Post exercise hot water immersion and hot water immersion in isolation enhance vascular, blood marker, and perceptual responses when compared to exercise alone.

Exercise and passive heating induce some similar vascular hemodynamic, circulating blood marker, and perceptual responses. However, it remains unknown whether post exercise hot water immersion can synergise exercise derived responses and if they differ from hot water immersion alone. This study investigated the acute responses to post moderate-intensity exercise hot water immersion (EX+HWI) when compared to exercise (EX+REST) and hot water immersion (HWI+HWI) alone. Sixteen physically inactive middle-aged adults (nine males and seven females) completed a randomized cross-over counterbalanced design. Each condition consisted of two 30-min bouts separated by 10 min of rest. Cycling was set at a power output equivalent to 50% V̇o2 peak . Water temperature was controlled at 40°C up to the mid sternum with arms not submerged. Venous blood samples and artery ultrasound scans were assessed at 0 (baseline), 30 (immediately post stressor one), 70 (immediately post stressor two), and 100 min (recovery). Additional physiological and perceptual measures were assessed at 10-min intervals. Brachial and superficial femoral artery shear rates were higher after EX+HWI and HWI+HWI when compared with EX+REST (p < 0.001). Plasma nitrite was higher immediately following EX+HWI and HWI+HWI than EX+REST (p < 0.01). Serum interleukin-6 was higher immediately after EX+HWI compared to EX+REST (p = 0.046). Serum cortisol was lower at 30 min in the HWI+HWI condition in contrast to EX+REST (p = 0.026). EX+HWI and HWI+HWI were more enjoyable than EX+REST (p < 0.05). Irrespective of whether hot water immersion proceeded exercise or heating, hot water immersion enhanced vascular and blood marker responses, while also being more enjoyable than exercise alone.

The effect of age and mitigation strategies during hot water immersion on orthostatic intolerance and thermal stress.

NEW FINDINGS: What is the central question of this study? The aim was to characterize adverse responses to whole-body hot water immersion and to investigate practical strategies to mitigate these effects. What is the main finding and its importance? Whole-body hot water immersion induced transient orthostatic hypotension and impaired postural control, which recovered to baseline within 10 min. Hot water immersion was well tolerated by middle-aged adults, but younger adults suffered from a greater frequency and severity of dizziness. Cooling the face with a fan or not immersing the arms can mitigate some of these adverse responses in younger adults. ABSTRACT: Hot water immersion improves cardiovascular health and sporting performance, yet its adverse responses are understudied. Thirteen young and 17 middle-aged adults (n = 30) were exposed to 2 × 30 min bouts of whole-body 39°C water immersion. Young adults also completed cooling mitigation strategies in a randomized cross-over design. Orthostatic intolerance and selected physiological, perceptual, postural and cognitive responses were assessed. Orthostatic hypotension occurred in 94% of middle-aged adults and 77% of young adults. Young adults exhibited greater dizziness upon standing (young subjects, 3 out of 10 arbitrary units (AU) vs. middle-aged subjects, 2 out of 10 AU), with four terminating the protocol early owing to dizziness or discomfort. Despite middle-aged adults being largely asymptomatic, both age groups had transient impairments in postural sway after immersion (P < 0.05), but no change in cognitive function (P = 0.58). Middle-aged adults reported lower thermal sensation, higher thermal comfort, and higher basic affect than young adults (all P < 0.01). Cooling mitigation trials had 100% completion rates, with improvements in sit-to-stand dizziness (P < 0.01, arms in, 3 out of 10 AU vs. arms out, 2 out of 10 AU vs. fan, 4 out 10 AU), lower thermal sensation (P = 0.04), higher thermal comfort (P < 0.01) and higher basic affect (P = 0.02). Middle-aged adults were predominantly asymptomatic, and cooling strategies prevented severe dizziness and thermal intolerance in younger adults.

Effects of Flywheel Training With Eccentric Overload on Standing Balance, Mobility, Physical Function, Muscle Thickness, and Muscle Quality in Older Adults.

