Effects of exercise training on mitochondrial and capillary growth in human skeletal muscle: A systematic review and meta-regression

Background: Skeletal muscle mitochondria and capillaries are crucial for aerobic fitness, and suppressed levels are associated with chronic and age-related diseases. Currently, evidence-based exercise training recommendations to enhance these characteristics are limited. It is essential to explore how factors, such as fitness level, age, sex, and disease affect mitochondrial and capillary adaptations to different exercise stimuli. Objectives: The main aim of this study was to compare the effects of low- or moderate intensity continuous endurance training (ET), high-intensity interval or continuous training (HIT), and sprint interval training (SIT) on changes in skeletal muscle mitochondrial content and capillarization. Secondarily, the effects on maximal oxygen consumption (VO2max), muscle fiber cross-sectional area, and fiber type proportion were investigated. Methods: A systematic literature search was conducted in PubMed, Web of Science, and SPORTDiscus databases, with no data restrictions, up to 2 February 2022. Exercise training intervention studies of ET, HIT, and SIT were included if they had baseline and follow-up measures of at least one marker of mitochondrial content or capillarization. In total, data from 5973 participants in 353 and 131 research articles were included for the mitochondrial and capillary quantitative synthesis of this review, respectively. Additionally, measures of VO2max, muscle fiber cross-sectional area, and fiber type proportion were extracted from these studies. Results: After adjusting for relevant covariates, such as training frequency, number of intervention weeks, and initial fitness level, percentage increases in mitochondrial content in response to exercise training increased to a similar extent with ET (23 ± 5%), HIT (27 ± 5%), and SIT (27 ± 7%) (P > 0.138), and were not influenced by age, sex, menopause, disease, or the amount of muscle mass engaged. Higher training frequencies (6 > 4 > 2 sessions/week) were associated with larger increases in mitochondrial content. Per total hour of exercise, SIT was ~ 2.3 times more efficient in increasing mitochondrial content than HIT and ~ 3.9 times more efficient than ET, while HIT was ~ 1.7 times more efficient than ET. Capillaries per fiber increased similarly with ET (15 ± 3%), HIT (13 ± 4%) and SIT (10 ± 11%) (P = 0.556) after adjustments for number of intervention weeks and initial fitness level. Capillaries per mm2 only increased after ET (13 ± 3%) and HIT (7 ± 4%), with increases being larger after ET compared with HIT and SIT (P  0.116), but ET and SIT exhibited opposing effects (P = 0.041). VO2max increased similarly with ET, HIT, and SIT, although HIT showed a tendency for greater improvement compared with both ET and SIT (P = 0.082), while SIT displayed the largest increase per hour of exercise. Higher training frequencies (6 > 4 > 2 sessions/week) were associated with larger increases in VO2max. Women displayed greater percentage gains in VO2max compared with men (P = 0.008). Generally, lower initial fitness levels were associated with greater percentage improvements in mitochondrial content, capillarization, and VO2max. SIT was particularly effective in improving mitochondrial content and VO2max in the early stages of training, while ET and HIT showed slower but steady improvements over a greater number of training weeks. Conclusions: The magnitude of change in mitochondrial content, capillarization, and VO2max to exercise training is largely determined by the initial fitness level, with greater changes observed in individuals with lower initial fitness. The ability to adapt to exercise training is maintained throughout life, irrespective of sex and presence of disease. While training load (volume × intensity) is a suitable predictor of changes in mitochondrial content and VO2max, this relationship is less clear for capillary adaptations.publishedVersio

Human skeletal muscle possesses an epigenetic memory of high-intensity interval training

