Exercise Training to Target Gait Unsteadiness in People with Diabetes

Balance impairment and an associated high fall rate in people with diabetes is common, and a huge burden to quality of life and healthcare systems. Causes of impaired balance are commonly attributed to both sensory and motor deficits, which includes impaired muscle strength and function. This study investigated the effects of resistance exercise training on balance control during walking over level ground and on stairs. Ten DM people (age: 62 years, BMI: 29kg/m2, VPT: 9V) and 6 DM people with DPN (age: 59 years, BMI: 27kg/m2, VPT: 31V) performed a 16-week intervention of weekly resistance exercise training to increase ankle and knee extensor muscle strength. Six DM controls did not take part in the intervention (age: 50 years, BMI: 26kg/m2, VPT: 12V). Balance during gait was quantified before and after the intervention, by separation between the body centre-of-mass and centre-of-pressure under the feet during both level and stair walking. Knee and ankle extensor muscle strength was assessed using a dynamometer. The exercise intervention increased strength of ankle plantar flexors (22%) and knee extensors (30%). Despite the increases in lower limb muscle strength produced by the intervention, no improvements in balance were seen post training. However, gait speed did increase by 8%, which previous research has shown to be associated with quality of life. Controls showed no training effects in any variables. Although this exercise intervention had a positive effect on gait by increasing walking speed, there was no effect on the control of balance. Previous research has identified that medio-lateral (side-to-side) balance is impaired in people with DPN. The muscles exercised in the present study mainly control the major sagittal plane (forwards-backwards) movements that occur during gait. Interventions targeting the lateral stabilising muscles of the hip and trunk, may show greater potential efficacy in redressing the balance impairment of this population

Muscle activation capacity: effects of method, stimuli number and joint angle

To assess the sensitivity of existing measurement methods for muscle activation capacity to potential errors introduced by a) evoking inadequate force by stimulation and b) neglecting differences in series elasticity between conditions, the effect of different number of stimuli and joint angle on the interpolation twitch interpolation technique [ITT = (1- superimposed stimulus torque / resting stimulus torque) x 100] and central activation ratio (CAR = maximal voluntary contraction torque / maximal voluntary contraction torque + superimposed stimulus torque) was examined. Ten subjects performed knee extension maximal voluntary contractions at 30 and 90o knee flexion angles (0o is full knee extension). Singlets, doublets, quadruplets and octuplets of supramaximal intensity were applied via percutaneous quadriceps muscle stimulation at rest and during the plateau phase of the contraction. A mixed-design 2 x 2 x 4 repeated factorial ANOVA was used to examine for differences in activation capacity between methods, knee joint angles and stimuli number, and simple effects tests were used for post hoc analysis where appropriate. Joint angle had a significant effect (P 0.05). It is, therefore, suggested that in the quantification of voluntary drive during contraction with the ITT and CAR methods, consideration be given not only to the number of stimuli applied but also to the effect of series elasticity due to joint angle differences, since these factors may affect differently the outcome of the calculation, depending on the approach followed

Skeletal muscle remodeling in response to eccentric vs. concentric loading: morphological, molecular, and metabolic adaptations

Skeletal muscle contracts either by shortening or lengthening (concentrically or eccentrically, respectively); however, the two contractions substantially differ from one another in terms of mechanisms of force generation, maximum force production and energy cost. It is generally known that eccentric action s generate greater force than isometric and concentric contractions and at a lower metabolic cost. Hence, by virtue of the greater mechanical loading involved in active lengthening, eccentric resistance training (ECC RT) is assumed to produce greater hypertrophy than concentric resistance training (CON RT). Nonetheless, prevalence of either ECC RT or CON RT in inducing gains in muscle mass is still an open issue, with some studies reporting greater hypertrophy with eccentric, some with concentric and some with similar hypertrophy within both training modes. Recent observations suggest that such hypertrophic responses to lengthening vs. shortening contractions are achieved by different adaptations in muscle architecture. Whilst the changes in muscle protein synthesis in response to acute and chronic concentric and eccentric exercise bouts seem very similar, the molecular mechanisms regulating the myogenic adaptations to the two distinct loading stimuli are still incompletely understood. Thus, the present review aims to, (a) critically discuss the literature on the contribution of eccentric vs. concentric loading to muscular hypertrophy and structural remodeling, and, (b) clarify the molecular mechanisms that may regulate such adaptations. We conclude that, when matched for either maximum load or work, similar increase in muscle size is found between ECC and CON RT. However, such hypertrophic changes appear to be achieved through distinct structural adaptations, which may be regulated by different myogenic and molecular responses observed between lengthening and shortening contractions

