A mathematical modelling study of an athlete's sprint time when towing a weighted sled

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s12283-013-0114-2.This study used a mathematical model to examine the effects of the sled, the running surface, and the athlete on sprint time when towing a weighted sled. Simulations showed that ratio scaling is an appropriate method of normalising the weight of the sled for athletes of different body size. The relationship between sprint time and the weight of the sled was almost linear, as long as the sled was not excessively heavy. The athlete’s sprint time and rate of increase in sprint time were greater on running surfaces with a greater coefficient of friction, and on any given running surface an athlete with a greater power-to-weight ratio had a lower rate of increase in sprint time. The angle of the tow cord did not have a substantial effect on an athlete’s sprint time. This greater understanding should help coaches set the training intensity experienced by an athlete when performing a sled-towing exercise

The within-participant correlation between perception of effort and heart rate-based estimations of training load in elite soccer players.

The measurement of relative physiological stress during training is important because this is the stimulus for the long-term adaptive response. Measurements of perceived exertion (RPE) have been reported to correlate with the heart rate during field-based training sessions. Nevertheless, there are few studies on how well RPE tracks with the heart rate over repeated training sessions in elite soccer players. Therefore, we aimed to quantify the within-participant correlations between variability in session-RPE (sRPE) and the heart rate in elite male soccer players, and to determine whether the playing position moderated these correlations. The field-based training of four central defenders, four wide defenders, six central midfielders, two wide midfielders and three attackers from an elite English Premier League squad were monitored over an entire in-season competitive period, giving a total of 1010 individual training sessions for study. Correlations between session-RPE and heart rates were quantified using a within-participant model. The correlation between changes in sRPE and heart rates was r = 0.75 (95% CI: 0.71-0.78). This correlation remained high across the various player positions (wide-defender, r = 0.81; central-defender, r = 0.74; wide midfielder, r = 0.70; central midfielder, r = 0.70; attacker, r = 0.84; P < 0.001). The correlation between changes in RPE and heart rates, measured during a season-long period of field-based training, is high in a sample of elite soccer players

Risk of Severe Knee and Hip Osteoarthritis in Relation to Level of Physical Exercise: A Prospective Cohort Study of Long-Distance Skiers in Sweden

Background: To complete long-distance ski races, regular physical exercise is required. This includes not only cross-country skiing but also endurance exercise during the snow-free seasons. The aim of this study was to determine whether the level of physical exercise is associated with future risk of severe osteoarthritis independent of previous diseases and injuries. Methodology/Principal Findings: We used a cohort that consisted of 48 574 men and 5 409 women who participated in the 90 km ski race Vasaloppet at least once between 1989 and 1998. Number of performed races and finishing time were used as estimates of exercise level. By matching to the National Patient Register we identified participants with severe osteoarthritis, defined as arthroplasty of knee or hip due to osteoarthritis. With an average follow-up of 10 years, we identified 528 men and 42 women with incident osteoarthritis. The crude rate was 1.1/1000 person-years for men and 0.8/1000 person-years for women. Compared with racing once, participation in &gt;= 5 races was associated with a 70% higher rate of osteoarthritis (multivariable-adjusted hazard ratio (HR) 1.72, 95% confidence interval (CI) 1.33 to 2.22). The association was dose-dependent with an adjusted HR of 1.09, 95% CI 1.05 to 1.13 for each completed race. A faster finishing time, in comparison with a slow finishing time, was also associated with an increased rate (adjusted HR 1.51, 95% CI 1.14 to 2.01). Contrasting those with 5 or more ski races and a fast finish time to those who only participated once with a slow finish time, the adjusted HR of osteoarthritis was 2.73, 95% CI 1.78 to 4.18. Conclusions/Significance: Participants with multiple and fast races have an increased risk of subsequent arthroplasty of knee and hip due to osteoarthritis, suggesting that intensive exercise may increase the risk

Towards a model of talent development in physical education

Traditional conceptions of talent generally emphasise the construction of threshold values and the development of relatively unitary abilities, and this approach still dominates talent development programmes for elite sport. Most researchers on high ability, however, now favour domain-specific, multidimensional conceptions of ability that stress the development of behavioural potential and its interaction with personal and environmental characteristics. This paper presents a model of talent in physical education, drawing together findings from a wide range of literature on the realisation and inhibition of abilities, international studies of effective school-based identification and provision strategies, and a conception of the subject as an integration and realisation of different forms of ability. In presenting this model, the authors aim to redress the imbalance within the current debate from an almost total concern with out-of-school clubs and the preparation for adult elite sport, in favour of a more equitable and inclusive approach, premised upon the unique importance of mainstream, curricular physical education within any talent development scheme

