Sports Medicine

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A Overweight/obesity-induced insulin resistance: overweight individuals and/or obese individuals with metabolic syndrome present with an excessive accumulation of lipid metabolites and increased plasma levels of pro-inflammatory cytokines. Local inflammation of the microvasculature in skeletal muscle activates the serine kinases protein kinase C, IκB kinase (IKK), and Jun amino-terminal kinase (JNK) that phosphorylate the insulin receptor substrate 1 (IRS1) on serine residues leading to inactivation of IRS1 and downstream inactivation of the insulin signaling cascade. Ceramide accumulation also prevents activation of the insulin signaling cascade in skeletal muscle and reduces insulin activation of AS160 and subsequent glucose transporter-4 (GLUT4) translocation and glucose uptake. B Putative mechanisms implicated in the regulation of glucose transport and myogenesis with combined hypoxic conditioning (HC) and exercise training. Exercise stimulates skeletal muscle release of interleukin-6 (IL-6), which further inhibits actions of pro-inflammatory cytokines and increases levels of anti-inflammatory cytokines and glucagon-like peptide-1 (GLP-1). Aerobic-based exercise and hypoxic conditioning have been shown to stimulate GLUT4 translocation, potentially via increases in adenosine monophosphate-activated protein kinase (AMPK)-mediated signaling. Resistance exercise combined with HC may promote myogenesis through regulation of the TNF-ɑ/NF-κB/IL-6/STAT3 pathway. Akt protein kinase B, AMP adenosine monophosphate, AS160 Akt substrate of 160 kDa, ATP adenosine triphosphate, Ca2 + calcium, CaMKll calcium/ calmodulin-dependent protein kinase II, CRP C-reactive protein, DAG diacylglycerol, FACoA long-chain fatty acyl-CoA, GP130 glycoprotein 130, IL-6Ra interleukin-6 receptor, alpha, JAK Janus kinase, Mrf4 myogenic regulatory factor-4, Myf5 myogenic factor-5, NF-κB nuclear factor kappa-light-chain-enhancer of activated B cells, PI3K phosphoinositide 3 kinase, PKC protein kinase C, PP2A protein phosphatase 2A, Ser serine kinase, STAT3 signal transducer and activator of transcription-3, Thr threonine, TNF-α tumor necrosis factor-α, ↑ increase/upregulation, ↓ decrease/downregulation; solid lines denote established pathways/mechanisms; broken lines denote putative pathways/mechanisms
Current and future integration of combined hypoxic conditioning and exercise training for overweight individuals and/or obese individuals with metabolic syndrome. Overweight individuals and/or individuals with obesity have been previously shown to reduce their physical activity levels owing to reduced enjoyment and also because of greater mechanical constraints due to greater joint/tendon stress, thus increasing the risk of injury. Accumulating evidence supports the integration of both resistance and aerobic-based exercise (including high-intensity interval training) and hypoxia as a therapeutic strategy to improve multiple health outcomes, including fat mass loss and enhanced blood glucose regulation, and reduce the mechanical load imposed on the musculoskeletal system compared with exercise undertaken in normoxia. With continued standardization of exercise training and hypoxic variables in future studies, the inclusion of combined hypoxic conditions and exercise performance with hypoxicators or in simulated altitude chambers provides a feasible strategy to assist in combatting the deleterious effects of obesity
Effects of passive hypoxia exposure or combined hypoxic condition and resistance, HIIT, or aerobic exercise on markers of appetite regulation and body composition
Obesity is a major global health issue and a primary risk factor for metabolic-related disorders. While physical inactivity is one of the main contributors to obesity, it is a modifiable risk factor with exercise training as an established non-pharmacological treatment to prevent the onset of metabolic-related disorders, including obesity. Exposure to hypoxia via normobaric hypoxia (simulated altitude via reduced inspired oxygen fraction), termed hypoxic conditioning, in combination with exercise has been increasingly shown in the last decade to enhance blood glucose regulation and decrease the body mass index, providing a feasible strategy to treat obesity. However, there is no current consensus in the literature regarding the optimal combination of exercise variables such as the mode, duration, and intensity of exercise, as well as the level of hypoxia to maximize fat loss and overall body compositional changes with hypoxic conditioning. In this narrative review, we discuss the effects of such diverse exercise and hypoxic variables on the systematic and myocellular mechanisms, along with physiological responses, implicated in the development of obesity. These include markers of appetite regulation and inflammation, body conformational changes, and blood glucose regulation. As such, we consolidate findings from human studies to provide greater clarity for implementing hypoxic conditioning with exercise as a safe, practical, and effective treatment strategy for obesity.
 
PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow chart of included studies
Changes in non-specific strength. A forest plot of the non-specific strength relative to a non-exercise control. Values represent Cohen’s d (95% confidence interval)
Change in specific strength. A forest plot of the specific strength relative to a non-exercise control. Values represent Cohen’s d (95% confidence interval)
Background Isotonic exercise is the most common mode of strength training. Isotonic strength is often measured in the movement that was exercised, but isometric and isokinetic movements are also commonly used to quantify changes in muscular strength. Previous research suggests that increasing strength in one movement may not lead to an increase in strength in a different movement. Quantifying the increase in strength in a movement not trained may be important for understanding strength training adaptations and making recommendations for resistance exercise and rehabilitation programs.Objective To quantify changes in non-specific strength relative to a control.DesignA systematic review and random effects meta-analysis was conducted investigating the effects of isotonic strength training on isotonic and isokinetic/isometric strength.Search and InclusionThis systematic review was conducted in Google scholar, PubMed, Academic Search Premier, and MENDELEY. To be included in this review paper the article needed to meet the following criteria: (1) report sufficient data for our variables of interest (i.e., changes in isotonic strength and changes in isokinetic or isometric strength); (2) include a time-matched non-exercise control; (3) be written in English; (4) include healthy human participants over the age of 18 years; (5) the participants had to train and test isotonically; (6) the participants had to be tested isokinetically or isometrically on a device different from that they trained on; (7) the non-specific strength task had to test a muscle involved in the training (i.e., could not have trained chest press and test handgrip strength); and (8) the control group and the experimental group had to perform the same number of strength tests.ResultsWe completed two separate searches. In the original search a total of 880 papers were screened and nine papers met the inclusion criteria. In the secondary search a total of 2594 papers were screened and three additional papers were added (total of 12 studies). The overall effect of resistance training on changes in strength within a movement that was not directly trained was 0.8 (Cohen’s d) with a standard error of 0.286. This overall effect was significant (t = 2.821, p = 0.01) and the 95% confidence interval (CI) is 0.22–1.4. The overall effect of resistance training on strength changes within a movement that was directly trained was 1.84 (Cohen’s d) with a standard error of 0.296. This overall effect was significant (t = 6.221, p < 0.001) and the 95% CI is 1.23–2.4.Conclusion The results of our meta-analysis suggest that strength increases in both the specific and non-specific strength tests. However, the smaller effect size associated with non-specific strength suggests that it will be difficult for a single study to meaningfully investigate the transfer of strength training adaptions.
 
Overview of Delphi procedure. The Delphi procedure was comprised of three total rounds (including a preparatory phase). Panelists were asked to complete an open-ended questionnaire (Round 1) resulting in 42 content statements. During Round 2, panelists rated each statement by level of importance. By Round 3, panelists had the opportunity to review their individual responses relative to the group and adjust their scores if desired. aNo change in number of statements after Round 2 (all statements rated > 3). bStatements were considered to achieve consensus if they earned a group mean score ≥ 7 after Round 3
Background Sport-related concussions (SRCs) affect millions of adolescents and young adults annually in the USA; however, current SRC consensus statements provide limited guidance on academic support for students within higher education.Objective To generate consensus on appropriate academic recommendations for clinicians, students, and academic stakeholders to support university students during their recovery.Methods Panelists participated in three stages of a modified Delphi procedure: the first stage included a series of open-ended questions after reviewing a literature review on post-SRC return-to-learn (RTL) in higher education; the second stage asked panelists to anonymously rate the recommendations developed through the first Delphi stage using a 9-point scale; and the final stage offered panelists the opportunity to change their responses and/or provide feedback based on the group’s overall ratings.ResultsTwenty-two panelists including clinicians, concussion researchers, and academic stakeholders (54.5% female) from 15 institutions and/or healthcare systems participated in a modified Delphi procedure. A total of 42 statements were developed after round one. Following the next two rounds, 27 statements achieved consensus amongst the panel resulting in the four-stage Post-Concussion Collegiate RTL Protocol.Conclusion There are several unique challenges when assisting university students back to the classroom after SRC. Explicit guidelines on when to seek additional medical care (e.g., if they are experiencing worsening or persistent symptoms) and how to approach their instructor(s) regarding academic support may help the student self-advocate. Findings from the present study address barriers and provide a framework for universities to facilitate a multidisciplinary approach amongst medical and academic stakeholders.
 
A graph illustrating the hypothesised hormetic effect of varying degrees of exercise on gut health and immunity. URTIs upper respiratory tract infections
The human gut microbiome is a complex ecosystem of microorganisms that play an important role in human health, influencing functions such as vitamin uptake, digestion and immunomodulation. While research of the gut microbiome has expanded considerably over the past decade, some areas such as the relationship between exercise and the microbiome remain relatively under investigated. Despite this, multiple studies have shown a potential bidirectional relationship between exercise and the gut microbiome, with some studies demonstrating the possibility of influencing this relationship. This, in turn, could provide a useful route to influence athletic performance via microbiome manipulation, a valuable prospect for many elite athletes and their teams. The evidence supporting the potential benefits of pursuing this route and associated future perspectives are discussed in this review.
 
Training modalities during periods with intensified training in football. The figure is based on Bangsbo [48, 80], Iaia et al. [76, 113], and Ade et al. [29]
The effect of speed endurance production (SET-P) and maintenance (SET-M) training on Yo-Yo intermittent recovery (IR) level 1 or 2 performance during a period of intensified training conducted in the late preparation phase or the competitive season in elite football players
A Correlation between change in muscle FXYD1 (phospholemman) activation, a regulatory subunit of the Na⁺/K⁺-ATPase, and change in mean sprint time during a repeated sprint test (10 × 20 m) over 2 weeks’ combined speed endurance production training and aerobic high-intensity training in semi-professional football players.
Adapted from Thomassen et al. [126]. B Correlation between change in muscle Na⁺/K⁺-ATPase β1 subunit content and change in Yo-Yo intermittent recovery (IR) level 1 performance over 10 weeks 10–20–30 training in sub-elite football players. Unpublished data from Hostrup et al. [131]
Because physical demands are surging in football (soccer, USA), clubs are more and more seeking players who have a high capacity to perform repeated intense exercise. High-intensity interval training (HIIT), comprising exercise performed at intensities near or exceeding the capacity of aerobic energy systems, effectively enhances the physical conditioning of players. But given that HIIT imposes high loads, it increases the risk of overload-associated match performance decline and injury. This makes some coaches inclined to conduct HIIT in the weeks leading up to the season and during the season. Therefore, the challenge is how to optimize and dose HIIT during these phases, as they can be decisive. Studies have highlighted the utility of conducting periods of intensified training to overcome the risk of overload while at the same time enhancing performance. During intensified training periods of typically a few weeks, intensity is increased by enlarging the amount of HIIT, for example, aerobic high-intensity training or speed endurance training, while volume at low-to-moderate intensity is significantly reduced. The outcome depends on training composition and prescription—most notably, intensity and duration of bouts and recovery. When work intervals are prescribed for a few minutes at intensities > 90% heart rate max (i.e., aerobic high-intensity training), then beneficial adaptations pertaining to aerobic power and capacity are apparent. But when work intervals are conducted at much higher intensities, as all-out efforts or sprinting of typically 10- to 40-s duration with longer recovery periods (i.e., speed endurance training), beneficial adaptations pertaining to anaerobic energy systems, ion handling, and fatigue resilience are commonly observed. In this review, we discuss the utility of conducting intensified training periods to enhance performance in elite football players during the late preparation phase and competitive season.
 
