Research in the exercise sciences: where we are and where do we go from here--Part II

Kinesiologists in Clinical Exercise Interventional Research for Stroke and Coronary Artery Disease: A Scoping Review

Background: Kinesiology contributions to research and implementation of programs for cardiovascular disease have not been documented. This scoping review assesses kinesiology affiliates participation in exercise interventional research. Methods: The review followed the Preferred Reporting Items for Systematic review and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) Checklist. Eligible studies included individuals diagnosed with coronary artery (CAD) or heart disease (CHD) or stroke participating in exercise interventions supervised or designed by a kinesiologist affiliate (exercise physiologist, kinesiologist, exercise trainer, exercise therapist). Results: The search in MEDLINE, Embase, Scopus, PsychINFO, SPORTDiscus, and CINAHL yielded 219 studies, including 13,874 participants (5,242 CAD, 4,526 CHD, and 4,106 post-stroke). Randomized controlled trials were the most common study design (52%). Kinesiologists were involved in 70% of the studies and supervised 23%. Forty percent did not specify the supervisor. Kinesiologists are involved in prevention and rehabilitation exercise studies that look to improve feasibility of practice, aerobic fitness, muscle and body composition, functional capacity, gait, neurological, psychosocial, and cardiovascular outcomes. Conclusions: Documentation of kinesiology contributions to research for patients with cardiovascular disease may enhance their acceptance in research and care for people with impaired cardiovascular health.

Cross-sectional insights into exercise physiology knowledge among medical students in Jordan

Objectives

Exercise physiology is a branch of physiology that studies how physical activity and exercise alter the structure and function of living organisms. Knowledge of exercise physiology is crucial to improve athletic performance, improve people's ability to cope with extreme circumstances and approach chronic diseases. This research aimed to evaluate the knowledge of future healthcare professionals, namely, the medical students in Jordan regarding exercise physiology.

Methods

Responses were collected from 524 undergraduate medical students enrolled in clinical clerkship. An online survey that evaluated participants' basic understanding of various physiological concepts related to physical exercises, such as respiratory exchange ratio, physical fitness, V̇O2 max and exercise at high altitudes was employed in the study.

Results

63.2% of participants had a poor level of exercise physiology knowledge. Misconceptions regarding V̇O2 max definition (93.3%), application (46.4%), significance (35.6%) and related physiological factors (48.7%) were observed. Students had misconceptions about physical fitness evaluation questions (52.5%, 39%, and 41.8%, respectively). Student proportions of 37%, 41%, 80.3% and 73.1% showed misconceptions about muscle groups and energy systems during training, training prescription variables, respiratory exchange ratio, and high-altitude performance, respectively. Significant differences in knowledge levels were found based on respondent characteristics (p < 0.05).

Conclusions

Knowledge of exercise physiology is more than desirable for medical professionals. Therefore, efforts must be made to increase awareness and improve knowledge about basic physiological fundamentals related to exercise physiology among medical students in Jordan, as they represent the backbone of healthcare professionals of the future who will deal with medical conditions related to physical activity and exercise.

Omics and the molecular exercise physiology

Exercise is a well-known non-pharmacologic agent used to prevent and treat a wide range of pathologic conditions such as metabolic and cardiovascular disease. In this sense, the classic field of exercise physiology has determined the main theoretical and practical bases of physiologic adaptations in response to exercise. However, the last decades were marked by significant advances in analytical laboratory techniques, where the field of biochemistry, genetics and molecular biology promoted exercise science to enter a new era. Regardless of its application, whether in the field of disease prevention or performance, the association of molecular biology with exercise physiology has been fundamental for unveiling knowledge of the molecular mechanisms related to the adaptation to exercise. This chapter will address the natural evolution of exercise physiology toward genetics and molecular biology, emphasizing the collection of integrated analytical approaches that composes the OMICS and their contribution to the field of molecular exercise physiology.

Effect of exercise intensity on Nrf2 signalling in young men

INTRODUCTION

The transcription factor Nrf2 is the master regulator of antioxidant defence. Recent data indicate a single bout of moderate-intensity stationary cycling at a constant workload upregulates Nrf2 signalling in young, but not older men; however, the role of exercise intensity on Nrf2 activation has not been tested. We hypothesised that a high-intensity interval session would elicit a greater Nrf2 response than moderate aerobic exercise.

