the primary factor among the studied parameters influencing gait speed.

Spatial distribution of stiffness between and within muscles in paretic and healthy individuals during prone and standing positions

This study investigated the inter- and intramuscular variability of plantar flexors stiffness during prone and standing positions at different muscle lengths in healthy and paretic individuals. To access tissue stiffness, shear wave elastography (SWE) measurements were carried out on two groups: control group (CG; n=14; age 43.9±9.6 years; body mass index [BMI]=24.5±2.5 kg/m2) and stroke survivor group (SSG; n=14; age 43.9±9.6 years; BMI=24.5±2.5 kg/m2). Shear Modulus (μ, kPa) within three plantar flexors (the gastrocnemius medialis [GM], gastrocnemius lateralis [GL], and soleus [SOL]) was obtained during two conditions: prone and standing position, at different angles of dorsiflexion (0°, 10°, and 20°). Measurements were also performed in different proximo-distal regions of each muscle. Muscle activation of the GM, GL, SOL, and tibialis anterior were evaluated during the two conditions. Results showed a high spatial stiffness variability between and within plantar flexors during dorsiflexion. The highest stiffness was observed in the GM, especially in the distal region at 20° in healthy and paretic muscles. In the prone position, the paretic muscle exhibits greater stiffness compared to the healthy muscle (p < 0.05). In contrast, in the standing position, an increase of stiffness in the healthy muscle compared to the paretic muscle was observed (p < 0.05). Thus, mechanical properties are differently affected by stroke depending on active and passive states of ankle muscles during dorsiflexion. In addition, the modification of ankle muscle state change stiffness distribution between and within plantar flexors.

Influence of Concurrent Exercise Training on Ankle Muscle Activation during Static and Proactive Postural Control on Older Adults with Sarcopenic Obesity: A Multicenter, Randomized, and Controlled Trial

Sarcopenic obesity (SO), characterized by age-related muscle loss and excess body fat, significantly impairs postural control. However, limited research has explored the effects of concurrent exercise training on neuromuscular strategies during postural control in older adults with SO. The study enrolled 50 older adults with SO, split into an intervention group (IG, n = 25, mean age = 76.1 ± 3.5 years; mean BMI = 34.4 ± 4.0 kg/m2) and a control group (CG, n = 25, mean age = 75.9 ± 5.4 years; mean BMI = 32.9 ± 2.3 kg/m2). Participants in the IG were engaged in 60-min Total Mobility Plus Program (TMP) sessions three times a week for four months, while the CG maintained their typical daily activities. Standardized evaluations were conducted both before and after the intervention. These assessments included the Romberg and Timed Up and Go (TUG) tests, as well as the measurement of Center of Pressure (CoP) displacements parameters under various conditions. Additionally, ankle muscle activities were quantified during postural control evaluations and maximal voluntary contractions of plantar and dorsal flexors. Post-intervention results revealed a significant reduction of the standing time measured in the Romberg (-15.6%, p < 0.005) and TUG (-34.6%, p < 0.05) tests. Additionally, CoP area and velocity were notably reduced in various conditions (p < 0.05). Postural control improvements were associated with an increase of strength (p < 0.05) and decrease of ankle muscle activation (p < 0.05). These findings highlight the reversibility of neuromuscular system alterations associated with the synergistic effects of sarcopenia and obesity, emphasizing the trainability of postural control regulation within this population. By incorporating these insights into clinical practice and public health strategies, it seems possible to optimize the health and well-being of older adults with SO.

The impact of obesity on static and proactive balance and gait patterns in sarcopenic older adults: an analytical cross-sectional investigation

Background

Obesity is increasingly recognized as a significant factor in the susceptibility of older adults to falls and related injuries. While existing literature has established a connection between obesity and reduced postural stability during stationary stances, the direct implications of obesity on walking dynamics, particularly among the older adults with sarcopenia, are not yet comprehensively understood.

Objective

Firstly, to investigate the influence of obesity on steady-state and proactive balance, as well as gait characteristics, among older adults with sarcopenic obesity (SO); and secondly, to unearth correlations between anthropometric characteristics and balance and gait parameters in the same demographic.

