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Long-Term Time-Course of Strength Adaptation to Minimal Dose Resistance Training Through Retrospective Longitudinal Growth Modeling
Research Quarterly for Exercise and Sport
Abstract
Public health guidelines for resistance training emphasize a minimal effective dose intending for individuals to engage in these behaviors long term. However, few studies have adequately examined the longitudinal time-course of strength adaptations to resistance training. Purpose: The aim of this study was to examine the time-course of strength development from minimal-dose resistance training in a large sample through retrospective training records from a private international exercise company. Methods: Data were available for analysis from 14,690 participants (60% female; aged 48 ± 11 years) having undergone minimal-dose resistance training (1x/week, single sets to momentary failure of six exercises) up to 352 weeks (~6.8 years) in length. Linear-log growth models examined strength development over time allowing random intercepts and slopes by participant. Results: All models demonstrated a robust linear-log relationship with the first derivatives (i.e., changes in strength with time) trending asymptotically such that by ~1-2 years strength had practically reached a "plateau." Sex, bodyweight, and age had minimal interaction effects. However, substantial strength gains were apparent; approximately ~30-50% gains over the first year reaching ~50-60% of baseline 6 years later. Conclusion: It is unclear if the "plateau" can be overcome through alternative approaches, or whether over the long-term strength gains differ. Considering this, our results support public health recommendations for minimal-dose resistance training for strength adaptations in adults.
... Resistance training should be a major component of what this group of exercise professionals prescribes, given its well-established benefits on the ageing musculoskeletal system [7]. Yet even the reliable use of resistance training in clinical and professional practice has recently come into question [21][22][23]. Therefore, this study begins to explore whether exercise prescription for older adults is aligned with the recommendations within the strength component of the Chief Medical Officers' physical activity guidelines. ...
... In addition, nearly all instructors (n=14) are not aligning their strength prescription with the frequency recommendation of 'at least two days-a-week' for their older adult clients. These findings corroborate a survey of UK-based practitioners delivering exercise to older adults with sarcopenia [23]. Despite having international consensus from their governing body that practitioners should be offering a programme with a prominent resistance component, resistance training was the main focus of the programmes only 9% of the time and was missing from their prescriptions entirely, 35% of the time [23,27]. ...
... These findings corroborate a survey of UK-based practitioners delivering exercise to older adults with sarcopenia [23]. Despite having international consensus from their governing body that practitioners should be offering a programme with a prominent resistance component, resistance training was the main focus of the programmes only 9% of the time and was missing from their prescriptions entirely, 35% of the time [23,27]. The same survey also indicated that 65% of the time, supervised exercise was offered once-a-week or less [23]. ...
... Indeed, resistance training interventions ≥12 months are uncommon. One way to overcome these difficulties is to conduct retrospective and/or cross-sectional analyses of large databases to understand strength adaptation (see (19,20,22,45)). For example, Steele et al. (45) recently reported that strength increases by ~50-60% over an approximate 6year period, but that ~30-50% of this occurs within the first year. Importantly, these results are in response to minimal dose resistance training (i.e., one training session per week, comprising six exercises and only one set to momentary muscle failure for each) in a general, non-athletic population. ...
... One way to overcome these difficulties is to conduct retrospective and/or cross-sectional analyses of large databases to understand strength adaptation (see (19,20,22,45)). For example, Steele et al. (45) recently reported that strength increases by ~50-60% over an approximate 6year period, but that ~30-50% of this occurs within the first year. Importantly, these results are in response to minimal dose resistance training (i.e., one training session per week, comprising six exercises and only one set to momentary muscle failure for each) in a general, non-athletic population. ...
... Importantly though, and as noted by Latella et al. (19), strength gain does not occur linearly. As recently suggested by Steele et al. (45) certain statistical approaches hold inherent limitations. Thus, alternative statistical approaches such as mixed effects growth modelling (as used to explore the effects of minimal dose resistance training [(45)]), may provide more robust information in this area. ...
Introduction: Several retrospective studies of strength sport athletes have reported strength adaptations over months to years, however, such adaptations are not linear. Methods: We explored changes in strength over time in a large, retrospective sample of powerlifting (PL) athletes. Specifically, we examined the rate and magnitude of strength adaptation based on age category and weight class for total strength, and the squat, bench press, and deadlift, respectively. Mixed effects growth modelling was performed for each operationalised performance outcome (squat, bench press, deadlift, and total) as the dependent variables with outcomes presented on both the raw untransformed time scale, and on the common logarithmic scale. Additionally, the fitted values were rescaled as a percentage. Results: Collectively, the greatest strength gains were in the earliest phase of PL participation (~7.5-12.5% increase in the first year, with only an ~12.5-20% increase after 10 years). Females tended to display faster progression, possibly because of lower baseline strength. Additionally, female Masters 3 and 4 athletes (>59 years) still displayed ~2.5-5.0% strength improvement, and only slight strength loss was observed in Masters 4 (>69 years) males (~0.35%/year). Conclusion: Although directly applicable to PL, these findings provide population level support for the role of consistent and continued strength training to improve strength across individuals, and importantly, to mitigate, or at least largely attenuate age-related declines in strength compared to established general population norms. This information should be used to encourage participation in strength sports, resistance training more generally, and to support future public health messaging.
... Given the relatively short and homogeneous durations included, there was limited ability to explore the functional form of changes over longer durations (e.g., playing seasons, years). In a recent large modelling study investigating the time-course of strength adaptations, Steele et al. [30] showed that linear-log growth models were appropriate to describe improvements of relatively untrained participants over the course of almost 7 years, with improvements tending to plateau after approximately 1 year. The training stimulus investigated by Steele et al. [30] focused on minimal dose resistance training (1x/week, single sets to momentary failure of six exercises), which is likely to have influenced the parameters obtained. ...
... In a recent large modelling study investigating the time-course of strength adaptations, Steele et al. [30] showed that linear-log growth models were appropriate to describe improvements of relatively untrained participants over the course of almost 7 years, with improvements tending to plateau after approximately 1 year. The training stimulus investigated by Steele et al. [30] focused on minimal dose resistance training (1x/week, single sets to momentary failure of six exercises), which is likely to have influenced the parameters obtained. Our analysis was limited to durations of no more than 26 weeks and thus we cannot draw inferences as to how results might change over longer time frames. ...
Background
Resistance exercise is the most common training modality included within strength and conditioning (S&C) practice. Understanding dose–response relationships between resistance training and a range of outcomes relevant to physical and sporting performance is of primary importance for quality S&C prescription.
Objectives
The aim of this meta-analysis was to use contemporary modelling techniques to investigate resistance-only and resistance-dominant training interventions, and explore relationships between training variables (frequency, volume, intensity), participant characteristics (training status, sex), and improvements across a range of outcome domains including maximum strength, power, vertical jump, change of direction, and sprinting performance.
Methods
Data were obtained from a database of training studies conducted between 1962 and 2018, which comprised healthy trained or untrained adults engaged in resistance-only or resistance-dominant interventions. Studies were not required to include a control group. Standardized mean difference effect sizes were calculated and interventions categorized according to a range of training variables describing frequency (number of sessions per week), volume (number of sets and repetitions performed), overall intensity (intensity of effort and load, categorised as low, medium or high), and intensity of load (represented as % of one-repetition maximum [1RM] prescribed). Contemporary modelling techniques including Bayesian mixed-effects meta-analytic models were fitted to investigate linear and non-linear dose-responses with models compared based on predictive accuracy.
Results
Data from a total of 295 studies comprising 535 groups and 6,710 participants were included with analyses conducted on time points ≤ 26 weeks. The best performing model included: duration from baseline, average number of sets, and the main and interaction effects between outcome domain and intensity of load (% 1RM) expressed non-linearly. Model performance was not improved by the inclusion of participant training status or sex.
Conclusions
The current meta-analysis represents the most comprehensive investigation of dose–response relationships across a range of outcome domains commonly targeted within strength and conditioning to date. Results demonstrate the magnitude of improvements is predominantly influenced by training intensity of load and the outcome measured. When considering the effects of intensity as a % 1RM, profiles differ across outcome domains with maximum strength likely to be maximised with the heaviest loads, vertical jump performance likely to be maximised with relatively light loads (~ 30% 1RM), and power likely to be maximised with low to moderate loads (40–70% 1RM).
... 17 LMMs are linear in their parameters but can include non-linear variables such as time from baseline allowing curvilinear changes over an intervention to be modelled. 18 A large observational analysis conducted by Steele et al. 19 of resistance training over seven years was shown to be appropriately modelled with linear-log growth such that 30-50% of improvements were obtained over the first year. In the context of most RCTs in strength and conditioning, however, interventions are generally short, and an assumption of linear change may be appropriate, estimable, and easier to interpret. ...
... Underpinning this study is the assumption that the response of individuals to a single training intervention can be adequately described by a linear model. Whilst long-term observational studies show that improvements to strength and conditioning interventions will be non-linear, 19 over the shorter-term which is typical of RCTs, a linear model may be appropriate. In our large meta-analysis, we identified an ordered effect with greater magnitude improvements obtained with intervention durations exceeding 10 weeks as compared to intervention durations of 6 to 10 weeks, and less than 6 weeks. ...
... Interventions such as these are valuable for the simplification of guidelines and recommendations. For example, muscle strengthening interventions such as RT are recommended for everyone in current physical activity guidelines and in such applications there is likely value in a simple approach to such recommendations (Steele et al., 2017;Steele et al., 2022). ...
... The reason for the apparent reduction in variation after introduction of an RT intervention observed here is not necessarily discernible from this analysis. Perhaps the introduction of an RT intervention has indirect effects that reduce other sources of random variation (e.g., diet, other physical activity etc.; Halliday et al. (2017)), or a ceiling effect on change (i.e., plateau in response; Steele et al. (2022)) has a constraining effect (Cortés Martínez, 2021). However, this potentially represents another interesting area of future study regarding variation; specifically, how to produce interventions that actually reduce variance in an outcome. ...
... First, our data confirmed significant strength increases as a result of machine-based strength training interventions. Values were of a similar magnitude to those reported previously in both large-scale meta-analyses [61] and in a large sample including older adults [62]. While this might be expected, it should not be overlooked. ...
Background/Objectives: Resistance training (RT) can improve the functional performance of older adults, maintaining independence and quality of life. It has been proposed that training interventions should implement exercises associated with the movements needed in everyday life. However, this strength training philosophy presents challenges, specifically to older adults, and the use of resistance machines might present an efficacious alternative. The aim of this systematic review and meta-analysis was to explore the impact of machine-based RT on strength and functional capacity in older adults. Methods: The inclusion criteria were for strength training interventions to be a minimum of 6 weeks, using only resistance machines, with pre- and post-intervention measurements of functional capacity of either a timed up-and-go and/or a sit-to-stand test, and including healthy older adults (>60 years). Results: Following the screening, 17 articles met the inclusion criteria for the systematic review, 15 of which were included in the meta-analysis for functional outcomes (n = 614 participants), and 11 of which were included in the meta-analysis for strength outcomes (n = 511 participants). Analyses revealed significant standardized mean change in favor of machine-based RT for functional outcomes (0.72, 95% CIs 0.39 to 1.07) and strength outcomes (0.71, 95% CIs 0.34 to 1.08) compared to control conditions (functional = 0.09, 95% CIs − 0.1 to 0.28, strength = 0.1, 95% CIs − 0.05 to 0.24). Substantial heterogeneity was noted in the manipulation of RT variables and the magnitude of effects between studies. Conclusions: The data presented support the idea that significant strength and functional performance outcomes are attainable using uncomplicated, machine-based RT.
... Firstly, our data confirmed significant strength increases as a result of machine-based strength training interventions. Values were of a similar magnitude to those reported previously in both large scale meta-analysis (Steele, Fisher, Smith, et al., 2023) and in a large sample including older adults (Steele, Fisher, Giessing, et al., 2023). While this might be expected, it should not be overlooked. ...
... However, this approach is not without limitations as there are multiple potential confounders and logistical constraints introduced by the accumulation of testing in a relatively short period of time [12]. It also assumes that the causal effect of the intervention is linear over time, which may not be the case longer durations of RT (i.e., linear-log trajectories may be more likely) [23,24]. ...