In vivo measurements of muscle specific tension in adults and children

This article is available open access through the publisher’s website at the link below. Copyright @ 2009 The Authors.To better understand the effects of pubertal maturation on the contractile properties of skeletal muscle in vivo, the present study investigated whether there are any differences in the specific tension of the quadriceps muscle in 20 adults and 20 prepubertal children of both sexes. Specific tension was calculated as the ratio between the quadriceps tendon force and the sum of the physiological cross-sectional area (PCSA) multiplied by the cosine of the angle of pennation of each head within the quadriceps muscle. The maximal quadriceps tendon force was calculated from the knee extension maximal voluntary contraction (MVC) by accounting for EMG-based estimates of antagonist co-activation, incomplete quadriceps activation using the interpolation twitch technique and magnetic resonance imaging (MRI)-based measurements of the patellar tendon moment arm. The PCSA was calculated as the muscle volume, measured from MRI scans, divided by optimal fascicle length, measured from ultrasound images during MVC at the estimated angle of peak quadriceps muscle force. It was found that the quadriceps tendon force and PCSA of men (11.4 kN, 214 cm2) were significantly greater than those of the women (8.7 kN, 152 cm2; P 0.05) between groups: men, 55 ± 11 N cm−2; women, 57.3 ± 13 N cm−2; boys, 54 ± 14 N cm−2; and girls, 59.8 ± 15 N cm−2. These findings indicate that the increased muscle strength with maturation is not due to an increase in the specific tension of muscle; instead, it can be attributed to increases in muscle size, moment arm length and voluntary activation level

In vivo human tendon mechanical properties: effect of resistance training in old age

Recent advances in ultrasound scanning have made it possible to obtain the mechanical properties of human tendons in vivo. Application of the in vivo method in elderly individuals showed that their patellar tendons stiffened in response to a 14- week resistance training program by ~65% both structurally and materially. The rate of muscle torque development increased by ~27%, indicating faster contractile force transmission to the skeleton. The present findings suggest that strength training in old age can at least partly reverse the deteriorating effect of ageing on tendon properties and function

Can we achieve biomimetic electrospun scaffolds with gelatin alone?

Introduction: Gelatin is a natural polymer commonly used in biomedical applications in combination with other materials due to its high biocompatibility, biodegradability, and similarity to collagen, principal protein of the extracellular matrix (ECM). The aim of this study was to evaluate the suitability of gelatin as the sole material to manufacture tissue engineering scaffolds by electrospinning.Methods: Gelatin was electrospun in nine different concentrations onto a rotating collector and the resulting scaffold’s mechanical properties, morphology and topography were assessed using mechanical testing, scanning electron microscopy and white light interferometry, respectively. After characterizing the scaffolds, the effects of the concentration of the solvents and crosslinking agent were statistically evaluated with multivariate analysis of variance and linear regressions.Results: Fiber diameter and inter-fiber separation increased significantly when the concentration of the solvents, acetic acid (HAc) and dimethyl sulfoxide (DMSO), increased. The roughness of the scaffolds decreased as the concentration of dimethyl sulfoxide increased. The mechanical properties were significantly affected by the DMSO concentration. Immersed crosslinked scaffolds did not degrade until day 28. The manufactured gelatin-based electrospun scaffolds presented comparable mechanical properties to many human tissues such as trabecular bone, gingiva, nasal periosteum, oesophagus and liver tissue.Discussion: This study revealed for the first time that biomimetic electrospun scaffolds with gelatin alone can be produced for a significant number of human tissues by appropriately setting up the levels of factors and their interactions. These findings also extend statistical relationships to a form that would be an excellent starting point for future research that could optimize factors and interactions using both traditional statistics and machine learning techniques to further develop specific human tissue