Methods

A cohort of 42 participants was categorized into control (CG; n = 22; age = 81.1 ± 4.0 years; BMI = 24.9 ± 0.6 kg/m²) and sarcopenic obese (SOG; n = 20; age = 77.7 ± 2.9 years; BMI = 34.5 ± 3.2 kg/m²) groups based on body mass index (BMI, kg/m²). Participants were assessed for anthropometric data, body mass, fat and lean body mass percentages (%), and BMI. Steady-state balance was gauged using the Romberg Test (ROM). Proactive balance evaluations employed the Functional Reach (FRT) and Timed Up and Go (TUG) tests. The 10-m walking test elucidated spatiotemporal gait metrics, including cadence, speed, stride length, stride time, and specific bilateral spatiotemporal components (stance, swing, 1st and 2nd double support, and single support phases) expressed as percentages of the gait cycle.

Results

The time taken to complete the TUG and ROM tests was significantly shorter in the CG compared to the SOG (p < 0.05). In contrast, the FRT revealed a shorter distance achieved in the SOG compared to the CG (p < 0.05). The CG exhibited a higher gait speed compared to the SOG (p < 0.05), with shorter stride and step lengths observed in the SOG compared to the CG (p < 0.05). Regarding gait cycle phases, the support phase was longer, and the swing phase was shorter in the SOG compared to the CG group (p < 0.05). LBM (%) showed the strongest positive correlation with the ROM (r = 0.77, p < 0.001), gait speed (r = 0.85, p < 0.001), TUG (r = -0.80, p < 0.001) and FRT (r = 0.74, p < 0.001).

Conclusion

Obesity induces added complexities for older adults with sarcopenia, particularly during the regulation of steady-state and proactive balance and gait. The percentage of lean body mass has emerged as a crucial determinant, highlighting a significant impact of reduced muscle mass on the observed alterations in static postural control and gait among older adults with SO.

Effects of Physical Activity Program on Body Composition, Physical Performance, and Neuromuscular Strategies during Walking in Older Adults with Sarcopenic Obesity: Randomized Controlled Trial

The potential impact of a specific physical activity program on biomechanical gait parameters and neuromuscular strategies around the ankle joint in older adults with sarcopenic obesity (SO) remains largely unexplored. The objective of this study was to investigate the effectiveness of a 24-week posture, strengthening, and motricity (PSM) program on improving neuromuscular strategies and biomechanical gait parameters in older adults with SO. 40 participants were randomly assigned to either the trained group (TG) and the control group (CG). Only the TG received the PSM program. Standardized evaluations were performed before and after the intervention, including walking tests on an instrumented gait analysis treadmill to evaluate biomechanical gait parameters and EMG activity of ankle muscles. After the PSM program, TG exhibited an increase in comfortable walking speed (+80%, p < 0.001) and step length (+38%, p < 0.05). Moreover, TG demonstrated a reduction in CoP velocity (-26%, p < 0.01). These gait modifications were associated with decreased muscle activity during the different gait phases (p < 0.05). The PSM program effectively improved gait and neuromuscular capacities in older adults with SO. Notably, these results shed light on the remarkable trainability of neuromuscular capacities in older adults with SO, despite the adverse effects of aging and obesity.

A Pilot Study on Attentional Focus in Prescribing Physical Exercise in Outpatients with Obesity

This pilot study compared the effects of two attentional focus strategies on fitness parameters and body composition in outpatients with obesity. This was a randomized, controlled study that enrolled 94 obese individuals and allocated them into an internal focus group (IF) or an external focus group (EF) while performing six weeks of a home-based training program. The home-based exercise program was the same for both groups except for the instructions that shifted the attention to an external or an internal condition. At the beginning and after the intervention period, participants were assessed for functional performance using the Functional Movement Screen (FMS), body balance using the Modified Balance Error Scoring System (M-BESS) and muscular strength with the Handgrip Strength Test (HST) and the Five-Repetition Sit-To-Stand (FRSTS) test. Concerning body composition and anthropometric parameters, the body mass index (BMI) and fat mass percentage (FM%) were calculated. Significant improvements, main interactions and effects of time and groups were highlighted in the EF group as compared to the IF group in FMS (35% vs. 21%), M-BESS (42% vs. 18%), HST (13% vs. 7%) and FRSTS (23% vs. 12%) measures, while FM% (5%) and BMI (6% vs. 5%) showed a similar improvement overtime (p < 0.001). In conclusion, our findings provide initial evidence that a 6-week training program performed following external focus instruction is able to promote significant enhancements in movement efficiency, balance and muscular strength as compared to an internal focus cue. Fitness coaches and therapists might consider integrating a specific attentional focus strategy when designing rehabilitation programs in subjects with obesity.