Preferred reporting items for systematic reviews and meta-analyses (PRISMA) flow diagram illustrating the search process
Unweighted percentage change in countermovement jump following metastable (n = 4) or stable resistance training (n = 4)
Background: Balance and resistance training applied as single-mode interventions have proven to enhance measures of balance and/or muscular fitness in youth and youth athletes. Less is known on the effectiveness of combined or sequenced balance and resistance training in youth and youth athletes. Objective: The objective of this scoping review was to describe the effects of concurrently performed balance and resistance training (i.e., metastable resistance training) and different sequencing schemes of balance and resistance training on measures of balance and/or muscular fitness in healthy youth and youth athletes. We additionally aimed to identify knowledge gaps in the literature. Methods: According to the principles of a scoping review, we followed a broad research question, identified gaps in the literature, and reported findings on the level of single studies but did not aggregate and meta-analyze outcomes across studies. For this purpose, systematic literature searches were conducted in the electronic databases PubMed (including MEDLINE), Web of Science, and SPORTDiscus from inception until August 2022. We included metastable resistance training and sequenced balance and resistance training studies in healthy youth and youth athletes aged 6–18 years that investigated the training-induced effects on measures of balance (e.g., stork balance test) and muscular fitness (e.g., countermovement jump test) in contrast to active/passive controls. The Physiotherapy Evidence Database (PEDro) scale was used to assess the risk of bias. The Strength of Recommendation Taxonomy (SORT) was applied for the whole scoping review on levels A (high strength of recommendation) to C (low strength of recommendation) and for individual studies on levels 1 (high-quality evidence) to 3 (low-quality evidence). Results: The strength of recommendation for the scoping review was level B based on inconsistent or limited-quality evidence. Eleven randomized controlled trials were eligible to be included in this scoping review and each study was rated as ‘limited-quality evidence’. A median PEDro score of 6 was computed across the included studies. Four studies examined the effects of metastable resistance training (e.g., plyometric training on unstable surfaces) on measures of balance and/or muscle fitness in youth athletes. The remaining seven studies investigated the impact of sequenced balance and resistance training (e.g., blocked balance training followed by blocked resistance training) on measures of balance and/or muscle fitness in youth and youth athletes. The duration of the intervention programs ranged from 6 to 10 weeks with 2-weekly to 3-weekly exercise sessions. Participants’ age range was 10–18 years (mean 15 years). Ten studies examined young male and female athletes from different sports (i.e., basketball, handball, soccer) and one study physical education students. Metastable resistance training compared with plyometric training performed on stable surfaces showed no extra effect on measures of balance and muscular fitness. Stable plyometric training appears to be even more effective to improve jump performance. Sequenced balance and resistance training in the form of a mesocycle of balance followed by plyometric training seems to be particularly effective to improve measures of balance and muscular fitness in young athletes. This scoping review identified knowledge gaps that may indicate future research avenues: (i) comparative studies should be designed to examine how sex, age, maturity status, and expertise level impact on the adaptive potential following metastable resistance training or sequenced balance and resistance training in youth and youth athletes, (ii) at least one established measure of balance and muscular fitness should always be included in study designs to allow future comparison between studies and to aggregate (meta-analyze) findings across studies and (iii) studies are needed that examine neuromuscular and tendomuscular adaptations following these exercise types as well as dosage effects. Conclusions: According to the results of this scoping review, balance training should be an essential training component for youth that is incorporated with the resistance training exercises or introduced at least a month before resistance and plyometric training within a periodized training program. More research is needed to examine the moderating roles of age, maturity status, and sex.
 
Three hypothetical trajectories of performance measured on a continuous scale over time during a single season for athletes who remain uninjured. Athletes may increase their performance over time (dashed line), have stable performance over time (solid line) or have decreasing performance over time (dotted line)
Hypothetical trajectories of an athlete who becomes injured in November and returns to sport in January. In A, the athlete’s theoretical performance would have remained constant had they not been injured (solid black line). The theoretical performance after injury (grey line, “injury-recovery” curve) decreases with injury and then gradually increases during recovery. The effect of injury on performance (grey shaded area) is the difference between the theoretical performance had they not been injured (not observed) and their performance on return to play (RTP). In B, the athlete’s theoretical performance had they never been injured increases throughout the season. In this context, the control group should represent what the performance of the athlete would have been at the time of RTP had they never been injured. Panel B illustrates the detrimental effect on performance if we compare to pre-injury levels. This includes (1) the area from A and (2) a detriment on performance compared with their immediate pre-injury state (dark grey area). C Illustrates that there is an additional detriment on performance when we compare their observed performance to what their performance would have been had they never been injured (black area). The performance had they never been injured is estimated from a control group that followed the same trajectory prior to injury
An athlete’s theoretical performance deteriorates over the course of the season. In this context, the athlete’s opportunity to rest may allow them to recover some of their earlier capacities so that their overall performance on returning to play is better than it would have been had they never been injured. RTP return to play
Hypothetical trajectories for performance with a standard time to return to play (RTP) or a delayed return to play (delayed RTP). In A, the athlete’s observed performance (grey injury-recovery curve after RTP) is compared to what the theoretical performance would have been had they only returned to play later (dotted line beginning at RTP). The effect on performance after the delayed RTP is beneficial (white cross-hatched area) because of the additional recovery time. If one wanted to consider the time the athlete was not playing between RTP and delayed RTP, the grey area between the dotted line and grey line would be considered as detrimental effects on performance. In B, the black solid line represents the performance trajectory of a replacement athlete who is not expected to perform as well as the injured athlete playing injured. If the team replaces the injured athlete with this low performance athlete, the team’s performance will be reduced during the time between RTP and delayed RTP. However, the injured athlete’s performance (and presumably the team’s performance) would be much improved once they return (white cross-hatched area). In C, the replacement athlete (black solid line) has a higher predicted performance than the injured athlete playing injured, but a lower predicted performance than the injured athlete in a healthy state. In this case, the team performance is increased between RTP and delayed RTP, and again after delayed RTP
Return-to-play decision making should be based on all the advantages and disadvantages of return to play for athletes, not just the risk of injury. For competitive athletes, this includes the effect of early versus delayed return to sport on performance. In this paper, we address the questions “How can I estimate the effect of injury on the individual’s performance at return to play?” and “What is the effect of delaying return to sport on the individual’s performance?”. To address these questions, we describe (1) some foundational concepts, design and analytical challenges related to estimating the causal effect of return to play timing on performance in the athlete, (2) additional challenges if one is interested in the effects of delaying return to play and (3) differences when the questions relate to the team’s performance. Although the analytical strategies described appear complicated, coaches and athletes make these judgements informally every day without explicitly stating their assumptions. Using a formal approach should help analysts provide the most valid answers to the questions asked by athletes and coaches. In brief, the choice of a comparison group depends on the research question and requires that one consider the hypothetical performance trajectory of the athlete had they never been injured. Thus, the optimal comparison group depends on the shape of the expected trajectory and the specific research question being asked.
 
PRISMA Flow diagram
Evidence Gap Map of gait biomechanics in people with and without patellofemoral pain
Background Patellofemoral pain (PFP) is a prevalent knee condition with many proposed biomechanically orientated etiological factors and treatments. Objective We aimed to systematically review and synthesize the evidence for biomechanical variables (spatiotemporal, kinematic, kinetic) during walking and running in people with PFP compared with pain-free controls, and determine if biomechanical variables contribute to the development of PFP. Design Systematic review and meta-analysis. Data sources We searched Medline, CINAHL, SPORTDiscus, Embase, and Web of Science from inception to October 2021. Eligibility criteria for selecting studies All study designs (prospective, case–control [± interventional component, provided pre-intervention data were reported for both groups], cross-sectional) comparing spatiotemporal, kinematic, and/or kinetic variables during walking and/or running between people with and without PFP. Results We identified 55 studies involving 1300 people with PFP and 1393 pain-free controls. Overall pooled analysis identified that people with PFP had slower gait velocity [moderate evidence, standardized mean difference (SMD) − 0.50, 95% confidence interval (CI) − 0.72, − 0.27], lower cadence (limited evidence, SMD − 0.43, 95% CI − 0.74, − 0.12), and shorter stride length (limited evidence, SMD − 0.46, 95% CI − 0.80, − 0.12). People with PFP also had greater peak contralateral pelvic drop (moderate evidence, SMD − 0.46, 95% CI − 0.90, − 0.03), smaller peak knee flexion angles (moderate evidence, SMD − 0.30, 95% CI − 0.52, − 0.08), and smaller peak knee extension moments (limited evidence, SMD − 0.41, 95% CI − 0.75, − 0.07) compared with controls. Females with PFP had greater peak hip flexion (moderate evidence, SMD 0.83, 95% CI 0.30, 1.36) and rearfoot eversion (limited evidence, SMD 0.59, 95% CI 0.03, 1.14) angles compared to pain-free females. No significant between-group differences were identified for all other biomechanical variables. Data pooling was not possible for prospective studies. Conclusion A limited number of biomechanical differences exist when comparing people with and without PFP, mostly characterized by small-to-moderate effect sizes. People with PFP ambulate slower, with lower cadence and a shortened stride length, greater contralateral pelvic drop, and lower knee flexion angles and knee extension moments. It is unclear whether these features are present prior to PFP onset or occur as pain-compensatory movement strategies given the lack of prospective data. Trial Registration PROSPERO # CRD42019080241.
 
PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow chart. Summary of the systematic literature search and study selection process
Influence of resistance training (RT) performed to set failure versus non-failure on muscle hypertrophy with subgroup analyses based on study ‘theme’ (A or B). Studies presented were grouped into broad themes that involved RT performed to either momentary muscular failure versus non-failure (Theme A), or set failure (defined as anything other than momentary muscular failure) versus non-failure (Theme B). Point estimates and error bars signify the standardised mean difference between set failure and non-failure conditions and 95% confidence interval (CI) values, respectively. AD anterior deltoid, EF elbow flexors, PM pectoralis major, Quads quadriceps, RF rectus femoris, SD standard deviation, SMD standardized mean difference, TB triceps brachii, VL vastus lateralis, VM vastus medialis
Influence of resistance training performed to high (> 25%) and moderate (20–25%) velocity loss on muscle hypertrophy based on studies in Theme C. Studies presented were grouped into Theme C that involved resistance training performed to different velocity loss thresholds. Point estimates and error bars signify the standardised mean difference (SMD) between high and moderate velocity loss conditions and 95% confidence interval (CI) values, respectively. PM pectoralis major, QF quadriceps femoris, RF rectus femoris, SD standard deviation, VeL velocity loss, VI vastus intermedius, VL vastus lateralis, VM vastus medialis
Individual standardised effect sizes (pre-intervention to post-intervention changes in muscle size) for all velocity loss conditions [low (< 20%), moderate (20–25%), high (> 25%)] in each study from Theme C. Data presented were extracted from studies grouped into Theme C that involved resistance training performed to different velocity loss thresholds. The size of the dot point is based on a standardised effect size and a horizontal ‘jitter’ was applied to limit the overlap of dot points (as such, the dot point position on the x-axis is not a true representation of the velocity loss achieved and is rather limited to 0, 10, 15, 20, 25, 40 and 50% velocity losses). Positive effect size values indicate increases in muscle size from pre-intervention to post-intervention for each velocity loss condition
Conceptual non-linear relationship between proximity-to-failure and muscle hypertrophy. Our results suggest that closer proximities-to-failure are associated with muscle hypertrophy in a non-linear manner. Although the order of resistance training conditions displayed allows for visual inspection of a potential non-linear relationship between proximity-to-failure and muscle hypertrophy, the true proximities-to-failure achieved in each of these resistance training conditions are unclear and likely vary. The far-right dot point represents the ‘momentary muscular failure’ condition. It is also likely that participants in the ‘set failure’ and ‘high velocity loss’ conditions reached momentary muscular failure at times. Data shown are effect size estimates for pre-intervention to post-intervention increases in muscle size for each resistance training condition
Background and Objective: This systematic review with meta-analysis investigated the influence of resistance training proximity-to-failure on muscle hypertrophy. Methods: Literature searches in the PubMed, SCOPUS and SPORTDiscus databases identified a total of 15 studies that measured muscle hypertrophy (in healthy adults of any age and resistance training experience) and compared resistance training performed to: (A) momentary muscular failure versus non-failure; (B) set failure (defined as anything other than momentary muscular failure) versus non-failure; or (C) different velocity loss thresholds. Results: There was a trivial advantage for resistance training performed to set failure versus non-failure for muscle hypertrophy in studies applying any definition of set failure [effect size=0.19 (95% confidence interval 0.00, 0.37), p=0.045], with no moderating effect of volume load (p=0.884) or relative load (p=0.525). Given the variability in set failure definitions applied across studies, sub-group analyses were conducted and found no advantage for either resistance training performed to momentary muscular failure versus non-failure for muscle hypertrophy [effect size=0.12 (95% confidence interval −0.13, 0.37), p=0.343], or for resistance training performed to high (>25%) versus moderate (20–25%) velocity loss thresholds [effect size=0.08 (95% confidence interval −0.16, 0.32), p=0.529]. Conclusion: Overall, our main findings suggest that (i) there is no evidence to support that resistance training performed to momentary muscular failure is superior to non-failure resistance training for muscle hypertrophy and (ii) higher velocity loss thresholds, and theoretically closer proximities-to-failure do not always elicit greater muscle hypertrophy. As such, these results provide evidence for a potential non-linear relationship between proximity-to-failure and muscle hypertrophy.
 
Influence of dietary-derived nicotinamide adenine dinucleotide (NAD⁺) precursors on the NAD⁺ metabolome in skeletal muscle. The supplementation of the NAD⁺ donors tryptophan (Try), nicotinic acid (NA), nicotinamide riboside (NR), and nicotinamide (NAM) activates a regulatory cascade of homeostatic mechanisms that converge to alter cellular levels of NAD⁺. The de novo synthesis pathway involves the metabolic break down of Try and NA metabolic pathways. Try is converted into quilonic acid via the kynurenine pathway, before undergoing phosphoribosylation from quinolinic acid phosphoribosyltransferase (QAPRT), to produce nicotinic acid mononucleotide (NAMN). Nicotinic acid is also converted into NAMN, as it undergoes phosphoribosylation from NA phosphoribosyltransferase (NAPRT). Following these reactions, NAMN is converted into nicotinic acid adenine dinucleotide (NAAD), via nicotinamide mononucleotide adenylyltransferase (NMNAT) activity. NAAD then undergoes amidation via NAD⁺ synthetase (NADS) to drive NAD⁺ synthesis. The NAD⁺ salvage pathway involves the metabolic break down of NR and NAM. NR and NAM can be sourced through the diet or via the activation of the NAD⁺ and nicotinamide mononucleotide (NMN) degrading ectoenzymes; CD73 and CD38, respectively. Free NAM can also be sourced via activation of ADP-ribosyltransferases (ARTs). Once NR and NAM cross the plasma membrane, they are converted into NMN. NR undergoes phosphorylation by the NR kinases 1 and 2 (NRK1 and NRK2), while NAM is modified through phosphoribosylation by NAM phosphoribosyltransferase (NAMPT). NMN is then converted into NAD⁺ via NMNAT. The activation or suppression of these metabolic cascades can influence NAD⁺ levels, which in turn alters the activity of the NAD⁺ sensors sirtuins (SIRTs) 1–7, to promote skeletal muscle adaptation. In parallel, the NAD⁺ consuming proteins PARP1/2 and CD38 compete with SIRTs for NAD⁺ and are thought to suppress skeletal muscle adaptation. Image created by BioRender.com
Effect of nicotinamide riboside (NR) loading and acute endurance exercise on the skeletal muscle nicotinamide adenine dinucleotide (NAD⁺) metabolome. The figure shows the effects of seven days of NR loading (NR SUPP) versus cellulose placebo on NAD⁺ metabolism in young male volunteers prior to an acute bout of endurance exercise. Specifically, NR loading had no effect on NR, NAD⁺, nicotinamide (NAM), and nicotinamide mononucleotide (NMN) content in skeletal muscle (A–D). However, deaminated NAD⁺ precursor, nicotinic acid riboside (NaR), and, methylated breakdown products, N-methyl-2-pyridone-5-carboxamide (Me2Py) and N-methyl-4-pyridone-5-carboxamide (Me4Py), were elevated following NR loading and sustained during the 3-h post-exercise period (E–G; ## denotes p < 0.05 placebo vs NR SUPP). Interestingly, the phosphoribosylated NAD⁺ precursor, nicotinic acid mononucleotide (NAMN), was only increased post-NR supplementation and exercise (H), whilst exercise alone had no effect on the NAD + metabolome in skeletal muscle (A–G). h hours. Image created by BioRender.com
Nicotinamide adenine dinucleotide (NAD⁺) is a vital energy intermediate in skeletal muscle. The discovery of dietary-derived NAD⁺ precursors has led to the rapid development of NAD⁺ therapeutics designed to manipulate NAD⁺ content in target tissues. Of those developed, nicotinamide riboside and nicotinamide mononucleotide have been reported to display health benefit in humans under clinical scenarios of NAD⁺ deficiency. In contrast, relatively little is known regarding the potential benefit of nicotinamide riboside and nicotinamide mononucleotide supplementation in healthy individuals, with questions remaining as to whether NAD⁺ therapeutics can be used to support training adaptation or improve performance in athletic populations. Examining animal and human nicotinamide riboside supplementation studies, this review discusses current evidence suggesting that NAD⁺ therapeutics do not alter skeletal muscle metabolism or improve athletic performance in healthy humans. Further, we will highlight potential reasons why nicotinamide riboside supplementation studies do not translate to healthy populations and discuss the futility of testing NAD⁺ therapeutics outside of the clinical populations where NAD⁺ deficiency is present.
 
Background Sided games (i.e., small sided, medium sided, large sided) involve tactical, technical, physical, and psychological elements and are commonly implemented in soccer training. Although soccer sided-games research is plentiful, a meta-analytical synthesis of external load exposure during sided games is lacking. Objective The objective of this systematic review and meta-analysis was to: (1) synthesize the evidence on high-speed and sprint running exposure induced by sided games in adult soccer players, (2) establish pooled estimates and intra-individual reliability for high-speed and sprint running exposure, and (3) explore the moderating effects of game format and playing constraints. Methods A literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Four databases (PubMed/MEDLINE, Scopus, SPORTDiscus, Web of Science Core Collection) were systematically searched up to 25 January, 2022. Eligibility criteria were adult soccer players (population); training programs incorporating sided games (intervention); game manipulations including number of players, pitch dimension, and game orientation (comparator); and high-speed, very high-speed, and sprint relative (m⋅min−1) running distances and associated intra-individual reliability (outcome). Eligible study risk of bias was evaluated using RoBANS. Pooled estimates for high-speed and sprint running exposure, and their intra-individual reliability, along with the moderating effect of tracking device running velocity thresholds, pitch dimension (i.e., area per player), and game orientation (i.e. score or possession), were determined via a multi-level mixed-effects meta-analysis. Estimate uncertainty is presented as 95% compatibility intervals (CIs) with the likely range of relative distances in similar future studies determined via 95% prediction intervals. Results A total of 104 and 7 studies met our eligibility criteria for the main and reliability analyses, respectively. The range of relative distances covered across small-sided games, medium-sided games, and large-sided games was 14.8 m⋅min−1 (95% CI 12.3–17.4) to 17.2 m⋅min−1 (95% CI 13.5–20.8) for high-speed running, 2.7 m⋅min−1 (95% CI 1.8–3.5) to 3.6 m⋅min−1 (95% CI 2.3–4.8) for very high-speed running, and 0.2 m⋅min−1 (95% CI 0.1–0.4) to 0.7 m⋅min−1 (95% CI 0.5–0.9) for sprinting. Across different game formats, 95% prediction intervals showed future exposure for high-speed, very high-speed running, and sprinting to be 0–46.5 m⋅min−1, 0–14.2 m⋅min−1, and 0–2.6 m⋅min−1, respectively. High-speed, very high-speed running, and sprinting showed poor reliability with a pooled coefficient of variation of 22.8% with distances being moderated by device speed thresholds, pitch dimension, and game orientation. Conclusions This review is the first to provide a detailed synthesis of exposure and intra-individual reliability of high-speed and sprint running during soccer sided games. Our estimates, along with the moderating influence of common programming variables such as velocity thresholds, area per player, and game orientation should be considered for informed planning of small-sided games, medium-sided games, and large-sided games soccer training. Clinical Trial Registration Open Science Framework available through https://osf.io/a4xr2/.
 