Most resistance training research focuses on inference from average intervention effects from observed group-level change scores (i.e., mean change of group A vs group B). However, many practitioners are more interested in training responses (i.e., causal effects of an intervention) on the individual level (i.e., causal effect of intervention A vs intervention B for individual X). To properly examine individual response variation, multiple confounding sources of variation (e.g., random sampling variability, measurement error, biological variability) must be addressed. Novel study designs where participants complete both interventions and at least one intervention twice can be leveraged to account for these sources of variation (i.e., n of 1 trials). Specifically, the appropriate statistical methods can separate variability into the signal (i.e., participant-by-training interaction) versus the noise (i.e., within-participant variance). This distinction can allow researchers to detect evidence of individual response variation. If evidence of individual response variation exists, researchers can explore predictors of the more favorable intervention, potentially improving exercise prescription. This review outlines the methodology necessary to explore individual response variation to resistance training, predict favorable interventions, and the limitations thereof.
... One of the most pronounced between group differences came in the form of maximal strength results. Participants in the group following the HCLF diet, as would be expected in this type of intervention [66,82,83], improved significantly in most of the strength assessments, whereas the situation was reversed for participants in the LCHF group. It is worth emphasizing that our study employed a large caloric deficit, which could have induced substantial fatigue in the later weeks of the experiment, potentially overshadowing any neurological adaptations resulting from the training regime. ...
Abstract
Purpose: The aim of this study was to compare High Carbohydrates Low Fat (HCLF) and Low Carbohydrate High Fat (LCHF) diets in terms of changes in body composition and maximal strength.
Patients/methods: The study involved 48 men aged 25 ± 2.5, divided into two groups, one of which (n=23) was following the LCHF diet and the other (n=25) the HCLF diet. Both groups performed the same resistance training protocol for 15 weeks. Maximal strength in squat, benchpress and deadlift was assessed pre- and post-intervention. Measurements of selected body
circumferences and tissue parameters were made using the multifunctional, multi-frequency,direct bioelectric impedance InBody 770 analyzer from InBody Co., Ltd (Cerritos, California,
USA). The team with the necessary qualifications and experience in research performed all the measurements and maintained participants’ oversight throughout the entire length of the study.
Results: Both nutritional approaches were effective in terms of reducing body fat mass. The HCLF group achieved greater skeletal muscle hypertrophy. Significant decreases in body
circumferences, especially in the abdominal area, were observed for both dietary approaches. Maximal strength significantly increased in the HCLF group and decreased in the LCHF group.
Conclusion: Holistic analysis of the results led to the conclusion that both dietary approaches may elicit positive adaptations in body composition. The two approaches constitute useful
alternatives for both recreational exercisers and physique athletes with body composition goals.
Keywords: resistance training; body composition; ketogenic diet; high carbohydrate diet; maximal strength.
... In an audit of NHS instructors, this once-a-week offering was found to be even more common − 86% of the time [30]. While once-a-week strength training to failure has been shown to increase strength [31], failure to follow the 'at least two days-a-week' recommendation within the guidelines is problematic as an insufficient exercise dose for those older adults not training to failure will likely not be able to achieve the goal of building muscular strength [32]. An ageing population lacking sufficient or optimal levels of muscular strength may be increasingly susceptible to early-onset (multi-)morbidity, resulting in unsustainable economic and healthcare stress. ...
Strength training recommendations have been embedded within the UK’s Chief Medical Officers’ physical activity guidelines since 2011. There is limited evidence that these recommendations are used by exercise instructors in the community to underpin strength training prescription in the older adult population. This study aimed to explore exercise instructors’ awareness and utilisation of the guidelines when prescribing strength training to older adults. Fifteen exercise instructors working with older adults in the UK participated in one online interview. A general inductive approach was conducted and thematic analysis allowed for major themes to be identified from the raw data. We found that most exercise instructors (n = 9), but not all (n = 6), were aware of the guidelines. Only one instructor (n = 1) had reportedly implemented the guidelines into their practice; other instructors reported that the guidelines were irrelevant. Instead, each of the instructors had their preferred sources of information that they relied on to underpin their exercise prescription, and each had their own interpretation of ‘evidence-based strength training.’ This individualised interpretation resulted in exceptionally varied prescription in the community and does not necessarily align with the progressive, evidence-based prescription known to build muscular strength. We suggest that (i) more detail on how to build muscular strength be embedded within the guidelines, (ii) a handbook on how to implement the guidelines be made available, (iii) theoretical and practical teaching materials and courses be updated, and/or (iv) a re-(education) of exercise instructors already in the field may be necessary to bring about a consistent, evidence-based strength prescription necessary for the best possible health and longevity outcomes for our ageing population.
... The reason for the apparent reduction in variation after the introduction of an RT intervention observed here is not necessarily discernible from this analysis. Perhaps, the introduction of an RT intervention has indirect effects that reduce other sources of random variation (e.g., diet, other physical activity, etc.; Halliday et al. (2017)), or a ceiling effect on change (i.e., plateau in response; Steele et al. (2022)) has a constraining effect (Cortés Martínez, 2021). However, this potentially represents another interesting area of future study regarding variation; specifically, how to produce interventions that actually reduce variance in an outcome. ...
Meta-analysis has become commonplace within sport and exercise science for synthesising and sum-marising empirical studies. However, most research in the field focuses upon mean effects, particularly the effects of interventions to improve outcomes such as fitness or performance. It is thought that individual responses to interventions vary considerably. Hence, interest has increased in exploring precision or personalised exercise approaches. Not only is the mean often affected by interventions, but variation may also be impacted. Exploration of variation in studies such as randomised controlled trials (RCTs) can yield insight into interindividual heterogeneity in response to interventions and help determine generalisability of effects. Yet, larger samples sizes than those used for typical mean effects are required when probing variation. Thus, in a field with small samples such as sport and exercise science, exploration of variation through a meta-analytic framework is appealing. Despite the value of embracing and exploring variation alongside mean effects in sport and exercise science, it is rarely applied to research synthesis through meta-analysis. We introduce and evaluate different effect size calculations along with models for meta-analysis of variation using relatable examples from resistance training RCTs.
... Another robust finding was the lack of association between knee muscle performance and self-reported function. While both knee extensor and flexor peak torque were statistically significant in the adjusted models (Table 3), the magnitude of the relationship is unlikely to be clinically relevant requiring an unrealistic peak torque increase (~i.e., 96 Nm (extensor) and ~48 Nm (flexor)) (Steele, et al., 2022;Tayfur et al., 2021) to surpass measurement error of 19.2 KOOS points (Collins, et al., 2016). The lack of a relationship between muscle performance and self-reported function is consistent with past studies in this population, (Davis, et al., 2017;Garcia et al., 2020) but counter to findings in people living with knee OA (Bartholdy, et al., 2017;Hall et al., 2018;Hu et al., 2018;Luc-Harkey, et al., 2018;Reid et al., 2015). ...
... Last, only a relatively narrow range of repetition durations were reported with the magnitude of their impact being relatively small and uncertain. As some resistance training protocols employ long repetition durations and low repetition numbers (e.g., 6 repetitions at 10-s concentric and 10-s eccentric) [303], the REPS ~ %1RM relationship might differ at more extreme repetition durations, and thus further research can explore this topic. ...
The maximal number of repetitions that can be completed at various percentages of the one repetition maximum (1RM) [REPS ~ %1RM relationship] is foundational knowledge in resistance exercise programming. The current REPS ~ %1RM relationship is based on few studies and has not incorporated uncertainty into estimations or accounted for between-individuals variation. Therefore, we conducted a meta-regression to estimate the mean and between-individuals standard deviation of the number of repetitions that can be completed at various percentages of 1RM. We also explored if the REPS ~ %1RM relationship is moderated by sex, age, training status, and/or exercise. A total of 952 repetitions-to-failure tests, completed by 7289 individuals in 452 groups from 269 studies, were identified. Study groups were predominantly male (66%), healthy (97%), < 59 years of age (92%), and resistance trained (60%). The bench press (42%) and leg press (14%) were the most commonly studied exercises. The REPS ~ %1RM relationship for mean repetitions and standard deviation of repetitions were best described using natural cubic splines and a linear model, respectively, with mean and standard deviation for repetitions decreasing with increasing %1RM. More repetitions were evident in the leg press than bench press across the loading spectrum , thus separate REPS ~ %1RM tables were developed for these two exercises. Analysis of moderators suggested little influences of sex, age, or training status on the REPS ~ %1RM relationship, thus the general main model REPS ~ %1RM table can be applied to all individuals and to all exercises other than the bench press and leg press. More data are needed to develop REPS ~ %1RM tables for other exercises.
... As we have seen, in so far as it has been tested, it is not clear that periodisation as it is typically studied produces superior outcomes, at least for strength and hypertrophy. Further, it is not clear that there is any evidence that it is possible to overcome the typical plateauing of adaptation that occurs over time [59][60][61] , or that particular ordering of training for specific adaptations enhances outcomes 50 . But, as it has typically been studied, periodisation in so far as we can discern some clarity regarding what it is, has not been strongly tested in that form. ...
In this chapter we present an overview of periodisation introduceing and discussing its definition and historical development. We then consider the common argument that strength and hypertrophic adaptations are optimised through the application of periodisation, and provide alternative interpretations that we think likely reflect more parsimonious explanations than appeals to periodisation ‘theory’. Lastly, we will consider its structure as a myth vs as a scientific theory in the Popperian sense. From our perspective and analysis, it does not feel unfair to label periodisation as a myth. At the very least it has strong elements of mythos about it particularly in terms of its origin and development. If periodisation is to take a step forward into the beginnings of a scientific theory, then consensus specification and definition such that it yields clear deductively testable consequences should be the next point in its journey from mythical origins.
... Lastly, only a relatively narrow range of repetition durations were reported with the magnitude of their impact being relatively small and uncertain. As some resistance training protocols employ long repetitions durations and low repetition numbers (e.g., 6 repetitions at 10 second concentric and 10 second eccentric) 39 it is likely that the REPS~%1RM relationship differs at more extreme repetition durations and thus further research should explore this topic. ...
The maximal number of repetitions that can be completed at various percentages of the one repetition maximum (1RM) (REPS~%1RM relationship) is foundational knowledge in resistance exercise programming. The current REPS~%1RM relationship is based on few studies and has not incorporated uncertainty into estimations or accounted for between-individual variation. Therefore, we conducted a meta-regression analysis to estimate the mean and between-individuals standard deviation of number of repetitions that can be completed at various percentages of 1RM. We also explored if the REPS~%1RM relationship is moderated by sex, age, training status, and/or exercise. A total of 952 repetitions-to-failure tests, completed by 7,270 individuals in 450 groups from 266 studies, were identified. Study groups were predominantly male (66%), healthy (97%), <59 years of age (92%), and resistance-trained (60%). The bench press (42%) and leg press (14%) were the most commonly studied exercises. The REPS~%1RM relationship for mean repetitions and standard deviation of repetitions were best described using natural cubic splines and a linear model, respectively, with mean and standard deviation for repetitions decreasing with increasing %1RM. More repetitions were evident in the leg press than bench press across the loading spectrum , thus separate REPS~%1RM tables were developed for these two exercises. Analysis of moderators suggested little influences of sex, age, or training status on the REPS~%1RM relationship, thus the general main model REPS~%1RM table can be applied to all individuals and to all exercises other than the bench press and leg press. More data are needed to develop REPS~%1RM tables for other exercises.
... The information presented by participants in this study is reflected in the current literature, where deloading is achieved through a multifaceted alteration in training demand, facilitated through a reduction in training volume (Bartolomei et al., 2014;Israetel et al., 2020;Painter et al., 2012;Redman et al., 2021;Vann et al., 2021) or training intensity of effort (Bartolomei et al., 2014;Schoenfeld et al., 2020;Winwood et al., 2015), as well as an alteration in exercise selection or order (Pistilli et al., 2008;Schoenfeld et al., 2020 Radaelli et al., 2013;Sooneste et al., 2013;Steele et al., 2022). However, given the lower intensity of effort employed during deloading, it is currently unclear how these variables should be organised and manipulated for adequate recovery without inducing a detraining effect. ...
