What Is the Evidence That Dietary Macronutrient Composition Influences Exercise Performance? A Narrative Review.

The introduction of the needle muscle biopsy technique in the 1960s allowed muscle tissue to be sampled from exercising humans for the first time. The finding that muscle glycogen content reached low levels at exhaustion suggested that the metabolic cause of fatigue during prolonged exercise had been discovered. A special pre-exercise diet that maximized pre-exercise muscle glycogen storage also increased time to fatigue during prolonged exercise.

Hiding unhealthy heart outcomes in a low-fat diet trial: the Women's Health Initiative Randomized Controlled Dietary Modification Trial finds that postmenopausal women with established coronary heart disease were at increased risk of an adverse outcome if they consumed a low-fat 'heart-healthy' diet.

The Women's Health Initiative Randomized Controlled Dietary Modification Trial (WHIRCDMT) was designed to test whether the US Department of Agriculture's 1977 Dietary Guidelines for Americans protects against coronary heart disease (CHD) and other chronic diseases. The only significant finding in the original 2006 WHIRCDMT publication was that postmenopausal women with CHD randomised to a low-fat 'heart-healthy' diet in 1993 were at 26% greater risk of developing additional CHD events compared with women with CHD eating the control diet. A 2017 WHIRCDMT publication includes data for an additional 5 years of follow-up.

Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review.

Low-carbohydrate high-fat (LCHF) diets are a highly contentious current topic in nutrition. This narrative review aims to provide clinicians with a broad overview of the effects of LCHF diets on body weight, glycaemic control and cardiovascular risk factors while addressing some common concerns and misconceptions. Blood total cholesterol and LDL-cholesterol concentrations show a variable, highly individual response to LCHF diets, and should be monitored in patients adhering to this diet.

Influence of Affective Stimuli on Leg Power Output and Associated Neuromuscular Parameters during Repeated High Intensity Cycling Exercises.

The aim of this study was to examine the impact of emotional eliciting pictures on neuromuscular performance during repetitive supramaximal cycling exercises (RSE). In a randomized order, twelve male participants were asked to perform five 6-s cycle sprints (interspaced by 24 s of recovery) on a cycle ergometer in front of neutral, pleasant or unpleasant pictures. During each RSE, mean power output (MPO) and electromyographic activity [root mean square (RMS) and median frequency (MF)] of the vastus lateralis and vastus medialis muscles were analyzed.

McArdle disease does not affect skeletal muscle fibre type profiles in humans.

Patients suffering from glycogen storage disease V (McArdle disease) were shown to have higher surface electrical activity in their skeletal muscles when exercising at the same intensity as their healthy counterparts, indicating more muscle fibre recruitment. To explain this phenomenon, this study investigated whether muscle fibre type is shifted towards a predominance in type I fibres as a consequence of the disease. Muscle biopsies from the Biceps brachii (BB) (n = 9) or Vastus lateralis (VL) (n = 8) were collected over a 13-year period from male and female patients diagnosed with McArdle disease, analysed for myosin heavy chain (MHC) isoform content using SDS-PAGE, and compared to healthy controls (BB: n = 3; VL: n = 10).

Potentiation and electrical stimulus frequency during self-paced exercise and recovery.

The aim of this study was to investigate the effect of potentiation on stimulation-induced muscle function during and after an intense bout of self-paced dynamic exercise. Ten active subjects performed a time trial involving repetitive concentric extension-flexion of the right knee using a Biodex dynamometer. Electrical stimulation before and after a 5 s maximal isometric voluntary contraction was performed before the start of the time trial and immediately (< 5 s) after each 20% of the time trial as well as 1, 2, 4 and 8 min after time trial termination.

Potentiation increases peak twitch torque by enhancing rates of torque development and relaxation.

The aim of this study was to measure the extent to which potentiation changes in response to an isometric maximal voluntary contraction. Eleven physically active subjects participated in two separate studies. Single stimulus of electrical stimulation of the femoral nerve was used to measure torque at rest in unpotentiated quadriceps muscles (study 1 and 2), and potentiated quadriceps muscles torque in a 10 min period after a 5 s isometric maximal voluntary contraction of the quadriceps muscles (study 1).

Low-carbohydrate and high-fat intake can manage obesity and associated conditions: occasional survey.

This study analyses 127 communications from individuals self-reporting their weight change following adoption of a low-carbohydrate, high-fat (LCHF) eating plan. Total combined self-reported weight loss was 1 900 kg (range 5 kg gain to 84 kg loss). The mean ± standard deviation weight loss of 15 (±12) kg is among the largest yet described.

The Women's Health Initiative Randomized Controlled Dietary Modification Trial: an inconvenient finding and the diet-heart hypothesis.