ABSTRACT: Hill, MW, Roberts, M, Price, MJ, and Kay, AD. Effects of flywheel training with eccentric overload on standing balance, mobility, physical function, muscle thickness, and muscle quality in older adults. J Strength Cond Res 36(11): 3190-3199, 2022-This study investigated the effects of a 6-week eccentric overload flywheel training program on vastus lateralis (VL) and gastrocnemius medialis (GM) muscle thickness and muscle quality (echo intensity), mobility (Timed Up and Go [TUG]), physical function (sit-to-stand), and balance (postural sway) performance. Nineteen subjects were assigned to either a flywheel training group ( n = 11, age = 66.4 ± 5.2 years) or a control group ( n = 8, age = 65.9 ± 3.8 years). The flywheel group underwent twice weekly squat and calf raise exercises for 6 weeks with outcome measures assessed before and after training or a time-matched control period. Throughout the training, subjects were instructed to contract as fast as possible with maximal effort during the concentric phase and to maximally resist the pull during the eccentric phase. The alpha value was a priori set at p < 0.05. Statistically significant ( p < 0.05) mean ( SD ) increases in right and left VL (7.6-9.6 ± 7.7-9.8%) and GM (8.6-8.7 ± 6.4-11.5%) muscle thickness and a reduction in VL (10.2-11.3 ± 5.9-7.9%) and GM (11.7-11.9 ± 5.6-9.6%) echo intensity were accompanied by faster TUG time (13.7 ± 7.0%) improved sit-to-stand performance (17.8-23.5 ± 7.6 - 13.4%) and reduced postural sway (29.7-42.3 ± 13.2-24.2%) after 6 weeks of flywheel training. There were no differences in any outcome measures between the treatment and control group at baseline ( p > 0.05). Overall, we observed substantial gains in muscle thickness and muscle quality, in addition to enhanced physical function, balance, and mobility performance among older adults after flywheel training, which may have important implications for preserving the functional capacity of older adults.

Isokinetic eccentric exercise substantially improves mobility, muscle strength and size, but not postural sway metrics in older adults, with limited regression observed following a detraining period.

INTRODUCTION: Eccentric exercise can reverse age-related decreases in muscle strength and mass; however, no data exist describing its effects on postural sway. As the ankle may be more important for postural sway than hip and knee joints, and with older adults prone to periods of inactivity, the effects of two 6-week seated isokinetic eccentric exercise programmes, and an 8-week detraining period, were examined in 27 older adults (67.1 ± 6.0 years). METHODS: Neuromuscular parameters were measured before and after training and detraining periods with subjects assigned to ECC (twice-weekly eccentric-only hip and knee extensor contractions) or ECCPF (identical training with additional eccentric-only plantarflexor contractions) training programmes. RESULTS: Significant (P < 0.05) increases in mobility (decreased timed-up-and-go time [- 7.7 to - 12.0%]), eccentric strength (39.4-58.8%) and vastus lateralis thickness (9.8-9.9%) occurred after both training programmes, with low-to-moderate weekly rate of perceived exertion (3.3-4.5/10) reported. No significant change in any postural sway metric occurred after either training programme. After 8 weeks of detraining, mobility (- 8.2 to - 11.3%), eccentric strength (30.5-50.4%) and vastus lateralis thickness (6.1-7.1%) remained significantly greater than baseline in both groups. CONCLUSION: Despite improvements in functional mobility, muscle strength and size, lower-limb eccentric training targeting hip, knee and ankle extensor muscle groups was not sufficient to influence static balance. Nonetheless, as the beneficial functional and structural adaptations were largely maintained through an 8-week detraining period, these findings have important implications for clinical exercise prescription as the exercise modality, low perceived training intensity, and adaptive profile are well suited to the needs of older adults.

Cardiorespiratory and perceptual responses to self-regulated and imposed submaximal arm-leg ergometry.