Background The perception of effort provides information on task difficulty and influences physical exercise regulation and human behavior. This perception differs from other-exercise related perceptions such as pain. There is no consensus on the role of group III/IV muscle afferents as a signal processed by the brain to generate the perception of effort. Objective The aim of this meta-analysis was to investigate the effect of pharmacologically blocking muscle afferents on the perception of effort. Methods Six databases were searched to identify studies measuring the ratings of perceived effort during physical exercise, with and without pharmacological blockade of muscle afferents. Articles were coded based on the operational measurement used to distinguish studies in which perception of effort was assessed specifically (effort dissociated) or as a composite experience including other exercise-related perceptions (effort not dissociated). Articles that did not provide enough information for coding were assigned to the unclear group. Results The effort dissociated group (n = 6) demonstrated a slight increase in ratings of perceived effort with reduced muscle afferent feedback (standard mean change raw, 0.39; 95% confidence interval 0.13–0.64). The group effort not dissociated (n = 2) did not reveal conclusive results (standard mean change raw, − 0.29; 95% confidence interval − 2.39 to 1.8). The group unclear (n = 8) revealed a slight ratings of perceived effort decrease with reduced muscle afferent feedback (standard mean change raw, − 0.27; 95% confidence interval − 0.50 to − 0.04). Conclusions The heterogeneity in results between groups reveals that the inclusion of perceptions other than effort in its rating influences the ratings of perceived effort reported by the participants. The absence of decreased ratings of perceived effort in the effort dissociated group suggests that muscle afferent feedback is not a sensory signal for the perception of effort.
 
Background A comprehensive examination of the sport-specific activities performed around the time of injury is important to hypothesise injury mechanisms, develop prevention strategies, improve management, and inform future investigations. The aim of this systematic review is to summarise the current literature describing the activities performed around the time of injury in football (soccer). Methods A systematic search was carried out in PubMed, Web of Science, SPORTDiscus, and OpenGrey. Studies were included if participants were football players aged > 13 years old and the activities performed at the time of injury were reported together with the total number of injuries. Risk of bias was assessed using an adapted version of checklists developed for prevalence studies. The activities reported by the studies were grouped to account for inconsistent reporting, and the proportion of each injury activity was calculated. Data were not meta-analysed due to high heterogeneity of methods and classification criteria. Results We included 64 studies reporting on 56,740 injuries in total. ACL injures were analysed by 12 studies, ankle/foot and knee injuries were analysed by five studies, thigh injuries were analysed by four studies, hip/groin injuries were analysed by three studies, and hamstring injuries were analysed by two studies. Five studies analysed more than one type of injury and 38 studies did not specify the type of injuries analysed. Running and kicking were the predominant activities leading to thigh and hamstring injuries. Changing direction and kicking were the predominant activities leading to hip and groin injuries and duels were the predominant activities leading to ankle injuries. Duels and pressing seem the predominant activities leading to ACL injuries, while results for other knee and general injuries were inconsistent. Conclusions A qualitative summary of the activities performed at the time of injury has been reported. The results need to be interpreted carefully due to the risk of bias observed in the included studies. If we are to meaningfully progress our knowledge in this area, it is paramount that future research uses consistent methods to record and classify injuries and activities leading up to and performed at the time of injury. Registration The protocol of this systematic review was registered at the Open Science Framework (https://doi.org/10.17605/OSF.IO/U96KV).
 
Preferred reporting items for systematic reviews and meta-analyses (PRISMA) flowchart for study inclusion
Overall findings of the comparison between single versus multiple sets performed per exercise on muscle strength and size, muscle quality, and functional capacity in middle-aged and older adults. CI confidence interval, MD mean difference, SMD standardized mean difference
Background Effective manipulation of the acute variables of resistance training is critical to optimizing muscle and functional adaptations in middle-aged and older adults. However, the ideal volume prescription (e.g., number of sets performed per exercise) in middle-aged and older adults remains inconclusive in the literature. Objective The effects of single versus multiple sets per exercise on muscle strength and size, muscle quality, and functional capacity in middle-aged and older adults were compared. Moreover, the effects of single versus multiple sets per exercise on muscular and functional gains were also examined, considering the influence of training duration. Methods Randomized controlled trials and non-randomized controlled trials comparing single versus multiple sets per exercise on muscle strength, muscle size, muscle quality, or functional capacity in middle-aged and older adults (aged ≥ 50 years) in the PubMed/MEDLINE, Web of Science, and Scopus databases (01/09/2021, updated on 15/05/2022) were identified. A random-effects meta-analysis was used. Results Fifteen studies were included (430 participants; 93% women; age 57.9–70.1 years). Multiple sets per exercise produced a greater effect than single sets on lower-limb strength (standardized mean difference [SMD] = 0.29; 95% confidence interval [CI] 0.07–0.51; mean difference [MD] = 1.91 kg; 95% CI 0.50–3.33) and muscle quality (SMD = 0.40; 95% CI 0.05–0.75) gains. There were no differences between single versus multiple sets per exercise for upper-limb strength (SMD = 0.13; 95% CI − 0.14 to 0.40; MD = 0.11 kg; 95% CI − 0.52 to 0.75), muscle size (SMD = 0.15; 95% CI − 0.07 to 0.37), and functional capacity (SMD = 0.01; 95% CI − 0.47 to 0.50) gains. In addition, there were no differences between single versus multiple sets on muscle strength and size gains for training durations ≤ 12 weeks or > 12 weeks. Conclusions Multiple sets per exercise produced greater lower-limb strength and muscle quality gains than single sets in middle-aged and older adults, although the magnitude of the difference was small. In contrast, single sets per exercise were sufficient to improve upper-limb strength, muscle size, and functional capacity in these populations. Despite these findings, researchers should conduct future high-quality, pre-registered, and blinded randomized controlled trials to strengthen the scientific evidence on this topic.
 
Serious knee injuries are gaining epidemiological importance. Especially in childhood, a very significant increase in knee ligament injuries, in particular ACL ruptures, can be observed. In Saxony alone, more than 70 ruptures of the anterior cruciate ligament occur each year as a result of accidents during physical education (PE). Six months after surgery, the students are normally classified as fully fit for sports and are allowed to participate in PE without restrictions. However, the number of reinjuries is very high which limits the quality of life of those affected in the long term and places a heavy financial burden on insurance companies.
 
Background Skeletal muscle has extraordinary regenerative capabilities against challenge, mainly owing to its resident muscle stem cells, commonly identified by Pax7⁺, which expediently donate nuclei to the regenerating multinucleated myofibers. This local reserve of stem cells in damaged muscle tissues is replenished by undifferentiated bone marrow stem cells (CD34⁺) permeating into the surrounding vascular system. Objective The purpose of the study was to provide a quantitative estimate for the changes in Pax7⁺ muscle stem cells (satellite cells) in humans following an acute bout of exercise until 96 h, in temporal relation to circulating CD34⁺ bone marrow stem cells. A subgroup analysis of age was also performed. Methods Four databases (Web of Science, PubMed, Scopus, and BASE) were used for the literature search until February 2022. Pax7⁺ cells in human skeletal muscle were the primary outcome. Circulating CD34⁺ cells were the secondary outcome. The standardized mean difference (SMD) was calculated using a random-effects meta-analysis. Subgroup analyses were conducted to examine the influence of age, training status, type of exercise, and follow-up time after exercise. Results The final search identified 20 studies for Pax7⁺ cells comprising a total of 370 participants between the average age of 21 and 74 years and 26 studies for circulating CD34⁺ bone marrow stem cells comprising 494 participants between the average age of 21 and 67 years. Only one study assessed Pax7⁺ cells immediately after aerobic exercise and showed a 32% reduction in exercising muscle followed by a fast repletion to pre-exercise level within 3 h. A large effect on increasing Pax7⁺ cell content in skeletal muscles was observed 24 h after resistance exercise (SMD = 0.89, p < 0.001). Pax7⁺ cells increased to ~ 50% above pre-exercise level 24–72 h after resistance exercise. For a subgroup analysis of age, a large effect (SMD = 0.81, p < 0.001) was observed on increasing Pax7⁺ cells in exercised muscle among adults aged > 50 years, whereas adults at younger age presented a medium effect (SMD = 0.64, p < 0.001). Both resistance exercise and aerobic exercise showed a medium overall effect in increasing circulating CD34⁺ cells (SMD = 0.53, p < 0.001), which declined quickly to the pre-exercise baseline level after exercise within 6 h. Conclusions An immediate depletion of Pax7⁺ cells in exercising skeletal muscle concurrent with a transient release of CD34⁺ cells suggest a replenishment of the local stem cell reserve from bone marrow. A protracted Pax7⁺ cell expansion in the muscle can be observed during 24–72 h after resistance exercise. This result provides a scientific basis for exercise recommendations on weekly cycles allowing for adequate recovery time. Exercise-induced Pax7⁺ cell expansion in muscle remains significant at higher age, despite a lower stem cell reserve after age 50 years. More studies are required to confirm whether Pax7⁺ cell increment can occur after aerobic exercise. Clinical Trial Registration Registered at the International Prospective Register of Systematic Reviews (PROSPERO) [identification code CRD42021265457].
 
Adapted motor and/or cognitive task-induced state fatigue framework with its interdependent dimensions and the respective determinants first proposed by Enoka and Duchateau [3] (a). The extent of state fatigue mirrored by these dimensions depends on several modulating factors (b) and can have negative consequences for the motor and cognitive capacity, which might negatively affect quality of life (c) particularly in vulnerable, deconditioned, and clinical populations. The bidirectional arrows indicate the interdependence between all dimensions. Please note that effort perception, affective valence, self-regulation and self-control, as well as time perception were added to the potential determinants of perceived motor fatigue compared to the framework of Enoka and Duchateau [3]. Furthermore, cognitive performance fatigue, perceived cognitive fatigue, and the potentially contributing factors were added to the framework. CNS central nervous system, ? unknown factors that should be added in the future
Adapted three-dimensional dynamical system framework of perceived motor fatigue first proposed by Venhorst et al. [5]. The bidirectional arrows indicate the interdependence between the dimensions
Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228–38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228–38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.
 
Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 flow diagram. *An in-depth list of excluded articles and the reasons can be found in Table 1 of the ESM
of types of studies (a) and participant type (b) included in the review
Frequency distribution of the body segments on which wearables were placed
of environments that studies were conducted within (a) overall, (b) indoor environments and (c) outdoor environments
Background Running gait assessment has traditionally been performed using subjective observation or expensive laboratory-based objective technologies, such as 3D motion capture or force plates. However, recent developments in wearable devices allow for continuous monitoring and analysis of running mechanics in any environment. Objective measurement of running gait is an important (clinical) tool for injury assessment and provides measures that can be used to enhance performance. Objectives To systematically review available literature investigating how wearable technology is being used for running gait analysis in adults. Methods A systematic search of literature was conducted in the following scientific databases: PubMed, Scopus, WebofScience, and SportDiscus. Information was extracted from each included article regarding the type of study, participants, protocol, wearable device(s), main outcomes/measures, analysis, and key findings. Results A total of 131 articles were reviewed: 56 investigated the validity of wearable technology, 22 examined the reliability and 77 focused on applied use. Most studies used inertial measurement units (IMU) (n=62) (i.e., a combination of accelerometers, gyroscopes, and magnetometers in a single unit) or solely accelerometers (n=40), with one using gyroscopes alone and 31 using pressure sensors. On average, studies used one wearable device to examine running gait. Wearable locations were distributed among the shank, shoe and waist. The mean number of participants was 26 (± 27), with an average age of 28.3 (± 7.0) years. Most studies took place indoors (n =93), using a treadmill (n =62), with the main aims seeking to identify running gait outcomes or investigate the effects of injury, fatigue, intrinsic factors (e.g., age, sex, morphology) or footwear on running gait outcomes. Generally, wearables were found to be valid and reliable tools for assessing running gait compared to reference standards. Conclusions This comprehensive review highlighted that most studies that have examined running gait using wearable sensors have done so with young adult recreational runners, using one IMU sensor, with participants running on a treadmill and reporting outcomes of ground contact time, stride length, stride frequency and tibial acceleration. Future studies are required to obtain consensus regarding terminology, protocols for testing validity and reliability of devices and suitability of gait outcomes.
 
Background and Objective Computer-based neurocognitive tests are widely used in sport-related concussion management, but the performance of these tests is not well understood in the participant population with attention-deficit/hyperactivity disorder (ADHD) and/or learning disorder (LD). This research estimates the sensitivity and specificity performance of the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) computer-based neurocognitive test in identifying concussion in this population.Methods Study participants consisted of collegiate university athletes and military service academy cadets from the National Collegiate Athletic Association-Department of Defense CARE Consortium who completed the ImPACT test between 2014 and 2021. Participants who self-identified as belonging to one of the subgroups of interest (ADHD with or without LD [ADHD:LD+/−], LD with or without ADHD [LD:ADHD+/−], ADHD and/or LD [ADHD a/o LD]) and completed a baseline (1874 ADHD:LD+/−, 779 LD:ADHD+/−, 2338 ADHD a/o LD) or 24–48 h post-concussion (175 ADHD:LD+/−, 77 LD:ADHD+/−, 216 ADHD a/o LD) ImPACT assessment were included. Sensitivity and specificity were calculated using a normative data method and three machine learning classification methods: logistic regression, classification and regression tree, and random forest.ResultsUsing the four methods, participants with ADHD:LD+/− had sensitivities that ranged from 0.474 to 0.697, and specificities that ranged from 0.538 to 0.686. Participants with LD:ADHD+/− had sensitivities that ranged from 0.455 to 0.688, and specificities that ranged from 0.456 to 0.588. For participants with ADHD a/o LD, sensitivities ranged from 0.542 to 0.755, and specificities ranged from 0.451 to 0.724.Conclusions For all subgroups and analytical methods, the results illustrate sensitivity and specificity values below typically accepted levels indicative of clinical utility. These findings support that using ImPACT alone may be insufficient to inform concussion diagnoses and encourages the use of a multi-dimensional concussion assessment.
 
Background There is evidence that in older adults the combination of strength training (ST) and endurance training (ET) (i.e., concurrent training [CT]) has similar effects on measures of muscle strength and cardiorespiratory endurance (CRE) compared with single-mode ST or ET, respectively. Therefore, CT seems to be an effective method to target broad aspects of physical fitness in older adults. Objectives The aim was to examine the effects of CT on measures of physical fitness (i.e., muscle strength, power, balance and CRE) in healthy middle-aged and older adults aged between 50 and 73 years. We also aimed to identify key moderating variables to guide training prescription. Study Design We conducted a systematic review with meta-analysis of randomized controlled trials. Data Sources The electronic databases PubMed, Web of Science Core Collection, MEDLINE and Google Scholar were systematically searched until February 2022. Eligibility Criteria for Selecting Studies We included randomized controlled trials that examined the effects of CT versus passive controls on measures of physical fitness in healthy middle-aged and older adults aged between 50 and 73 years. Results Fifteen studies were eligible, including a total of 566 participants. CT induced moderate positive effects on muscle strength (standardized mean difference [SMD] = 0.74) and power (SMD = 0.50), with a small effect on CRE (SMD = 0.48). However, no significant effects were detected for balance (p > 0.05). Older adults > 65 years (SMD = 1.04) and females (SMD = 1.05) displayed larger improvements in muscle strength compared with adults ≤ 65 years old (SMD = 0.60) and males (SMD = 0.38), respectively. For CRE, moderate positive effects (SMD = 0.52) were reported in those ≤ 65 years old only, with relatively larger gains in females (SMD = 0.55) compared with males (SMD = 0.45). However, no significant differences between all subgroups were detected. Independent single training factor analysis indicated larger positive effects of 12 weeks (SMD = 0.87 and 0.88) compared with 21 weeks (SMD = 0.47 and 0.29) of CT on muscle strength and power, respectively, while for CRE, 21 weeks of CT resulted in larger gains (SMD = 0.62) than 12 weeks (SMD = 0.40). For CT frequency, three sessions per week produced larger beneficial effects (SMD = 0.91) on muscle strength compared with four sessions (SMD = 0.55), whereas for CRE, moderate positive effects were only noted after four sessions per week (SMD = 0.58). A session duration of > 30–60 min generated larger improvements in muscle strength (SMD = 0.99) and power (SMD = 0.88) compared with > 60–90 min (SMD = 0.40 and 0.29, respectively). However, for CRE, longer session durations (i.e., > 60–90 min) seem to be more effective (SMD = 0.61) than shorter ones (i.e., > 30–60 min) (SMD = 0.34). ET at moderate-to-near maximal intensities produced moderate (SMD = 0.64) and small positive effects (SMD = 0.49) on muscle strength and CRE, respectively, with no effects at low intensity ET (p > 0.05). Finally, intra-session ST before ET produced larger gains in muscle strength (SMD = 1.00) compared with separate sessions (SMD = 0.55), whereas ET and ST carried out separately induced larger improvements in CRE (SMD = 0.58) compared with intra-session ET before ST (SMD = 0.49). Conclusions CT is an effective method to improve measures of physical fitness (i.e., muscle strength, power, and CRE) in healthy middle-aged and older adults aged between 50 and 73 years, regardless of sex. Results of independent single training factor analysis indicated that the largest effects on muscle strength were observed after 12 weeks of training, > 30–60 min per session, three sessions per week, higher ET intensities and when ST preceded ET within the same session. For CRE, the largest effects were noted after 21 weeks of training, four sessions per week, > 60–90 min per session, higher ET intensities and when ET and ST sessions were performed separately. Regarding muscle power, the largest effects were observed after 12 weeks of training and > 30–60 min per session.
 
Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) flow diagram of study inclusion
Background Many children aged 0–5 years do not meet the WHO physical activity guidelines. To develop effective, evidence-based interventions, it is necessary to understand which factors are associated with physical activity in early childhood. Objective To summarize the current evidence on correlates of physical activity in 0- to 5-year-old children. Methods First, a systematic umbrella review was conducted following PRISMA guidelines. PubMed, Embase, PsycINFO, and SPORTDiscus were searched up to May 2020 for systematic reviews examining the association between potential correlates and quantitatively measured physical activity in children aged 0–5.9 years. Included reviews were assessed on methodological quality, and results were categorized according to the socio-ecological model. Second, 31 international researchers of physical activity in young children participated in an expert panel to reflect on the outcomes of the umbrella review and propose directions for future research. Results Twenty-one reviews were included that examined a total of 98 potential correlates. When synthesizing all reviews, 23 correlates were found with consistent evidence for an association with a physical activity outcome. For most other potential correlates there was inconsistent evidence across reviews for associations with physical activity in young children. Although there was little overlap between the correlates identified in the umbrella review and determinants suggested by the expert panel, both confirmed the importance of socio-cultural, policy, and physical environmental factors in general. Conclusion Multiple correlates of young children's physical activity were identified. However, various methodological challenges (e.g., measurement instruments) and the large heterogeneity (e.g., study samples, correlates, and outcome measures) hindered formulating definitive conclusions. Moreover, none of the reviews reported on the interrelatedness between correlates, which would align with more holistic understandings of behavior. Our findings indicate the urgent need for establishing a common ground in definitions, assessment methods, and analytical methods to further the field of physical activity research in this tremendously important age group. Prospero Registration Number CRD42020184159.
 
Factors influencing the time course and magnitude of transient changes in circulating concentrations of ketone bodies after acute ingestion of exogenous ketone supplements, and mechanisms of potential benefit and impairment of consequent effects in athletic contexts. ATP adenosine triphosphate, KB ketone bodies, MPB muscle protein breakdown, MPS muscle protein synthesis, mTORC mechanistic target of rapamycin complex, PDH pyruvate dehydrogenase
The ketone bodies acetoacetate (AcAc) and β-hydroxybutyrate (βHB) have pleiotropic effects in multiple organs including brain, heart, and skeletal muscle by serving as an alternative substrate for energy provision, and by modulating inflammation, oxidative stress, catabolic processes, and gene expression. Of particular relevance to athletes are the metabolic actions of ketone bodies to alter substrate utilisation through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. There has been long-standing interest in the development of ingestible forms of ketone bodies that has recently resulted in the commercial availability of exogenous ketone supplements (EKS). These supplements in the form of ketone salts and ketone esters, in addition to ketogenic compounds such as 1,3-butanediol and medium chain triglycerides, facilitate an acute transient increase in circulating AcAc and βHB concentrations, which has been termed ‘acute nutritional ketosis’ or ‘intermittent exogenous ketosis’. Some studies have suggested beneficial effects of EKS to endurance performance, recovery, and overreaching, although many studies have failed to observe benefits of acute nutritional ketosis on performance or recovery. The present review explores the rationale and historical development of EKS, the mechanistic basis for their proposed effects, both positive and negative, and evidence to date for their effects on exercise performance and recovery outcomes before concluding with a discussion of methodological considerations and future directions in this field.
 
