Myra A. Nimmo

Contractile muscle volume and agonist-antagonist coactivation account for differences in torque between young and older women

It is controversial whether specific tension (the ratio between muscle strength and size) declines with aging. Therefore, contractile muscle volume was estimated separately from the intramuscular noncontractile tissue by magnetic resonance imaging, and maximum isometric torque was measured in the knee extensors and flexors of 10 young (22.8 ± 5.7 years) and 10 older (69.5 ± 2.4 years) healthy active women. Specific tension was lower in the older women both in the extensors (93.1 ± 20.1 kN·m−2 vs. 112.1 ± 12.3 kN·m−2; P < 0.05) and in the flexors (100 ± 31 kN·m−2 vs. 142.7 ± 23.9 kN·m−2; P < 0.01). This was accompanied by an increase in the percentage coactivation of the knee flexors during knee extension. These data suggest that the lower level of muscle torque in the older women can be explained not only by smaller contractile muscle mass but also by increased coactivation of the antagonist muscles during knee extension.

Variations in Regional Sweat Composition in Normal Human Males

This project aimed to quantify the regional distribution of sweat composition over the skin surface and to determine whether sweat constituent concentrations collected from regional sites can estimate whole‐body concentrations. Ten males cycled for 90 min in a 20°C (50% relative humidity) environment at 45% peak aerobic power. Sweat was collected from eleven skin regions and the whole body, using a wash‐down technique. Strong relationships were evident between the regional and whole‐body sweat [Na+] and [Cl‐], such that the thigh and calf exhibited greater correlation coefficients than area‐weighted means derived from four and eight skin regions. Therefore, in this particular protocol the whole‐body sweat [Na+] and [Cl‐] could be predicted from regional sweat collections. Relationships between sweat constituents were evident for sweat [Na+] and pH, and sweat [K+] and [lactate] when data were pooled between skin regions and subjects. To our knowledge this is the first investigation to report a positive relationship between sweat [K+] and [lactate]. The exact mechanism responsible for the positive relationship between sweat [K+] and [lactate] is uncertain although it is speculated to occur at the secretory coil.

Muscle function in elite master weightlifters.

PURPOSE To determine whether explosive power and isometric strength of the lower-limb muscles in elite master Olympic weightlifters declines at a similar rate to nontrained healthy controls with increasing age. METHODS 54 elite level masters weightlifters (aged 40-87), who were competitors at the World Masters Weightlifting Championships (1999), were compared with a similar number of aged-matched, healthy untrained individuals. Isometric knee extensor strength and lower-limb explosive power were tested. Extent of antagonist co-contraction during isometric knee extension was determined by EMG and power loading characteristics by using a variable inertial system. Muscle volume was estimated using anthropometry. RESULTS On average, the weightlifters were able to generate 32% more peak power (P < 0.05) in the lower limbs and 32% more isometric knee extensor force (P < 0.05) than the control subjects. No significant differences in lower-leg volume were observed between the two groups. Peak power declined at a similar rate with increasing age in the weightlifters and controls (1.2 and 1.3% of a 45-yr-olds value per year), as did strength, but at a lower rate (0.6 and 0.5% per year). The inertial load at which the weightlifters achieved their maximal peak power output was greater (P < 0.05) than the controls. The torque generated at this optimal inertia was also greater in the weightlifters (P < 0.05), whereas the time taken for the weightlifters to reach their maximal peak power was on average 13% shorter (P < 0.05). No differences in antagonist co-contraction during isometric knee extension were observed between the two groups. CONCLUSIONS Muscle power and isometric strength decline at a similar rate with increasing age in elite master weightlifters and healthy controls. In spite of inertial load optimization, muscle power declined in both groups at approximately twice the rate of isometric strength. Although similar rates of decline were observed, the absolute differences between the weightlifters and controls were such that an 85-yr-old weightlifter was as powerful as a 65-yr-old control subject. This would therefore represent an apparent age advantage of approximately 20 yr for the weightlifters.