PURPOSE: This study compared cardiorespiratory and perceptual responses to exercise using self-regulated and imposed power outputs distributed between the arms and legs. METHODS: Ten males (age 21.7 ± 3.4 years) initially undertook incremental arm-crank ergometry (ACE) and cycle ergometry (CYC) tests to volitional exhaustion to determine peak power output (Wpeak). Two subsequent tests involved 20-min combined arm-leg ergometry (ALE) trials, using imposed and self-regulated protocols, both of which aimed to elicit an exercising heart rate of 160 beats min-1. During the imposed trial, arm and leg intensity were set at 40% of each ergometer-specific Wpeak. During the self-regulated trial, participants were asked to self-regulate cadence and resistance to achieve the target heart rate. Heart rate (HR), oxygen uptake ([Formula: see text]), pulmonary ventilation ([Formula: see text]), and ratings of perceived exertion (RPE) were recorded continuously. RESULTS: As expected, there were no differences between imposed and self-regulated trials for HR, [Formula: see text], and [Formula: see text] (all P ≥ 0.05). However, central RPE and local RPE for the arms were lower during self-regulated compared imposed trials (P ≤ 0.05). Lower RPE during the self-regulated trial was related to preferential adjustments in how the arms (33 ± 5% Wpeak) and legs (46 ± 5% Wpeak) contributed to the exercise intensity. CONCLUSIONS: This study demonstrates that despite similar metabolic and cardiovascular strain elicited by imposed and self-regulated ALE, the latter was perceived to be less strenuous, which is related to participants doing more work with the legs and less work with the arms to achieve the target intensity.

Carrying heavy asymmetrical loads increases postural sway during quiet standing in older adults.

Holding asymmetrical loads in the hands is common during many daily and occupational activities which, depending on the load mass, may alter postural stability. The purpose of this study was to determine the effect of load magnitude held asymmetrically in the hand on postural sway in older people. Eighteen healthy older adults (age 65.9 ± 5.7 years) were assessed in the following conditions; (1) standing without an external load (0%), (2) standing while holding a grocery bag containing 5%, (3) 10% and (4) 20% body mass in the dominant hand. The total displacement of the centre of pressure (COP) in the anteroposterior and mediolateral directions (cm), mean COP velocity (cm s-1) and COP area (cm2) were used to indirectly assess postural sway. The COP area (R 2 = 0.96), anteroposterior (R 2 = 0.85) and mediolateral (R 2 = 0.84) COP displacement increased linearly with additional load. The 20% load condition elicited the greatest increase in postural sway (d = 2.1-3.6) compared to 0%, while the 5% load had no effects on sway (P ≥ 0.05). In contrast, the mean COP velocity decreased by similar amounts when holding a load at 5% (d = 1.6), 10% (d = 1.4) and 20% (d = 1.5) body mass, compared to 0% (all P < 0.001). The slower COP velocity, combined with greater COP displacements may suggest that postural reactions were restricted and/or delayed. From a fall-prevention perspective, it is advised that older people avoid holding asymmetrical external loads greater than 5% of body mass.

The effect of high-intensity cycling training on postural sway during standing under rested and fatigued conditions in healthy young adults.

PURPOSE: The purpose of this study was to investigate whether high-intensity cycling training leads to adapted responses of balance performance in response to exercise-induced muscle fatigue. METHODS: Eighteen healthy adults were assigned to either 3-weeks (n = 8, age 20.1 ± 2.6 years, height 177 ± 5 cm, mass 73.6 ± 5.1 kg) or 6-weeks (n = 10, age 24.3 ± 5.8 years, height 179 ± 6 cm, mass 81.0 ± 15.8 kg) of high-intensity training (HIT) on a cycle ergometer. The centre of pressure (COP) displacement in the anteroposterior (COPAP) direction and COP path length (COPL) were measured before and after the first and final high-intensity training sessions. RESULTS: Pre-training, exercise-induced fatigue elicited an increase in COPAP (3-weeks; p = 0.001, 6-weeks; p = 0.001) and COPL (3-weeks; p = 0.002, 6-weeks; p = 0.001) returning to pre-exercise levels within 10-min of recovery. Following 3-weeks of training, significant increases in COPAP (p = 0.001) and COPL (p = 0.002) were observed post-fatigue, returning to pre-exercise levels after 15-min of recovery. After 6-weeks of training no significant increases in sway (COPAP; p = 0.212, COPL; p = 0.998) were observed following exercise-induced fatigue. CONCLUSIONS: In summary, 3 weeks of HIT resulted in longer recovery times following fatigue compared to pre-training assessments. After 6 weeks of HIT, postural sway following fatigue was attenuated. These results indicate that HIT could be included in injury prevention programmes, however, caution should be taken during early stages of the overreaching process.

