Modulation of exercise-induced gene expression in human skeletal muscle by exercise intensity, training status and short-term endurance training

A single bout of exercise generates a robust, but transient, increase in mRNA abundance for a multitude of genes, which is thought to contribute to the recovery from and adaptation to exercise. Adaptation to exercise training is mediated by the accumulation of pulses of elevated mRNA after individual exercise bout within a training program, leading to longer term increases in protein abundance that culminate in physiological adaptations. Several signalling pathways involving cytoplasmic protein kinases, transcription factors and their coregulators are recognised as regulators by which activation transduces physiological stimuli into transcriptional adaptations. This thesis examined the modulation of gene expression in human skeletal muscle under varying physiological conditions, including divergent exercise intensities, untrained and trained muscle, and short-term endurance training. Compared to low intensity isocaloric exercise (400 kcal, 40%VO2peak), a single bout of high intensity exercise (80% VO2peak) resulted in greater activation of the signalling kinases AMPK and CaMKII, coincident with a larger increase in mRNA abundance of PGC-1α and FOXO1A during recovery. A single bout exercise induced an increase in PGC-1α. FOXO1A, and PDK4 mRNA abundance in both untrained and trained muscle. This may form part of a transcriptional response that contributes to exercise-induced alterations in skeletal muscle metabolism such as glucose sparing and increased fat oxidation during recovery from exercise. Fourteen consecutive days of endurance training resulted in the accumulation of mRNA and corresponding protein for some (ERRα, COXIV), but not all (FOXO1A, PDK4), reportedly acute exercise-responsive genes. This suggests that certain genes are involved in the restoration of homeostasis after acute exercise, whereas others are involved in adaptation to regular exercise. Our results illustrate the well-described phenomenology of skeletal muscle plasticity and suggest that transcript level adjustments underlie modulation of skeletal muscle metabolism and phenotype by regular exercise

Case Study: Transition to a Vegan Diet in an Elite Male Gaelic Football Player

Vegan diets are increasingly of interest to athletes, but require a well-planned approach in order to mitigate the risk of potential adverse effects on nutrient intakes, and consequently performance. This case study reports the process of an elite male Gaelic football player (age 25 years; height, 1.88 m; body mass, 87.8 kg; lean body mass, 73.26 kg; body fat, 11.3%) transitioning from an omnivorous diet to a vegan diet at the beginning of a competitive season. The report encompasses key considerations in the planning and provision of nutrition support in this context, in addition to iterations needed based on challenges presented by the athlete. Analysis of nutrient intake (Nutritics Dietary Analysis Software), body composition (dual X-ray absorptiometry; Lunar iDXA, GE Healthcare), and running performance during match-play (global positioning system-based tracking; STATSports Apex) each indicated that with adequate knowledge and education, and appropriate planning, commitment and iterative feedback, the athlete was able to meet nutrition targets on a vegan diet without compromising key performance indicators compared to the omnivorous diet of the previous season. We anticipate that this case study will assist practitioners to recognize the key considerations to address when working with athletes transitioning to a vegan diet

Evolution of Free Volume Elements in Amorphous Polymers Undergoing Uniaxial Deformation: a Molecular Dynamics Simulation Study

Amorphous polymers are considered promising materials for separations due to their excellent transport properties and low fabrication costs. The separation performance of a membrane material is characterized by its permeability (overall throughput of components), and selectivity (efficiency of separation). Both permeability and selectivity are controlled by the diffusion of different penetrants through the matrix, which is strongly influenced by the distribution and morphology of the free volume elements (FVEs). FVEs are void spaces in the polymer matrix that result from the inefficient packing of bulky and rigid groups on the polymer backbone. Thus, FVEs dictate the efficiency of membrane polymers, and it is imperative to understand how processing conditions such as high pressure influence their structure. In this paper, we apply uniaxial tensile deformation on three polymers, namely polystyrene (PS), polymethylpentene (PMP), and HAB-6FDA thermally rearranged polymer (TRP), at varying temperatures and strain rates. We calculate the stress strain curve, tensile modulus, and free volume element evolution at these conditions. We find that PMP and PS with low and moderate glass transition temperature, respectively, exhibit the most change in mechanical properties as a function of strain rate and temperature. The properties of TRP, however, do not vary as much. We also find that FVEs become larger with deformation, and the extent of this change is in line with the overall change of mechanical properties of the material.Comment: Brendan Wernisch and Mohammed Al Otmi contributed equally to this wor