The effect of a pedometer-based community walking intervention "Walking for Wellbeing in the West" on physical activity levels and health outcomes: a 12-week randomized controlled trial

BackgroundRecent systematic reviews have suggested that pedometers may be effective motivational tools to promote walking. However, studies tend to be of a relatively short duration, with small clinical based samples. Further research is required to demonstrate their effectiveness in adequately powered, community based studies.ObjectiveUsing a randomized controlled trial design, this study assessed the impact of a 12-week graduated pedometer-based walking intervention on daily step-counts, self-reported physical activity and health outcomes in a Scottish community sample not meeting current physical activity recommendations.MethodSixty-three women and 16 men (49.2 years ± 8.8) were randomly assigned to either an intervention (physical activity consultation and 12-week pedometer-based walking program) or control (no action) group. Measures for step-counts, 7-day physical activity recall, affect, quality of life (n = 79), body mass, BMI, % body fat, waist and hip circumference (n = 76), systolic/diastolic blood pressure, total cholesterol and HDL cholesterol (n = 66) were taken at baseline and week 12. Analyses were performed on an intention to treat basis using 2-way mixed factorial analyses of variance for parametric data and Mann Whitney and Wilcoxon tests for non-parametric data.ResultsSignificant increases were found in the intervention group for step-counts (p < .001), time spent in leisure walking (p = .02) and positive affect (p = .027). Significant decreases were found in this group for time spent in weekday (p = .003), weekend (p = .001) and total sitting (p = .001) with no corresponding changes in the control group. No significant changes in any other health outcomes were found in either group. In comparison with the control group at week 12, the intervention group reported a significantly greater number of minutes spent in leisure time (p = .008), occupational (p = .045) and total walking (p = .03), and significantly fewer minutes in time spent in weekend (p = .003) and total sitting (p = .022).ConclusionA pedometer-based walking program, incorporating a physical activity consultation, is effective in promoting walking and improving positive affect over 12 weeks in community based individuals. The discussion examines possible explanations for the lack of significant changes in health outcomes. Continued follow-up of this study will examine adherence to the intervention and possible resulting effects on health outcomes.

The effect of physical activity on mediators of inflammation.

Being physically active and undertaking exercise on a regular basis are critical lifestyle behaviours which protect against the development of numerous chronic metabolic conditions. One of the key mechanisms by which physical activity exerts favourable health effects appears to be due to its capacity to reduce chronic low‐grade inflammation. Single bouts of exercise have a potent anti‐inflammatory influence with recent advances describing important effects of acute exercise on inflammatory mediators produced within skeletal muscle (myokines), adipose tissue (adipokines) and leucocytes. The accumulated effects of physical activity or exercise training on systemic inflammation have been studied widely within epidemiological research; however, information from intervention trials is still emerging. Current data suggest that the most marked improvements in the inflammatory profile are conferred with exercise performed at higher intensities, with combined aerobic and resistance exercise training potentially providing the greatest benefit. The purpose of this review is to describe recent advances in our understanding surrounding the acute and chronic effects of physical activity on key mediators of inflammation. Within this, particular attention is given to the interleukin‐6 system owing to its apparent centrality in mediating the anti‐inflammatory effects of exercise.

Effects of active, passive or no warm-up on metabolism and performance during high-intensity exercise

