Stephen Bird

Resistance training improves metabolic health in type 2 diabetes: a systematic review

This paper systematically reviews the effect of resistance training (RT) on glycemic control and insulin sensitivity in adults with type 2 diabetes. Twenty studies were included, with the volume, frequency and intensity of RT varying markedly. Supervised RT improved glycemic control and insulin sensitivity, however, when supervision was removed compliance and glycemic control decreased. Evidence indicates the mechanisms behind the improvements to glucose tolerance require further elucidation. Although research demonstrates apparent benefits of RT for individuals with diabetes, further research is required to elucidate the minimum effective dose by describing frequency, intensity and the duration of acute and chronic improvements.

Aging and the force-velocity relationship of muscles.

Aging in humans is associated with a loss in neuromuscular function and performance. This is related, in part, to the reduction in muscular strength and power caused by a loss of skeletal muscle mass (sarcopenia) and changes in muscle architecture. Due to these changes, the force-velocity (f-v) relationship of human muscles alters with age. This change has functional implications such as slower walking speeds. Different methods to reverse these changes have been investigated, including traditional resistance training, power training and eccentric (or eccentrically-biased) resistance training. This review will summarise the changes of the f-v relationship with age, the functional implications of these changes and the various methods to reverse or at least partly ameliorate these changes.

Effect of a carbohydrate mouth rinse on simulated cycling time-trial performance commenced in a fed or fasted state

It is presently unclear whether the reported ergogenic effect of a carbohydrate (CHO) mouth rinse on cycling time-trial performance is affected by the acute nutritional status of an individual. Hence, the aim of this study was to investigate the effect of a CHO mouth rinse on a 60-min simulated cycling time-trial performance commenced in a fed or fasted state. Twelve competitive male cyclists each completed 4 experimental trials using a double-blinded Latin square design. Two trials were commenced 2 h after a meal that contained 2.5 g·kg(-1) body mass of CHO (FED) and 2 after an overnight fast (FST). Prior to and after every 12.5% of total time during a performance ride, either a 10% maltodextrin (CHO) or a taste-matched placebo (PLB) solution was mouth rinsed for 10 s then immediately expectorated. There were significant main effects for both pre-ride nutritional status (FED vs. FST; p < 0.01) and CHO mouth rinse (CHO vs. PLB; p < 0.01) on power output with an interaction evident between the interventions (p < 0.05). The CHO mouth rinse improved mean power to a greater extent after an overnight fast (282 vs. 273 W, 3.4%; p < 0.01) compared with a fed state (286 vs. 281 W, 1.8%; p < 0.05). We concluded that a CHO mouth rinse improved performance to a greater extent in a fasted compared with a fed state; however, optimal performance was achieved in a fed state with the addition of a CHO mouth rinse.

A review of guidelines for cardiac rehabilitation exercise programmes: Is there an international consensus?:

Background Cardiac rehabilitation is an important component in the continuum of care for individuals with cardiovascular disease, providing a multidisciplinary education and exercise programme to improve morbidity and mortality risk. Internationally, cardiac rehabilitation programmes are implemented through various models. This review compared cardiac rehabilitation guidelines in order to identify any differences and/or consensus in exercise testing, prescription and monitoring. Methods Guidelines, position statements and policy documents for cardiac rehabilitation, available internationally in the English language, were identified through a search of electronic databases and government and cardiology society websites. Information about programme delivery, exercise testing, prescription and monitoring were extracted and compared. Results Leading cardiac rehabilitation societies in North America and Europe recommend that patients progress from moderate- to vigorous-intensity aerobic endurance exercise over the course of the programme, with resistance training included as an important adjunct, for maintaining independence and quality of life. North American and European guidelines also recommend electrocardiograph-monitored exercise stress tests. Guidelines for South America and individual European nations typically include similar recommendations; however, those in the United Kingdom, Australia and New Zealand specify lower-intensity exercise and less technical assessment of functional capacity. Conclusion Higher-intensity aerobic training programmes, supplemented by resistance training, have been recommended and deemed safe for cardiac rehabilitation patients by many authorities. Based on research evidence, this may also provide superior outcomes for patients and should therefore be considered when developing an international consensus for exercise prescription in cardiac rehabilitation.