Effectiveness of motivational interviewing and physical activity on prescription on leisure exercise time in subjects suffering from mild to moderate hypertension

<p>Abstract</p> <p>Background</p> <p>Physical inactivity is considered to be the strongest individual risk factor for poor health in Sweden. It has been shown that increased physical activity can reduce hypertension and the risk of developing cardiovascular diseases. The objective of the present pilot study was to investigate whether a combination of Motivational Interviewing (MI) and Physical Activity on Prescription (PAP) would increase leisure exercise time and subsequently improve health-related variables.</p> <p>Methods</p> <p>This pilot study was of a repeated measures design, with a 15 months intervention in 31 patients with mild to moderate hypertension. Primary outcome parameter was leisure exercise time and secondary outcome parameters were changes in blood pressure, Body Mass Index (BMI), waist circumference, lipid status, glycosylated haemoglobin (HbA1c) and maximal oxygen uptake (VO_{2 max}). Assessments of the outcome parameters were made at baseline and after 3, 9 and 15 months.</p> <p>Results</p> <p>Leisure exercise time improved significantly from < 60 min/week at baseline to a mean activity level of 300 (± 165) minutes/week at 15 months follow up. Furthermore, statistically significant improvements (p < 0.05) were observed in systolic (-14,5 ± 8.3 mmHg) and diastolic blood pressure (-5,1 ± 5.8 mmHg), heart rate (-4.9 ± 8.7 beats/min, weight (-1.2 ± 3.4 kg) BMI -0.6 ± 1.2 kg/m²), waist circumference (-3.5 ± 4.1 cm) as well as in VO_{2 max}(2.94 ± 3.8 ml/kg and 0.23, ± 0.34 lit/min) upon intervention as compared to baseline.</p> <p>Conclusions</p> <p>A 15 month intervention period with MI, in combination with PAP, significantly increased leisure exercise time and improved health-related variables in hypertensive patients. This outcome warrants further research to investigate the efficacy of MI and PAP in the treatment of mild to moderate hypertension.</p

Predictors of stable return-to-work in non-acute, non-specific spinal pain: low total prior sick-listing, high self prediction and young age. A two-year prospective cohort study

<p>Abstract</p> <p>Background</p> <p>Non-specific spinal pain (NSP), comprising back and/or neck pain, is one of the leading disorders in long-term sick-listing. During 2000-2004, 125 Swedish primary-care patients with non-acute NSP, full-time sick-listed 6 weeks-2 years, were included in a randomized controlled trial to compare a cognitive-behavioural programme with traditional primary care. This prospective cohort study is a re-assessment of the data from the randomized trial with the 2 treatment groups considered as a single cohort. The aim was to investigate which baseline variables predict a stable return-to-work during a 2-year period after baseline: objective variables from function tests, socioeconomic, subjective and/or treatment variables. Stable return-to-work was a return-to-work lasting for at least 1 month from the start of follow-up.</p> <p>Methods</p> <p><it>Stable return-to-work </it>was the outcome variable, the above-mentioned factors were the predictive variables in multiple-logistic regression models, one per follow-up at 6, 12, 18 and 24 months after baseline. The factors from univariate analyzes with a <it>p</it>-value of at most .10 were included. The non-significant variables were excluded stepwise to yield models comprising only significant factors (<it>p </it>< .05). As the comparatively few cases made it risky to associate certain predictors with certain time-points, we finally considered the predictors which were represented in at least 3 follow-ups. They are presented with odds ratios (OR) and 95% confidence intervals.</p> <p>Results</p> <p>Three variables qualified, all of them represented in 3 follow-ups: <it>Low total prior sick-listing </it>(including all diagnoses) was the strongest predictor in 2 follow-ups, 18 and 24 months, OR 4.8 [1.9-12.3] and 3.8 [1.6-8.7] respectively, <it>High self prediction </it>(the patients' own belief in return-to-work) was the strongest at 12 months, OR 5.2 [1.5-17.5] and <it>Young age </it>(max 44 years) the second strongest at 18 months, OR 3.5 [1.3-9.1].</p> <p>Conclusions</p> <p>In primary-care patients with non-acute NSP, the strong predictors of stable return-to-work were 2 socioeconomic variables, <it>Low total prior sick-listing </it>and <it>Young age</it>, and 1 subjective variable, <it>High self-prediction</it>. Objective variables from function tests and treatment variables were non-predictors. Except for <it>Young age</it>, the predictors have previously been insufficiently studied, and so our study should widen knowledge within clinical practice.</p> <p>Trial registration</p> <p>Trial registration number for the original trial NCT00488735.</p