... a) Choice of exercise: select bodyweight exercises that utilize the major muscle groups. According to the minimal dose approach for resistance training [31][32][33], As little as 2-exercises per major muscle group can improve strength and functional ability in younger and older adults [31]. Therefore, the choice of exercises should be based on training status, goals and time constraints. ...
The COVID Pandemic and cost of living crisis have created renewed interest in home gymnasiums, and outdoor exercise regimes as the stay-at-home economy continues to grow. Emerging from the revolution in stay-at-home exercise has renewed interest in bodyweight exercise training regimes which have stood the test of time against conventional exercise modalities. This mini-review highlights the benefits of bodyweight exercise to develop muscular strength and endurance and provides recommendations on using bodyweight training to improve muscular strength and endurance.
... 26 Naturally, the minimal adaptive dose is likely to be individually specific 25 and change in time; otherwise, a plateau (or even a decrease) in adaptation may be observed. 23 In addition, according to the principle of specificity, 1,26 load orientation and exercise mode reflect what the load is targeting and is the main driver of training adaptations. 10,12,24,26 However, microdosing mainly focuses on resistance and endurance training, 6,7,13,14 although additional parameters, such as change of direction, range of motion, repeated sprint ability, or maximal sprinting speed, could also be, in principle, microdosed. ...
Purpose:
Microdosing of exercise aims to deliver smaller daily training doses but at a higher weekly frequency, adding up to a similar weekly volume as in nonmicrodosed training. This commentary critically discusses this concept, which appears to be a rebranding of the "old" distributed practice of motor learning.
Development:
We propose that microdosing should relate to the minimal dose that develops or at least maintains the selected capacities or skills as this training dose matters to practitioners, especially during the in-season period. Moreover, microdosing has been applied mainly to develop strength and endurance, but abilities such as sprinting and changing direction could also be microdosed, as well as technical-tactical skills.
Conclusions:
The concept of microdosing should be reframed to avoid redundancy with the concept of distributed practice while providing valuable information concerning the minimum doses that still generate the intended effects and the thresholds that determine whether a dose is "micro" or not.
Introduction
Several retrospective studies of strength sport athletes have reported strength adaptations over months to years; however, such adaptations are not linear.
Methods
We explored changes in strength over time in a large, retrospective sample of powerlifting (PL) athletes. Specifically, we examined the rate and magnitude of strength adaptation based on age category and weight class for PL competition total, and the squat, bench press, and deadlift, respectively. Mixed effects growth modelling was performed for each operationalised performance outcome (squat, bench press, deadlift, and total) as the dependent variables, with outcomes presented on both the raw, untransformed time scale and on the common logarithmic scale. Additionally, the fitted values were rescaled as a percentage.
Results
Collectively, the greatest strength gains were in the earliest phase of PL participation (~ 7.5–12.5% increase in the first year, and up to an ~ 20% increase after 10 years). Females tended to display faster progression, possibly because of lower baseline strength. Additionally, female Masters 3 and 4 athletes (> 59 years) still displayed ~ 2.5–5.0% strength improvement, but a slight strength loss was observed in Masters 4 (> 69 years) males (~ 0.35%/year).
Conclusion
Although directly applicable to PL, these findings provide population-level support for the role of consistent and continued strength training to improve strength across the age span and, importantly, to mitigate, or at least largely attenuate age-related declines in strength compared to established general population norms. This information should be used to encourage participation in strength sports, resistance training more generally, and to support future public health messaging.
Deloading refers to a purposeful reduction in training demand with the intention of enhancing preparedness for successive training cycles. Whilst deloading is a common training practice in strength and physique sports, little is known about how the necessary reduction in training demand should be accomplished. Therefore, the purpose of this research was to determine current deloading practices in competitive strength and physique sports. Eighteen strength and physique coaches from a range of sports (weightlifting, powerlifting, and bodybuilding) participated in semi-structured interviews to discuss their experiences of deloading. The mean duration of coaching experience at ≥ national standard was 10.9 (SD = 3.9) years. Qualitative content analysis identified Three categories: definitions, rationale, and application. Participants conceptualised deloading as a periodic, intentional cycle of reduced training demand designed to facilitate fatigue management, improve recovery, and assist in overall training progression and readiness. There was no single method of deloading; instead, a reduction in training volume (achieved through a reduction in repetitions per set and number of sets per training session) and intensity of effort (increased proximity to failure and/or reduction in relative load) were the most adapted training variables, along with alterations in exercise selection and configuration. Deloading was typically prescribed for a duration of 5 to 7 days and programmed every 4 to 6 weeks, although periodicity was highly variable. Additional findings highlight the underrepresentation of deloading in the published literature, including a lack of a clear operational definition.
This study investigated the impact of intensity in a low-volume RT on sarcopenia indicators in postmenopausal women (PTW). Thirty-two participants were randomly assigned to either a control group (CT, n = 10), a LL-RT group (n = 10) that performed one set of 25–30 repetition maximum per exercise or a high-load RT group (HI-RT, n = 12) that performed one set of 8–12 repetition maximum per exercise. The RT groups performed 8 exercises, with 90 seconds of rest between exercises, 2 times a week for 24-weeks. Muscle mass (MM) of limbs (upper and lower) was assessed by DEXA, muscle strength (MS) was measured by the 1-RM leg press test, and physical performance by the TUG test and the 30-second sit to stand test. The ANCOVA (covariates: age, antihypertensive drugs, hormone replacement therapy and pre-time values) was used to analyze the gains (Δ) between groups, with a significance level of 5%. After 24-weeks of RT, lower and upper limb MM (together/summed) increased in both HI-RT (Δ = 0.60 kg; 95% CI: 0.23–1.0 kg) and LI-RT (Δ = 0.48 kg; 95% CI: 0.06–0.91 kg) in relation to CT (Δ=-0.03 kg; 95% CI: -0.43–0.37 kg) with no difference between them (p = 0.016; ƞ²=0.27 (large); observed power = 0.83). However, upper limb MM increased only in the HI-RT. For MS, the HI-RT group (Δ = 40 kg; 95% CI: 21–58 kg) showed greater gains compared to the CT (Δ = -5 kg; CI 95%: -24–14 kg) and LL (Δ = 12 kg; 95% CI: -8–33 kg) (p = 0.001 η ² = 0.35, Power = 0.98). Even though LI-RT promotes MM gains in lower limbs, HI-RT should be considered in low-volume training to promote gains in MS and also in MM in upper limbs in the PTW.
Aims
This study considered the effects of supervised, low volume, high intensity of effort resistance training compared to continued routine care in persons with type II diabetes.
Methods
We utilized a randomized parallel-group time-series design. All participants completed baseline testing (T0) and then participated in an educational training intervention regarding the management of their diabetes and were followed up for six months, during which they received routine care before being retested (T1). Participants were then randomly allocated to either continue with routine care (CON) or receive the high intensity of effort resistance training intervention (HIT). Participants from both groups were retested again after six months (T2). All participants were followed up for a further 12 months before being finally tested (T3). Data were available from 57 participants who completed the whole duration of the study (HIT, n = 29; CON, n = 28) for measures of anthropometry (body mass, waist circumference, and BMI), body composition (body fat mass, body fat percentage, lean mass, and visceral fat mass), total body water, phase angle, HbA1c, fasted blood glucose, and subjective wellbeing (WHO-5).
Results
During the initial 6-months of routine care significant improvements were noted for waist circumference, body fat mass, lean mass, body fat percentage, lean mass percentage, visceral fat mass, HbA1c, fasted blood glucose, and subjective wellbeing. During the successive 6-months (intervention) and 18-months (follow-up), data suggest that many of these positive changes during the initial 6-months were negated or reversed for CON. In contrast, participants engaging in HIT continued to show positive changes for waist circumference, body fat mass, lean mass, body fat percentage, lean mass percentage, and visceral fat. For blood markers and wellbeing, HbA1c continued to decrease, fasted blood glucose decreased, and subjective wellbeing continued to increase. These positive responses were still evidenced and significantly different compared to CON after the 12-month follow-up.
Conclusion
The results of this exploratory pragmatic trial suggest that the addition of high intensity of effort RT alongside routine care can have a positive impact on a range of outcomes in type 2 diabetics having undergone prior routine care.
Background: Since many people choose to perform resistance training unsupervised, and a lack of supervision within strength training is reported to result in inadequate workout quality, we aimed to compare outcomes for resistance training with and without supervision. Methods: A systematic review and meta-analysis were performed for performance/functional outcomes and/or body composition measurements. Results: 12 studies were included in the review; 301 and 276 participants were in supervised and unsupervised groups, respectively. The main model for all performance/function effects revealed a small, standardised point estimate favouring SUP (0.28 [95%CI = 0.02 to 0.55]). For sub-grouped outcome types, there was very poor precision of robust estimates for speed, power, function, and endurance. However, for strength there was a moderate effect favouring SUP (0.40 [95%CI = 0.06 to 0.74]). The main model for all body composition effects revealed a trivial standardised point estimate favouring SUP (0.07 [95%CI = -0.01 to 0.15]). Conclusions: Supervised resistance training, compared to unsupervised training, might produce a small effect on increases in performance/function, most likely in strength, but has little impact on body composition outcomes.
Objectives
To describe new WHO 2020 guidelines on physical activity and sedentary behaviour.
Methods
The guidelines were developed in accordance with WHO protocols. An expert Guideline Development Group reviewed evidence to assess associations between physical activity and sedentary behaviour for an agreed set of health outcomes and population groups. The assessment used and systematically updated recent relevant systematic reviews; new primary reviews addressed additional health outcomes or subpopulations.
Results
The new guidelines address children, adolescents, adults, older adults and include new specific recommendations for pregnant and postpartum women and people living with chronic conditions or disability. All adults should undertake 150–300 min of moderate-intensity, or 75–150 min of vigorous-intensity physical activity, or some equivalent combination of moderate-intensity and vigorous-intensity aerobic physical activity, per week. Among children and adolescents, an average of 60 min/day of moderate-to-vigorous intensity aerobic physical activity across the week provides health benefits. The guidelines recommend regular muscle-strengthening activity for all age groups. Additionally, reducing sedentary behaviours is recommended across all age groups and abilities, although evidence was insufficient to quantify a sedentary behaviour threshold.
Conclusion
These 2020 WHO guidelines update previous WHO recommendations released in 2010. They reaffirm messages that some physical activity is better than none, that more physical activity is better for optimal health outcomes and provide a new recommendation on reducing sedentary behaviours. These guidelines highlight the importance of regularly undertaking both aerobic and muscle strengthening activities and for the first time, there are specific recommendations for specific populations including for pregnant and postpartum women and people living with chronic conditions or disability. These guidelines should be used to inform national health policies aligned with the WHO Global Action Plan on Physical Activity 2018–2030 and to strengthen surveillance systems that track progress towards national and global targets.
Strength is a fundamental component of athletic performance and development. This investigation examined the long-term strength development of powerlifting (PL) athletes. The rate of strength gain/day was assessed in 1897 PL athletes (F = 626, M = 1,271) over a 15-year period (2003–2018). Independent T-tests explored sex differences in baseline absolute (kg) and relative strength (kg·body mass−1 [bm]) recorded from the first competition, and strength gain/day (kg·d−1). Analyses based on initial strength quartiles were conducted using one-way analysis of variances with significance set at p < 0.05. Bivariate correlational analysis tested for relationships between strength gain/day and baseline strength, the number of competitions, and mean days between competitions. Males had greater absolute (M: 513.3 ± 99.8 kg, F: 289.4 ± 55.7 kg, p < 0.001) and relative (M: 5.89 ± 1.04 kg·bm−1, F: 4.27 ± 0.85 kg·bm−1, p < 0.001) strength at baseline. Overall, strength gain/day (F: 0.12 ± 0.69 kg·d−1, M: 0.15 ± 0.44 kg·d−1, p = 0.318) was similar between sexes. However, the strongest males showed a lower rate of strength improvement (0.102 kg·d−1) compared with least strong males (0.211 kg·d−1), p = 0.010. No differences were observed across quartiles for females. Correlational analyses revealed significant but weak negative relationships between strength gain/day and the mean days between competitions for females (r2 = −0.120, p = 0.003) and males (r2 = −0.190, p < 0.001). Similar relationships were observed for baseline strength (r2 = −0.073, p = 0.009) and the number of competitions (r2 = −0.111, p < 0.001) for males. The results suggest similar strength adaptation between sexes. The strongest males improve more slowly, possibly due to a ceiling effect. Collectively, the findings provide novel evidence of real-world long-term strength adaptations that may be particularly useful to understand athlete development, to aid periodized programming, and to benchmark strength over time.