Human skeletal muscle displays an epigenetic memory of resistance exercise induced-hypertrophy. It is unknown, however, whether high-intensity interval training (HIIT) also evokes an epigenetic muscle memory. This study used repeated training intervention interspersed with a detraining period to assess epigenetic memory of HIIT. Twenty healthy subjects (25 ± 5 yr) completed two HIIT interventions (training and retraining) lasting 2 mo, separated by 3 mo of detraining. Measurements at baseline, after training, detraining, and retraining included maximal oxygen consumption (V̇o2max). Vastus lateralis biopsies were taken for genome-wide DNA methylation and targeted gene expression analyses. V̇o2max improved during training and retraining (P 0.58). Thousands of differentially methylated positions (DMPs) predominantly demonstrated a hypomethylated state after training, retained even after 3-mo of exercise cessation and into retraining. Five genes, ADAM19, INPP5a, MTHFD1L, CAPN2, and SLC16A3, possessed differentially methylated regions (DMRs) with retained hypomethylated memory profiles and increased gene expression. The retained hypomethylation during detraining was associated with an enhancement in expression of the same genes even after 3 mo of detraining. SLC16A3, INPP5a, and CAPN2 are involved in lactate transport and calcium signaling. Despite similar physiological adaptations between training and retraining, memory profiles were found at epigenetic and gene expression level, characterized by retained hypomethylation and increased gene expression after training into long-term detraining and retraining. These genes were associated with calcium signaling and lactate transport. Although significant memory was not observed in physiological parameters, our novel findings indicate that human skeletal muscle possesses an epigenetic memory of HIIT.publishedVersio

Youth athletes’ framing of nutritional supplements: Performance enhancement and food

Prior studies have revealed how some nutritional supplements used to enhance performance in sports are considered problematic because they are associated with doping. In this study, frame analysis is applied to scrutinise interviews conducted with 24 ambitious youth athletes enrolled in elite sport schools. The analysis enables exploration of the athletes’ understanding and meaning-making concerning the so-called grey zone supplements in terms of two major frames. The first performance frame is expected as the context is elite youth sport, and many aspects of the athletes’ lives revolve around athletic progress. However, the more interesting finding is that this performance frame permeates almost all aspects of the young athletes’ lives, including how food is both understood and consumed. The second frame implies the framing of nutritional supplements as food. Here, the use of supplements is rationalised by practical concerns such as hectic training and teaching schedules that leave little time for meals, with supplements becoming a quick fix to meet energy needs. Hence, meaning-making concerning the grey zone supplements gives rise to an alternative framing linked to food and eating, although an overarching logic of performance also exerts a significant impact.publishedVersio

Part II of a two-step mixed-methods approach in developing the Growth Talent Mindsets for Sports Coaches Intervention 2.0: The coaches’ perceptions of delivery and possible psychological processes of change

The current study follows up on the first-time implementation of the GrowTMindS Intervention described in Part I, with an overall aim of improving sports coaches’ beliefs in their talent as a coach (coach talent mindset, C-TM) and their athletes’ talent (athlete talent mindset, A-TM) as being malleable. By drawing on the user-centered design approach, we first refined the intervention using the insight provided by the coaches in Part I. A mixed-method approach then evaluated the second-time implementation, which included 33 participants (Mage = 38.76, SD = 16.55; 13 women, 20 men) in the quantitative strand and 11 informants (Mage = 39.09, SD = 14.10; 5 women, 6 men) in the sequential qualitative strand. The coaches represented the sports of swimming, bandy, ski sports, golf, and orienteering. The quantitative results indicate that the intervention targeted the coaches’ talent mindsets as their growth C-TM and A-TM scores increased from pre-test to post-test a year and a half after the intervention. The qualitative findings substantiate these results, showing how an increase at scale also appears meaningful concerning their belief in their own and their athletes’ developments. The findings also helped us to understand how the embracing, or possibly refuting, of intervention delivery may substantiate different trajectories of change, and thereby provided insight into the difficulty of targeting and the complexity of psychological processes and behavioral change. By considering the changes in coaches’ growth C-TM and A-TM, we assume that the GrowTMindS Intervention is ready for testing in a Phase III efficacy trial.publishedVersio

Snow sports-specific extension of the IOC consensus statement: Methods for recording and reporting epidemiological data on injury and illness in sports