Neuropathy-Related Unsteadiness and Psychosocial Outcomes in Diabetes—Preliminary Findings

Diabetes is a well-established risk factor for psychological distress and reduced quality of life (QoL). This may be part due to biomechanical challenges posed by diabetic peripheral neuropathy (DPN)-related unsteadiness leading to increased risk of falling and reduced physical activity (PA). This cross-sectional study explores relationships between physical (DPN-unsteadiness and PA) and psychosocial outcomes (depression, fear of falling [FoF], and QoL). The preliminary results of 15 type 2 DM people with DPN (age: 67 years; 13M; VPT 24V) indicate that quality of life (NeuroQoL) and depression (Hospital Anxiety and Depression Scale) are strongly associated with objective DPN-unsteadiness (Berg Balance test: r=-.64, p=.01 and r=.63, p=.01; respectively) and FoF (Falls Self-Efficacy Scale: r=.61, p=.02 and r=-.55 p=.03; respectively). Moreover, DPN-unsteadiness (Berg balance score: 47 ±6) and FoF are associated with reduced vigorous exercise PA levels (r=.53, p=.04 and r=-.51, p=.05; respectively), as well as total moderate PA levels (r=-.45, p=.09 and r=.45, p=.09; respectively); measured by General Practice Assessment Questionnaire. Finally, FoF correlates strongly with DPN-unsteadiness (r=-0.79, p<0.001), demonstrating a potential reason why balance impairment may have the negative impact upon PA and QoL. Whilst prospective data are needed to solidify these findings, the preliminary results are robust and support the strong links between the biomechanical impact of DPN and psychosocial outcomes, including depression and fear of falling, and reduced QoL. These data indicate that there is an unmet need for the development of multifaceted interventions that address both psychological distress and biomechanical challenges experienced by patients with this debilitating complication of diabetes

Associations between long-term exercise participation and lower limb joint and whole-bone geometry in young and older adults

Introduction: Features of lower limb bone geometry are associated with movement kinematics and clinical outcomes including fractures and osteoarthritis. Therefore, it is important to identify their determinants. Lower limb geometry changes dramatically during development, partly due to adaptation to the forces experienced during physical activity. However, the effects of adulthood physical activity on lower limb geometry, and subsequent associations with muscle function are relatively unexplored. Methods: 43 adult males were recruited; 10 young (20–35 years) trained i.e., regional to world-class athletes, 12 young sedentary, 10 older (60–75 years) trained and 11 older sedentary. Skeletal hip and lower limb geometry including acetabular coverage and version angle, total and regional femoral torsion, femoral and tibial lateral and frontal bowing, and frontal plane lower limb alignment were assessed using magnetic resonance imaging. Muscle function was assessed recording peak power and force of jumping and hopping using mechanography. Associations between age, training status and geometry were assessed using multiple linear regression, whilst associations between geometry and muscle function were assessed by linear mixed effects models with adjustment for age and training. Results: Trained individuals had 2° (95% CI:0.6°–3.8°; p = 0.009) higher femoral frontal bowing and older individuals had 2.2° (95% CI:0.8°–3.7°; p = 0.005) greater lateral bowing. An age-by-training interaction indicated 4° (95% CI:1.4°–7.1°; p = 0.005) greater acetabular version angle in younger trained individuals only. Lower limb geometry was not associated with muscle function (p > 0.05). Discussion: The ability to alter skeletal geometry via exercise in adulthood appears limited, especially in epiphyseal regions. Furthermore, lower limb geometry does not appear to be associated with muscle function

Muscular adaptations to resistance exercise in the elderly

Neuropathic, metabolic, hormonal, nutritional and immunologic factors contribute to the development of sarcopenia. This loss of muscle mass associated with ageing, is a main cause of muscle weakness, but the loss of muscle strength typically exceeds that of muscle size, with a resulting decrease in force per unit of muscle cross-sectional area. Recent evidence suggests that, in addition to a reduction in neural drive and in fibre specific tension, changes in muscle architecture contribute significantly to the loss of muscle force through alterations in muscle mechanical properties. Older muscle, however, maintains a high degree of plasticity in response to increased loading since considerable hypertrophy and a reversal of the alterations in muscle architecture associated with ageing are observed with resistive training