Assessing Post-Driving Discomfort and Its Influence on Gait Patterns

Professional drivers need constant attention during long driving periods and sometimes perform tasks outside the truck. Driving discomfort may justify inattention, but it does not explain post-driving accidents outside the vehicle. This study aims to study the discomfort developed during driving by analysing modified preferred postures, pressure applied at the interface with the seat, and changes in pre- and post-driving gait patterns. Each of the forty-four volunteers drove for two hours in a driving simulator. Based on the walking speed changes between the two gait cycles, three homogeneous study groups were identified. Two groups performed faster speeds, while one reduced it in the post-steering gait. While driving, the pressure at the interface and the area covered over the seat increased throughout the sample. Preferred driving postures differed between groups. No statistical differences were found between the groups in the angles between the segments (flexed and extended). Long-time driving develops local or whole-body discomfort, increasing interface pressure over time. While driving, drivers try to compensate by modifying their posture. After long steering periods, a change in gait patterns can be observed. These behaviours may result from the difficulties imposed on blood circulation by increasing pressure at this interface.

Effects of a Randomized Home-Based Quality of Movement Protocol on Function, Posture and Strength in Outpatients with Obesity

The aim of this study was to determine the effects of two different home-based training interventions on functional parameters and body composition in obese patients. Sixty-four obese patients were recruited at the IRCCS Istituto Auxologico Italiano and randomly assigned into a movement quality group (MQ) and a conventional training group (CT). In the MQ, the training protocol combined various stimuli based on whole-body movement patterns, mobility, motor control and diaphragmatic breathing. The CT included traditional bodyweight resistance-training exercises. All patients were tested for movement efficiency (Functional Movement Screen, FMS), postural control (Modified Balance Error Scoring System, M-BESS), breathing pattern (Total Faulty Breathing Scale, TFBS), muscular strength (Handgrip Strength Test, HST and Five Repetition Sit to Stand, FRSTS) and body composition (Waist Circumference, WC, Body Mass Index, BMI, Body fat mass percentage, Fat Mass) before and after a 6-week period of training. Significant interactions and main effects of time (p < 0.0001) were found in MQ compared to CT in the FMS, M-BESS and TFBS parameters, while muscular strength (HST, FRSTS) and body composition parameters improved similarly in both groups with a main effect of time (p < 0.05). These findings suggest that a 6-week movement quality training is effective in ameliorating postural control and movement efficiency with similar improvements in muscular strength and body composition compared with a mere traditional home-based training. Fitness coaches and practitioners might consider the MQ intervention as a valuable alternative to conventional training when treating obesity.

Medial Ankle Stability Evaluation With Dynamic Ultrasound: Establishing Natural Variations in the Healthy Cohort

INTRODUCTION

Destabilizing injuries to the deltoid ligament have relied on radiographic stress examination for diagnosis, with a focus on medial clear space (MCS) widening. Recently, studies have demonstrated the use of ultrasonography to assess deltoid ligament injury, but not the medial ankle stability. The purpose of this study was to assess the MCS via ultrasonography while weight-bearing and with a gravity stress test (GST) in the uninjured ankle as a means of establishing normative values for future comparison.

METHODS

Twenty-six participants with no reported ankle injury in their premedical history were included. The MCS was examined using ultrasonography with the patient lying in a lateral decubitus position to replicate a GST with the ankle held in a neutral and plantarflexed position as well as while weight-bearing. The MCS was assessed in mm at the anteromedial and inferomedial aspect of the ankle joint.