Effects of eccentrically biased versus conventional weight training in older adults.

INTRODUCTION We compared the effects of eccentrically biased (EB) and conventional (CONV) resistance training on muscle architecture, one-repetition maximum (1RM), isometric strength, isokinetic force-velocity characteristics, functional capacity, and pulse wave velocity in older men and women. METHODS Twenty-eight older adults participated in the study (mean ± SD: age = 68 ± 5 yr). Of these, 13 were allocated to a waitlist control, 10 of whom progressed to training (CONV, n = 12; EB, n = 13). Training was twice a week for 16 wk. EB involved three sets of 10 concentric lifts at 50% of 1RM with the eccentric portion of repetitions performed unilaterally, alternating between limbs with each repetition. CONV involved two sets of 10 repetitions at 75% of 1RM. EB and CONV were matched for total work. Isokinetic knee extensor strength was assessed across a range of velocities (0-360°·s(-1)). Functional capacity was assessed via a 6-m fast walk test, a timed up and go test, stair climb and descent power test, and vertical jump test. Vastus lateralis and gastrocnemius medialis architecture were assessed using ultrasonography. RESULTS Both EB and CONV improved 1RM (Δ 23%-35%, P < 0.01). Compared to the control group, both training regimens improved 6-m fast walk (Δ 5%-7%, P < 0.01) and concentric torque at 60 and 120°·s(-1) (Δ 6%-8%, P < 0.05). Significant improvements were evident in EB for isometric and concentric torque at 240 and 360°·s(-1) (Δ 6%-11%, P < 0.05), vastus lateralis thickness (Δ 5%, P < 0.05), and stair climb (Δ 5%, P < 0.01). Timed up and go (Δ 5%, P < 0.01), stair descent (Δ 4%, P < 0.05), and vertical jump (Δ 7%, P < 0.01) improved in CONV. Pulse wave velocity, pennation angle, and fascicle length remained unchanged in both training groups. CONCLUSIONS EB seems superior to CONV at increasing torque at high contraction velocities, whereas CONV seems more effective at improving some functional performance measures and vertical jump. This has important implications for preserving functional capacity.

Reliability of ultrasonographic measurement of the architecture of the vastus lateralis and gastrocnemius medialis muscles in older adults

Objective:  To determine the test‐retest reliability of measurements of thickness, fascicle length (Lf) and pennation angle (θ) of the vastus lateralis (VL) and gastrocnemius medialis (GM) muscles in older adults.

“I don’t have the heart”: a qualitative study of barriers to and facilitators of physical activity for people with coronary heart disease and depressive symptoms

BackgroundPhysical activity has been shown to reduce depression in people with coronary heart disease (CHD), however many people with CHD do not engage in sufficient levels of physical activity to reap its positive effects. People with depression and CHD are at particular risk of non-adherence to physical activity. Little is known about the barriers to and facilitators of physical activity for people with CHD and depressive symptoms. Using qualitative interviews, the aim of this study was to explore the barriers to and facilitators of physical activity for cardiac patients with depressive symptoms.MethodsFifteen participants with CHD and depressive symptoms (assessed using the Cardiac Depression Scale) participated in in-depth semi-structured interviews. The interviews were focussed on investigating participants’ experiences of physical activity since their cardiac event. Interviews were content analysed to determine major themes.ResultsParticipants identified a number of barriers to and facilitators of physical activity. Barriers included having negative perceptions towards health and life changes as a result of the cardiac event, having low mood and low motivation to exercise, feeling physically restricted towards or fearful of exercise, lacking knowledge regarding exercise and perceiving external barriers. Facilitators included having a reason for exercising, being able to identify the psychological benefits of exercise, having positive social support and using psychological strategies. ‘Inactive’ participants reported more barriers and fewer facilitators than did ‘active’ participants.ConclusionsThe barriers reported in this study were highly salient for a number of participants. Health professionals and researchers can use this information to assist people with CHD and depressive symptoms to identify and possibly overcome barriers to physical activity. Relevant barriers and facilitators could be taken into account to increase their effectiveness when designing interventions to encourage physical activity maintenance in this population.