The effects of acute arm crank ergometry and cycle ergometry on postural sway and attentional demands during quiet bipedal standing.

Current evidence suggests that acute bouts of lower limb exercise elicits a number of adverse effects on both sensory and motor components of postural control. The effects of acute exercise on quiet standing balance while concurrently performing an attentional task remains equivocal. This study aimed to compare the alterations in postural control and attentional demands elicited by upper and lower limb exercise. Twelve healthy young males (mean ± SD age, 22.2 ± 3.2 years) were examined on six separate occasions. The first two visits determined maximal aerobic fitness on an arm crank ergometer (ACE) and cycle ergometer (CYC). Subsequently, participant's postural sway was assessed during single- (ST) and dual-task (DT) conditions before and immediately after moderate- and high-intensity exercise engaging the upper or lower body musculature. The order of the four exercise tests was counterbalanced. The centre of pressure displacement in the anteroposterior (COPAP) and mediolateral (COPML) directions and the COP path length (COPL) were computed using a force platform. A time × mode interaction was observed for COPAP (ST; p = 0.011, DT; p = 0.018) and COPML (ST; p = 0.001). CYC elicited large (ES; 1.6-2.0) increases in COPAP and COPML, but there were no differences between aerobic and anaerobic tests (p > 0.05). The effect of cognitive load appeared to increase sway in the frontal plane following anaerobic CYC (p = 0.001) but not ACE (p < 0.05). Exercise has different effects on frontal and sagittal plane sway following different cognitive loads. In particular, COPML was increased at the cost of maintaining attentional performance following exercise.

The influence of false interoceptive feedback on emotional state and balance responses to height-induced postural threat.

Postural threat elicits a robust emotional response (e.g., fear and anxiety about falling), with concomitant modifications in balance. Recent theoretical accounts propose that emotional responses to postural threats are manifested, in part, from the conscious monitoring and appraisal of bodily signals ('interoception'). Here, we empirically probe the role of interoception in shaping emotional responses to a postural threat by experimentally manipulating interoceptive cardiac feedback. Sixty young adults completed a single 60-s trial under the following conditions: Ground (no threat) without heart rate (HR) feedback, followed by Threat (standing on the edge of a raised surface), during which participants received either false heart rate feedback (either slow [n = 20] or fast [n = 20] HR feedback) or no feedback (n = 20). Participants provided with false fast HR feedback during postural threat felt more fearful, reported feeling less stable, and rated the task more difficult than participants who did not receive HR feedback, or those who received false slow HR feedback (Cohen's d effect size = 0.79 - 1.78). However, behavioural responses did not significantly differ across the three groups. When compared to the no HR feedback group, false slow HR feedback did not significantly affect emotional or behavioural responses to the postural threat. These observations provide the first experimental evidence for emerging theoretical accounts describing the role of interoception in the generation of emotional responses to postural threats.

Effect of low versus high balance training complexity on balance performance in male adolescents.

OBJECTIVE: The current study aimed to determine the effects of low (i.e., balance task only) versus high (i.e., balance task combined with an additional motor task like dribbling a basketball) balance training complexity (6 weeks of training consisting of 2 × 30 min balance exercises per week) on measures of static and dynamic balance in 44 healthy male adolescents (mean age: 13.3 ± 1.6 years). RESULTS: Irrespective of balance training complexity, significant medium- to large-sized pretest to posttest improvements were detected for static (i.e., One-Legged Stance test, stance time [s], 0.001 < p ≤ 0.008) and dynamic (i.e., 3-m Beam Walking Backward test, steps [n], 0.001 < p ≤ 0.002; Y-Balance-Test-Lower-Quarter, reach distance [cm], 0.001 < p ≤ 0.003) balance performance. Further, in all but one comparison (i.e., stance time with eyes opened on foam ground) no group × test interactions were found. These results imply that balance training is effective to improve static and dynamic measures of balance in healthy male adolescents, but the effectiveness seems unaffected by the applied level of balance training complexity.