The International Olympic Committee’s (IOC) consensus statement on ‘methods for recording and reporting of epidemiological data on injury and illness in sport’ recommended standardising methods to advance data collection and reporting consistency. However, additional aspects need to be considered when these methods are applied to specific sports settings. Therefore, we have developed a snow sports-specific extension of the IOC statement to promote the harmonisation of injury and illness registration methods among athletes of all levels and categories in the different disciplines governed by the International Ski and Snowboard Federation (FIS), which is also applicable to other related snow sports such as biathlon, ski mountaineering, and to some extent, para snow sports. The panel was selected with the aim of representing as many different areas of expertise/backgrounds, perspectives and diversity as possible, and all members were assigned to thematic subgroups based on their profiles. After panel formation, all members were provided with an initial draft of this extension, which was used as a basis for discussion of aspects specific to the discipline, application context, level and sex within their snow sports subgroup topic. The outcomes were then aligned with the IOC’s existing consensus recommendations and incorporated into a preliminary manuscript draft. The final version of this snow sports-specific extension was developed and approved in two iterative rounds of manuscript revisions by all consensus panel members and a final meeting to clarify open discussion points. This snow sports-specific extension of the IOC statement is intended to guide researchers, international and national sports governing bodies, and other entities recording and reporting epidemiological data in snow sports to help standardise data from different sources for comparison and future research.publishedVersio

The impact of injuries on sports-related analgesic use in Danish youth elite athletes: A 4-week prospective cohort study

Objectives: Investigate the association between injury severity and sports-related analgesic use, and explore the types and reasons for analgesic use in Danish youth elite athletes. Design: 4-week prospective cohort study. Methods: 713 youth elite athletes (44 % female) aged 15–20 years provided information on demographics, sports specific questions, and injury severity. We categorized injury severity based on the amount of impact on sports participation: 1) no injury (reference), 2) injury not affecting sports participation, 3) injury causing modifications in sports participation, and 4) injury causing complete absence from sport. Participants were asked weekly over 4 weeks about the number of days with sports-related analgesic use, types, and reasons for use. Mixed-effects regression models were used to assess the association between injury severity and prevalence (yes/no) and frequency (days/week) of analgesic use. Results: Analgesic use at least once during the four weeks was reported by 224 athletes (31 %), with a mean weekly prevalence of 13 %. The odds of analgesic use increased with injury severity compared with the reference group; injury not affecting sports participation: OR 2.6 (95 % CI 1.6–4.2), injury causing modifications in sports participation: OR 3.2 (95 % CI 2.0–5.2), injury causing complete absence from sport: OR 3.6 (95 % CI 1.5-8.7) (test for trend; p = ＜0.001). The rate (frequency) of analgesic use also increased with injury severity (test for trend; p = 0.003). Athletes most commonly used analgesics to treat pain/injury after sports participation (62 %), and paracetamol was most frequently used (84 %). Conclusions: Injury severity was associated with increased odds and rate of analgesic use.publishedVersio

Part I of a two-step mixed-methods approach in developing the Growth Talent Mindsets for Sports Coaches Intervention: The design and targeting of the intervention

The overall aim of this two-part study was to develop an intervention targeting sports coaches’ mindsets about their talent as a coach (coach talent mindset, C-TM) and their athletes’ talent (athlete talent mindset, A-TM), called the GrowTMindS Intervention. In this Part I, the intervention was developed drawing on a user-centered design approach and implemented in a coach education program in Norway. The study involved 31 coaches (5 women, 26 men) from 22 to 69 years of age, representing the sports of bandy, golf, ski sports, swimming, and volleyball. Using a mixed-methods approach, the quantitative results showed that the coaches increased their A-TM from pretest to post-test, while their C-TM, which was high at baseline, remained more challenging to target. The qualitative findings helped us understand how most coaches, through reflective processes, perceived the delivery of the intervention as sense-making and substantiated their commitment to growth talent mindsets. The qualitative findings also highlighted areas for refinement and tailoring of the intervention to target all coaches’ talent mindsets. Overall, the study was considered a necessary first step in developing an intervention showing significant and meaningful changes in coaches’ self-reported talent mindsets, consistent with the guidelines of wise psychological intervention and behavior change.publishedVersio