The aim of this study was to determine the influence of type of warm-up on metabolism and performance during high-intensity exercise. Eight males performed 30 s of intense exercise at 120% of their maximal power output followed, 1 min later, by a performance cycle to exhaustion, again at 120% of maximal power output. Exercise was preceded by active, passive or no warm-up (control). Muscle temperature, immediately before exercise, was significantly elevated after active and passive warm-ups compared to the control condition (36.9 - 0.18°C, 36.8 - 0.18°C and 33.6 - 0.25°C respectively; mean - sx ) ( P ≪ 0.05). Total oxygen consumption during the 30 s exercise bout was significantly greater in the active and passive warm-up trials than in the control trial (1017 - 22, 943 - 53 and 838 - 45 ml O 2 respectively). Active warm-up resulted in a blunted blood lactate response during high-intensity exercise compared to the passive and control trials (change = 5.53 - 0.52, 8.09 - 0.57 and 7.90 - 0.38 mmol· l -1 respectively) ( P ≪ 0.05). There was no difference in exercise time to exhaustion between the active, passive and control trials (43.9 - 4.1, 48.3 - 2.7 and 46.9 - 6.2 s respectively) ( P = 0.69). These results indicate that, although the mechanism by which muscle temperature is elevated influences certain metabolic responses during subsequent high-intensity exercise, cycling performance is not significantly affected.

Effects of central sympathetic inhibition on heart rate variability during steady-state exercise in healthy humans

The profound reduction in heart rate variability (HRV) that occurs during exercise is thought to be, at least in part, the result of sympathetic nervous system activation. Moxonidine is a centrally acting anti‐sympathetic drug, which suppresses sympathetic nervous system outflow by stimulation of central imidazoline receptors located in the rostral ventro‐lateral medulla. This study was designed to investigate the combined effects of central sympathetic inhibition with moxonidine and steady‐state dynamic exercise on HRV. Ten normal males participated in a double‐blind cross‐over study, taking either placebo or 0·4 mg of moxonidine. The subjects were studied at rest and during steady‐state exercise. HRV was measured considering both time and frequency domain parameters. As a non‐linear measure, the Poincaré scatter‐plot was measured and analysed quantitatively. Ventilation and gas exchange were also measured during exercise. In addition, plasma catecholamines were measured at rest and during exercise. The only parameter changed, at rest, by moxonidine was the blood pressure which was reduced. During exercise, moxonidine reduced plasma noradrenaline (NA), compared with the placebo (P<0·01). The only change observed in HRV during exercise was a significant reduction of the continuous long‐term standard deviation (SD2) of the Poincaré scatter‐plot of the R‐R interval (P<0·05). However, the potential and prognostic significance of this result needs to be further assessed.

Determination of inflammatory and prominent proteomic changes in plasma and adipose tissue after high intensity intermittent training in overweight and obese males

This study aimed to determine whether 2 wk of high-intensity intermittent training (HIIT) altered inflammatory status in plasma and adipose tissue in overweight and obese males. Twelve participants [mean (SD): age 23.7 (5.2) yr, body mass 91.0 (8.0) kg, body mass index 29.1 (3.1) kg/m2] undertook six HIIT sessions over 2 wk. Resting blood and subcutaneous abdominal adipose tissue samples were collected and insulin sensitivity determined, pre- and posttraining. Inflammatory proteins were quantified in plasma and adipose tissue. There was a significant decrease in soluble interleukin-6 receptor (sIL-6R; P = 0.050), monocyte chemotactic protein-1 (MCP-1, P = 0.047), and adiponectin (P = 0.041) in plasma posttraining. Plasma IL-6, intercellular adhesion molecule-1 (ICAM-1), tumor necrosis factor-α (TNF-α), IL-10, and insulin sensitivity did not change. In adipose tissue, IL-6 significantly decreased (P = 0.036) and IL-6R increased (P = 0.037), while adiponectin tended to decrease (P = 0.056), with no change in ICAM-1 posttraining. TNF-α, MCP-1, and IL-10 were not detectable in adipose tissue. Adipose tissue homogenates were then resolved using one-dimensional gel electrophoresis, and major changes in the adipose tissue proteome, as a consequence of HIIT, were evaluated. This proteomic approach identified significant reductions in annexin A2 (P = 0.046) and fatty acid synthase (P = 0.016) as a response to HIIT. The present investigation suggests 2 wk of HIIT is sufficient to induce beneficial alterations in the resting inflammatory profile and adipose tissue proteome of an overweight and obese male cohort.