RESULTS

With weight-bearing, the average anterior MCS and inferior MCS were 3.6 and 3.3 mm, respectively. During the GST in neutral ankle position, the average anterior MCS was 4.1 mm, whereas the average inferior MCS was 4.0 mm. When measured during the GST in plantarflexed ankle position, the averages anterior MCS and inferior MCS increased to 4.4 mm. MCS values were notably higher with GST than with weight-bearing measurements (P < 0.001). MCS values were notably higher with the foot in a plantarflexed compared with a neutral position when doing GST (P < 0.001). No notable differences in MCS distance were found when comparing laterality (P > 0.05). Height had a notable effect on all MCS values (P < 0.05). Inter- and intra-rater reliabilities for ultrasonographic MCS measurements were all excellent (interclass correlation coefficient >0.75).

DISCUSSION

Ultrasound can reliably measure the MCS of the ankle while doing dynamic stress manoeuvres. With the deltoid ligament intact, a GST increases MCS widening more than weight-bearing, and holding the ankle in plantarflexion while doing a gravity stress view, further increases this difference.

LEVELS OF EVIDENCE

Diagnostic studies-investigating a diagnostic test: Level III.

Relation of Physical Activity Level to Postural Balance in Obese and Overweight Spanish Adult Males: A Cross-Sectional Study

The aim of this study was to analyze the influence of physical activity level on postural control in obese and overweight Spanish adult males. Forty-three males aged between 25 and 60 years old were included. Anthropometric, body composition, and physical activity variables were assessed, and postural control was evaluated using the Sensory Organization Test. No correlation was found between the level of physical activity and postural control, assessed by the Sensory Organization Test within the whole sample. However, within the group with a higher total fat mass percentage, non-sedentary individuals presented improved scores on the somatosensory organization test when compared to sedentary individuals (96.9 ± 1.8 vs. 95.4 ± 1.2; p < 0.05) and poorer scores on the composite equilibrium score (73.4 ± 7.2 vs. 79.2 ± 6.9; p < 0.05). The altered integration of somatosensory inputs most likely affects the tuning, sequencing, and execution of balance strategies in sedentary men with a high total fat mass percentage.

Gait initiation differences between overweight and normal weight individuals

Accidental falls often occur during gait initiation. Excess body weight has been identified as a risk factor for accidental falls. This study aimed to examine the differences of gait initiation between overweight and normal-weight individuals. Fourteen overweight and 14 normal-weight young adults participated in the study. They were instructed to perform the gait initiation task under single-task and dual-task conditions. Dependent variables for the assessment of gait initiation included spatial-temporal measures and postural stability measures. The results showed that overweight could compromise postural stability during gait initiation, primarily by decreasing margin of stability in the anterior-posterior direction. Cognitive task interference with gait initiation was found to be similar between the overweight and normal weight groups. The findings from the present study can aid in better understanding the mechanisms associated with increased fall risks among overweight individuals. They also highlight the importance of overweight control in fall prevention. Practitioner summary: Overweight was found to compromise postural stability during gait initiation, primarily by decreasing margin of stability in the anterior-posterior direction. The findings highlight the importance of overweight control in fall prevention. Abbreviations: ANOVA: analyses of variance; AP: anterior-posterior; APA: anticipatory postural adjustment; BOS: base of support; BW: Body weight; COM: centre-of-mass; COP: center-of-pressure; CT: cognitive task; GI: Gait initiation; GRF: ground reaction force; HC: heel-contact; HO: heel-off; ML: medial-lateral; MOS: margin of stability; SD: standard deviation; SE: step execution; SL: step length; SW: step width; VEL_COM: velocity of the COM; XCOM: extrapolated center of mass.

Pedobarographic Statistical Parametric Mapping may identify specific plantar pressure patterns in patients with diabetes mellitus among different degrees of peripheral neuropathy: A pilot study

AIMS

Peripheral neuropathy (PN) in patients with diabetes can lead to changes in the distribution of plantar pressure during walking, which can be recorded with pedobarography. Compared to traditional spatial data reduction analysis, the pedobarographic Statistical Parametric Mapping (pSPM) allows comparison of the footprints with the advantage that sub-regions do not need to be defined a priori. Aim of the study was to test the potential of pSPM in identifying specific distribution of spatial pressure in different stages of PN.

METHODS

PN was defined according to usual tools (i.e., tendon reflexes and sensory tests). Four groups were compared: patients with diabetes without PN (n = 24; 239 steps); with signs of mild PN (n = 12; 117 steps); with signs of severe PN (n = 6; 52 steps) and a control group without diabetes (n = 12; 124 steps). Traditional spatial data reduction and pSPM were performed to compare plantar pressures in the different groups.

