Dinesh Samuel

Quadriceps muscle tone, elasticity and stiffness in older males: Reliability and symmetry using the MyotonPRO

BACKGROUND The MyotonPRO (Myoton Ltd; London) is a new portable device for measuring muscle mechanical properties (e.g. tone) and its reliability has yet to be established. Little is known about between-limb symmetry of mechanical properties in healthy older people, despite symmetry often being used as a measure of unilateral abnormalities in clinical assessment. Since quadriceps is important for mobility, it was selected for the present study. AIMS To investigate: (i) between-day intra-rater reliability of a novice user of MyotonPRO; (ii) between-side symmetry of mechanical properties of quadriceps in older males. METHODS Twenty healthy, community dwelling, right-lower-limb-dominant males (mean age 71.7, range 65-82 years) were studied. With the participant in relaxed supine lying, the MyotonPRO applied two consecutive sets of 10 taps to induce muscle oscillations of rectus femoris, from which measurements of decrement (elasticity), frequency (tone), and stiffness were obtained. Tests were performed on two occasions at the same time and day of the week, one week apart. RESULTS Repeated measurements had very high within-day (intraclass correlation coefficient, ICC 3,1>0.90) and high between-day (ICC 3,2>0.70; mean of two measurement sets) reliability. There was no statistically significant difference between muscle mechanical properties of the dominant and non-dominant muscles (<2.5% difference; p>0.05), thereby indicating symmetry. CONCLUSIONS High intra-rater reliability was established for MyotonPRO measurements of quadriceps in healthy older males, which were symmetrical between sides. These findings indicate that larger studies are warranted to establish normal reference ranges of data with which to compare patients with muscle abnormalities.

The biomechanical functional demand placed on knee and hip muscles of older adults during stair ascent and descent

Age-related decline in physical capabilities may lead to older adults experiencing difficulty in performing everyday activities due to high demands placed on the muscles of their lower extremity. This study aimed to determine the biomechanical functional demand in terms of joint moments and maximal muscle capabilities at the knee and hip joints while older adults performed stair ascent (SA) and stair descent (SD). Eighty-four healthy older adults aged 60-88 years were tested. A torque dynamometer attached to a purpose-built plinth was utilized to measure muscle moments at the knee and hip joints. Participants also underwent full body 3-D biomechanical assessment of stair ascent and descent using an 8-camera VICON system (120Hz) with 3 Kistler force plates. Stair negotiation required knee extensor moments in excess of the maximum isometric muscle strength available (SA 103%, SD 120%). For the hip, the levels of demand were high, but were slightly lower than those of the knee joint. Stair negotiation placed a high level of demand on the knee extensors with demand in SA reaching maximal isometric capacity and demand in SD exceeding maximal isometric capacity. The levels of demand leave little reserve capacity for the older adult to draw on in unexpected situations or circumstances.

Effect of ageing on isometric strength through joint range at knee and hip joints in three age groups of older adults.

Background: Strength of lower extremity muscles is an important determinant of mobility-based functional activities. Loss of strength with age produces functional limitation in activities of daily living such as rising from a chair or stair negotiation. However, there is limited information on the effect of age-related changes on the torque-producing ability of muscles through their ranges of joint motion. Objective: To investigate the effect of ageing on the torque-producing ability of lower extremity muscles in a large sample of older adults in three age groups. Methods: Eighty-two volunteers participated in this study and were divided into six groups according to their chronological age (60s, 70s and 80s and above) and gender (male, female). Isometric muscle strength was measured at the knee and hip joints at three positions through the joint range using a custom-built strain gauge torque dynamometer and a purpose built plinth. Results: The peak torque of major muscle groups of the knee and hip joints decreased with increasing age at all the three joint positions at which strength was tested. The 80-year-olds had 20% lower strength compared to the 60-year-olds. Age-related decrease in muscle strength was significant when comparing 80-year-olds with the 60-year-olds (p < 0.05). Strength loss was noted to be higher at the inner (muscle is shortened from mid-position) and outer (muscle is lengthened from mid-position) ranges of muscle action when compared with the mid-range position (mid-position). Gender-based differences were significant for all the strength tests (p < 0.05). Conclusions: Strength decreased with increasing age at all the positions within joint range of motion for knee and hip joints. However, the percentage loss of muscle strength was different at different positions in the joint range. Our findings suggest that muscle strength was more preserved in the middle range of muscle function compared to the inner and outer range of muscle action. In older people, lower extremity muscles might be required to produce higher moments in joint positions that are not within the optimum mid-position for muscle action.