Background and Objective Meta-analysis and meta-regression are often highly cited and may influence practice. Unfortunately, statistical errors in meta-analyses are widespread and can lead to flawed conclusions. The purpose of this article was to review common statistical errors in meta-analyses and to document their frequency in highly cited meta-analyses from strength and conditioning research. Methods We identified five errors in one highly cited meta-regression from strength and conditioning research: implausible outliers; overestimated effect sizes that arise from confusing standard deviation with standard error; failure to account for correlated observations; failure to account for within-study variance; and a focus on within-group rather than between-group results. We then quantified the frequency of these errors in 20 of the most highly cited meta-analyses in the field of strength and conditioning research from the past 20 years. Results We found that 85% of the 20 most highly cited meta-analyses in strength and conditioning research contained statistical errors. Almost half (45%) contained at least one effect size that was mistakenly calculated using standard error rather than standard deviation. In several cases, this resulted in obviously wrong effect sizes, for example, effect sizes of 11 or 14 standard deviations. Additionally, 45% failed to account for correlated observations despite including numerous effect sizes from the same study and often from the same group within the same study. Conclusions Statistical errors in meta-analysis and meta-regression are common in strength and conditioning research. We highlight five errors that authors, editors, and readers should check for when preparing or critically reviewing meta-analyses.
 
Background Velocity loss (VL) experienced in a set during resistance training is often monitored to control training volume and quantify acute fatigue responses. Accordingly, various VL thresholds are used to prescribe resistance training and target different training adaptations. However, there are inconsistencies in the current body of evidence regarding the magnitude of the acute and chronic responses to the amount of VL experienced during resistance training. Objective The aim of this systematic review was to (1) evaluate the acute training volume, neuromuscular, metabolic, and perceptual responses to the amount of VL experienced during resistance training; (2) synthesize the available evidence on the chronic effects of different VL thresholds on training adaptations; and (3) provide an overview of the factors that might differentially influence the magnitude of specific acute and chronic responses to VL during resistance training. Methods This review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Five databases were searched, and studies were included if they were written in English, prescribed resistance training using VL, and evaluated at least one (1) acute training volume, neuromuscular, metabolic, or perceptual response or (2) training adaptation. Risk of bias was assessed using a modified Cochrane Collaboration’s tool for assessing the risk of bias in randomized trials. Multilevel and multivariate meta-regressions were performed where possible. Results Eighteen acute and 19 longitudinal studies met the inclusion criteria, of which only one had more than one risk of bias item assessed as high risk. Based on the included acute studies, it seems that the number of repetitions per set, blood lactate concentration, and rating of perceived exertion generally increase, while countermovement jump height, running sprint times, and velocity against fixed loads generally decrease as VL increases. However, the magnitude of these effects seems to be influenced, among other factors, by the exercise and load used. Regarding training adaptations, VL experienced during resistance training did not influence muscle strength and endurance gains. Increases in VL were associated with increases in hypertrophy (b = 0.006; 95% confidence interval [CI] 0.001, 0.012), but negatively affected countermovement jump (b = − 0.040; 95% CI − 0.079, − 0.001), sprint (b = 0.001; 95% CI 0.001, 0.002), and velocity against submaximal load performance (b = − 0.018; 95% CI − 0.029, − 0.006). Conclusions A graded relationship exists between VL experienced during a set and acute training volume, neuromuscular, metabolic, and perceptual responses to resistance training. However, choice of exercise, load, and individual trainee characteristics (e.g., training history) seem to modulate these relationships. The choice of VL threshold does not seem to affect strength and muscle endurance gains whereas higher VL thresholds are superior for enhancing hypertrophy, and lower VL thresholds are superior for jumping, sprinting, and velocity against submaximal loads performance. Clinical Trial Registration The original protocol was prospectively registered (https://osf.io/q4acs/) with the Open Science Framework.
 
Model of different categories of injury prevention in sports, adapted from Jamoulle [8], Kuelhein et al. [9], and Martins et al. [10]
Injury prevention framework in sports
Prevention has traditionally been categorized into three main areas: primary, secondary, and tertiary. In this Current Opinion, we present and discuss the concept of quaternary prevention in sports. Quaternary prevention aims to protect individuals from interventions that likely cause more harm than good, such as overdiagnosis, overtreatment, and overmedication. It includes preventing all types of harm associated with training and clinical interventions. Therefore, any sports injury prevention model or strategy should acknowledge the risks associated with training-related (i.e., overreaching and overuse) and clinical-related (i.e., overdiagnosis, over medicalization, and overtreatment) features. We propose a conceptual framework that integrates quaternary prevention into the contemporary injury prevention models in sports, taking into account that injury prevention is just one branch of the managerial, decision-making, and active hazard control process of risk management that athletes, coaches, and health and performance staff need to deal with. Therefore, we argue that integrating the concept of quaternary prevention into any form of prevention will significantly protect athletes from excessive, inappropriate, and ethically questionable interventions that may likely cause more harm than good.
 
Short-term recovery of muscle and liver glycogen stores after exhaustive exercise using different combinations of monosaccharides. Fructose-glucose carbohydrate mixtures have been demonstrated to be very effective in replenishment of both muscle and liver glycogen stores. On the other hand, while glucose-based carbohydrates cause robust rates of muscle glycogen replenishment, liver glycogen synthesis rates are inferior as compared to a combination of fructose-glucose- and galactose-glucose-based carbohydrates. No data are currently available for muscle glycogen synthesis rates after ingesting a galactose-glucose mixture. It is hypothesized (but not established) that combining fructose-galactose-glucose-based carbohydrates would be optimal for post-exercise repletion of both glycogen pools. CHO carbohydrate
Framework for carbohydrate periodization based on the demands of the upcoming exercise session. Exercise intensity domain selection refers to the highest intensity attained during the exercise session. The exact carbohydrate requirements are to be personalized based on the expected energy demands of each exercise session. CHO carbohydrates, CP critical power, LT1 lactate threshold 1, LT2 lactate threshold 2, MLSS maximal lactate steady state
The importance of carbohydrate as a fuel source for exercise and athletic performance is well established. Equally well developed are dietary carbohydrate intake guidelines for endurance athletes seeking to optimize their performance. This narrative review provides a contemporary perspective on research into the role of, and application of, carbohydrate in the diet of endurance athletes. The review discusses how recommendations could become increasingly refined and what future research would further our understanding of how to optimize dietary carbohydrate intake to positively impact endurance performance. High carbohydrate availability for prolonged intense exercise and competition performance remains a priority. Recent advances have been made on the recommended type and quantity of carbohydrates to be ingested before, during and after intense exercise bouts. Whilst reducing carbohydrate availability around selected exercise bouts to augment metabolic adaptations to training is now widely recommended, a contemporary view of the so-called train-low approach based on the totality of the current evidence suggests limited utility for enhancing performance benefits from training. Nonetheless, such studies have focused importance on periodizing carbohydrate intake based on, among other factors, the goal and demand of training or competition. This calls for a much more personalized approach to carbohydrate recommendations that could be further supported through future research and technological innovation (e.g., continuous glucose monitoring). Despite more than a century of investigations into carbohydrate nutrition, exercise metabolism and endurance performance, there are numerous new important discoveries, both from an applied and mechanistic perspective, on the horizon.
 
Overlapping goals of resistance training in the oncology setting
Squat exercise provides substantial mechanical stimulus to the quadriceps muscle and sarcomere
Adequate biomechanical strain and mechanical loading promotes cellular and mechanical mechanisms to strengthen the bones
There are many benefits to the addition of exercise to cancer treatment and survivorship, particularly with resistance training regimens that target hypertrophy, bone mineral density, strength, functional mobility, and body composition. These goals are best achieved through a series of individualized high-intensity compound movements that mirror functional mobility patterns and sufficiently stress the musculoskeletal system. As a result of adequate stress, the body will engage compensatory cellular mechanisms that improve the structural integrity of bones and muscles, stimulate metabolism and the immune system, optimize functional performance, and minimize mechanical injury risk. The current evidence suggests that application of the above exercise principles, practiced in a safe environment under expert observation, may offer patients with cancer an effective means of improving overall health and cancer-specific outcomes. The following article poses several important questions certified exercise specialists and physicians should consider when prescribing resistance exercise for patients with cancer.
 
Hormone levels according to an idealized menstrual cycle (28 days).
Adapted from Draper et al. [18]. Changing levels of female sex hormones are characterized by the phases of the menstrual cycle. EL early luteal, LF late follicular, MF mid-follicular, ML mid-luteal
Key considerations in body composition across a woman’s lifespan and nutritional considerations to address body composition changes
Energy needs and protein timing considerations for A pre-menopausal and B post-menopausal active women. Total daily calorie estimations were based on the Harris-Benedict equation and relevant activity factor based on activity level. For the peri-menopausal woman, her calorie intake has been reduced by 10% to ultimately reach a hypocaloric intake for a weight loss goal. kg kilograms, BW body weight, lightly active light exercise/sports 1–3 days/week, moderately active moderate exercise/sports 3–5 days/week, very active hard exercise/sports 6–7 days a week
Considerations for magnesium intake across the female lifespan and for factors influencing magnesium deficiency. MND micronutrient deficiency, DNI drug nutrient interactions, PCOS polycystic ovary syndrome, CVD = cardiovascular disease
Supplement considerations for the active female individual
Women are the largest consumers of dietary supplements. Dietary supplements can play a role in health and performance, particularly for women. Growing evidence and innovations support the unique physiological and nutrient timing needs for women. Despite the need for more nutrition and exercise-specific research in women, initial data and known physiological differences between sexes related to the brain, respiration, bone, and muscle support new product development and evidence-based education for active women regarding the use of dietary supplements. In this narrative review, we discuss hormonal and metabolic considerations with the potential to impact nutritional recommendations for active women. We propose four potential areas of opportunity for ingredients to help support the health and well-being of active women, including: (1) body composition, (2) energy/fatigue, (3) mental health, and (4) physical health.
 
Brazilian epidemiological scenario: The solid lines show the mean number of new COVID-19 cases per million, orange for host states and blue for all other states. Shaded areas represent the 95% confidence interval of cases per million on the corresponding date. Copa América testing results: Bars represent the number of positive tests in the corresponding week of the tournament per group. Note that positive cases in the first week were likely to have originated prior to the start of the tournament
Major sporting events were suspended during the most acute phase of the COVID-19 pandemic. Competitions are resuming with enhanced hygiene protocols and altered mechanics. While risks for players and staff have been studied, the impact of large-scale tournaments on the communities that host them remains largely unstudied. CONMEBOL Copa América is one of the first wide-scale international tournaments to be conducted in its original format since the beginning of the COVID-19 pandemic. The tournament saw 10 national teams compete in four Brazilian cities during a period of heightened viral transmission. The analysis of over 28,000 compulsory PCR tests showed that positive cases did not lead to the uncontrolled spread of the disease among staff and players. More importantly, the data indicate that locally hired staff were not exposed to increased risk while working. The Copa América experience shows that international sporting competitions can be conducted safely even under unfavourable epidemiological situations.
 