RESULTS

In patients with PN, traditional spatial data reduction analysis showed lower plantar pressures with PN severity. pSPM analysis is able to better define the initial changes: mild PN patients presents higher pressures on the anterior side of the metatarsal heads compared to patients without neuropathy. Patients with severe PN are characterised by higher pressures under the medial foot arch compared to other groups.

CONCLUSIONS

pSPM may identify specific features of plantar pressure distribution during walking in patients with mild PN and may become a useful screening tool for a timely identification of this complication.

Is Ankle Plantar Flexor Strength Associated With Balance and Walking Speed in Healthy People? A Systematic Review and Meta-Analysis

OBJECTIVE

The purpose of this study was to investigate the association between ankle plantar flexor muscle (PF) strength and balance and walking speed in healthy adults.

METHODS

Four databases (Ovid MEDLINE, Ovid EMBASE, CINAHL Plus, and SPORTDiscus) were searched from inception to December 2019. Studies with any design were included if the association between PF strength and balance and walking speed was investigated among healthy adults. Articles were screened for eligibility independently by 2 reviewers. Study characteristics and Pearson r values derived from the association between PF strength and balance and walking speed were extracted. Thirty-four studies were eligible. The main group of interest in the studies was older adults. Pearson r values were transformed to rz values using Fisher z-transformation. Meta-analysis of rz values was conducted and then back-transformed to r.

RESULTS

In older adults, PF maximal isometric strength had a positive weak association with static balance (r = 0.20; 95% CI = 0.08-0.32), a positive moderate association with dynamic reactive balance (r = 0.42; 95% CI = 0.32-0.57) and proactive balance (r = 0.55; 95% CI = 0.18-1.06), and a positive weak association with preferred walking speed (r = 0.29; 95% CI = 0.19-0.41) and maximum walking speed (r = 0.34; 95% CI = 0.06-0.63). In younger adults, there was a moderate association between early-phase PF rate of torque development and reactive balance (0.42 < r < 0.52).

CONCLUSIONS

PF strength appears to be moderately associated with dynamic reactive and proactive balance and weakly associated with static balance and walking speed. This finding highlights the potential role of PF strength in dynamic reactive and proactive balance.

IMPACT

This meta-analysis showed that ankle PF strength might be important for challenging dynamic balance tasks.

Added body mass alters plantar shear stresses, postural control, and gait kinetics: Implications for obesity

Context

Obesity is a growing global health concern. The increased body mass and altered mass distribution associated with obesity may be related to increases in plantar shear that putatively leads to physical functional deficits. Therefore, measurement of plantar shear may provide unique insights on the effects of body mass and body distribution on physical function or performance.

Purpose

1) To investigate the effects of body mass and distribution on plantar shear. 2) To examine how altered plantar shear influences postural control and gait kinetics.

Hypothesis

1) a weighted vest forward distributed (FV) would shift the center of pressure (CoP) location forward during standing compared with a weighted vest evenly distributed (EV), 2) FV would increase plantar shear spreading forces more than EV during standing, 3) FV would increase postural sway during standing while EV would not, and 4) FV would elicit greater compensatory changes during walking than EV.

Methods

Twenty healthy young males participated in four different tests: 1) static test (for measuring plantar shear and CoP location without acceleration, 2) bilateral-foot standing postural control test, 3) single-foot standing postural test, and 4) walking test. All tests were executed in three different weight conditions: 1) unweighted (NV), 2) EV with 20% added body mass, and 3) FV, also with 20% added body mass. Plantar shear stresses were measured using a pressure/shear device, and several shear and postural control metrics were extracted. Repeated measures ANOVAs with Holms post hoc test were used to compare each metric among the three conditions (α = 0.05).

Results

FV and EV increased both AP and ML plantar shear forces compared to NV. FV shifted CoP forward in single-foot trials. FV and EV showed decreased CoP range and velocity and increased Time-to-Boundary (TTB) during postural control compared to NV. EV and FV showed increased breaking impulse and propulsive impulse compared to NV. In addition, EV showed even greater impulses than FV. While EV increased ML plantar shear spreading force, FV increased AP plantar shear spreading force during walking.