One goal of the US$700 million Women's Health Initiative Randomized Controlled Dietary Modification Trial was to determine whether post-menopausal women who adopted what was regarded as a 'heart healthy' low-fat diet, high in vegetables, fruits and grains, reduced their risk of developing cardiovascular disease. The trial substantially favoured the outcome in the intervention group, who also received an intensive nutritional and behaviour education programme not offered to the control group. These studies neatly disprove the diet-heart hypothesis since adoption of 'heart healthy' eating not only failed to influence future cardiac events in the healthy but it increased such events in the unhealthy and worsened diabetic control in those with type 2 diabetes mellitus.

Brain stimulation modulates the autonomic nervous system, rating of perceived exertion and performance during maximal exercise.

Background: The temporal and insular cortex (TC, IC) have been associated with autonomic nervous system (ANS) control and the awareness of emotional feelings from the body. Evidence shows that the ANS and rating of perceived exertion (RPE) regulate exercise performance. Non-invasive brain stimulation can modulate the cortical area directly beneath the electrode related to ANS and RPE, but it could also affect subcortical areas by connection within the cortico-cortical neural networks.

Evidence of cardiac functional reserve upon exhaustion during incremental exercise to determine VO2max.

Background: There remains considerable debate regarding the limiting factor(s) for maximal oxygen uptake (VO2max). Previous studies have shown that the central circulation may be the primary limiting factor for VO2max and that cardiac work increases beyond VO2max.

Aim: We sought to evaluate whether the work of the heart limits VO2max during upright incremental cycle exercise to exhaustion.

High oxidative capacity and type IIx fibre content in springbok and fallow deer skeletal muscle suggest fast sprinters with a resistance to fatigue.

Some wild antelopes are fast sprinters and more resistant to fatigue than others. This study therefore investigated two wild antelope species to better understand their reported performance capability. Muscle samples collected post mortem from the vastus lateralis and longissimus lumborum of fallow deer (Dama dama) and springbok (Antidorcas marsupialis) were analysed for myosin heavy chain isoform content, citrate synthase, 3-hydroxyacyl CoA dehydrogenase, phosphofructokinase, lactate dehydrogenase and creatine kinase activities.

UCT taught me how to challenge beliefs.

The world's first successful human heart transplantation on 2 December 1967 inspired me to study medicine at the University of Cape Town Faculty of Health Sciences. There I learned 5 key elements for a successful career in either medicine or science or both - perfectionism, passion, compassion, the dispassionate investigation of all the available evidence, and the need to challenge established beliefs for which the scientific evidence appears imperfect. Challenging such beliefs enabled us to prove that hyponatraemic encephalopathy was caused by persistent and heroic over-drinking during prolonged exercise, usually lasting more than 4 hours, and was unrelated to salt losses in sweat and urine; to understand that the brain not the muscles must regulate the exercise performance, and thus develop the Central Governor Model of Exercise; and to reconsider the dietary causes of the obesity and diabetic epidemic.

Fatigue is a Brain-Derived Emotion that Regulates the Exercise Behavior to Ensure the Protection of Whole Body Homeostasis.

An influential book written by A. Mosso in the late nineteenth century proposed that fatigue that "at first sight might appear an imperfection of our body, is on the contrary one of its most marvelous perfections. The fatigue increasing more rapidly than the amount of work done saves us from the injury which lesser sensibility would involve for the organism" so that "muscular fatigue also is at bottom an exhaustion of the nervous system.

Black wildebeest skeletal muscle exhibits high oxidative capacity and a high proportion of type IIx fibres.

The aim of the study was to investigate the skeletal muscle characteristics of black wildebeest (Connochaetes gnou) in terms of fibre type and metabolism. Samples were obtained post mortem from the vastus lateralis and longissimus lumborum muscles and analysed for myosin heavy chain (MHC) content. Citrate synthase (CS), 3-hydroxyacyl co A dehydrogenase (3HAD), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and creatine kinase (CK) activities were measured spectrophotometrically to represent the major metabolic pathways in these muscles.

Perceptual cues in the regulation of exercise performance - physical sensations of exercise and awareness of effort interact as separate cues.

It has been argued that the physical sensations induced by exercise, measured as the ratings of perceived exertion (RPE), are distinct from the sense of effort. This study aimed to determine whether a new measure of task effort - the Task Effort and Awareness (TEA) score - is able to measure sensations distinct from those included in the conventional RPE scale. Seven well-trained cyclists completed a maximal effort 100 km time trial (TT) and a submaximal trial at 70% of the power sustained during the TT (70% TT).

Time to move beyond a brainless exercise physiology: the evidence for complex regulation of human exercise performance.

In 1923, Nobel Laureate A.V. Hill proposed that maximal exercise performance is limited by the development of anaerobiosis in the exercising skeletal muscles.