Towards a design tool for visualizing the functional demand placed on older adults by everyday living tasks

This paper discusses the development of a design tool using data calculated from the biomechanical functional demand on joints in older adults during activities of daily living, portrayed using a visual ‘traffic-light’ system. Whole body movements of 84 older adults were analysed using a 3D motion capture system and reaction forces were measured by force platforms, and translated into a 3D software model. Although originally intended as a tool for designers, the early evaluation of this method of visualizing the data suggests that it may be of value across those involved in the professional care of older adults.

Age-associated changes in hand grip and quadriceps muscle strength ratios in healthy adults

Background and aims: Muscle strength may decline with age differentially in the upper and lower limbs. This information is difficult to capture through a single measure. The present study therefore aimed to characterize the relative changes in handgrip and lower limb muscle strength with aging by expressing them as a ratio. Methods: Thirty-eight healthy volunteers aged 20–82 years performed maximal voluntary contractions (MVC) of quadriceps and handgrip using a custombuilt transducer and a Jamar dynamometer respectively. Results: The grip-quadriceps ratios for young adults was similar in males and females (0.75); indicating knee extensor force exceeded grip force by approximately 25%. Ratios were increased in older adults (p=0.05), and strength of the two muscle groups was approximately equal (1.1). Pearson’s correlation coefficients for grip against quadriceps strength were r=0.63 (young males), r=0.83 (young females), r=0.35 (older males) and r=0.05 (older females). Conclusions: The ratio used demonstrated clear differences between the age groups. The reduced muscle strength with increasing age was expected, but the higher grip/quadriceps strength ratios quantify a greater loss of quadriceps than grip strength with aging. It remains to be investigated whether the relatively greater rate of decline in quadriceps strength seen in healthy older people is more exaggerated in those who are frail, which would have implications for using grip strength as a physical marker of lower limb strength and function in those at risk of immobility and falls.

Parameters Representing Muscle Tone, Elasticity and Stiffness of Biceps Brachii in Healthy Older Males: Symmetry and Within-Session ReliabilityUsing the MyotonPRO

Background: Clinical assessments of muscle tone are subjective, often using the non-affected side for comparison. The MyotonPRO offers portable, non-invasive, objective measurement of mechanical properties of muscles. Objective: This study aimed to investigate between-limb symmetry for mechanical properties of biceps brachii (BB) in older males and within-session intra-rater reliability of a novice user of the MyotonPRO device. Methods: Twenty community-dwelling, right-handed males aged 65-85 years (mean 71.7; SD ± 4.9) were studied. Exclusion criteria: history of neurological and musculoskeletal conditions, medications affecting muscle tone, and body mass index >30 kg/m2. The device applied 10 mechanical impulses at one second intervals, producing damped oscillations, from which frequency (non-neural tone), stiffness and logarithmic decrement (elasticity) were measured. With the participant resting supine, two consecutive sets of 10 recordings were taken bilaterally from BB. Results: Percentage mean differences between-sides for larger and smaller values were 12% (tone), 14% (stiffness) and 27% (elasticity), which were statistically significant (p<0.001). Within-session reliability was excellent for all three parameters (ICC 3,2: all 0.99). Bland and Altman plots confirmed good agreement, without bias. Conclusion: Symmetry of BB mechanical properties in a group of older males was less than 15% for tone and stiffness but not elasticity. Within-session intra-rater reliability of a novice user was excellent for all three parameters. Reliability over different days needs to be investigated. These findings indicate potential clinical application of the MyotonPRO for assessing abnormalities of muscle parameters in patients with neurological or musculoskeletal conditions, using comparison with the contralateral side (absolute difference), as well as databases of normative reference values from healthy control groups of different ages, gender and activity levels.