Conclusion

Added body mass increases plantar shear spreading forces. Body mass distribution had greater effects during dynamic tasks. In addition, healthy young individuals seem to quickly adapt to external stimuli to control postural stability. However, as this is a first step study, follow-up studies are necessary to further support the clinical role of plantar shear in other populations such as elderly and individuals with obesity or diabetes.

The Influence of Body Fat Distribution on Postural Balance and Muscle Quality in Women Aged 60 Years and Over

The aim of this study was to investigate the influence of body fat distribution on postural balance and lower-limb muscle quality in women aged 60 years and over. Two hundred and twenty-two volunteers took part in this cross-sectional analysis. Participants underwent body fat distribution assessment using dual-energy x-ray absorptiometry and were classified as nonobese, gynoid obese, or android obese. Postural balance was assessed during quiet standing, with and without vision restriction, using a force platform. Specific torque was defined as the ratio of knee extensors peak torque (evaluated by an isokinetic dynamometer) to the lean mass of the same limb (evaluated by dual-energy x-ray absorptiometry). Compared with nonobese participants, both obese groups exhibited higher range of postural sway along the anteroposterior and mediolateral axes (P < .05). However, there were no differences between participants with gynoid and android obesity. The android obese group exhibited greater speed of postural sway in the condition without vision restriction than both nonobese (P = .040) and gynoid obese (P = .004) groups. Regarding muscle quality, only participants with gynoid obesity (P = .004) presented lower specific torque than their nonobese peers. These results may be clinically useful when designing falls prevention exercises targeting the obese population.

Differences in lower extremity muscular coactivation during postural control between healthy and obese adults

INTRODUCTION

It is well established that obesity is associated with deterioration in postural control that may reduce obese adults' autonomy and increase risks of falls. However, neuromuscular mechanisms through which postural control alterations occur in obese adults remain unclear.

OBJECTIVE

To investigate the effects of obesity on muscle coactivation at the ankle joint during static and dynamic postural control.

MATERIALS AND METHODS

A control group (CG; n = 20; age = 32.5 ± 7.6 years; BMI = 22.4 ± 2.2 Kg/m²) and an obese group (OG; n = 20; age = 34.2 ± 5.6 years; BMI = 38.6 ± 4.1 Kg/m²) participated in this study. Static postural control was evaluated by center of pressure (CoP) displacements during quiet standing. Dynamic postural control was assessed by the maximal distance traveled by the CoP during a forward lean test. Electromyography activity data for the gastrocnemius medialis (GM), soleus (SOL) and tibialis anterior (TA) were collected during both quiet standing and forward lean tests. Muscle activities were used to calculate two separate coactivation indexes (CI) between ankle plantar and dorsal flexors (GM/TA and SOL/TA, respectively).

RESULTS

CoP displacements were higher in the OG than in the CG for quiet standing (p < 0.05). When leaning forward, the maximal distance of the CoP was higher in the CG than in the OG (p < 0.05). Only the CI value calculated for SOL/TA was higher in the OG than in the CG for both static and dynamic tasks (p < 0.05). The SOL/TA CI value in the OG was positively correlated with CoP displacements during quiet standing (r = 0.79; p < 0.05).

CONCLUSION

Obesity increases muscle coactivation of the soleus and tibialis anterior muscles at the ankle joint during both static and dynamic postural control. This adaptive neuromuscular response may represent a joint stiffening strategy for enhancing stability. Consequently, increased ankle muscle coactivation could not be considered as a good adaptation in obese adults.

Interactions among obesity and age-related effects on the gait pattern and muscle activity across the ankle joint

OBJECTIVE

The purposes of this study were to investigate the combined effects of age and obesity on gait and to analyze the relationship between age and obesity on ankle muscle activities during walking.