The Between-Competition Running Demands of Elite Hurling Match-Play

The current study aimed to investigate the differences in running demands between the National Hurling League (NHL) and the Championship, and within playing positions. GPS (10 Hz, STATSports Apex GNSS) were used to analyse the running demands during 34 games (2017–2020 seasons) of the Championship and the NHL. The running demands (total-, relative-, high-speed- [\u3e17 km·h−1] and sprint [≥22 km·h−1] distance, number and length of sprints, and peak speed) were compared between competitions. Greater total- [ES = 0.32], relative- [ES = 0.26], and sprint-distance [ES = 0.41], and number of sprints [ES = 1.29] were completed in the Championship. The high-speed distance was similar between competitions. Half-backs and half-forwards covered greater total- (ES = 0.91 and 0.21, respectively), relative- (ES = 1.14 and 0.68, respectively), high-speed- (ES = 0.69 and 0.44, respectively), and sprint-distance (ES = 0.50 and 1.26, respectively), number of sprints (ES = 2.66 and 1.73, respectively), and peak speed (ES = 1.09 and 1.32, respectively) in the Championship. There was no difference (p \u3c 0.05) in the sprint distance covered between positions in the Championship. The results showed that the Championship is more physically demanding. The findings present key implications for the transition between competitions

Effects of a Long Chain n-3 Polyunsaturated Fatty Acid-rich Multi-ingredient Nutrition Supplement on Body Composition and Physical Function in Older Adults with Low Skeletal Muscle Mass.

Six months of supplementation with a multi-ingredient nutrition supplement was investigated in older adults with low skeletal muscle mass given the recently purported benefits of such approaches. Community-dwelling older adults (age, 74.9 ± 3.6 y; M/F, 18/19) participated in a double-blind, placebo-controlled, randomized trial involving daily consumption of either fruit juice placebo (PLA) or supplement (SUPP) in the form of a 200-mL carton of a juice-based emulsion of long chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) (3000 mg as 1500 mg docosahexaenoic acid and 1500 mg eicosapentaenoic acid), whey protein isolate (8 g), vitamin D3 (400 IU), and resveratrol (150 mg). Body composition, physical function, and circulating markers of metabolic health were assessed at baseline (PRE), and after 3 (MID) and 6 (POST) months of supplementation. Lean body mass (LBM) was unchanged in either group, but fat mass increased in SUPP by 1.41 (0.75, 2.07) kg at POST (+6.4%

‘There’s a perfect way to do things, and there’s a real way to do things’: Attitudes, beliefs and practices of strength and conditioning coaches in elite international women's rugby union

Optimal physical performance is a product of specific and tailored training. There are well-established sex differences in anatomical, physiological, and performance factors between biological males and females, which may have implications for physical preparation. A potential knowledge gap exists in relation to sex-specific differences in physical preparation because practitioners largely rely upon empirical evidence collected in male subjects for reference when devising interventions for female athletes. Therefore, this study explored the attitudes, beliefs and practices of strength and conditioning coaches (n = 8; M/F, 6/2) in elite level (international) women's rugby union using semi-structured interviews (mean ± standard deviation duration 59 ± 15 minutes). The interviews explored differences in coaching elite female rugby players compared to males, with specific focus on training methodologies and understanding of pertinent aspects of female physiology. Reflexive thematic analysis was utilised to generate a rich qualitative dataset. Analysis resulted in the identification of higher-order themes: developmental stage of women's rugby, physical preparation, and education. Additional subthemes were created to facilitate organisation and presentation of data. The majority of coaches consider sex-specificity when devising physical preparation interventions as a function of training experience, rather than physiological between-sex differences, yet there were conflicting, and often erroneous understanding of female-specific considerations. To the authors knowledge, this is the first study to investigate attitudes, beliefs, and practices in elite level strength and conditioning coaches regarding sex-specific differences, and as such, illustrates the current understanding and opinions of practitioners in international level women's rugby union

"Male athletes play well to feel good, and female athletes feel good to play well": Attitudes, beliefs, and practices pertaining to perceived sex-related differences in communication and interpersonal approach of strength and conditioning coaches in international women's rugby union.