Update on the effects of physical activity on insulin sensitivity in humans

Purpose and methods This review presents established knowledge on the effects of physical activity (PA) on whole-body insulin sensitivity (SI) and summarises the findings of recent (2013–2016) studies. Discussion and conclusions Recent studies provide further evidence to support the notion that regular PA reduces the risk of insulin resistance, metabolic syndrome and type 2 diabetes, and SI improves when individuals comply with exercise and/or PA guidelines. Many studies indicate a dose response, with higher energy expenditures and higher exercise intensities, including high intensity interval training (HIIT), producing greater benefits on whole-body SI, although these findings are not unanimous. Aerobic exercise interventions can improve SI without an associated increase in cardiorespiratory fitness as measured by maximal or peak oxygen consumption. Both aerobic and resistance exercise can induce improvements in glycaemic regulation, with some suggestions that exercise regimens including both may be more efficacious than either exercise mode alone. Some studies report exercise-induced benefits to SI that are independent of habitual diet and weight loss, while others indicate an association with fat reduction, hence the debate over the relative importance of PA and weight loss continues. During exercise, muscle contraction stimulated improvements in SI are associated with increases in AMPK activity, which deactivates TCB1D1, promoting GLUT4 translocation to the cell membrane and thereby increasing glucose uptake. Postexercise, increases in Akt deactivate TCB1D4 and thereby increase GLUT4 translocation to the cell membrane. The reduction in intramuscular saturated fatty acids and concomitant reductions in ceramides, but not diacylglycerols, provide a potential link between intramuscular lipid content and SI. Increased skeletal muscle capillarisation provides another independent adaptation through which SI is improved, as does enhanced β cell activity. Recent studies are combining exercise interventions with dietary and feeding manipulations to investigate the potential for augmenting the exercise-induced improvements in SI and glycaemic control.

Acute changes to biomarkers as a consequence of prolonged strenuous running

Background A single bout of strenuous running exercise results in perturbations to numerous biomarkers. An understanding of these is important when analysing samples from individuals who have recently performed such exercise. Methods A literature search was undertaken using the search terms, exercise, marathon and delayed onset of muscle soreness. The search was then refined using the terms for key biomarkers known to be altered by exercise. Results The magnitude of changes to biomarkers is proportional to the severity of the running bout. Familiar, moderate intensity running exercise produces brief transient changes in common biomarkers such as lactate, whereas more severe bouts of running exercise, such as marathons and ultra-marathon events can produce changes to biomarkers that are normally associated with pathology of the muscles, liver and heart. Examples being changes to concentrations and/or activity of myoglobin, leucocytes, creatine kinase, bilirubin, cardiac troponins, lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase. While persisting for longer, these changes are also transient and full recovery occurs within days, without any apparent long-term adverse consequences. Additionally, unfamiliar exercise involving forceful eccentric muscle contractions, such as running downhill, can cause increases in creatine kinase and delayed onset of muscle soreness that peaks 36–72 h after the exercise bout. Conclusions Strenuous running exercise can produce changes to biomarkers that are normally associated with disease and injury, but these do not necessarily reflect chronic pathology.

From evidence to policy: reflections on emerging themes in health-enhancing physical activity.

Based on a detailed reading of the six preceding papers, in conjunction with a reflection on the socio-political forces shaping lifestyles in the UK at the turn of the millennium, we come to four interrelated conclusions. First, sport and exercise science needs to move beyond evidence-based practice to evidence-based policy. Second, sport and exercise science needs to make health-enhancing physical activity a political issue at both national and local level. Third, transport, not health policy, may be the key to promoting health-enhancing physical activity. And, fourth, young people deserve our special attention. In reaching these four interrelated conclusions, we attempt both to shape evidence based policy and future research agendas in exercise science. To achieve an international perspective, we also present a short case note from Australia.