Linear mixed‐effects models are powerful tools for analysing complex datasets with repeated or clustered observations, a common data structure in ecology and evolution. Mixed‐effects models involve complex fitting procedures and make several assumptions, in particular about the distribution of residual and random effects. Violations of these assumptions are common in real datasets, yet it is not always clear how much these violations matter to accurate and unbiased estimation.
Here we address the consequences of violations in distributional assumptions and the impact of missing random effect components on model estimates. In particular, we evaluate the effects of skewed, bimodal and heteroscedastic random effect and residual variances, of missing random effect terms and of correlated fixed effect predictors. We focus on bias and prediction error on estimates of fixed and random effects.
Model estimates were usually robust to violations of assumptions, with the exception of slight upward biases in estimates of random effect variance if the generating distribution was bimodal but was modelled by Gaussian error distributions. Further, estimates for (random effect) components that violated distributional assumptions became less precise but remained unbiased. However, this particular problem did not affect other parameters of the model. The same pattern was found for strongly correlated fixed effects, which led to imprecise, but unbiased estimates, with uncertainty estimates reflecting imprecision.
Unmodelled sources of random effect variance had predictable effects on variance component estimates. The pattern is best viewed as a cascade of hierarchical grouping factors. Variances trickle down the hierarchy such that missing higher‐level random effect variances pool at lower levels and missing lower‐level and crossed random effect variances manifest as residual variance.
Overall, our results show remarkable robustness of mixed‐effects models that should allow researchers to use mixed‐effects models even if the distributional assumptions are objectively violated. However, this does not free researchers from careful evaluation of the model. Estimates that are based on data that show clear violations of key assumptions should be treated with caution because individual datasets might give highly imprecise estimates, even if they will be unbiased on average across datasets.
Objectives: The accepted wisdom within resistance training is that differing loads and corresponding repetition maximum (RM) ranges are optimal for inducing specific adaptations. For example, prominent organizations and their respective publications have typically prescribed heavy loads for maximal strength increases (>85% 1RM/<6RM), more moderate loads for hypertrophy (67-85% 1RM/6-12RM) and lighter loads for local muscular endurance (LME; <67% 1RM/>12RM). Since we believe these recommendations originate from a misunderstanding and misinterpretation of DeLorme's strength-endurance continuum, the aim of this narrative review is to discuss the preponderance of research surrounding training load and strength and LME adaptations. Design & Methods: Narrative Review Results: The current body of literature fails to support recommendations for the use of specific loads for specific strength, hypertrophy or LME adaptations. Furthermore, that the strength-endurance continuum originally presented by DeLorme was never intended to compare the use of heavier- and lighter-load resistance training, but rather to consider the adaptations to strength training and aerobically based endurance exercise. Finally, a lack of clarity considering absolute- and relative- LME has confounded understanding of this adaptation. Conclusions: The body of research supports that absolute LME appears to adapt as a result of maximal strength increases. However, relative LME shows minimal response to strength training with either heavier- or lighter-loads. We present the limitations of the current body of research and promote specifically detailed recent research as well as the importance of generality of strength and LME in both sporting and real-world settings.
Background:
Sarcopenia, the loss of muscle strength and mass, predicts adverse outcomes and becomes common with age. There is recognition that sarcopenia may occur at younger ages in those with long-term conditions (LTCs) as well as those with multimorbidity (the presence of two or more LTCs), but their relationships have been little explored. Our aims were to describe the prevalence of sarcopenia in UK Biobank, a large sample of men and women aged 40-70 years, and to explore relationships with different categories of LTCs and multimorbidity.
Methods:
We used data from 499 046 participants in the baseline of UK Biobank. Our main outcome was probable sarcopenia based on maximum grip strength below sex-specific cut-points. Participants' LTCs were recorded during an interview and categorized against a hierarchy. We used logistic regression to examine the independent associations between each category of LTCs and probable sarcopenia, including adjustment for age, sex, and body mass index. We also examined the association with multimorbidity.
Results:
Probable sarcopenia had an overall prevalence of 5.3% and increased with age. The categories with the strongest associations with probable sarcopenia were musculoskeletal/trauma [OR 2.17 (95% CI: 2.11, 2.23)], endocrine/diabetes [OR 1.49 (95% CI: 1.45, 1.55)], and neurological/psychiatric [OR 1.39 (95% CI: 1.34, 1.43)] LTCs. Almost half of the sample (44.5%) had multimorbidity, and they were at nearly twice the odds of probable sarcopenia [OR 1.96 (95% CI: 1.91, 2.02)] compared with those without.
Conclusions:
We have shown an overall prevalence of 5.3% of probable sarcopenia at ages 40-70 in UK Biobank. The risk of probable sarcopenia was higher in those with some categories of LTCs, suggesting that these groups may stand to benefit from assessment of sarcopenia, during mid-life as well as old age.
Increases in muscular strength may increase sports performance, reduce injury risk, are associated with a plethora of health markers, as well as exerting positive psychological effects. Due to their efficiency and effectiveness in increasing total body muscular strength, multi-joint exercises like the powerlifts, i.e.: the squat (SQ), bench-press (BP) and deadlift (DL), are widely used by active individuals as well as athletes in the pursuit of increasing strength. To date, the concept of a minimum dose, i.e. “what is the minimum one needs to do to increase 1-repetition maximum (1RM) strength?” has not been directly examined in the literature, especially in the context of the powerlifts. This review aims to explore the current available evidence around the minimum effective training dose required to increase 1RM strength in trained individuals in an attempt to enhance the practical guidelines around resistance-training as well as provide active individuals, athletes and coaches with more flexibility when designing a training protocol.
One reviewer independently conducted the search in a PRISMA systematic approach using PubMed, SportDiscus and Google Scholar databases. The databases were searched with the following search terms/phrases and Boolean operators: “training volume” AND “powerlifting” OR “1RM strength” OR “powerlifters”, “low volume” AND “powerlifting” OR “powerlifting” OR “1RM strength”, “high vs low volume” AND “powerlifting” OR “1RM strength”, “minimum effective training dose 1RM”. Meta-analyses were performed to estimate the change in 1RM strength for the lowest dose group in the included studies.
From the initial 2629 studies, 6 studies met our inclusion criteria. All identified studies showed that a single set performed minimum 1 time and maximum 3 times per week was sufficient to induce significant 1RM strength gains. Meta-analysis of 5 studies showed an estimated increase for overall 1RM of 12.09 kg [95% CIs 8.16 kg–16.03 kg], an increase of 17.48 kg [95% CIs 8.51 kg–26.46 kg] for the SQ, and 8.25 kg [95% CIs 0.68 kg–15.83 kg] for the BP. All of the included studies contained details on most of the variables comprising “training dose”, such as: weekly and per session sets and repetitions as well as intensity of effort. Specific information regarding load (%1RM) was not provided by all studies.
The results of the present systematic review suggest that performing a single set of 6–12 repetitions with loads ranging from approximately 70–85% 1RM 2–3 times per week with high intensity of effort (reaching volitional or momentary failure) for 8–12 weeks can produce suboptimal, yet significant increases in SQ and BP 1RM strength in resistance-trained men. However, because of the lack of research, it is less clear as to whether these improvements may also be achievable in DL 1RM strength or in trained women and highly trained strength athletes.
This systematic review was registered with PROSPERO (CRD42018108911).
Background
Activities of daily living (ADLs) and instrumental activities of daily living (IADLs) are essential for independent living and are predictors of morbidity and mortality in older populations. Older adults who are dependent in ADLs and IADLs are also more likely to have poor muscle measures defined as low muscle mass, muscle strength, and physical performance, which further limit their ability to perform activities. The aim of this systematic review and meta‐analysis was to determine if muscle measures are predictive of ADL and IADL in older populations.
Methods
A systematic search was conducted using four databases (MEDLINE, EMBASE, Cochrane, and CINAHL) from date of inception to 7 June 2018. Longitudinal cohorts were included that reported baseline muscle measures defined by muscle mass, muscle strength, and physical performance in conjunction with prospective ADL or IADL in participants aged 65 years and older at follow‐up. Meta‐analyses were conducted using a random effect model.
Results
Of the 7760 articles screened, 83 articles were included for the systematic review and involved a total of 108 428 (54.8% female) participants with a follow‐up duration ranging from 11 days to 25 years. Low muscle mass was positively associated with ADL dependency in 5/9 articles and 5/5 for IADL dependency. Low muscle strength was associated with ADL dependency in 22/34 articles and IADL dependency in 8/9 articles. Low physical performance was associated with ADL dependency in 37/49 articles and with IADL dependency in 9/11 articles. Forty‐five articles were pooled into the meta‐analyses, 36 reported ADL, 11 reported IADL, and 2 reported ADL and IADL as a composite outcome. Low muscle mass was associated with worsening ADL (pooled odds ratio (95% confidence interval) 3.19 (1.29–7.92)) and worsening IADL (1.28 (1.02–1.61)). Low handgrip strength was associated with both worsening ADL and IADL (1.51 (1.34–1.70); 1.59 (1.04–2.31) respectively). Low scores on the short physical performance battery and gait speed were associated with worsening ADL (3.49 (2.47–4.92); 2.33 (1.58–3.44) respectively) and IADL (3.09 (1.06–8.98); 1.93 (1.69–2.21) respectively). Low one leg balance (2.74 (1.31–5.72)), timed up and go (3.41 (1.86–6.28)), and chair stand test time (1.90 (1.63–2.21)) were associated with worsening ADL.
Conclusions
Muscle measures at baseline are predictors of future ADL and IADL dependence in the older adult population.
A total of 3,782 performance results for male and female weightlifters, ages 14–30 from 123 countries, from Youth, Junior, and Senior World Championships and Olympic Games 2013–2017 were used to estimate the age at peak performance in Olympic weightlifting and quantify performance development from adolescence to adulthood. The age at peak performance was estimated for men and women globally and for different geographic regions. Overall, male and female weightlifters achieve their peak performance in weightlifting at similar ages. The median peak age is 26.0 years (95% CI: 24.9, 27.1) for men and 25.0 years (95% CI: 23.9, 27.4) for women, at the 90th percentile of performances. The median peak age was 26.3 years for men (95% CI: 24.5, 29.6) and 26.4 years for women (95% CI: 24.5, 29.6), at the 50th percentile. It is a novel finding that the age at peak performance varies for male and female athletes from different geographic regions (Western Europe, Eastern Europe, Middle East, Far East, North- and South America). For some regions men reach peak performance at a younger age than women, while this relationship is reversed for other regions. A possible explanation could be that socio-economic factors influence the pool of available athletes and thus may under- or overestimate the true peak age. Unlike in track and field where the discipline might determine specific body types, weightlifters at all ages compete in body weight classes, enabling us to compare performance levels and annual rate of change for athletes of different body mass. We quantified increases in performance in Olympic weightlifting for male and female adolescents. Sex-specific differences arise during puberty, boys outperform girls, and there is a rapid increase in their performance levels before the further growth slows down. The largest annual rate of increase in the total weight lifted was achieved between 16 and 17 years of age for both sexes with lower body mass and between 21 and 22 years with higher body mass. Such new information may help to establish progression trajectories for young athletes.