Time-course of balance training-related changes on static and dynamic balance performance in healthy children.

OBJECTIVE: In healthy children, there is evidence of improvements in static and dynamic balance performance following balance training. However, the time-course of balance training-related changes is unknown. Thus, we determined the effects of balance training after one, three, and six weeks of exercise on measures of static and dynamic balance in healthy children (N = 44, 20 females, mean age: 9.6 ± 0.5 years, age range: 9-11 years). RESULTS: Participants in the intervention group (2 × 25 min balance exercises per week) compared to those in the control group (2 × 25 min track and field exercises and soccer practice per week) significantly improved their static (i.e., by measuring stance time in the One-Legged Stance test) and dynamic (i.e., by counting step number in the 3-m Beam Walking Backward test) balance performance. Late effects (after 6 weeks) occurred most frequently followed by mid-term effects (after 3 weeks) and then early effects (after 1 week). These findings imply that balance training is effective to improve static and dynamic measures of balance in healthy children, whereby the effectiveness increases with increasing training period. TRIAL REGISTRATION: Current Controlled Trials ISRCTN16518737 (retrospectively registered at 24th August, 2023).

Exploring how arm movement moderates the effect of lower limb muscle fatigue on dynamic balance in healthy youth.

Background: In young adults, there is evidence that free arm movements do not help to compensate muscle fatigue-induced deteriorations in dynamic balance performance. However, the postural control system in youth is immature, and as a result, the use of arm movements may provide a compensatory "upper body strategy" to correct fatigue-related balance impairments. Thus, the purpose of the present study was to compare the effects of free vs. restricted arm movement on dynamic balance performance prior and following exercise-induced muscle fatigue. Methods: Forty-three healthy youth (19 females; mean age: 12.8 ± 1.9 years) performed the Y Balance Test-Lower Quarter before and immediately after a fatiguing exercise (i.e., repetitive vertical bipedal box jumps until failure) using two different arm positions: free (move the arms freely) and restricted (keep the arms akimbo) arm movement. Results: Muscle fatigue (p ≤ 0.033; 0.10 ≤ η p 2 ≤ 0.33) and restriction of arm movement (p ≤ 0.005; 0.17 ≤ η p 2 ≤ 0.46) resulted in significantly deteriorated dynamic balance performance. However, the interactions between the two did not reach the level of significance (p ≥ 0.091; 0.01 ≤ η p 2 ≤ 0.07). Conclusion: Our findings indicate that the use of an "upper body strategy" (i.e., free arm position) has no compensatory effect on muscle fatigue-induced dynamic balance deteriorations in healthy youth.

Influence of lower-limb muscular and tendon mechanical properties and strength on countermovement jump performance.

BACKGROUND: The aim of the study is to examine the relationship between measures of muscle and tendon mechanical properties and strength on countermovement jump (CMJ) performance. METHODS: Twenty-six physically active participants (males; N.=16: females; N.=10) were tested. Testing comprised of measuring the mechanical properties of lower limb muscles and tendons using myotonometry, isometric and isokinetic knee extensor strength through dynamometry, and CMJ's with a force platform. RESULTS: Large positive correlations were observed between CMJ jump height and Achilles tendon stiffness (N/m) (r=0.56) and Achilles tendon tone (Hz) (r=0.553). Large negative correlations were found between CMJ height and Achilles tendon elasticity (r=-0.658), and Achilles tendon relaxation (r=-0.572), and Achilles tendon creep (r=-0.589). Large correlations (r=0.592 to 0.659) were observed between CMJ height and all measures of isometric and isokinetic dynamometry measures. Achilles tendon stiffness, elasticity level and relaxation, and isokinetic peak concentric torque (N.m) explained 63% of this variance. CONCLUSIONS: Greater stiffness of the Achilles tendon may improve CMJ performance due to the improved transfer of concentric and eccentric force of the knee extensor muscles. Practitioners need to implement specific interventions to target increasing Achilles tendon stiffness to improve countermovement jump performance.