METHODS

Nrf2 signalling in response to two 30-min cycling protocols (high-intensity interval and constant workload) was compared in young men (25 ± 1y, n = 16). Participants completed exercise trials in random order with blood collected pre-, immediately post-, and 30-mins post exercise. Five participants completed a control trial without any physical activity. Nrf2 signalling was determined by measuring protein expression of Nrf2 in whole cell and nuclear fractions. Plasma 8-isoprostanes as well as peripheral mononuclear cell glutathione reductase (GR) and superoxide dismutase activity were measured as markers of oxidative stress.

RESULTS

The exercise trials elicited significant increases in nuclear Nrf2 (p < .01), but increases in whole cell Nrf2 did not reach statistical significance. GR activity and plasma 8-isoprostanes increased significantly in response to exercise (p < .05), and GR response was higher in the high-intensity trial (p < .05).

CONCLUSION

Our findings indicate that acute aerobic exercise elicits activation of nuclear Nrf2, regardless of exercise intensity, but that higher-intensity exercise results in greater activity of GR. Future experiments should explore the effect of exercise mode and duration on Nrf2 signalling, and the role of intensity in compromised populations.

The effects of aerobic and anaerobic exercises on circulating soluble-Klotho and IGF-I in young and elderly adults and in CAD patients

Different studies support the notion that chronic aerobic exercises training can influence the circulating levels of soluble-Klotho (s-Klotho) and insulin-like growth factor 1 (IGF-I). The effects of s-Klotho include improving the quality of life, alleviating the negative impact of age on the body's work capacity, and possibly increasing longevity. This review provides an overview of the latest findings in this field of research in humans. The different modes of dynamic exercise and their impact on circulating levels of s-Klotho and IGF-I in young adult athletes, untrained young adults, trained healthy older adults, untrained healthy older adults, and coronary artery disease (CAD) patients are reviewed and discussed. Together these findings suggest that long-lasting (chronic) aerobic exercise training is probably one of the antiaging factors that counteract the aging and CAD process by increasing the circulating s-Klotho and lowering the IGF-I levels. However, following anaerobic exercise training the opposite occurs. The exact metabolic and physiological pathways involved in the activity of these well-trained young and master sportsmen should be further studied and elucidated. The purpose of this review was to provide a clarification regarding the roles of s-Klotho and intensities and durations of different exercise on human health.

Quantitative genomics of voluntary exercise in mice: transcriptional analysis and mapping of expression QTL in muscle

Motivation and ability both underlie voluntary exercise, each with a potentially unique genetic architecture. Muscle structure and function are one of many morphological and physiological systems acting to simultaneously determine exercise ability. We generated a large (n = 815) advanced intercross line of mice (G4) derived from a line selectively bred for increased wheel running (high runner) and the C57BL/6J inbred strain. We previously mapped quantitative trait loci (QTL) contributing to voluntary exercise, body composition, and changes in body composition as a result of exercise. Using brain tissue in a subset of the G4 (n = 244), we have also previously reported expression QTL (eQTL) colocalizing with the QTL for the higher-level phenotypes. Here, we examined the transcriptional landscape of hind limb muscle tissue via global mRNA expression profiles. Correlations revealed an ∼1,168% increase in significant relationships between muscle transcript expression levels and the same exercise and body composition phenotypes examined previously in the brain. The exercise trait most often significantly correlated with gene expression in the brain was running duration while in the muscle it was maximum running speed. This difference may indicate that time spent engaging in exercise behavior may be more influenced by central (neurobiological) mechanisms, while intensity of exercise may be largely controlled by peripheral mechanisms. Additionally, we used subsets of cis-acting eQTL, colocalizing with QTL, to identify candidate genes based on both positional and functional evidence. We discuss three plausible candidate genes (Insig2, Prcp, Sparc) and their potential regulatory role.