Statistical inference often fails to replicate. One reason is that many results may be selected for drawing inference because some threshold of a statistic like the P-value was crossed, leading to biased reported effect sizes. Nonetheless, considerable non-replication is to be expected even without selective reporting, and generalizations from single studies are rarely if ever warranted. Honestly reported results must vary from replication to replication because of varying assumption violations and random variation; excessive agreement itself would suggest deeper problems, such as failure to publish results in conflict with group expectations or desires. A general perception of a “replication crisis” may thus reflect failure to recognize that statistical tests not only test hypotheses, but countless assumptions and the entire environment in which research takes place. Because of all the uncertain and unknown assumptions that underpin statistical inferences, we should treat inferential statistics as highly unstable local descriptions of relations between assumptions and data, rather than as providing generalizable inferences about hypotheses or models. And that means we should treat statistical results as being much more incomplete and uncertain than is currently the norm. Acknowledging this uncertainty could help reduce the allure of selective reporting: Since a small P-value could be large in a replication study, and a large P-value could be small, there is simply no need to selectively report studies based on statistical results. Rather than focusing our study reports on uncertain conclusions, we should thus focus on describing accurately how the study was conducted, what problems occurred, what data were obtained, what analysis methods were used and why, and what output those methods produced.
Valentin Amrhein, Sander Greenland, Blake McShane and more than 800 signatories call for an end to hyped claims and the dismissal of possibly crucial effects.
When data are not normally distributed (e.g. skewed, zero-inflated, binomial, or count data) researchers are often uncertain whether it may be legitimate to use tests that assume Gaussian errors (e.g. regression, t -test, ANOVA, Gaussian mixed models), or whether one has to either model a more specific error structure or use randomization techniques.
Here we use Monte Carlo simulations to explore the pros and cons of fitting Gaussian models to non-normal data in terms of risk of type I error, power and utility for parameter estimation.
We find that Gaussian models are remarkably robust to non-normality over a wide range of conditions, meaning that P -values remain fairly reliable except for data with influential outliers judged at strict alpha levels. Gaussian models also perform well in terms of power and they can be useful for parameter estimation but usually not for extrapolation. Transformation of data before analysis is often advisable and visual inspection for outliers and heteroscedasticity is important for assessment. In strong contrast, some non-Gaussian models and randomization techniques bear a range of risks that are often insufficiently known. High rates of false-positive conclusions can arise for instance when overdispersion in count data is not controlled appropriately or when randomization procedures ignore existing non-independencies in the data.
Overall, we argue that violating the normality assumption bears risks that are limited and manageable, while several more sophisticated approaches are relatively error prone and difficult to check during peer review. Hence, as long as scientists and reviewers are not fully aware of the risks, science might benefit from preferentially trusting Gaussian mixed models in which random effects account for non-independencies in the data in a transparent way.
Tweetable abstract
Gaussian models are remarkably robust to even dramatic violations of the normality assumption.
Age-related loss of muscle mass and function, also called sarcopenia, was recently added to the ICD-10 as an independent condition. However, declines in muscle mass and function are inevitable during the adulthood aging process. Concerning muscle strength as a crucial aspect of muscle function, maximum knee extension strength might be the most important physical parameter for independent living in the community. In this study, we aimed to determine the age-related decline in maximum isokinetic knee extension (MIES) and flexion strength (MIFS) in adult men. The primary study hypothesis was that there is a slight gradual decrease of MIES up to ≈age 60 years with a significant acceleration of decline after this “changepoint.” We used a closed kinetic chain system (leg-press), which is seen as providing functionally more relevant results on maximum strength, to determine changes in maximum isokinetic hip/leg extensor (MIES) and flexor strength (MIFS) during adulthood in men. Apart from average annual changes, we aimed to identify whether the decline in maximum lower extremity strength is linear. MIES and MIFS data determined by an isokinetic leg-press of 362 non-athletic, healthy, and community-dwelling men 19–91 years old were included in the analysis. A changepoint analysis was conducted based on a multiple regression analysis adjusted for selected co-variables that might confound the proper relationship between age and maximum strength. In summary, maximum isokinetic leg-strength decline during adulthood averaged around 0.8–1.0% p.a.; however, the reduction was far from linear. MIES demonstrated a non-significant reduction of 5.2 N/p.a. (≈0.15% p.a.) up to the estimated breakpoint of 52.0 years and an accelerated loss of 44.0 N/p.a. (≈1.3% p.a.; p < 0.001). In parallel, the decline in MIFS (10.0 N/p.a.; ≈0.5% p.a.) prior to the breakpoint at age 59.0 years was significantly more pronounced. Nevertheless, we observed a further marked accelerated loss of MIFS (25.0 N/p.a.; ≈1.3% p.a.) in men ≥60 years. Apart from the “normative value” and closed kinetic chain aspect of this study, the practical application of our results suggests that sarcopenia prophylaxis in men should be started in the 5th decade in order to address the accelerated muscle decline of advanced age.
Results of regression models, like estimates, are typically presented as tables that are easy to understand. Sometimes pure estimates are not helpful and difficult to interpret. This is especially true for interaction terms in logistic regression or even more complex models, or transformed terms (quadratic or cubic terms, polynomials, splines), where the estimates are no longer interpretable in a direct way. In such cases, marginal effects are far easier to understand. In particular, the visualization of marginal effects makes it possible to intuitively get the idea of how predictors and outcome are associated, even for complex models.
ggeffects is an R-package that aims at easily calculating marginal effects for a broad range of different regression models. This is achieved by three core ideas that describe the philosophy of the function design: 1) Functions are type-safe and always return a data frame with the same, consistent structure; 2) there is a simple, unique approach to calculate marginal effects for many different models; 3) the package supports "labelled data" (Lüdecke 2018), which allows human readable annotations for graphical outputs. This means, users do not need to care about any expensive steps after modelling to visualize the results.
Objective: A growing area of discourse within sports medicine and resistance training is that of periodization. This has been represented as variation in load and subsequently repetitions as well as volume, with a view to maximize strength and hypertrophy adaptations. A number of recent review articles have attempted to draw overarching conclusions from the present body of literature in an effort to provide definitive guidelines. However, there are numerous variables within resistance training that are often overlooked, and in the context of periodization, might significantly impact adaptation. Design & Methods: Narrative Review Results: The present piece confers need for clarity in terminology of effort rather than intensity, as well as discussing how variety of load might impact volume-load, discomfort, muscle damage and recovery. Furthermore, this article discusses often overlooked variables such as variety in exercise selection, detraining periods, and supervision, which are all evidenced to impact strength and hypertrophy adaptations. Conclusions: Our opinion is that without inclusion of these variables any guidelines surrounding periodization for strength or hypertrophy are limited in application. We conclude by highlighting areas for future research, as well as practical recommendations within this field.
Background
Current recommendations on resistance training (RT) frequency for gains in muscular strength are based on extrapolations from limited evidence on the topic, and thus their practical applicability remains questionable.
Objective
To elucidate this issue, we conducted a systematic review and meta-analysis of the studies that compared muscular strength outcomes with different RT frequencies.
Methods
To carry out this review, English-language literature searches of the PubMed/MEDLINE, Scopus, and SPORTDiscus databases were conducted. The meta-analysis was performed using a random-effects model. The meta-analysis models were generated with RT frequencies classified as a categorical variable as either 1, 2, 3, or 4+ times/week, or, if there were insufficient data in subgroup analyses, the training frequencies were categorized as 1, 2, or 3 times/week. Subgroup analyses were performed for potential moderators, including (1) training volume; (2) exercise selection for the 1 repetition maximum (RM) test (for both multi-joint and single-joint exercises); (3) upper and lower body strength gains; (4) training to muscular failure (for studies involving and not involving training to muscular failure); (5) age (for both middle-aged/older adults and young adults); and (6) sex (for men and for women). The methodological quality of studies was appraised using the modified Downs and Black checklist.
Results
A total of 22 studies were found to meet the inclusion criteria. The average score on the Downs and Black checklist was 18 (range 13–22 points). Four studies were classified as being of good methodological quality, while the rest were classified as being of moderate methodological quality. Results of the meta-analysis showed a significant effect (p = 0.003) of RT frequency on muscular strength gains. Effect sizes increased in magnitude from 0.74, 0.82, 0.93, and 1.08 for training 1, 2, 3, and 4+ times per week, respectively. A subgroup analysis of volume-equated studies showed no significant effect (p = 0.421) of RT frequency on muscular strength gains. The subgroup analysis for exercise selection for the 1RM test suggested a significant effect of RT frequency on multi-joint (p < 0.001), but not single-joint, 1RM test results (p = 0.324). The subgroup analysis for upper and lower body showed a significant effect of frequency (p = 0.004) for upper body, but not lower body, strength gains (p = 0.070). In the subgroup analysis for studies in which the training was and was not carried out to muscular failure, no significant effect of RT frequency was found. The subgroup analysis for the age groups suggested a significant effect of training frequency among young adults (p = 0.024), but not among middle-aged and older adults (p = 0.093). Finally, the subgroup analysis for sex indicated a significant effect of RT frequency on strength gains in women (p = 0.030), but not men (p = 0.190).
Conclusions
The results of the present systematic review and meta-analysis suggest a significant effect of RT frequency as higher training frequencies are translated into greater muscular strength gains. However, these effects seem to be primarily driven by training volume because when the volume is equated, there was no significant effect of RT frequency on muscular strength gains. Thus, from a practical standpoint, greater training frequencies can be used for additional RT volume, which is then likely to result in greater muscular strength gains. However, it remains unclear whether RT frequency on its own has significant effects on strength gain. It seems that higher RT frequencies result in greater gains in muscular strength on multi-joint exercises in the upper body and in women, and, finally, in contrast to older adults, young individuals seem to respond more positively to greater RT frequencies. More evidence among resistance-trained individuals is needed as most of the current studies were performed in untrained participants.
In science publishing and many areas of research, the status quo is a lexicographic decision rule in which any result is first required to have a p-value that surpasses the 0.05 threshold and only then is consideration--often scant--given to such factors as prior and related evidence, plausibility of mechanism, study design and data quality, real world costs and benefits, novelty of finding, and other factors that vary by research domain. There have been recent proposals to change the p-value threshold, but instead we recommend abandoning the null hypothesis significance testing paradigm entirely, leaving p-values as just one of many pieces of information with no privileged role in scientific publication and decision making. We argue that this radical approach is both practical and sensible.
Background
Strength training set organisation and its relationship to the development of muscular strength have yet to be clearly defined. Current meta-analytical research suggests that different population groups have distinctive muscular adaptations, primarily due to the prescription of the strength training set dose. Objectives
We conducted a meta-analysis with restrictive inclusion criteria and examined the potential effects of low (LWS), medium (MWS) or high weekly set (HWS) strength training on muscular strength per exercise. Secondly, we examined strength gain variations when performing multi-joint or isolation exercises, and probed for a potential relationship between weekly set number and stage of subjects’ training (trained versus untrained). Methods
Computerised searches were performed on PubMed, MEDLINE, SWETSWISE, EMBASE and SPORTDiscus™ using the terms ‘strength training’, ‘resistance training’, ‘single sets’, ‘multiple sets’ and ‘volume’. As of September 2016, 6962 potentially relevant studies were identified. After review, nine studies were deemed eligible per pre-set inclusion criteria. Primary data were pooled using a random-effect model. Outcomes for strength gain, strength gain with multi-joint and isolation exercise were analysed for main effects. Sensitivity analyses were calculated for several subgroups by separating the data set and by calculation of separate analyses for each subgroup. Heterogeneity between studies was assessed using the Cochran Q and I2 statistics. ResultsPre- versus post-training strength analysis comprised 61 treatment groups from nine studies. For combined multi-joint and isolation exercises, pre- versus post- training strength gains were greater with HWS compared with LWS [mean effect size (ES) 0.18; 95% CI 0.06–0.30; p = 0.003]. The mean ES for LWS was 0.82 (95% CI 0.47–1.17). The mean ES for HWS was 1.01 (95% CI 0.70–1.32). Separate analysis of the effects of pre- versus post-training strength for LWS or MWS observed marginally greater strength gains with MWS compared with LWS (ES 0.15; 95% CI 0.01–0.30; p = 0.04). The mean ES for LWS was 0.83 (95% CI 0.53–1.13). The mean ES for MWS was 0.98 (95% CI 0.62–1.34). For multi-joint exercises, greater strength gains were observed with HWS compared with LWS (ES 0.18; 95% CI 0.01–0.34; p = 0.04). The mean ES for LWS was 0.81 (95% CI 0.65–0.97). The mean ES for HWS was 1.00 (95% CI 0.77–1.23). For isolation exercises, greater strength gains were observed with HWS compared with LWS (ES 0.23; 95% CI 0.06–0.40; p = 0.008). The mean ES for LWS was 0.95 (95% CI 0.30–1.60). The mean ES for HWS was 1.10 (95% CI 0.26–1.94). For multi-joint and isolation exercise-specific one repetition maximum (1 RM), marginally greater strength gains were observed with HWS compared with LWS (ES 0.14; 95% CI −0.01 to 0.29; p = 0.06). The mean ES for LWS was 0.80 (95% CI 0.47–1.13). The mean ES for HWS was 0.97 (95% CI 0.68–1.26). Conclusion
This meta-analysis presents additional evidence regarding a graded dose–response relationship between weekly sets performed and strength gain. The use of MWS and HWS was more effective than LWS, with LWS producing the smallest pre- to post-training strength difference. For novice and intermediate male trainees, the findings suggest that LWSs do not lead to strength gains compared with MWS or HWS training. For those trainees in the middle ground, not a novice and not advanced, the existing data provide a relationship between weekly sets and strength gain as set configurations produced different pre- to post-training strength increases. For well trained individuals, the use of either MWS or HWS may be an appropriate dose to produce strength gains.