Knowledge and communication about the menstrual cycle among rhythmic gymnasts, ballerinas, and dancers

While moderate exercise supports regular menstrual cycle (MC) function, many female athletes experience MC symptoms that negatively influence their training and performance. Hereby, knowledge and communication about this topic are important to promote an athlete’s health and wellbeing. Hence, this study aimed to assess the knowledge and communication surrounding the MC among Norwegian rhythmic gymnasts, ballerinas, and dancers. In total, 116 rhythmic gymnasts, ballerinas, and dancers aged ≥ 16 years training ≥ 3 days per week completed an electronic questionnaire. Of these, 63% (n = 73) reported a lack of knowledge about the MC’s influence on physical fitness and performance, and 39% (n = 45) rated their coaches’ or pedagogues’ knowledge as low. With only 32% of participants discussing the MC with their coaches/pedagogues, communication was found to be limited. Seventy-three percent felt uncomfortable during training or competition due to their attire and recommended darker colors and more options in size and layering. The study highlights a significant gap in knowledge and communication about the MC among female athletes and coaches/pedagogues in aesthetic sports. It also recommends improving athletes’ choice of attire for greater comfort and confidence.publishedVersio

Device-measured 24-hour movement behaviors and blood pressure: A 6-part compositional individual participant data analysis in the ProPASS consortium

Background: Blood pressure (BP)–lowering effects of structured exercise are well-established. Effects of 24-hour movement behaviors captured in free-living settings have received less attention. This cross-sectional study investigated associations between a 24-hour behavior composition comprising 6 parts (sleeping, sedentary behavior, standing, slow walking, fast walking, and combined exercise-like activity [eg, running and cycling]) and systolic BP (SBP) and diastolic BP (DBP). Methods: Data from thigh-worn accelerometers and BP measurements were collected from 6 cohorts in the Prospective Physical Activity, Sitting and Sleep consortium (ProPASS) (n=14 761; mean±SD, 54.2±9.6 years). Individual participant analysis using compositional data analysis was conducted with adjustments for relevant harmonized covariates. Based on the average sample composition, reallocation plots examined estimated BP reductions through behavioral replacement; the theoretical benefits of optimal (ie, clinically meaningful improvement in SBP [2 mm Hg] or DBP [1 mm Hg]) and minimal (ie, 5-minute reallocation) behavioral replacements were identified. Results: The average 24-hour composition consisted of sleeping (7.13±1.19 hours), sedentary behavior (10.7±1.9 hours), standing (3.2±1.1 hours), slow walking (1.6±0.6 hours), fast walking (1.1±0.5 hours), and exercise-like activity (16.0±16.3 minutes). More time spent exercising or sleeping, relative to other behaviors, was associated with lower BP. An additional 5 minutes of exercise-like activity was associated with estimated reductions of –0.68 mm Hg (95% CI, –0.15, –1.21) SBP and –0.54 mm Hg (95% CI, –0.19, 0.89) DBP. Clinically meaningful improvements in SBP and DBP were estimated after 20 to 27 minutes and 10 to 15 minutes of reallocation of time in other behaviors into additional exercise. Although more time spent being sedentary was adversely associated with SBP and DBP, there was minimal impact of standing or walking. Conclusions: Study findings reiterate the importance of exercise for BP control, suggesting that small additional amounts of exercise are associated with lower BP in a free-living setting.publishedVersio

What happens to the “social” in psychosocial?: Exploring epistemic practices and therapeutic culture in teacher education

This paper examines the role of the psychosocial as an influential epistemic category in the context of a globalised therapeutic culture. Drawing on empirical data from fieldwork conducted at a teacher education institution in Norway, we conceptualise the psychosocial as epistemic practice and analyse three interrelated social levels: the individual level, concerned with teachers’ performance as social caretakers; the community level, characterised by a diagnosing gaze on individual pupils; and the societal level, understood as structural threats to well-being. Our study suggests that these epistemic practices favour psychological diagnosis and individual protection over shared knowledge and broader social awareness.publishedVersio