Jeanette M. Thom

Metabolic cost, mechanical work, and efficiency during walking in young and older men

Aim:  To investigate mechanical work, efficiency, and antagonist muscle co‐activation with a view to better understand the cause of the elevated metabolic cost of walking (CW) in older adults.

The influence of menstrual cycle phase on skeletal muscle contractile characteristics in humans

1 The influence of the different phases of the menstrual cycle on skeletal muscle contractile characteristics was studied in 19 regularly menstruating women. Muscle function was measured when (i) oestrogen and progesterone concentrations were low (menstruation), (ii) oestrogen was elevated and progesterone was low (late follicular phase), and (iii) oestrogen and progesterone were both elevated (luteal phase). 2 Maximal isometric quadriceps strength, fatiguability and electrically stimulated contractile properties were measured. Isokinetic knee flexion and extension strength and fatiguability were also assessed as well as handgrip strength. Menstrual cycle phases were confirmed through measurement of oestrogen, progesterone, follicle stimulating hormone and luteinising hormone. 3 No significant changes were found in any of the muscle function parameters throughout the menstrual cycle (n = 15). The muscle function measurements showed no significant correlations with any of the female reproductive hormone concentrations. 4 These results suggest that the fluctuations in female reproductive hormone concentrations throughout the menstrual cycle do not affect muscle contractile characteristics.

Sarcoplasmic reticulum function and muscle contractile character following fatiguing exercise in humans

1 This study examined the alterations in calcium release, calcium uptake and calcium ATPase activity of skeletal muscle sarcoplasmic reticulum in response to a bout of intense dynamic knee extensor exercise, and the relationship between these changes and alterations in muscle contractile characteristics in the human quadriceps. 2 In biopsy samples taken from the vastus lateralis, sarcoplasmic reticulum calcium release and calcium uptake were significantly depressed (P < 0.01 and 0.05, respectively) immediately following the exercise with no alteration in the sarcoplasmic reticulum Ca2+‐ATPase activity. 3 A 33 % reduction in the maximum voluntary isometric torque was found following the exercise, with reduced torques from electrically evoked isometric contractions at low frequencies of stimulation (10 and 20 Hz) but not at higher frequencies (50 and 100 Hz). 4 The depressed calcium release was correlated (P < 0.05) with a decreased ratio of torques generated at 20:50 Hz, indicating an involvement in low frequency fatigue; however, no correlations between the muscle relaxation times or rates of change of torque and calcium uptake were observed.

Benefits of exercise in Rheumatoid Arthritis.

This paper aims to highlight the importance of exercise in patients with rheumatoid arthritis (RA) and to demonstrate the multitude of beneficial effects that properly designed exercise training has in this population. RA is a chronic, systemic, autoimmune disease characterised by decrements to joint health including joint pain and inflammation, fatigue, increased incidence and progression of cardiovascular disease, and accelerated loss of muscle mass, that is, “rheumatoid cachexia”. These factors contribute to functional limitation, disability, comorbidities, and reduced quality of life. Exercise training for RA patients has been shown to be efficacious in reversing cachexia and substantially improving function without exacerbating disease activity and is likely to reduce cardiovascular risk. Thus, all RA patients should be encouraged to include aerobic and resistance exercise training as part of routine care. Understanding the perceptions of RA patients and health professionals to exercise is key to patients initiating and adhering to effective exercise training.

Gastrocnemius muscle–tendon behaviour during walking in young and older adults

Aim:  Age‐related differences in muscle architectural and tendon mechanical properties have been observed in vivo under static conditions and during single joint contractions. The aim of this study was to determine if there are age‐related differences in gastrocnemius fascicle–tendon interactions during a fundamental locomotor task – walking.

Muscle Quality, Architecture, and Activation in Cachectic Patients with Rheumatoid Arthritis

Objective. To explore muscle-specific force (force per physiological cross-sectional area, or PCSA) and muscle activation in cachectic patients with rheumatoid arthritis (RA). Methods. In 14 muscle-wasted patients with RA and age and sex matched healthy controls, vastus lateralis (VL) force and voluntary activation capacity were assessed during maximal isometric contractions with electromyography and superimposed electrical stimulations. VL PCSA was determined from ultrasound measures of fiber fascicle length (Lf), pennation angle, and volume, together with assessments of body composition by dual energy x-ray absorptiometry and objective physical function. Results. Although patients with RA had reduced physical function, lower muscle mass, and VL volume relative to controls, there were no differences in muscle-specific force and activation. PCSA, force, and pennation angle tended to be lower in RA, with no differences in Lf. Conclusion. Muscle-specific force and activation are not compromised and thus are unlikely to contribute to reduced function in cachectic patients with RA.

Skeletal muscle properties in rheumatoid arthritis patients.

PURPOSE Disability in patients with rheumatoid arthritis (RA) is a multifactorial process involving various unaccounted factors. Loss of lean body mass plays an important role in impaired physical function, and exercise studies in RA have shown promising results in restoring muscle mass, strength, and function. However, no comprehensive assessment of the muscle characteristics has been undertaken to determine whether qualitative changes in muscle also contribute to RA disability. This study explores the physiological muscle properties of a community-based population with stable RA. METHODS Vastus lateralis (VL) force and physiological cross-sectional area (PCSA), voluntary muscle activation capacity, and contractile properties were assessed in 23 patients with stable RA (age = 60 ± 2 yr (mean ± SEM); 16 women) and age- and sex-matched healthy controls (age = 60 ± 3 yr). Measurements with EMG were obtained during maximal isometric knee extension contractions, with resting and superimposed electrical stimulations. Concentric knee extension contractions were also assessed. Pennation angle and VL volume were measured with ultrasound to determine fiber fascicle length and PCSA. Muscle-specific force was calculated (VL force/VL PCSA). Body composition using dual-energy x-ray absorptiometry and objective physical function were also measured. RESULTS The patients displayed typical features of RA with reduced physical function (P = 0.001-0.09), a trend toward lower appendicular lean mass (P = 0.09) and increased total body fat (P < 0.05) relative to controls. However, there were no differences in specific force, contractile properties, voluntary activation capacity, and contraction velocity (P = 0.41-0.99). VL PCSA was reduced (P < 0.05) with minor architectural changes in patients with RA. CONCLUSIONS Physiological properties of muscle that determine specific force are not compromised in patients with stable RA despite deficits in physical function.