Effects of Eccentric Resistance Training on Lower-Limb Passive Joint Range of Motion: A Systematic Review and Meta-analysis.

INTRODUCTION: Substantial increases in joint range of motion (ROM) have been reported after eccentric resistance training; however, between-study variability and sample size issues complicate the interpretation of the magnitude of effect. METHODS: PubMed, Medline, and SPORTDiscus databases were searched for studies examining the effects of eccentric training on lower-limb passive joint ROM in healthy human participants. Meta-analysis used an inverse-variance random-effects model to calculate the pooled standardized difference (Hedge's g ) with 95% confidence intervals. RESULTS: Meta-analysis of 22 ROM outcomes (17 studies, 376 participants) revealed a large increase in lower-limb passive joint ROM ( g = 0.86 (95% confidence intervals, 0.65-1.08)). Subgroup analyses revealed a moderate increase after 4-5 wk ( g = 0.63 (0.27-0.98)), large increase after 6-8 wk ( g = 0.98 (0.73-1.24)), and moderate increase after 9-14 wk ( g = 0.75 (0.03, 1.46)) of training. Large increases were found in dorsiflexion ( g = 1.12 (0.78-1.47)) and knee extension ( g = 0.82 (0.48-1.17)), but a small increase in knee flexion was observed ( g = 0.41 (0.05-0.77)). A large increase was found after isokinetic ( g = 1.07 (0.59-1.54)) and moderate increase after isotonic ( g = 0.77 (0.56-0.99)) training. CONCLUSIONS: These findings demonstrate the potential of eccentric training as an effective flexibility training intervention and provide evidence for "best practice" guidelines. The larger effect after isokinetic training despite <50% training sessions being performed is suggestive of a more effective exercise mode, although further research is needed to determine the influence of contraction intensity and to confirm the efficacy of eccentric training in clinical populations.

Exploring the relationship of static and dynamic balance with muscle mechanical properties of the lower limbs in healthy young adults.

There is emerging evidence that mechanical properties of in vivo muscle tissues are associated with postural sway during quiet standing. However, it is unknown if the observed relationship between mechanical properties with static balance parameters generalise to dynamic balance. Thus, we determined the relationship between static and dynamic balance parameters with muscle mechanical properties of the ankle plantar flexors [lateral gastrocnemius (GL)] and knee extensors [vastus lateralis (VL)] in vivo. Twenty-six participants (men = 16, women = 10; age = 23.3 ± 4.4 years) were assessed for static balance [centre of pressure (COP) movements during quiet standing], dynamic balance (reach distances for the Y-balance test) and mechanical properties (stiffness and tone) of the GL and VL measured in the standing and lying position. Significant (p < .05) small to moderate inverse correlations were observed between the mean COP velocity during quiet standing with stiffness (r = -.40 to -.58, p = .002 to .042) and tone (r = -0.42 to -0.56, p = 0.003 to 0.036) of the GL and VL (lying and standing). Tone and stiffness explained 16%-33% of the variance in the mean COP velocity. Stiffness and tone of the VL measured in the lying (supine) condition were also inversely significantly correlated with Y balance test performance (r = -0.39 to -0.46, p = 0.018 to 0.049). These findings highlight that individuals with low muscle stiffness and tone exhibit faster COP movements during quiet standing, indicative of reduced postural control but also reveal that low VL stiffness and tone are associated with greater reach distances in a lower extremity reaching task, indicative of greater neuromuscular performance.

Effect of arm movement on balance performance in children: role of expertise in gymnastics.

OBJECTIVE: Studies have shown that balance performance is better in gymnasts compared to age-/sex-matched controls and further studies revealed superior performance when arms were free to move during assessment of balance. However, it is unknown whether free arm movement during balance testing differentially affects balance performance with respect to sports expertise (i.e., gymnasts are less affected than age-/sex-matched controls). Therefore, we investigated the effect of arm movement on balance performance in young female gymnasts compared to age-/sex-matched controls while performing balance tasks with various difficulty levels. RESULTS: In both samples, balance performance (except for the timed one-legged stance) was significantly better during free compared to restricted arm movement conditions and this was especially observed in the highest task difficulty condition of the 3-m beam walking backward test. These findings revealed that balance performance is positively affected by free arm movements, but this does not seem to be additionally influenced by the achieved expertise level in young gymnasts.