Background
Periodization is a logical method of organizing training into sequential phases and cyclical time periods in order to increase the potential for achieving specific performance goals while minimizing the potential for overtraining. Periodized resistance training plans are proposed to be superior to non-periodized training plans for enhancing maximal strength. Objective
The primary aim of this study was to examine the previous literature comparing periodized resistance training plans to non-periodized resistance training plans and determine a quantitative estimate of effect on maximal strength. Methods
All studies included in the meta-analysis met the following inclusion criteria: (1) peer-reviewed publication; (2) published in English; (3) comparison of a periodized resistance training group to a non-periodized resistance training group; (4) maximal strength measured by 1-repetition maximum (1RM) squat, bench press, or leg press. Data were extracted and independently coded by two authors. Random-effects models were used to aggregate a mean effect size (ES), 95% confidence intervals (CIs) and potential moderators. ResultsThe cumulative results of 81 effects gathered from 18 studies published between 1988 and 2015 indicated that the magnitude of improvement in 1RM following periodized resistance training was greater than non-periodized resistance training (ES = 0.43, 95% CI 0.27–0.58; P < 0.001). Periodization model (β = 0.51; P = 0.0010), training status (β = −0.59; P = 0.0305), study length (β = 0.03; P = 0.0067), and training frequency (β = 0.46; P = 0.0123) were associated with a change in 1RM. These results indicate that undulating programs were more favorable for strength gains. Improvements in 1RM were greater among untrained participants. Additionally, higher training frequency and longer study length were associated with larger improvements in 1RM. Conclusion
These results suggest that periodized resistance training plans have a moderate effect on 1RM compared to non-periodized training plans. Variation in training stimuli appears to be vital for increasing maximal strength, and longer periods of higher training frequency may be preferred.
It is well known that physical activity and exercise is associated with a lower risk of a range of morbidities and all-cause mortality. Further, it appears that risk reductions are greater when physical activity and/or exercise is performed at a higher intensity of effort. Why this may be the case is perhaps explained by the accumulating evidence linking physical fitness and performance outcomes (e.g. cardiorespiratory fitness, strength, and muscle mass) also to morbidity and mortality risk. Current guidelines about the performance of moderate/vigorous physical activity using aerobic exercise modes focuses upon the accumulation of a minimum volume of physical activity and/or exercise, and have thus far produced disappointing outcomes. As such there has been increased interest in the use of higher effort physical activity and exercise as being potentially more efficacious. Though there is currently debate as to the effectiveness of public health prescription based around higher effort physical activity and exercise, most discussion around this has focused upon modes considered to be traditionally ‘aerobic’ (e.g. running, cycling, rowing, swimming etc.). A mode customarily performed to a relatively high intensity of effort that we believe has been overlooked is resistance training. Current guidelines do include recommendations to engage in ‘muscle strengthening activities’ though there has been very little emphasis upon these modes in either research or public health effort. As such the purpose of this debate article is to discuss the emerging higher effort paradigm in physical activity and exercise for public health and to make a case for why there should be a greater emphasis placed upon resistance training as a mode in this paradigm shift.
Prior resistance training (RT) recommendations and position stands have discussed variables that can be manipulated when producing RT interventions. However, one variable that has received little discussion is set end points (i.e. the end point of a set of repetitions). Set end points in RT are often considered to be proximity to momentary failure and are thought to be a primary variable determining effort in RT. Further, there has been ambiguity in use and definition of terminology that has created issues in interpretation of research findings. The purpose of this paper is to: 1) provide an overview of the ambiguity in historical terminology around set end points; 2) propose a clearer set of definitions related to set end points; and 3) highlight the issues created by poor terminology and definitions. It is hoped this might permit greater clarity in reporting, interpretation, and application of RT interventions for researchers and practitioners.
The purpose of this paper was to systematically review the current literature and elucidate the effects of total weekly resistance training (RT) volume on changes in measures of muscle mass via meta-regression. The final analysis comprised 34 treatment groups from 15 studies. Outcomes for weekly sets as a continuous variable showed a significant effect of volume on changes in muscle size (P = 0.002). Each additional set was associated with an increase in effect size (ES) of 0.023 corresponding to an increase in the percentage gain by 0.37%. Outcomes for weekly sets categorised as lower or higher within each study showed a significant effect of volume on changes in muscle size (P = 0.03); the ES difference between higher and lower volumes was 0.241, which equated to a percentage gain difference of 3.9%. Outcomes for weekly sets as a three-level categorical variable (<5, 5-9 and 10+ per muscle) showed a trend for an effect of weekly sets (P = 0.074). The findings indicate a graded dose-response relationship whereby increases in RT volume produce greater gains in muscle hypertrophy.
Recently we documented age-related attenuation of efferent drive to contracting skeletal muscle. It remains elusive if this indication of reduced muscle strength is present with lifelong strength training. For this purpose, we examined evoked potentials in the calf muscles of 11 (71±4years) strength trained master athletes (MA) contrasted to 10 (71±4years) sedentary (SO) and 11 (73±6years) recreationally active (AO) old subjects, as well as 9 (22±2years) young controls. As expected, MA had higher leg press maximal strength (MA: 185±32kg; AO: 128±15kg; SO: 106±11kg; young: 147±22kg, p<0.01) and rate of force development (MA: 5588±2488N∙s(-1); AO: 2156±1100N∙s(-1); SO: 2011±825N∙s(-1); young: 3663±1140N∙s(-1), p<0.05) than the other groups. MA also exhibited higher m.soleus normalized V-waves during MVC (Vsup/Msup: 0.28±0.15) than AO (0.13±0.06, p<0.01) and SO (0.11±0.05, p<0.01), yet lower than young (0.45±0.12, p<0.01). No differences were apparent between the old groups in H-reflex recorded at rest or during MVC (Hmax/Mmax; Hsup/Msup), and all were lower (p<0.01) than young. MA (34.4±2.1ms) had shorter (p<0.05) H-reflex latency compared to AO (36.4±3.7ms) and SO (37.3±3.2ms), but longer (p<0.01) than young (30.7±2.0ms). Using interpolated twitch analysis MA (89±7%) had similar plantar flexion voluntary activation as young (90±6%), and this was higher (p<0.05), or tended to be higher (p=0.06-0.09) than SO (83±10%) and AO (84±5%). These observations suggest that lifelong strength training has a protective effect against age-related attenuation of efferent drive. In contrast, no beneficial effect seems to derive from habitual recreational activity, indicating that strength training may be particularly beneficial for counteracting age-related loss of neuromuscular function.
Epidemiological studies have shown that weaker grip strength in later life is associated with disability, morbidity, and mortality. Grip strength is a key component of the sarcopenia and frailty phenotypes and yet it is unclear how individual measurements should be interpreted. Our objective was to produce cross-sectional centile values for grip strength across the life course. A secondary objective was to examine the impact of different aspects of measurement protocol.
We combined 60,803 observations from 49,964 participants (26,687 female) of 12 general population studies in Great Britain. We produced centile curves for ages 4 to 90 and investigated the prevalence of weak grip, defined as strength at least 2.5 SDs below the gender-specific peak mean. We carried out a series of sensitivity analyses to assess the impact of dynamometer type and measurement position (seated or standing).
Our results suggested three overall periods: an increase to peak in early adult life, maintenance through to midlife, and decline from midlife onwards. Males were on average stronger than females from adolescence onwards: males' peak median grip was 51 kg between ages 29 and 39, compared to 31 kg in females between ages 26 and 42. Weak grip strength, defined as strength at least 2.5 SDs below the gender-specific peak mean, increased sharply with age, reaching a prevalence of 23% in males and 27% in females by age 80. Sensitivity analyses suggested our findings were robust to differences in dynamometer type and measurement position.
This is the first study to provide normative data for grip strength across the life course. These centile values have the potential to inform the clinical assessment of grip strength which is recognised as an important part of the identification of people with sarcopenia and frailty.
Maximum likelihood or restricted maximum likelihood (REML) estimates of the
parameters in linear mixed-effects models can be determined using the lmer
function in the lme4 package for R. As for most model-fitting functions in R,
the model is described in an lmer call by a formula, in this case including
both fixed- and random-effects terms. The formula and data together determine a
numerical representation of the model from which the profiled deviance or the
profiled REML criterion can be evaluated as a function of some of the model
parameters. The appropriate criterion is optimized, using one of the
constrained optimization functions in R, to provide the parameter estimates. We
describe the structure of the model, the steps in evaluating the profiled
deviance or REML criterion, and the structure of classes or types that
represents such a model. Sufficient detail is included to allow specialization
of these structures by users who wish to write functions to fit specialized
linear mixed models, such as models incorporating pedigrees or smoothing
splines, that are not easily expressible in the formula language used by lmer.
Recent advances in the statistical theory of hierarchical linear models should enable important breakthroughs in the measurement of psychological change and the study of correlates of change. A two-stage model of change is proposed here. At the first, or within-subject stage, an individual's status on some trait is modeled as a function of an individual growth trajectory plus random error. At the second, or between-subjects stage, the parameters of the individual growth trajectories vary as a function of differences between subjects in background characteristics, instructional experiences, and possible experimental treatments. This two-stage conceptualization, illustrated with data on Head Start children, allows investigators to model individual change, predict future development, assess the quality of measurement instruments for distinguishing among growth trajectories, and study systematic variation in growth trajectories as a function of background characteristics and experimental treatments. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
This article illustrates the use of applied Bayesian statistical methods in modeling the trajectory of adult grip strength and in evaluating potential risk factors that may influence that trajectory.
The data consist of from 1 to 11 repeated grip strength measurements from each of 498 men and 533 women age 18-96 years in the Fels Longitudinal Study (Roche AF. 1992. Growth, maturation and body composition: the Fels longitudinal study 1929-1991. Cambridge: Cambridge University Press). In this analysis, the Bayesian framework was particularly useful for fitting a nonlinear mixed effects plateau model with two unknown change points and for the joint modeling of a time-varying covariate. Multiple imputation (MI) was used to handle missing values with posterior inferences appropriately adjusted to account for between-imputation variability.
On average, men and women attain peak grip strength at the same age (36 years), women begin to decline in grip strength sooner (age 50 years for women and 56 years for men), and men lose grip strength at a faster rate relative to their peak; there is an increasing secular trend in peak grip strength that is not attributable to concurrent secular trends in body size, and the grip strength trajectory varies with birth weight (men only), smoking (men only), alcohol consumption (men and women), and sports activity (women only).
Longitudinal data analysis requires handling not only serial correlation but often also time-varying covariates, missing data, and unknown change points. Bayesian methods, combined with MI, are useful in handling these issues.