The figure illustrates leverage points through which COVID-19 could directly and/or indirectly induce low V˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}O2peak and exercise intolerance in patients post-COVID-19. Parameters on the left side of the figure reflect the status quo of the gears (i.e. pulmonary system, cardiovascular system and periphery) and are indicative of organ limitations. The original concept of the gear system explaining determinants of V˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}O2peak is available in Wasserman [9]. a-vO2 diff arteriovenous oxygen difference. CO cardiac output, COVID-19 coronavirus disease 2019, CRF cardiorespiratory fitness, FEV1 forced expiratory volume in 1 s, FVC forced vital capacity, Hb haemoglobin, HR heart rate, SV stroke volume, V˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}O2peak peak oxygen uptake
Medians of V˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}O2peak (A), DLCO (B) and V̇E/V̇CO2 (C) weighted by sample size of respective studies or study visits in case a cohort was tested several times. Bubble area represents the sample size of studies. Bubble colour reflects COVID-19 severity of the majority of patients in the respective study (yellow = mild, dark red = critical). Grey bubbles: classification according to COVID-19 severity not possible. DLCO lung diffusion capacity using carbon monoxide, LT long term, MT medium term, ST short term, V̇E/V̇CO2 ventilatory efficiency, V˙\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}O2peak peak oxygen uptake
Patients recovering from COVID-19 often report symptoms of exhaustion, fatigue and dyspnoea and present with exercise intolerance persisting for months post-infection. Numerous studies investigated these sequelae and their possible underlying mechanisms using cardiopulmonary exercise testing. We aimed to provide an in-depth discussion as well as an overview of the contribution of selected organ systems to exercise intolerance based on the Wasserman gears. The gears represent the pulmonary system, cardiovascular system, and periphery/musculature and mitochondria. Thirty-two studies that examined adult patients post-COVID-19 via cardiopulmonary exercise testing were included. In 22 of 26 studies reporting cardiorespiratory fitness (herein defined as peak oxygen uptake—VO2peak), VO2peak was < 90% of predicted value in patients. VO2peak was notably below normal even in the long-term. Given the available evidence, the contribution of respiratory function to low VO2peak seems to be only minor except for lung diffusion capacity. The prevalence of low lung diffusion capacity was high in the included studies. The cardiovascular system might contribute to low VO2peak via subnormal cardiac output due to chronotropic incompetence and reduced stroke volume, especially in the first months post-infection. Chronotropic incompetence was similarly present in the moderate- and long-term follow-up. However, contrary findings exist. Peripheral factors such as muscle mass, strength and perfusion, mitochondrial function, or arteriovenous oxygen difference may also contribute to low VO2peak. More data are required, however. The findings of this review do not support deconditioning as the primary mechanism of low VO2peak post-COVID-19. Post-COVID-19 sequelae are multifaceted and require individual diagnosis and treatment.
 
Allocation of replication studies to volunteer laboratories
Introduction To improve the rigor of science, experimental evidence for scientific claims ideally needs to be replicated repeatedly with comparable analyses and new data to increase the collective confidence in the veracity of those claims. Large replication projects in psychology and cancer biology have evaluated the replicability of their fields but no collaborative effort has been undertaken in sports and exercise science. We propose to undertake such an effort here. As this is the first large replication project in this field, there is no agreed-upon protocol for selecting studies to replicate. Criticism of previous selection protocols include claims they were non-randomised and non-representative. Any selection protocol in sports and exercise science must be representative to provide an accurate estimate of replicability of the field. Our aim is to produce a protocol for selecting studies to replicate for inclusion in a large replication project in sports and exercise science. Methods The proposed selection protocol uses multiple inclusion and exclusion criteria for replication study selection, including: the year of publication and citation rankings, research disciplines, study types, the research question and key dependent variable, study methods and feasibility. Studies selected for replication will be stratified into pools based on instrumentation and expertise required, and will then be allocated to volunteer laboratories for replication. Replication outcomes will be assessed using a multiple inferential strategy and descriptive information will be reported regarding the final number of included and excluded studies, and original author responses to requests for raw data.
 
Flowchart of included injuries in the analysis. COR Conocimiento, Organización y Rendimiento, MRI magnetic resonance imaging, SMT semitendinosus, TMCH hamstring cramping suring exercise, TMH hamstring strain, TMXX thigh muscle strain/ spasm/ trigger points, TMYH hamstring trigger points
Return to play (RTP) by grade: all muscles (left), and for biceps femoris long head (right)
Return to play (RTP) biceps femoris long head grade 3r by location, and related to the myotendinous junction. Injury located at the distal third affecting the distal myotendinous junction (MTJ) (Dd), injury located at the distal third affecting the proximal MTJ (Dp), injury located at the middel third affecting the distal MTJ (Md), injury located at the middel third affecting the proximal MTJ (Mp), injury located at the proximal third affecting the proximal MTJ (Pp)
Return to play (RTP) of grade 3r biceps femoris long head (BFlh) and semitendinosus injuries (left). Return to play of grade 3r BFlh in partial vs complete tendon injury (right). MTJ myotendinous junction
Background and Objective Muscle injuries are one of the main daily problems in sports medicine, football in particular. However, we do not have a reliable means to predict the outcome, i.e. return to play from severe injury. The aim of the present study was to evaluate the capability of the MLG-R classification system to grade hamstring muscle injuries by severity, offer a prognosis for the return to play, and identify injuries with a higher risk of re-injury. Furthermore, we aimed to assess the consistency of our proposed system by investigating its intra-observer and inter-observer reliability. Methods All male professional football players from FC Barcelona, senior A and B and the two U-19 teams, with injuries that occurred between February 2010 and February 2020 were reviewed. Only players with a clinical presentation of a hamstring muscle injury, with complete clinic information and magnetic resonance images, were included. Three different statistical and machine learning approaches (linear regression, random forest, and eXtreme Gradient Boosting) were used to assess the importance of each factor of the MLG-R classification system in determining the return to play, as well as to offer a prediction of the expected return to play. We used the Cohen’s kappa and the intra-class correlation coefficient to assess the intra-observer and inter-observer reliability. Results Between 2010 and 2020, 76 hamstring injuries corresponding to 42 different players were identified, of which 50 (65.8%) were grade 3r, 54 (71.1%) affected the biceps femoris long head, and 33 of the 76 (43.4%) were located at the proximal myotendinous junction. The mean return to play for grades 2, 3, and 3r injuries were 14.3, 12.4, and 37 days, respectively. Injuries affecting the proximal myotendinous junction had a mean return to play of 31.7 days while those affecting the distal part of the myotendinous junction had a mean return to play of 23.9 days. The analysis of the grade 3r biceps femoris long head injuries located at the free tendon showed a median return to play time of 56 days while the injuries located at the central tendon had a shorter return to play of 24 days (p = 0.038). The statistical analysis showed an excellent predictive power of the MLG-R classification system with a mean absolute error of 9.8 days and an R-squared of 0.48. The most important factors to determine the return to play were if the injury was at the free tendon of the biceps femoris long head or if it was a grade 3r injury. For all the items of the MLG-R classification, the intra-observer and inter-observer reliability was excellent (k > 0.93) except for fibres blurring (κ = 0.68). Conclusions The main determinant for a long return to play after a hamstring injury is the injury affecting the connective tissue structures of the hamstring. We developed a reliable hamstring muscle injury classification system based on magnetic resonance imaging that showed excellent results in terms of reliability, prognosis capability and objectivity. It is easy to use in clinical daily practice, and can be further adapted to future knowledge. The adoption of this system by the medical community would allow a uniform diagnosis leading to better injury management.
 
Background Research has shown the effectiveness of sedentary behaviour interventions on reducing sedentary time. However, no systematic review has studied where the reduced sedentary time after such interventions is displaced to. Objective Our objective was to synthesize the evidence from interventions that have reduced sedentary behaviour and test the displacement of sedentary time into physical activity (light physical activity [LPA], moderate-to-vigorous physical activity [MVPA], standing, and stepping). Methods Two independent researchers performed a systematic search of the EBSCOhost, PubMed, Scopus, and Web of Science electronic databases. Meta-analyses were performed to examine the time reallocated from sedentary behaviour to physical activity during working time and the whole day in intervention trials (randomized/non-randomized controlled/non-controlled). Results A total of 36 studies met all the eligibility criteria and were included in the systematic review, with 26 studies included in the meta-analysis. Interventions showed a significant overall increase in worksite LPA (effect size [ES] 0.24; 95% confidence interval [CI] 0.05 to 0.43; P < 0.013) and daily LPA (ES 0.62; 95% CI 0.34 to 0.91; P = 0.001). A statistically significant increase in daily MVPA was observed (ES 0.47; 95% CI 0.26 to 0.67; P < 0.001). There was a significant overall increase in worksite standing time (ES 0.76; 95% CI 0.56 to 0.95; P < 0.001), daily standing time (ES 0.52; 95% CI 0.38 to 0.65; P < 0.001), and worksite stepping time (ES 0.12; 95% CI 0.04 to 0.20; P = 0.002). Conclusions Effective interventions aimed at reducing sedentary behaviour result in a consistent displacement of sedentary time to LPA and standing time, both at worksites and across the whole day, whereas changes in stepping time or MVPA are dependent on the intervention setting. Strategies to reduce sedentary behaviour should not be limited to worksite settings, and further efforts may be required to promote daily MVPA. Trial Registration PROSPERO registration number CRD42020153958.
 
Flow diagram of the selection process
Risk of bias in a individual crossover studies; b individual randomized controlled studies. aD1 bias arising from the randomization process, D2 bias arising from period and carryover effects, D3 bias due to deviations from intended intervention, D4 bias due to missing outcome data, D5 bias in measurement of the outcome, D6 bias in selection of the reported result, X high risk of bias, − some concerns regarding bias, + low risk of bias. bD1 bias arising from the randomization process, D2 bias due to deviations from intended intervention, D3 bias due to missing outcome data, D4 bias in measurement of the outcome, D5 bias in selection of the reported result, X high risk of bias, − some concerns regarding bias, + low risk of bias
Risk of bias for a all crossover studies; b all randomized controlled studies
Introduction Mental fatigue (MF) is a psychobiological state that impairs cognitive as well as physical performance in different settings. Recently, numerous studies have sought ways to counteract these negative effects of MF. An overview of the explored countermeasures for MF is, however, lacking. Objectives The objective of this review is to provide an overview of the different MF countermeasures currently explored in literature. Countermeasures were classified by the timing of application (before, during or after the moment of MF) and type of intervention (behavioural, physiological and psychological). Methods The databases of PubMed (MEDLINE), Web of Science and PsycINFO were searched until March 7, 2022. Studies were eligible when MF was induced using a task with a duration of at least 30 min, when they assessed MF markers in at least two out of the three areas wherein MF markers have been defined (i.e., behavioural, subjective and/or [neuro]physiological) and used a placebo or control group for the countermeasure. Results A total of 33 studies investigated one or more countermeasures against MF. Of these, eight studies assessed a behavioural countermeasure, 22 a physiological one, one a psychological countermeasure and two a combination of a behavioural and psychological countermeasure. The general finding was that a vast majority of the countermeasures induced a positive effect on behavioural (e.g., task or sport performance) and/or subjective MF markers (e.g., visual analogue scale for MF or alertness). No definitive conclusion could be drawn regarding the effect of the employed countermeasures on (neuro)physiological markers of MF as only 19 of the included studies investigated these measures, and within these a large heterogeneity in the evaluated (neuro)physiological markers was present. Discussion Within the physiological countermeasures it seems that the use of odours during a MF task or caffeine before the MF task are the most promising interventions in combating MF. Promising behavioural (e.g., listening to music) and psychological (e.g., extrinsic motivation) countermeasures of MF have also been reported. The most assumed mechanism through which these countermeasures operate is the dopaminergic system. However, this mechanism remains speculative as (neuro)physiological markers of MF have been scarcely evaluated to date. Conclusion The present systematic review reveals that a wide range of countermeasures have been found to successfully counteract MF on a subjective, (neuro)physiological and/or behavioural level. Of these, caffeine, odours, music and extrinsic motivation are the most evidenced for countering MF. To provide in-detail practical guidelines for the real-life application of MF countermeasures, more research must be performed into the underlying mechanisms and into the optimal dosage and time of application/intake.
 