Time course analysis reveals gene-specific transcript and protein kinetics of adaptation to short-term aerobic exercise training in human skeletal muscle

Repeated bouts of episodic myofibrillar contraction associated with exercise training are potent stimuli for physiological adaptation. However, the time course of adaptation and the continuity between alterations in mRNA expression and protein content are not well described in human skeletal muscle. Eight healthy, sedentary males cycled for 60 min at 80% of peak oxygen consumption (VO_2peak) each day for fourteen consecutive days, resulting in an increase in VO_2peak of 17.5±3.8%. Skeletal muscle biopsies were taken at baseline, and on the morning following (+16 h after exercise) the first, third, seventh, tenth and fourteenth training sessions. Markers of mitochondrial adaptation (Cyt c and COXIV expression, and citrate synthase activity) were increased within the first week of training, but the mtDNA/nDNA ratio was unchanged by two weeks of training. Accumulation of PGC-1α and ERRα protein during training suggests a regulatory role for these factors in adaptations of mitochondrial and metabolic gene expression. A subset of genes were transiently increased after one training session, but returned to baseline levels thereafter, which is supportive of the concept of transcriptional capacity being particularly sensitive to the onset of a new level of contractile activity. Thus, gene-specific temporal patterns of induction of mRNA expression and protein content are described. Our results illustrate the phenomenology of skeletal muscle plasticity and support the notion that transcript level adjustments, coupled to accumulation of encoded protein, underlie the modulation of skeletal muscle metabolism and phenotype by regular exercise.

Rationale and resources for teaching the mathematical modeling of athletic training and performance

A number of professions rely on exercise prescription to improve health or athletic performance, including coaching, fitness/personal training, rehabilitation, and exercise physiology. It is therefore advisable that the professionals involved learn the various tools available for designing effective training programs. Mathematical modeling of athletic training and performance, which we henceforth call "performance modeling," is one such tool. Two models, the critical power (CP) model and the Banister impulse-response (IR) model, offer complementary information. The CP model describes the relationship between work rates and the durations for which an individual can sustain them during constant-work-rate or intermittent exercise. The IR model describes the dynamics by which an individual's performance capacity changes over time as a function of training. Both models elegantly abstract the underlying physiology, and both can accurately fit performance data, such that educating exercise practitioners in the science of performance modeling offers both pedagogical and practical benefits. In addition, performance modeling offers an avenue for introducing mathematical modeling skills to exercise physiology researchers. A principal limitation to the adoption of performance modeling is a lack of education. The goal of this report is therefore to encourage educators of exercise physiology practitioners and researchers to incorporate the science of performance modeling in their curricula and to serve as a resource to support this effort. The resources include a comprehensive review of the concepts associated with the development and use of the models, software to enable hands-on computer exercises, and strategies for teaching the models to different audiences.

Redox biology of exercise: an integrative and comparative consideration of some overlooked issues

The central aim of this review is to address the highly multidisciplinary topic of redox biology as related to exercise using an integrative and comparative approach rather than focusing on blood, skeletal muscle or humans. An attempt is also made to re-define ‘oxidative stress’ as well as to introduce the term ‘alterations in redox homeostasis’ to describe changes in redox homeostasis indicating oxidative stress, reductive stress or both. The literature analysis shows that the effects of non-muscle-damaging exercise and muscle-damaging exercise on redox homeostasis are completely different. Non-muscle-damaging exercise induces alterations in redox homeostasis that last a few hours post exercise, whereas muscle-damaging exercise causes alterations in redox homeostasis that may persist for and/or appear several days post exercise. Both exhaustive maximal exercise lasting only 30 s and isometric exercise lasting 1–3 min (the latter activating in addition a small muscle mass) induce systemic oxidative stress. With the necessary modifications, exercise is capable of inducing redox homeostasis alterations in all fluids, cells, tissues and organs studied so far, irrespective of strains and species. More importantly, ‘exercise-induced oxidative stress’ is not an ‘oddity’ associated with a particular type of exercise, tissue or species. Rather, oxidative stress constitutes a ubiquitous fundamental biological response to the alteration of redox homeostasis imposed by exercise. The hormesis concept could provide an interpretative framework to reconcile differences that emerge among studies in the field of exercise redox biology. Integrative and comparative approaches can help determine the interactions of key redox responses at multiple levels of biological organization.