We conducted a 2-year (42 weeks of consecutive training in each year, separated by 10 weeks of testing and vacation time) randomized, controlled trial of weight training in 142 healthy male and female subjects, aged 60 to 80 years. Measurements included dynamic strength, symptom-limited endurance in cycling, treadmill walking and stair climbing, muscle size, and bone mineral density and content of the lumbar spine and whole body. One hundred and thirteen subjects completed the study (57 exercise, 56 control), with a mean attendance of 85% among the exercisers. Muscle strength was unchanged in the control subjects but increased (collapsed across age and gender) from 32% (leg press) to 90% (military press) in the exercisers. Symptom-limited endurance in cycling, treadmill walking, and stair climbing increased in the exercisers by (mean +/- SE) 6.2 +/- 0.8%, 29.2 +/- 7.3%, and 57 +/- 12%, respectively; the only change in the controls was an unanticipated 33% increase in stair climbing performance during the first year. These values were unchanged in the controls. Cross-sectional area of the knee extensors increased by 8.7 +/- 0.9% in the trained subjects and was unchanged in controls. Measures of whole body, lumbar spine bone mineral density, and lumbar spine bone mineral content were unchanged in the exercisers, but whole body bone mineral content decreased by 1%. In contrast, there were small increases (< 4.0%) in bone mineral density among the controls. Long-term weight training proved to be a safe and well-tolerated mode of exercise for the elderly. Increased strength was associated with muscle hypertrophy in each year, and with increased endurance in cycling, walking, and stair climbing. There were no changes in bone mineral density but a small reduction in whole body bone mineral content.
The present study examines age-related changes in skeletal muscle size and function after 12 yr. Twelve healthy sedentary men were studied in 1985-86 (T1) and nine (initial mean age 65.4 +/- 4.2 yr) were reevaluated in 1997-98 (T2). Isokinetic muscle strength of the knee and elbow extensors and flexors showed losses (P < 0.05) ranging from 20 to 30% at slow and fast angular velocities. Computerized tomography (n = 7) showed reductions (P < 0.05) in the cross-sectional area (CSA) of the thigh (12.5%), all thigh muscles (14.7%), quadriceps femoris muscle (16.1%), and flexor muscles (14. 9%). Analysis of covariance showed that strength at T1 and changes in CSA were independent predictors of strength at T2. Muscle biopsies taken from vastus lateralis muscles (n = 6) showed a reduction in percentage of type I fibers (T1 = 60% vs. T2 = 42%) with no change in mean area in either fiber type. The capillary-to-fiber ratio was significantly lower at T2 (1.39 vs. 1. 08; P = 0.043). Our observations suggest that a quantitative loss in muscle CSA is a major contributor to the decrease in muscle strength seen with advancing age and, together with muscle strength at T1, accounts for 90% of the variability in strength at T2.
It is widely but incorrectly believed that the t-test and linear regression are valid only for Normally distributed outcomes. The t-test and linear regression compare the mean of an outcome variable for different subjects. While these are valid even in very small samples if the outcome variable is Normally distributed, their major usefulness comes from the fact that in large samples they are valid for any distribution. We demonstrate this validity by simulation in extremely non-Normal data. We discuss situations in which in other methods such as the Wilcoxon rank sum test and ordinal logistic regression (proportional odds model) have been recommended, and conclude that the t-test and linear regression often provide a convenient and practical alternative. The major limitation on the t-test and linear regression for inference about associations is not a distributional one, but whether detecting and estimating a difference in the mean of the outcome answers the scientific question at hand.
Bending the Aging Curve provides fitness professionals with a multifaceted periodized training program specifically for older adults. With this book and DVD package, you will find the tools you need to help your clients slow the physical decline that can accompany aging:
—Training strategies for improving body composition, flexibility, bone density, muscular strength and power, and cardiovascular fitness that can be customized to fit each client
—73 translational exercises that simulate everyday activities and help older clients to translate their new strengths into improved daily function and increased independence
—A series of tests that will allow you to assess your clients’ strengths and weaknesses, design programs that address their needs, and keep them motivated during their training
—A spreadsheet in which you can record clients’ test results and view their percentile rankings for their sex and age groups
—Videos of the translational exercises that let you and your clients see these unique activities in action to ensure accuracy and safety
—Video case studies of four sample clients that show the progression from testing to targeted training to the translational exercise cycle to help you understand how to design programs that meet your clients’ varying needs and goals
This one-of-a-kind resource presents a scientifically substantiated and practically proven training system that can extend the vitality of our aging population. Signorile offers an engaging explanation of the research behind his diagnosis and prescription model while maintaining a focus on the practical components of program design. You will learn to use tests to diagnose your clients’ needs and then prescribe training cycles with the appropriate mix of work, active recovery, and skill practice to maximize functional improvements. The photos and step-by-step instructions for each of the tests and exercises found in the book and the video clips on the DVD make it easy to quickly implement this training system with your clients.
Maintaining independence as we age depends on a multitude of factors. Bending the Aging Curve offers a comprehensive approach to designing exercise interventions that address all of these factors. With its targeted strategies, you’ll be able to help your clients stay active, energetic, and self-reliant, regardless of their age.
Shaw, MP, Andersen, V, Sæterbakken, AH, Paulsen, G, Samnøy, LE, and Solstad, TEJ. Contemporary training practices of Norwegian powerlifters. J Strength Cond Res XX(X): 000-000, 2020-The aim of this study was to explore the contemporary training practices of Norwegian powerlifters. One hundred twenty-four Norwegian powerlifters completed an electronic questionnaire that surveyed their current training practices with a focus on 2 areas: (a) training content and (b) training design and monitoring. One hundred seventeen respondents met the inclusion criteria, and the sample included World, European, and Norwegian champions. Where data were dichotomized, chi-square tests were used. The most frequently reported (58.1%) category of training was 5-6 times per week, with no statistically significant associations between levels of competitors (international vs. noninternational) (X(1) = 0.414, p = 0.52). The most frequently reported load used in training was 71-80% 1 repetition maximum. The majority of Norwegian (76.9%) powerlifters train with variable resistance, with those competing internationally more likely to use elastic bands (X(1) = 4.473, p = 0.034). 32.5% of respondents reported that they included weightlifting exercises in their training. Norwegian powerlifters' training differs from practices previously identified in the literature, with a higher prevalence of elastic resistance, particularly for those competing internationally, and a decreased use of weightlifting exercises at all levels. Norwegian powerlifters train frequently (5 or more times per week) and with submaximal loads.
The periodization of resistance exercise is often touted as the most effective strategy for optimizing muscle size and strength adaptations. This narrative persists despite a lack of experimental evidence to demonstrate its superiority. In addition, the general adaptation syndrome, which provides the theoretical framework underlying periodization, does not appear to provide a strong physiological rationale that periodization is necessary. Hans Selye conducted a series of rodent studies which used toxic stressors to facilitate the development of the general adaptation syndrome. To our knowledge, normal exercise in humans has never been shown to produce a general adaptation syndrome. We question whether there is any physiological rationale that a periodized training approach would facilitate greater adaptations compared with nonperiodized approaches employing progressive overload. The purpose of this article is to briefly review currently debated topics within strength and conditioning and provide some practical insight regarding the implications these reevaluations of the literature may have for resistance exercise and periodization. In addition, we provide some suggestions for the continued advancement within the field of strength and conditioning.
The generality of strength suggests that a "strong" individual will typically exhibit higher values of strength across a wide range of strength tasks for a given muscle relative to their weaker counterpart. This concept is often extended to adaptation, suggesting that increasing strength on a given movement or strength task with a given muscle should reflect an increase in other movements or tasks using that same muscle. The concept of a generality of strength adaptation appears less supported in the literature. Objective: To elaborate on recommendations for strength assessment, providing a focus on the "generality of strength" and the "generality of strength adaptation." Design & Methods: We reviewed the literature on a generality of strength. In addition, we examined the resistance training literature to provide evidence and discussion on a generality of strength adaptation. Results/Conclusions: The generality of strength adaptation, even across strength skills using the same muscle on related movements seems quite low. Although some studies show a weak generality of strength adaptation and others show no generality of strength adaptation, it appears that increases in strength diminish as the strength assessment becomes farther removed from the actual training stimulus. (Journal of Trainology 2019;8:5-8)
The purpose of this study was to evaluate the rates of performance change for American female weightlifters over 10 years of competition. Athlete performance results were gathered from the United States Weightlifting open access, results archive, database. Data was delimited to athletes (N ≥ 750) that competed in Youth or Junior Nationals to ensure athletes were <21yrs old at the first recorded competition. Competition results were converted to strength to mass (SM) ratios to control for the effect of bodyweight on performance. Starting with the first competition date, the highest SM for the snatch (SNT), clean and jerk (CJ) and combined total (T), in three month segments for three years, and six month segments over 10 years, were recorded. Observed percentage change in SM and Cohen’s d effect size (ES) between each 3-and 6-month segment and the first competition (baseline), for the SNT, CJ and T, was determined. Positive change in rate of performance peaked between time segments baseline-6mo and 7mo–12mo for the SNT (+8.7%, SM 0.68±0.19 to 0.74±0.19, ES=0.34), CJ (+7.7%, SM 0.90±0.24 to 0.97±0.24, ES=0.31) and T (+8.2%, SM 1.57±0.41 to 1.71±0.42 ES=0.34). Total performance increase over 10yrs for the SNT was 27.7% (Year 1 SM 0.68±0.18, year 10 SM 1.13±0.24, ES=0.96), the CJ 22.2% (Year 1 SM 0.90±0.23, year 10 SM 1.40±0.30, ES=0.84), and T 25.0% (Year 1 SM 1.56±0.41, year 10 SM 2.53±0.53, ES=0.91). Observed rates in performance change could be useful for weightlifting coaches as a barometer for evaluating training program outcomes over time.
Objective: The aim of the present systematic review and meta-analysis was to determine the relationship between muscular strength and all-cause mortality risk and to examine the sex-specific impact of muscular strength on all-cause mortality in apparently healthy population.
Data Sources: Two authors systematically searched MEDLINE, EMBASE and SPORTDiscus databases and conducted manual searching of reference lists of selected articles.
Study Selection: Eligible cohort studies were those that examined the association of muscular strength with all-cause mortality in apparently healthy population. The hazard ratio (HR) estimates with 95% confidence interval (CI) were pooled by using random effects meta-analysis models after assessing heterogeneity across studies.
Data extraction: Two authors independently extracted data.
Data Synthesis: Thirty-eight studies with 1,907,580 participants were included in the meta-analysis. The included studies had a total of 63,087 deaths. Higher levels of handgrip strength were associated with a reduced risk of all-cause mortality (HR= 0.69; 95% CI, 0.64–0.74) compared to lower muscular strength, with a slightly stronger association in women (HR= 0.60; 95% CI, 0.51–0.69) than men (HR= 0.69; 95% CI, 0.62–0.77) (all p<0.001). Also, adults with higher levels of muscular strength, as assessed by knee extension strength test, had a 14% lower risk of death (HR= 0.86: 95% CI, 0.80–0.93; p < 0.001) compared to adults with lower muscular strength.
Conclusions: Higher levels of upper- and lower-body muscular strength are associated with a lower risk of mortality in adult population, regardless of the age and follow-up period. Muscular strength tests can be easily performed to identify people with a lower muscular strength and, consequently, with an increased risk of mortality.
Objective:
Researchers often perform arbitrary outcome transformations to fulfil the normality assumption of a linear regression model. This manuscript explains and illustrates that in large data settings, such transformations are often unnecessary, and worse, may bias model estimates.
Design:
Linear regression assumptions are illustrated using simulated data and an empirical example on the relation between time since type 2 diabetes diagnosis and glycated haemoglobin (HbA1c). Simulation results were evaluated on coverage; e.g., the number of times the 95% confidence interval included the true slope coefficient.
Results:
While outcome transformations bias point estimates, violations of the normality assumption in linear regression analyses do not. Instead this normality assumption is necessary to unbiasedly estimate standard errors, and hence confidence intervals and p-values. However, in large sample sizes (e.g., where the number of observations per variable is larger than 10) violations of this normality assumption do not noticeably impact results. Contrary to this, assumptions on, the parametric model, absence of extreme observations, homoscedasticity and independency of the errors, remain influential even in large sample size settings.
Conclusions:
Given that modern healthcare research typically includes thousands of subjects focussing on the normality assumption is often unnecessary, does not guarantee valid results, and worse more may bias estimates due to the practice of outcome transformations.