Measurement of ageing effects on muscle tone and mechanical properties of rectus femoris and biceps brachii in healthy males and females using a novel hand-held myometric device

BACKGROUND Age and gender effects on muscle tone and mechanical properties have not been studied using hand-held myometric technology. Monitoring changes in muscle properties with ageing in community settings may provide a valuable assessment tool for detecting those at risk of premature decline and sarcopenia. OBJECTIVE This study aimed to provide objective data on the effects of ageing and gender on muscle tone and mechanical properties of quadriceps (rectus femoris) and biceps brachii muscles. METHODS In a comparative study of 123 healthy males and females (aged 18-90 years; n=61 aged 18-35; n=62 aged 65-90) muscle tone, elasticity and stiffness were measured using the MyotonPRO device. RESULTS Stiffness was greater and elasticity lower in older adults for BB and RF (p<0.001). Tone was significantly greater in older adults for BB but not for RF when data for males and females were combined (p=0.28). There were no gender differences for BB in either age group. In RF, males had greater stiffness (young males 292 vs females 233 N/m; older males 328 vs females 311 N/m) and tone (young 16.4 vs 13.6 Hz; older 16.7 vs 14.9 Hz). Elasticity in RF was lower in young males than females but did not differ between the older groups (both males and females log decrement 1.6). CONCLUSIONS Stiffness and tone increased with ageing and elasticity decreased. These findings have implications for detecting frailty using a novel biomarker. Age and gender differences are important to consider when assessing effects of pathological conditions on muscle properties in older people.

The functional demand (FD) placed on the knee and hip of older adults during everyday activities

Age-related decline in physical capacity and diminishing physiological reserves may increase the demand placed on lower extremity joints during everyday activities. This study aimed to characterize the FD at the knee and hip joints of older adults during various mobility activities. Eighty-four healthy participants (60-88 years) performed strength tests using a custom-built dynamometer. Biomechanical assessment of gait, chair rise (CR) and sit-down (CSt), stair ascent (SA) and descent (SD) was performed using an 8-camera VICON system (120Hz) and Kistler force plates. Comparisons between groups (60s, 70s and 80s) were made using ANOVA. The FD was defined as the muscle moment generated during a task, divided by the maximum isometric strength (expressed as a percentage). FD was higher in the 80s age group compared to those in the 60s. The demand on hip and knee extensors was normally higher than those of flexors across all the activities. The knee extensor demand during gait (101%), SA (103%) and SD (120%), and hip extensor demand during gait (127%) were high requiring moments in excess of the maximum isometric muscle strength available at these joints. FD during CR and CSt was comparatively lower with knee extensor demands of 73% and 69% and hip extensor demands of 88% and 51%, respectively. Gait, SA and SD placed high demands on the knee extensors while hip extensor demand was high for gait, CR, CSt and SA. The levels of demand leave little reserve capacity for the older adult to draw on in unexpected circumstances.

Validity of measuring distal vastus medialis muscle using rehabilitative ultrasound imaging versus magnetic resonance imaging

UNLABELLED Objective quantification of muscle size can aid clinical assessment when treating musculoskeletal conditions. To date the gold standard of measuring muscle morphology is magnetic resonance imaging (MRI). However, theres a growing body of evidence validating rehabilitative ultrasound imaging (RUSI) against MRI. OBJECTIVE This study aimed to validate RUSI against MRI for the linear measurements of the distal fibres of vastus medialis muscle in the thigh. Twelve healthy male participants were recruited from a local university population. The distal portion of their right vastus medialis was imaged with the participant in long-sitting, using MRI and RUSI whilst the leg was in extension and neutral hip rotation. Cross sectional area (CSA) and three linear measures were taken from the MRI and these were compared with the same linear measures from RUSI. Statistical analysis included comparison of MRI and RUSI measures using the paired t-test and intra-class correlation coefficients (ICC 3,1). Mean differences between the linear measures taken from the MRI and RUSI were -0.5 mm to 2.9 mm (95% confidence intervals -0.6-8.3 mm), which were not statistically different (p > 0.05) and were highly correlated (ICCs 3,1 0.84-0.94). Correlations between the three linear measurements and muscle CSA ranged from r = 0.23 to 0.87, the greatest being muscle thickness. Multiplying the linear measures did not improve the correlation of 0.87 found for muscle thickness. Linear measures of vastus medialis depth made using RUSI were shown to be as valid as using MRI. Muscle thickness measures using RUSI could be used within an objective assessment of this muscle.

InclusiveCAD: a software resource for designers

Rapid and unprecedented population ageing poses a serious social and economic challenge across the developed world. Shifts in dependency ratios point to escalating welfare and pensions costs which require radical and imaginative responses from Government and industry. The key to this is maintaining a healthy population that is able and willing to work longer before retirement and can remain independent for as long as possible afterwards as well as bringing disabled people into mainstream life and employment. ontributions focus on the following topics. This chapter focuses on design issues for a more inclusive world, explaining InclusiveCA as a software resource for designers involved in the development and evaluation of truly usable and accessible systems for users with special needs.