Effective communication and rapport building with athletes are key tenets of coaching. As the majority of empirical evidence to date has adopted an androcentric view of strength and conditioning, a potential knowledge gap exists regarding sex-related differences in physical preparation and coaching approaches. Therefore, this study explored the attitudes, beliefs and practices of strength and conditioning coaches (n = 8; M/F, 6/2) in elite level (international) women's rugby union using semi-structured interviews (mean ±standard deviation duration 59 ± 15 min). The interviews explored differences in coaching practices for elite female rugby players compared to males, with a specific focus on the interpersonal aspects of the athlete-coach relationship. Reflexive thematic analysis was used to generate a rich qualitative dataset. The analysis resulted in the identification of higher order themes: athlete engagement, and interpersonal approach. The coaches in this study consistently perceived important differences between male and female players in factors related to engagement and interpersonal approach. Coaches adopted differing coaching practices for male and female athletes. This study provides important contextual evidence for the understanding of differences in the interpersonal relationships of female rugby players compared to male athletes from the perspective of elite-level strength coaches

Physical Match Demands of International Women’s Rugby Union: A Three-Year Longitudinal Analysis of a Team Competing in The Women’s Six Nations Championship

There is a paucity of studies describing the physical match demands of elite international women’s rugby union, which limits coaches’ ability to effectively prepare players for the physical demands required to compete at the elite level. Global positioning system technologies were used to measure the physical match demands of 53 international female rugby union players during three consecutive Women’s Six Nations Championships (2020–2022), resulting in 260 individual match performances. Mixed-linear modelling was used to investigate differences in physical match demands between positions. Significant effects (p < 0.05) of the position were observed for all variables, with the exception of relative distances (m.min−1) at velocities of 1.01–3.00 m·s−1 (p = 0.094) and 3.01–5.00 m·s−1 (p = 0.216). This study provides valuable data on the physical match demands of elite international women’s rugby union match play that may aid practitioners in the physical preparation of players to compete at this level. Training methodologies for elite-level female rugby union players should consider the unique demands across positional groups with specific considerations of high-velocity running and collision frequency

The Effect of Hormonal Contraceptive Use on Skeletal Muscle Hypertrophy, Power and Strength Adaptations to Resistance Exercise Training: A Systematic Review and Multilevel Meta-analysis

Background: Resistance exercise training is widely used by general and athletic populations to increase skeletal muscle hypertrophy, power and strength. Endogenous sex hormones influence various bodily functions, including possibly exercise performance, and may influence adaptive changes in response to exercise training. Hormonal contraceptive (HC) use modulates the profile of endogenous sex hormones, and therefore, there is increasing interest in the impact, if any, of HC use on adaptive responses to resistance exercise training. Objective: Our aim is to provide a quantitative synthesis of the effect of HC use on skeletal muscle hypertrophy, power and strength adaptations in response to resistance exercise training. Methods: A systematic review with meta-analysis was conducted on experimental studies which directly compared skeletal muscle hypertrophy, power and strength adaptations following resistance exercise training in hormonal contraceptive users and non-users conducted before July 2023. The search using the online databases PUBMED, SPORTDiscus, Web of Science, Embase and other supplementary search strategies yielded 4669 articles, with 8 articles (54 effects and 325 participants) meeting the inclusion criteria. The methodological quality of the included studies was assessed using the “Tool for the assessment of study quality and reporting in exercise”. Results: All included studies investigated the influence of oral contraceptive pills (OCP), with no study including participants using other forms of HC. The articles were analysed using a meta-analytic multilevel maximum likelihood estimator model. The results indicate that OCP use does not have a significant effect on hypertrophy [0.01, 95% confidence interval (CI) [− 0.11, 0.13], t = 0.14, p = 0.90), power (− 0.04, 95% CI [− 0.93, 0.84], t = − 0.29, p = 0.80) or strength (0.10, 95% CI [− 0.08, 0.28], t = 1.48, p = 0.20). Discussion: Based on the present analysis, there is no evidence-based rationale to advocate for or against the use of OCPs in females partaking in resistance exercise training to increase hypertrophy, power and/or strength. Rather, an individualised approach considering an individual’s response to OCPs, their reasons for use and menstrual cycle history may be more appropriate. Registration: The review protocol was registered on PROSPERO (ID number and hyperlink: CRD42022365677)

EFFECTS OF STATIC STRETCHING ON MAXIMAL ISOKINETIC TORQUE

The effects of 20 seconds of agonist (AGO), antagonist (ANT) or no (NO) pre-exercise stretch on concentric (CON) and eccentric (ECC) maximal isokinetic torque produced at the knee were examined. Twelve male semi-pro rugby players performed dominant isokinetic knee extension following the specified stretch protocol. One-way Repeated Measures ANOVA revealed AGO to be significantly less (p < 0.05) than the other protocols for both CON (270 28 Nm) and ECC (309 42 Nm) torque. There was no difference between the ANT or NO for either CON (303 35 Nm and 304 38 Nm, respectively) or ECC (341 40 Nm and 33644 Nm). The results support the theory that pre-exercise agonist stretching may lead to performance decrements in maximal concentric torque production