Developing a new curvilinear allometric model to improve the fit and validity of the 20-m shuttle run test as a predictor of cardiorespiratory fitness in adults and youth

This is an accepted manuscript of an article published by Springer in Sports Medicine on 24 September 2020, available online at: https://doi.org/10.1007/s40279-020-01346-0 The accepted version of the publication may differ from the final published version.Background and Objectives: Doubts have been raised concerning the validity of the 20m shuttle run test (20mSRT) as a predictor of cardiorespiratory fitness (CRF) in youth based on Léger’s equation/model. An alternative allometric model has been published recently that is thought to provide, not only a superior fit (criterion validity) but also a more biologically and physiologically interpretable model (construct validity). The purposes of this study were to explore whether allometry can provide a more valid predictor of CRF using 20mSRT compared with Léger’s equation/model. Methods: We fitted and compared Léger’s original model and an alternative allometric model using two cross-sectional datasets (youth, n=306; adult n=105) that contained measurements of CRF (V ̇O2peak /V ̇O2max) and 20mSRT performance. Quality-of-fit was assessed using explained variance (R2) and Bland and Altman’s limits of agreement. Results: The allometric models provided superior fits for the youth (explained variance R2=71.9%) and adult (R2=77.7%) datasets compared with Léger’s equation using their original fixed (R2=35.2%) or re-estimated parameter models (R2=65.9%), confirming that the allometric models demonstrate acceptable criterion validity. However, the allometric models also identified a non-linear “J-shaped” increase in energy cost (V ̇O2peak/V ̇O2max) with faster final shuttle-run speeds, (fitted speed exponent =1.52; 95% CI 1.38 to 1.65). Conclusion: Not only do allometric models provide more accurate predictions of CRF (V ̇O2peak/V ̇O2max; ml.kg-1.min-1) for both youth and adults (evidence of criterion validity), the “J-shaped” rise in energy demand with increasing final shuttle-run speed also provides evidence of construct validity, resulting in a more plausible, physiologically sound and interpretable model

The effects of an extensive exercise programme on the progression of Mild Cognitive Impairment (MCI): study protocol for a randomised controlled trial

Background Exercise interventions to prevent dementia and delay cognitive decline have gained considerable attention in recent years. Human and animal studies have demonstrated that regular physical activity targets brain function by increasing cognitive reserve. There is also evidence of structural changes caused by exercise in preventing or delaying the genesis of neurodegeneration. Although initial studies indicate enhanced cognitive performance in patients with mild cognitive impairment (MCI) following an exercise intervention, little is known about the effect of an extensive, controlled and regular exercise regimen on the neuropathology of patients with MCI. This study aims to determine the effects of an extensive exercise programme on the progression of MCI. Methods/design This randomised controlled clinical intervention study will take place across three European sites. Seventy-five previously sedentary patients with a clinical diagnosis of MCI will be recruited at each site. Participants will be randomised to one of three groups. One group will receive a standardised 1-year extensive aerobic exercise intervention (3 units of 45 min/week). The second group will complete stretching and toning (non-aerobic) exercise (3 units of 45 min/week) and the third group will act as the control group. Change in all outcomes will be measured at baseline (T0), after six months (T1) and after 12 months (T2). The primary outcome, cognitive performance, will be determined by a neuropsychological test battery (CogState battery, Trail Making Test and Verbal fluency). Secondary outcomes include Montreal Cognitive Assessment (MoCA), cardiovascular fitness, physical activity, structural changes of the brain, quality of life measures and measures of frailty. Furthermore, outcome variables will be related to genetic variations on genes related to neurogenesis and epigenetic changes in these genes caused by the exercise intervention programme. Discussion The results will add new insights into the prevailing notion that exercise may slow the rate of cognitive decline in MCI