MATERIALS AND METHODS

4 groups; the young non-obese control group (CG, n = 50, age = 31.8 ± 4.5 years; BMI = 21.4 ± 2.2 kg/m²), the young obese group (OB, n = 30, age = 35.4 ± 4.1 years; BMI = 38.6 ± 3.5 kg/m²), the non-obese older adults group (OA, n = 20, age = 76.1 ± 3.5 years; BMI = 24.4 ± 1.1 kg/m²) and the obese older adults group (OBOA, n = 20, age = 79.6 ± 5.7 years; BMI = 35.5 ± 2.7 kg/m²) walked on an instrumented gait analysis treadmill at their preferred walking speed. Spatiotemporal parameters, walking cycle phases, Vertical ground reaction force (GRFv) and center of pressure (CoP) velocity were sampled from the treadmill software. Electromyography (EMG) activity of the gastrocnemius medialis (GM), the soleus (SOL) and tibialis anterior (TA) were also collected during the walking test. A forward stepwise multiple regression analysis was performed to determine if body weight or age could predict ankle muscle activities during the different walking cycle phases.

RESULTS

Compared to OB, OBOA walked with higher CoP velocity, shorter stride, spending more time in support phase (p < .05). These manifestations were associated with higher TA and SOL activities during the 1st double support (1st DS) and higher TA activity during the single support (SS) (p < .05). Compared to OA, OBOA walked with lower GRFv, shorter and wider stride and spend more time in SU (p < .05). Moreover, SOL, TA and GM activities of OBOA were higher compared to OAG during 1st DS, SS and 2nd Double support (2nd DS), respectively (p < .05). During the 1ST DS, the stepwise multiple regression revealed that age accounted for 87% of the variance of TA activity. The addition of age contributed a further 16% to explain the variance TA activity. During the SS, age accounted for 64% and 46% of the variance of SOL and TA activity respectively. The addition of the body weight added further 15% and 66% of the variation of SOL and TA activity respectively. During the 2nd DS, body weight accounted for 86% of the variance and the addition of the body weight added a further 17% to explain the high level of GM.

CONCLUSION

Age in obese adults and obesity in older adults should be considered separately to evaluate neuromuscular responses during walking and, subsequently, optimize the modality of treatment and rehabilitation processes in obese individuals in order to reduce and/or prevent the risk of falls.

Prevalence and factors associated with obesity among the oldest old

PURPOSE

To determine the prevalence of overweight and obesity, and to identify factors associated with obesity, among the oldest old.

METHODS

For this study, data from follow-up (FU) wave 7 and FU wave 8 of the "Study on Needs, Health Service Use, Costs and Health-Related Quality of Life in a Large Sample of Oldest-Old Primary Care Patients (85+)" (AgeQualiDe) were used. At FU wave 7, the mean age was 88.9 years (SD: 2.9; 85-100 years). Body-mass-index (BMI) categories were defined according to the World Health Organization (WHO) thresholds: underweight (BMI < 18.5 kg/m²), normal weight (18.5 kg/m² ≤ BMI < 25 kg/m²), overweight (25 kg/m² ≤ BMI < 30 kg/m²), and obesity (BMI ≥ 30 kg/m²). Longitudinal regression analysis was used to determine factors associated with obesity.

RESULTS

At FU wave 7, 3.0 % were underweight, 48.9 % were normal weight, 37.9 % were overweight, and 10.2 % were obese. Regressions showed that the probability of obesity decreased with age (OR: 0.77 [95 % CI: .593-.999]) and less chronic conditions (OR: 1.32 [95 % CI: 1.11-1.57]). The probability of obesity was not associated with sex, educational level, marital status, social isolation, visual impairment, hearing impairment, depression, and dementia.

CONCLUSION

Nearly half of the individuals in very late life had excess weight. Thus, excess weight remains a major challenge, even in very old age. Given the demographic ageing in upcoming decades, this is an issue which we should be aware of.

Influence of Obesity and Impact of a Physical Activity Program on Postural Control and Functional and Physical Capacities in Institutionalized Older Adults: A Pilot Study