A plethora of research has supported the numerous health benefits of resistance training as we age, including positive relationships between muscular strength, muscle mass and reduced all-cause mortality. As such, resistance training has been referred to as medicine. However, participation and adherence remains low, with time constraints and perceived difficulty often cited as barriers to resistance training. With this in mind, we aimed to summarise the benefits which might be obtained as a product of a minimal dose approach. In this sense, participation in resistance training might serve as a prophylactic to delay or prevent the onset of biological aging. A short review of studies reporting considerable health benefits resulting from low volume resistance training participation is presented, specifically considering the training time, frequency, intensity of effort, and exercises performed. Research supports the considerable physiological and psychological health benefits from resistance training and suggests that these can be obtained using a minimal dose approach (e.g. ≤60min, 2d-wk(-1)), using uncomplicated equipment/methods (e.g. weight stack machines). Our hope is that discussion of these specific recommendations, and provision of an example minimal dose workout, will promote resistance training participation by persons who might otherwise have not engaged. We also encourage medical professionals to use this information to prescribe resistance exercise like a drug whilst having an awareness of the health benefits and uncomplicated methods.
Resistance exercise is believed to be important for improving several biomarkers of health and contributing to decreased all-cause mortality. However, a careful examination of the literature reveals a growing body of cross-sectional studies finding stronger associations between strength independent of physical activity on these various outcomes and biomarkers (i.e., C - reactive protein, homocysteine, total cholesterol) of health. Considering that engagement in resistance type exercise is associated with an increase in strength, such cross-sectional data is often used to promote engagement in resistance training. When one examines the cross-sectional studies together with the experimental work, however, this relationship becomes less clear. For example, being in a higher tertile or quartile for grip strength may be associated with more favorable biomarkers or health outcomes, yet, experimental work shows that grip strength does not change with traditional resistance exercise. This seems to suggest that our interpretation and application of this literature may be incorrect. It is our opinion that much of the cross-sectional work may more accurately illustrate inherent differences between individuals who are “weak” and individuals who are “strong”. In addition, there is conflicting experimental evidence and a lack of longitudinal support that resistance exercise may have a meaningful effect on long-term health outcomes. Using this evidence, we present our “human baseline hypothesis”, which proposes that the baseline value of strength that a person possesses prior to training may be a more appropriate indicator regarding long-term health outcomes than the act of training itself.
Resistance training (RT) increases strength in older adults, but there have been few studies of long-term RT or detraining in older adults. Postmenopausal participants (51-71 years of age) were randomized to RT or a control group for Year 1. For Year 2, participants chose whether to resistance train or not. Three groups emerged: train/train (n = 8; 60 ± 4 years), train/no train (n = 11; 62 ± 3 years), or controls (n = 17; 58 ± 6 years). Both training groups increased strength (p < .05) in Year 1. In Year 2, train/train maintained strength, whereas train/no train lost strength for knee extension (p < .001) but not for arm pull-down. Controls did not change. Reported physical activity levels were significantly increased in trainers in Year 1 and remained high regardless of RT in Year 2 (p < .05). Therefore, sustained changes in strength and physical activity behavior might be possible even if RT is discontinued.
Baker, DG. 10-year changes in upper body strength and power in elite professional rugby league players-The effect of training age, stage, and content. J Strength Cond Res 27(2): 285-292, 2013-The purpose of this investigation was to observe changes in maximal upper body strength and power across a 10-year period in professional athletes who were experienced resistance trainers. Six professional rugby league players were observed with test data reported according to 2 important training stages in their professional careers. The first stage (1996-1998) monitored the changes as the subjects strived to establish themselves as elite professionals in their sport. The remaining test data are from the latter stage (2000-2006), which is characterized by a longer competition schedule and shorter periods devoted to improving physical preparation. The changes in upper body strength, assessed by the 1 repetition maximum bench press and mean maximum power during bench press throws with various barbell resistances of 40-80 kg, were assessed by effect size (ES) and smallest worthwhile change (SWC) statistics. Large increases in strength and power of approximately 22-23% were reported across the 10-year period, however, only small changes (as determined by ES) in strength or power occurred after year 2000 till 2006. This result of only small changes in strength or power despite 6 years of intense resistance training was attributed to 3 main factors. Key among them are the possible existence of a "strength ceiling" for experienced resistance trainers, the Long-term Athlete Development model, and possibly an inappropriate volume of strength-endurance training from 2004 to 2005. The fact that an SWC in strength and power occurred in the year after the cessation of strength-endurance training suggests that training program manipulation is still an influencing factor in continuing strength and power gains in experienced resistance trainers.
A simulation study is performed to investigate the robustness of the maximum likelihood estimator of fixed effects from a linear mixed model when the error distribution is misspecified. Inference for the fixed effects under the assumption of independent normally distributed errors with constant variance is shown to be robust when the errors are either non-gaussian or heteroscedastic, except when the error variance depends on a covariate included in the model with interaction with time. Inference is impaired when the errors are correlated. In the latter case, the model including a random slope in addition to the random intercept is more robust than the random intercept model. The use of Cholesky residuals and conditional residuals to evaluate the fit of a linear mixed model is also discussed.
The purpose of this study was to assess the magnitude of upper and lower body strength changes in highly trained professional rugby union players after 2 years of training. An additional purpose was to examine if the changes in strength were influenced by the starting strength level, lean mass index (LMI), or chronological age. This longitudinal investigation tracked maximal strength and body composition over 3 consecutive years in 20 professional rugby union athletes. Maximal strength in the bench press and back squat and body composition was assessed during preseason resistance training sessions each year. The athletes completed a very rigorous training program throughout the duration of this study consisting of numerous resistance, conditioning and skills training sessions every week. The primary findings of this study were as follows: (a) Maximal upper and lower body strength was increased by 6.5-11.5% after 2 years of training (p = 0.000-0.002 for bench press; p = 0.277-0.165 for squat); (b) magnitude of the improvement was negatively associated with initial strength level (r = -0.569 to -0.712, p ≤ 0.05); (c) magnitude of improvement in lower body maximal strength was positively related to the change in LMI (an indicator of hypertrophy; r = 0.692-0.880, p ≤ 0.05); and (d) magnitude of improvement was not associated with the age of professional rugby union athletes (r = -0.068 to -0.345). It appears particularly important for training programs to be designed for continued muscle hypertrophy in highly trained athletes. Even in professional rugby union athletes, this must be achieved in the face of high volumes of aerobic and skills training if strength is to be increased.
A method is described for the minimization of a function of n variables, which depends on the comparison of function values at the (n + 1) vertices of a general simplex, followed by the replacement of the vertex with the highest value by another point. The
simplex adapts itself to the local landscape, and contracts on to the final minimum. The method is shown to be effective and
computationally compact. A procedure is given for the estimation of the Hessian matrix in the neighbourhood of the minimum,
needed in statistical estimation problems.
The primary objective of this study was to investigate current powerlifting training methods in light of anecdotal evidence purporting increased similarity with the explosive training practices of weightlifters. The study also assessed the prevalence of contemporary training practices frequently recommended for powerlifters in the popular literature. A 20-item survey was distributed to 32 elite British powerlifters at an International competition. The subject group included multiple national, international, and commonwealth champions and record holders. Based on 2007 competition results, the average Wilks score of the group was 450.26 +/- 34.7. The response rate for the surveys was 88% (28 of 32). The survey was sectioned into 6 areas of inquiry: a) repetition speed, b) explosive training load, c) resistance materials used, d) adjunct power training methods, e) exercise selection, and f) training organization. The results demonstrate that the majority of powerlifters train with the intention to explosively lift maximal and submaximal loads (79 and 82%, respectively). Results revealed that 39% of the lifters regularly used elastic bands and that 57% incorporated chains in their training. Evidence for convergence of training practices between powerlifters and weightlifters was found when 69% of the subjects reported using the Olympic lifts or their derivatives as part of their powerlifting training. Collectively, the results demonstrate that previous notions of how powerlifters train are outdated. Contemporary powerlifters incorporate a variety of training practices that are focused on developing both explosive and maximal strength.
Neuromuscular and hormonal adaptations to prolonged strength training were investigated in nine elite weight lifters. The average increases occurred over the 2-yr follow-up period in the maximal neural activation (integrated electromyogram, IEMG; 4.2%, P = NS), maximal isometric leg-extension force (4.9%, P = NS), averaged concentric power index (4.1%, P = NS), total weight-lifting result (2.8%, P less than 0.05), and total mean fiber area (5.9%, P = NS) of the vastus lateralis muscle, respectively. The training period resulted in increases in the concentrations of serum testosterone from 19.8 +/- 5.3 to 25.1 +/- 5.2 nmol/l (P less than 0.05), luteinizing hormone (LH) from 8.6 +/- 0.8 to 9.1 +/- 0.8 U/l (P less than 0.05), follicle-stimulating hormone (FSH) from 4.2 +/- 2.0 to 5.3 +/- 2.3 U/l (P less than 0.01), and testosterone-to-serum sex hormone-binding globulin (SHBG) ratio (P less than 0.05). The annual mean value of the second follow-up year for the serum testosterone-to-SHBG ratio correlated significantly (r = 0.84, P less than 0.01) with the individual changes during the 2nd yr in the averaged concentric power. The present results suggest that prolonged intensive strength training in elite athletes may influence the pituitary and possibly hypothalamic levels, leading to increased serum levels of testosterone. This may create more optimal conditions to utilize more intensive training leading to increased strength development.
The aim of this study was to describe changes in grip strength over a follow-up period of approximately 27 yr and to study the associations of rate of strength decline with weight change and chronic conditions. The data are from the Honolulu Heart Program, a prospective population-based study established in 1965. Participants at exam 1 were 8,006 men (ages 45-68 yr) who were of Japanese ancestry and living in Hawaii. At follow-up, 3,741 men (age range, 71-96 yr) participated. Those who died before the follow-up showed significantly lower grip-strength values at baseline than did the survivors. The average annualized strength change among the survivors was -1.0%. Steeper decline (>1.5%/yr) was associated with older age at baseline, greater weight decrease, and chronic conditions such as stroke, diabetes, arthritis, coronary heart disease, and chronic obstructive pulmonary disease. The risk factors for having very low hand-grip strength at follow-up, here termed grip-strength disability (</=21 kg, the lowest 10th percentile), were largely same as those for steep strength decline. However, the age-adjusted correlation between baseline and follow-up strength was strong (r = 0.557, P < 0.001); i.e., those who showed greater grip strength at baseline were also likely to do so 27 yr later. Consequently, those in the lowest grip-strength tertile at baseline had about eight times greater risk of grip-strength disability than those in the highest tertile because of their lower reserve of strength. In old age, maintenance of optimal body mass may help prevent steep strength decrease and poor absolute strength.
The purpose of this study was to determine the effects of increasing training volume from one set to three sets on muscular strength, muscular endurance, and body composition in adult recreational weight lifters.
Forty-two adults (age 39.7 +/- 6.2 yr; 6.2 +/- 4.6 yr weight training experience) who had been performing one set using a nine-exercise resistance training circuit (RTC) for a minimum of 1 yr participated in this study. Subjects continued to perform one set (EX-1; N = 21) or performed three sets (EX-3; N = 21) of 8-12 repetitions to muscular failure 3 d x wk(-1) for 13 wk using RTC. One repetition maximums (1-RM) were measured for leg extension (LE), leg curl (LC), chest press (CP), overhead press (OP), and biceps curl (BC). Muscular endurance was evaluated for the CP and LE as the number of repetitions to failure using 75% of pretraining 1-RM. Body composition was estimated using the sum of seven skinfold measures.
Both groups significantly improved muscular endurance and 1 RM strength (EX-1 by: 13.6% LE; 9.2% LC; 11.9% CP; 8.7% OP; 8.3% BC; and EX-3 by: 12.8% LE; 12.0% LC; 13.5% CP; 12.4% OP; 10.3% BC) (P < 0.05). Both groups significantly improved lean body mass (P < 0.05). No significant differences between groups were found for any of the test variables (P > 0.05).
Both groups significantly improved muscular fitness and body composition as a result of the 13 wk of training. The results show that one-set programs are still effective even after a year of training and that increasing training volume over 13 wk does not lead to significantly greater improvements in fitness for adult recreational weight lifters.