Rationale for combined exercise and cognition-focused interventions to improve functional independence in people with dementia.

Evidence suggests that exercise and some cognition-focused intervention approaches can be used to elicit functional improvements in older people and, to some degree, those diagnosed with dementia. Independently, the two intervention types have been found to improve functional performance in people with dementia. The mechanisms underpinning these improvements come from comparable and diverse pathways. This suggests that it may be beneficial for the two intervention types to be coupled as part of regular care in individuals with a range of cognitive impairments. The aims of this review are threefold. The first aim is to present evidence to support the use for combining exercise and cognition-focused interventions. This will be achieved by reviewing the mechanisms of both approaches in improving functional performance in older people and in people with dementia and summarising recent progress. The increased risk of depression, falls and cardiovascular disease risk in people with dementia will also be highlighted. The second aim is to discuss the parameters of the two approaches that should be considered when combining them in terms of possible efficient models, especially in relation to exercise protocols as this is where the current literature shows the most promising outcomes. Maximisation of the efficacy of preventative and treatment interventions which focus on both cognitive functioning and physical health should lead to improving and extending functional independence. Key aspects of any combined intervention would involve the inclusion of both cardiovascular and other types of exercises, including falls reduction, and exercises addressing memory and executive function via goal setting in the real-life context. The third aim is to explore some of the issues that may arise when attempting to incorporate interventions into the regular treatment of people with dementia. Consideration must also be given to caregivers and the education of health professionals as well as to the mode of intervention itself. Further research is necessary in order to discern the most effective types of both intervention models. Provision of combined interventions might enhance the improvements in functional independence in people with dementia over and above the interventions being used separately.

Exercise Performance over the Menstrual Cycle in Temperate and Hot, Humid Conditions.

PURPOSE This study investigated the effects of the menstrual cycle on prolonged exercise performance both in temperate (20°C, 45% relative humidity) and hot, humid (32°C, 60% relative humidity) conditions. METHODS For each environmental condition, 12 recreationally active females were tested during the early follicular (day 3-6) and midluteal (day 19-25) phases, verified by measurement of estradiol and progesterone. For all four tests, thermoregulatory, cardiorespiratory, and perceptual responses were measured during 60 min of exercise at 60% of maximal oxygen consumption followed by an incremental test to exhaustion. RESULTS No differences in exercise performance between menstrual cycle phases were found during temperate conditions (n = 8) despite a higher resting and submaximal exercise core temperature (Tc) in the luteal phase. In hot, humid conditions (n = 8), however, prolonged exercise performance, as exercise time to fatigue, was significantly reduced during the luteal phase. This finding was not only accompanied by higher resting and submaximal exercise Tc but also a higher rate of increase in Tc during the luteal phase. Furthermore, submaximal exercise HR, minute ventilation, and RPE measures were higher during the luteal phase in hot, humid conditions. No significant differences were found over the menstrual cycle in heat loss responses (partitional calorimetry, sweat rate, upper arm sweat composition) and Tc at exhaustion. CONCLUSION In temperate conditions, no changes in prolonged exercise performance were found over the menstrual cycle, whereas in hot, humid conditions, performance was decreased during the luteal phase. The combination of both exercise and heat stress with the elevated luteal phase Tc at the onset of exercise resulted in physiological and perceptual changes and a greater thermosensitivity, which may explain the decrease in performance.

The AgeWell study of behavior change to promote health and wellbeing in later life: study protocol for a randomized controlled trial

BackgroundLifestyle factors playing a role in the development of late-life disability may be modifiable. There is a need for robust evidence about the potential for prevention of disability through behavior change interventions.Methods/designThis feasibility study involves the development, implementation and initial testing of a behavior change intervention in a naturalistic setting. A small-scale randomized controlled trial (RCT) will investigate the implementation of a goal-setting intervention aimed at promoting behavior change in the domains of physical and cognitive activity in the context of a community resource center for over-50s. Healthy older participants attending the center (n = 75) will be randomized to one of three conditions: control (an interview involving a general discussion about the center); goal-setting (an interview involving identification of up to five personal goals in the domains of physical activity, cognitive activity, diet and health, and social engagement); or goal-setting with mentoring (the goal-setting interview followed by bi-monthly telephone mentoring). All participants will be reassessed after 12 months. Primary outcomes are levels of physical and cognitive activity. Secondary outcomes address psychosocial (self-efficacy, mood, quality of life), cognitive (memory and executive function), and physical fitness (functional and metabolic) domains. Cost-effectiveness will also be examined.DiscussionThis study will provide information about the feasibility of a community-based lifestyle intervention model for over-50s and of the implementation of a goal-setting intervention for behavior change, together with initial evidence about the short-term effects of goal-setting on behavior.Trial RegistrationCurrent Controlled Trials ISRCTN30080637 (http://www.controlled-trials.com)