Schematic of search strategy process
Eccentric training as a method to enhance athletic performance is a topic of increasing interest to both practitioners and researchers. However, data regarding the effects of performing the eccentric actions of an exercise at increased velocities are limited. This narrative review aimed to provide greater clarity for eccentric methods and classification with regard to temporal phases of exercises. Between March and April 2021, we used key terms to search the PubMed, SPORTDiscus, and Google Scholar databases within the years 1950–2021. Search terms included ‘fast eccentric’, ‘fast velocity eccentric’, ‘dynamic eccentric’, ‘accentuated eccentric loading’, and ‘isokinetic eccentric’, analysing both the acute and the chronic effects of accelerated eccentric training in human participants. Review of the 26 studies that met the inclusion criteria identified that completing eccentric tempos of < 2 s increased subsequent concentric one repetition maximum performance, velocity, and power compared with > 4 s tempos. Tempos of > 4 s duration increased time under tension (TUT), whereas reduced tempos allowed for greater volume to be completed. Greater TUT led to larger accumulation of blood lactate, growth hormone, and testosterone when volume was matched to that of the reduced tempos. Overall, evidence supports eccentric actions of < 2 s duration to improve subsequent concentric performance. There is no clear difference between using eccentric tempos of 2–6 s if the aim is to increase hypertrophic response and strength. Future research should analyse the performance of eccentric actions at greater velocities or reduced time durations to determine more factors such as strength response. Tempo studies should aim to complete the same TUT for protocols to determine measures for hypertrophic response.
 
PRISMA flowchart showing the stages and number of records in the systematic review
Background Investigators have proposed that various physical head and neck characteristics, such as neck strength and head and neck size, are associated with protection from mild traumatic brain injury (mTBI/concussion). Objectives To systematically review the literature and investigate potential relationships between physical head and neck characteristics and mTBI risk in athletic and military populations. Methods A comprehensive search of seven databases was conducted: MEDLINE, EMBASE, CINAHL, Scopus, SPORTDiscus, Cochrane Library, and Web of Science. Potential studies were systematically screened and reviewed. Studies on military and athletic cohorts were included if they assessed the relationship between physical head-neck characteristics and mTBI risk or proxy risk measures such as head impact kinematics. Results The systematic search yielded a total of 11,723 original records. From these, 22 studies met our inclusion criteria (10 longitudinal, 12 cross-sectional). Relevant to our PECO (Population, Exposure, Comparator, and Outcomes) question, exposures included mTBI incidence and head impact kinematics (acceleration, velocity, displacement) for impacts during sport play and training and in controlled laboratory conditions. Outcome characteristics included head and neck size (circumference, mass, length, ratios between these measures), neck strength and endurance, and rate of force development of neck muscles. Discussion We found mixed evidence for head and neck characteristics acting as risk factors for and protective factors against mTBI and increased susceptibility to head impacts. Head-neck strength and size variables were at times associated with protection against mTBI incidence and reduced impact kinematics (14/22 studies found one or more head-neck variable to be associated with protection); however, some studies did not find these relationships (8/22 studies found no significant associations or relationships). Interestingly, two studies found stronger and larger athletes were more at risk of sustaining high impacts during sport. Strength and size metrics may have some predictive power, but impact mitigation seems to be influenced by many other variables, such as behaviour, sex, and impact anticipation. A meta-analysis could not be performed due to heterogeneity in study design and reporting. Conclusion There is mixed evidence in the literature for the protective capacity of head and neck characteristics. We suggest field-based mTBI research in the future should include more dynamic anthropometric metrics, such as neck stiffness and response to perturbation. In addition, laboratory-based mTBI studies should aim to standardise design and reporting to help further uncover these complicated relationships.
 
Practical guidelines for using the Feeling Scale, Talk Test, and the rating of perceived exertion scale to monitor exercise intensities consistent with the moderate (green), heavy (yellow), and severe (red) intensity domains
Prescribing exercise intensity is crucial in achieving an adequate training stimulus. While numerous objective methods exist and are used in practical settings for exercise intensity prescription, they all require anchor measurements that are derived from a maximal or submaximal graded exercise test or a series of submaximal or supramaximal exercise bouts. Conversely, self-reported subjective methods such as the Talk Test (TT), Feeling Scale (FS) affect rating, and rating of perceived exertion (RPE) do not require exercise testing prior to commencement of the exercise training and therefore appear as more practical tools for exercise intensity prescription. This review is intended to provide basic information on reliability and construct validity of the TT, FS, and RPE measurements to delineate intensity domains. The TT and RPE appear to be valid measures of both the ventilatory threshold and the respiratory compensation threshold. Although not specifically examined, the FS showed tendency to demarcate ventilatory threshold, but its validity to demarcate the respiratory compensation threshold is limited. Equivocal stage of the TT, RPE of 10–11, and FS ratings between fairly good (+ 1) and good (+ 3) are reflective of the ventilatory threshold, while negative stage of the TT, RPE of 13–15, and FS ratings around neutral (0) are reflective of the respiratory compensation threshold. The TT and RPE can effectively be used to elicit homeostatic disturbances consistent with the moderate, heavy, and severe intensity domains, while physiological responses to constant FS ratings show extensive variability around ventilatory threshold to be considered effective in demarcating transition between moderate and heavy intensity domains.
 
Optimal performance in time-constrained and dynamically changing environments depends on making reliable predictions about future outcomes. In sporting tasks, performers have been found to employ multiple information sources to maximise the accuracy of their predictions, but questions remain about how different information sources are weighted and integrated to guide anticipation. In this paper, we outline how predictive processing approaches, and active inference in particular, provide a unifying account of perception and action that explains many of the prominent findings in the sports anticipation literature. Active inference proposes that perception and action are underpinned by the organism’s need to remain within certain stable states. To this end, decision making approximates Bayesian inference and actions are used to minimise future prediction errors during brain–body–environment interactions. Using a series of Bayesian neurocomputational models based on a partially observable Markov process, we demonstrate that key findings from the literature can be recreated from the first principles of active inference. In doing so, we formulate a number of novel and empirically falsifiable hypotheses about human anticipation capabilities that could guide future investigations in the field.
 
Background Physical properties of water cause physiological changes in the immersed human body compared with the land environment. Understanding the magnitude of cardiorespiratory alterations might ensure adequate intensity control during aquatic exercise programs. Objective We aimed to compare the oxygen uptake (VO2), heart rate (HR), and rating of perceived exertion (RPE) parameters during aquatic and land incremental tests. Methods Four databases (PubMed, LILACS, EMBASE, and SPORTDiscus) were searched in September 2020. Eligibility criteria included studies in a crossover design comparing aquatic and land incremental tests for healthy individuals with at least one of the following parameters: VO2 (maximal, VO2max; anaerobic threshold, VO2AT), HR (HRmax; HRAT), and RPE (RPEmax; RPEAT). The random-effects meta-analysis included mean difference and 95% confidence interval for VO2 and HR or standardized mean difference for RPE. The Joanna Briggs Institute Critical Appraisal tool was adapted to assess methodological quality. Results Twenty-eight studies were eligible and included in the meta-analysis. Aquatic protocols showed lower values compared with land for VO2max (− 7.07 mL.kg⁻¹.min⁻¹; − 8.43 to − 5.70; n = 502), VO2AT (− 6.19 mL.kg⁻¹.min⁻¹; − 7.66 to − 4.73; n = 145), HRmax (− 11.71 bpm; − 13.84 to − 9.58; n = 503), and HRAT (− 15.29 bpm; − 19.05 to − 11.53; n = 145). RPEmax (0.01; − 0.16 to 0.18; n = 299) and RPEAT (− 0.67; − 1.35 to 0.02; n = 55) values were similar between aquatic and land protocols. Conclusions Our study reinforces the specificity of the environment during incremental tests for prescribing exercises based on physiological parameters as VO2 and HR parameters presented lower values in aquatic protocols than land protocols. Conversely, RPE seems an interchangeable measure of exercise intensity, with similar values during the protocols in both environments. Substantial levels of heterogeneity were present for the VO2max and HRmax meta-analyses, and as such, results should be interpreted with attention. Protocol Registration This study was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD42020212508).
 
PRISMA-ScR PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) flow diagram
Esports are a contemporary phenomenon, with millions of people involved. Still, scientific literature on the topic is scarce. Anecdotal reports, mostly based on what is known from videogames practice, have associated esports with unhealthy lifestyles and health-related problems. The present scoping review aimed to provide an overview of findings from studies regarding the health and well-being in adult esports players, while identifying the most studied topics in the field and those still lacking scientific research. The search was conducted in MEDLINE, Scopus, Web of Science, B-on, and ESCBO databases. Studies regarding health consequences of esports practice conducted with adult esports players were included. No exclusion criteria concerning age, sex, esports modality, or esports level were applied, but articles related to other forms of video gaming or gambling were excluded. The search was limited to peer-reviewed articles. Opinion and review articles were excluded. There were 1416 articles retrieved from which 33 met the inclusion criteria. Lifestyle habits, sleep, exercise and physical health (including musculoskeletal health), physiological demands, and mental health were the main topics of investigation. Several gaps in the literature were identified, namely studies on cardiovascular, respiratory, or metabolic health, or consuming-related risks. Also, the lack of homogeneous methodologies and definitions used in esports-related studies was identified. Esports practice has been associated with different health-related symptoms, but more studies using more robust methodologies and appropriate research design are needed. Topics such as cardiovascular health or the use of performance-enhancing drugs are lacking.
 
Top-cited authors
Lisa Michele Barnett
  • Deakin University
Martin Buchheit
  • Paris Saint Germain Football Club
Urs Granacher
  • University of Freiburg
David F Stodden
  • University of South Carolina
Francisco B Ortega
  • University of Granada