Effect of arm movement and task difficulty level on balance performance in healthy children: are there sex differences?

OBJECTIVE: In children, studies have shown that balance performance is worse in boys compared to girls and further studies revealed inferior performance when arm movement was restricted during balance assessment. However, it remains unclear whether restriction of arm movement during balance testing differentially affects children's balance performance (i.e., boys more than girls). Thus, we compared the influence of arm movement on balance performance in healthy boys versus girls (mean age: ~ 11.5 years) while performing balance tasks with various difficulty level. RESULTS: In nearly all tests, balance performance (i.e., timed one-legged stance, 3-m beam walking backward step number, Lower Quarter Y-Balance test reach distance) was significantly worse during restricted compared to free arm movement but without any differences between sexes or varying levels of task difficulty. These findings indicated that balance performance is negatively affected by restriction of arm movement, but this does not seem to be additionally influenced by children's sex and the level of task difficulty.

Altered mitochondrial microenvironment at the spotlight of musculoskeletal aging and Alzheimer's disease.

Emerging evidence has linked Alzheimer's disease (AD) onset with musculoskeletal aging via a muscle-brain crosstalk mediated by dysregulation of the mitochondrial microenvironment. This study investigated gene expression profiles from skeletal muscle tissues of older healthy adults to identify potential gene biomarkers whose dysregulated expression and protein interactome were involved in AD. Screening of the literature resulted in 12 relevant microarray datasets (GSE25941, GSE28392, GSE28422, GSE47881, GSE47969, GSE59880) in musculoskeletal aging and (GSE4757, GSE5281, GSE16759, GSE28146, GSE48350, GSE84422) in AD. Retrieved differentially expressed genes (DEGs) were used to construct two unique protein-protein interaction networks and clustering gene modules were identified. Overlapping module DEGs in the musculoskeletal aging and AD networks were ranked based on 11 topological algorithms and the five highest-ranked ones were considered as hub genes. The analysis revealed that the dysregulated expression of the mitochondrial microenvironment genes, NDUFAB1, UQCRC1, UQCRFS1, NDUFS3, and MRPL15, overlapped between both musculoskeletal aging and AD networks. Thus, these genes may have a potential role as markers of AD occurrence in musculoskeletal aging. Human studies are warranted to evaluate the functional role and prognostic value of these genes in aging populations with sarcopenia and AD.

Effect of Arm Movement and Task Difficulty on Balance Performance in Children, Adolescents, and Young Adults.

Background: Studies have shown that restricted compared to free arm movement negatively affects balance performance during balance assessment and this is reinforced when the level of task difficulty (e.g., varying stance/walk conditions, sensory manipulations) is increased. However, it remains unclear whether these findings apply to individuals with differences in the development of the postural control system. Thus, we examined the influence of arm movement and task difficulty on balance performance in children, adolescents, and young adults. Methods: Static, dynamic, and proactive balance performance were assessed in 40 children (11.5 ± 0.6 years), 30 adolescents (14.0 ± 1.1 years), and 41 young adults (24.7 ± 3.0 years) using the same standardized balance tests [i.e., one-legged stance (OLS) time with eyes opened/closed and/or on firm/foam ground, 3-m beam (width: 6, 4.5, or 3 cm) walking backward step number, Lower Quarter Y-Balance test (YBT-LQ) reach distance] with various difficulty levels under free vs. restricted arm movement conditions. Results: In all but one test, balance performance was significantly better during free compared to restricted arm movement. Arm by age interactions were only observed for the YBT-LQ and post hoc analyses revealed significantly greater performance differences between free and restricted arm movement, especially, in young adults. Arm by age by task difficulty interactions were found for the OLS and the 3-m beam walking backward test. Post hoc analyses showed significantly greater performance differences between free and restricted arm movement during high vs. low levels of task difficulty and this was more pronounced in children and adolescents. Conclusions: Regardless of age, static, dynamic, and proactive balance performance benefited from arm movements and this was especially noted for youth performing difficult balance tasks.