Objective: To evaluate the role of obesity in the effects of physical activity (PA) on postural control and functional and physical capacities in the older adults and to assess the effectiveness of a PA program on these capacities. Methods: Six obese (age = 78.8 [3.7] y; body mass index > 30 kg/m2), 7 overweight (age = 80.9 [2.8] y; 25 < body mass index < 30 kg/m2), and 6 normal weight (age = 80.8 [5.7] y; body mass index < 25 kg/m2) older adults performed the time up and go test, the 6-minute walk test, and the Tinetti test. Static and dynamic (forward leaning) postural control tests were also assessed. All these tests were similarly assessed 4 months later, during which only the obese group and overweight group participated in a PA program. Results: Before PA, results of the time up and go test, 6-minute walk test, Tinetti test, quiet standing, and forward lean tests revealed that physical capacities and static and dynamic postural control were impaired in the obese group when compared to the normal weight group. After PA, results of quiet standing, physical and functional tests were improved for obese group. Conclusions: Obesity is an additional constraint to age-related postural control and functional and physical capacities deteriorations. Nevertheless, a PA program is effective in improving balance and functional capacities in obese older adults.

sEMG Activation of the Flexor Muscles in the Foot during Balance Tasks by Young and Older Women: A Pilot Study

Objective: In this publication, we suggest that young adults and seniors use various defense mechanisms to counteract loss of balance. One of the hypotheses is the change in the coordination of antagonistic muscle groups, especially within the ankles. In this study, we tried to determine if there is a relationship between the condition from resilient, to pre-frail, to frail and the ability to maintain balance during free standing and balance tasks. The aim of the study was to define the importance of muscle activity in the ankle joint, dorsal flexor of the foot for the following: tibialis anterior (TA), plantar flexor of the foot gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and peroneus longus (PER), during balance tasks with eyes open (EO) and closed (EC). We hypothesized that there are differences in the activity and co-activation of the tested muscles in young and older women, which may indicate an increased risk of falls and walking disorders. Materials and methods: A group of 20 women qualified for the study. The group was divided into two subgroups, young (G1) and elderly women (G2). The aim of the study was to define the importance of muscle activity in the ankle joint, dorsal flexor of the foot for the following: tibialis anterior (TA), plantar flexor of the foot gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and peroneus longus (PER), during balance tasks with eyes open (EO) and closed (EC). Results: In this study, we observed significant differences between groups in the maximum and mean values of electromyography activity (EMG) activation of the examined muscles on different types of surfaces and with open and closed eyes. Older women generated higher values of EMG activation in all muscles except the gastrocnemius medialis muscle. The results were significant for co-activation at rest for muscles as follows: tibialis anterior and gastrocnemius medialis with eyes closed (p = 0.01) and peroneus and gastrocnemius lateralis at rest with eyes open (p = 0.03), eyes closed (p = 0.04), and on a foam (p = 0.02). The sEMG amplitude of the tested muscles means that agonist muscle activity changed relative to antagonistic muscle activity. Conclusions: Activation of sEMG and coordination of ankle muscles during balance tasks change with age. It can be hypothesized that assessment of balance during free standing and equivalent tasks can predict the state of frailty, after taking into account other physiological variables that are believed to affect balance control.

A high-fat diet impacts memory and gene expression of the head in mated female Drosophila melanogaster

Obesity predisposes humans to a range of life-threatening comorbidities, including type 2 diabetes and cardiovascular disease. Obesity also aggravates neural pathologies, such as Alzheimer's disease, but this class of comorbidity is less understood. When Drosophila melanogaster (flies) are exposed to high-fat diet (HFD) by supplementing a standard medium with coconut oil, they adopt an obese phenotype of decreased lifespan, increased triglyceride storage, and hindered climbing ability. The latter development has been previously regarded as a potential indicator of neurological decline in fly models of neurodegenerative disease. Our objective was to establish the obesity phenotype in Drosophila and identify a potential correlation, if any, between obesity and neurological decline through behavioral assays and gene expression microarray. We found that mated female w1118 flies exposed to HFD maintained an obese phenotype throughout adult life starting at 7 days, evidenced by increased triglyceride stores, diminished life span, and impeded climbing ability. While climbing ability worsened cumulatively between 7 and 14 days of exposure to HFD, there was no corresponding alteration in triglyceride content. Microarray analysis of the mated female w1118 fly head revealed HFD-induced changes in expression of genes with functions in memory, metabolism, olfaction, mitosis, cell signaling, and motor function. Meanwhile, an Aversive Phototaxis Suppression assay in mated female flies indicated reduced ability to recall an entrained memory 6 h after training. Overall, our results support the suitability of mated female flies for examining connections between diet-induced obesity and nervous or neurobehavioral pathology, and provide many directions for further investigation.