Effects of menstrual cycle phase and oral contraceptive use on intermittent exercise

Abstract Five women using low-dose, monophasic oral contraceptive (OC) agents (OC group) and ten normally menstruating women (Non-OC group) performed a treadmill protocol to determine the effect of OCs and the menstrual cycle (MC) on intermittent exercise performance and some commonly used metabolic markers. The Non-OC group were tested once in the mid-follicular phase (MFP) and once in the late luteal phase (LLP) of the MC, while the OC group performed their first test within 1 week of taking the OC (T1) and their second test 1 week later (T2). Despite performance time being the same in both groups [mean (SD), Non-OC group: 77.7 (14.9) s versus OC group: 77.7 (21.1)s], plasma ammonia concentration ([NH3]pl) was higher in the Non-OC group when compared to the OC group throughout recovery (P < 0.05). No differences were found in blood lactate (BLa), maximum heart rate or aural temperature (Tau) between groups. Within the Non-OC group Tau increased with exercise in both phases (P < 0.05), however Tau was higher in the LLP at rest [36.1 (0.3)°C) and 1 min post-exercise [37.1 (0.6)°C), when compared to the MFP [35.8 (0.3) and 36.9 (0.7)°C, rest and 1 min post-exercise respectively, P < 0.05]. Within the OC group T1 resulted in a higher peak BLa [11.2 (0.4) mmol/l] and [NH3]pl (143.0 (26.2) Umol/l] when compared to T2 [BLa, 9.6 (0.9); [NH3], 119.4 (48.1), P<0.05]. These results suggest that: (1) exercise performance does not vary between the MFP and the LLP of the MC, nor does it appear to be affected by the number of days using the OC, and (2) an altered metabolism occurs both between groups (Non-OC versus OC) and within the OC group.

Does physical activity counselling enhance the effects of a pedometer-based intervention over the long-term: 12-month findings from the walking for wellbeing in the west study

BackgroundPedometers provide a simple, cost effective means of motivating individuals to increase walking yet few studies have considered if short term changes in walking behaviour can be maintained in the long-term. The role of physical activity consultations in such interventions is unclear. The purpose of this study was to assess the sustainability of pedometer-based interventions and empirically examine the role of physical activity consultations using long-term results of a community-based walking study.Methods79 low active Scottish men and women (63 women and 16 men) from the Walking for Wellbeing in the West intervention study were randomly assigned to receive either: Group 1; pedometer-based walking programme plus physical activity consultations or Group 2; pedometer-based walking programme and minimal advice. Step counts (Omron HJ-109E Step-O-Meter pedometer), 7 day recall of physical activity (IPAQ long), mood (PANAS) and quality of life (EuroQol EQ-5D) were assessed pre-intervention and 12, 24 and 48 weeks after receiving the intervention. Body mass, body mass index and waist and hip circumference were assessed pre-intervention and 12 and 24 weeks after receiving the intervention. Analyses were performed on an intention to treat basis (baseline value carried forward for missing data) using mixed-factorial ANOVAs and follow-up t-tests.ResultsA significant main effect of time (p < 0.001) was found for step-counts attributable to significant increases in steps/day between: pre-intervention (M = 6941, SD = 3047) and 12 weeks (M = 9327, SD = 4136), t(78) = - 6.52, p < 0.001, d = 0.66; pre-intervention and 24 weeks (M = 8804, SD = 4145), t(78) = - 4.82, p < 0.001, d = 0.52; and pre-intervention and 48 weeks (M = 8450, SD = 3855), t(78) = - 4.15, p < 0.001, d = 0.44. Significant effects were found for several variables of self-reported physical activity, mood and quality of life and are discussed. No other significant effects in health related outcomes were found.ConclusionBoth interventions successfully increased and maintained step counts over 12 months. Physical activity consultations may encourage individuals to be active in other ways beyond walking and to reduce sitting time.Trial Registration NumberCurrent Controlled Trials Ltd ISRCTN88907382