Prediction of Marathon Performance using Artificial Intelligence.

Although studies used machine learning algorithms to predict performances in sports activities, none, to the best of our knowledge, have used and validated two artificial intelligence techniques: artificial neural network (ANN) and k-nearest neighbor (KNN) in the running discipline of marathon and compared the accuracy or precision of the predicted performances. Official French rankings for the 10-km road and marathon events in 2019 were scrutinized over a dataset of 820 athletes (aged 21, having run 10 km and a marathon in the same year that was run slower, etc.). For the KNN and ANN the same inputs (10-km race time, body mass index, age and sex) were used to solve a linear regression problem to estimate the marathon race time. No difference was found between the actual and predicted marathon performances for either method (p>0,05). All predicted performances were significantly correlated with the actual ones, with very high correlation coefficients (r>0,90; p<0,001). KNN outperformed ANN with a mean absolute error of 2,4 vs 5,6%. The study confirms the validity of both algorithms, with better accuracy for KNN in predicting marathon performance. Consequently, the predictions from these artificial intelligence methods may be used in training programs and competitions.

Effect of Physical Fatigue Elicited by Continuous and Intermittent Exercise on Motor Imagery Ability.

Purpose: The ability to perform motor imagery (MI) might be impaired by the physical fatigue elicited during training. Interestingly, there is also theoretical support for a more limited influence of fatigue in the existing literature. Method: We evaluated MI ability before and after two exercise protocols: (i) a continuous exercise of 20 min performed on a cycle ergometer at 80% of the secondary ventilatory threshold (Continuous exercise), and (ii) an intermittent exercise of 20 min involving sprints at maximal intensity performed with regular intervals (Intermittent exercise). MI ability evaluations were performed using validated behavioral (mental chronometry) and psychometric (subjective reports) methods. MI ability evaluations included mental rehearsal of a motor sequence which involved the main effectors of the exercise protocols (walking), and mental rehearsal of a motor task which did not involve the main somatic effectors of the exercise protocols (pointing movements with the upper limbs). Results: Mental chronometry showed that MI ability was degraded only after Intermittent exercise, while self-report measures of MI vividness revealed that MI ability was primarily impaired during MI of the walking task. Conclusions: Present results suggest that Intermittent exercise engaging anaerobic processes of energy expenditure, but not Continuous exercise engaging aerobic processes of energy expenditure, impaired MI ability. Findings are discussed in relation to the internal models theory of motor simulation, specifically changes in current state of the motor system under the fatigued state-affecting motor predictions. Present findings may contribute to successful applications of MI training in sports and rehabilitation.

Feasibility and Health Benefits of an Individualized Physical Activity Intervention in Women With Metastatic Breast Cancer: Intervention Study.

BACKGROUND: There is limited knowledge regarding the potential benefits of physical activity in patients with metastatic breast cancer. OBJECTIVE: The Advanced stage Breast cancer and Lifestyle Exercise (ABLE) Trial aimed to assess the feasibility of a physical activity intervention in women with metastatic breast cancer and to explore the effects of physical activity on functional, psychological, and clinical parameters. METHODS: The ABLE Trial was a single-arm, 6-month intervention study with a home-based, unsupervised, and personalized walking program using an activity tracker. At baseline and 6 months, we assessed anthropometrics, functional fitness, physical activity level, sedentary behavior, quality of life, fatigue, and tumor progression. Paired proportions were compared using the McNemar test and changes of parameters during the intervention were analyzed using the Wilcoxon signed-rank test, the Mann-Whitney test, and Spearman rank correlations. RESULTS: Overall, 49 participants (mean age 55 years; recruitment rate 94%) were enrolled and 96% adhered to the exercise prescription (attrition rate 2%). Statistically significant improvements in the 6-minute walking distance test (+7%, P<.001) and isometric quadriceps strength (+22%, P<.001), as well as decreases in body mass index (-2.5%, P=.03) and hip circumference (-4.0%, P<.001) were observed at 6 months. Quality of life remained stable and a nonstatistically significant decrease (-16%, P=.07) in fatigue was observed. CONCLUSIONS: The high recruitment and adherence rates suggest the willingness of patients with metastatic breast cancer to participate in a physical activity program. The beneficial outcomes regarding physical fitness and anthropometry of this unsupervised physical activity program may encourage these patients to maintain a physically active lifestyle. Future randomized controlled trials with larger sample sizes are warranted. TRIAL REGISTRATION: ClinicalTrials.gov NCT03148886; https://clinicaltrials.gov/ct2/show/NCT03148886.

Performance Factors in a Mountain Ultramarathon.

This study aimed to determine mountain ultra-marathon (MUM) performance factors in a large group of endurance mountain runners. Maximal aerobic speed (MAS) was assessed one week prior to the MUM. The level and graded (10%) energy cost of running, stiffness, knee extensors force (KEf), and jump height on a counter movement jump (CMJ) were measured in 24 male ultra runners before (pre) and immediately after (post) the Interlacs Trail (75 km and 3 930/3 700 m d+/d-). Performance time was correlated with MAS (r=- 0.74, p<0.001), fraction of MAS (FMAS) sustained (r=- 0.89, p<0.001), KEf (r=- 0.51, p<0.05), and KEf loss (r=- 0.51, p<0.05). A multiple regression analysis was performed using performance time in minutes (T) and the calculated individual characteristics, resulting in T=- 11.852×FMAS-37.195×MAS-0.118×KEf+2090.581 (R2=0.98, with 95% confidence interval). Contrary to expectations, performance was neither correlated to the level or uphill energy cost of running nor to the changes of these costs post-MUM. To perform in a MUM, training should take into account muscle strength of the KE, MAS and FMAS.

Comparison of Level and Graded Treadmill Tests to Evaluate Endurance Mountain Runners.

Mountain endurance running has increased in popularity in recent years. Thus the aim of the present study was to determine if maximal oxygen uptake (VO2max) and energy cost of running (Cr) measured during level and uphill running are associated. Ten high level male endurance mountain runners performed three maximal oxygen uptake tests at three slope conditions (0, 12.5 and 25%). Metabolic data, step frequency (SF) and step length (SL) were recorded. No significant differences were found in VO2max (63.29 (±3.84), 63.97 (±3.54) and 63.70 (±3.58) mlO2/kg(-1)/min(-1)) or associated metabolic data at 0, 12.5 and 25% slope respectively. High intra-individual correlations were found between metabolic data measured in the three conditions. The energy cost of running was significantly different between slopes (0.192 (±0.01), 0.350 (±0.029) and 0.516 (±0.035) mlO2/kg(-1)/min(-1), p < 0.01), 0, 12.5 and 25% respectively. However, Cr0% was not correlated with either Cr25% or Cr12.5% (rs = 0.09 and rs = 0.10), in contrast, Cr25% and Cr12.5% were correlated (rs = 0.78). Step length was positively correlated with speed under the three slope conditions. Step frequency was significantly lower at 25 compared to 12.5 and 0% slope. We found that the maximum aerobic power did not differ between level and graded treadmill tests. However, the increase in Cr on the inclined versus level conditions varied between subjects. None of the measured anthropometric or kinematic variables could explain the higher increase in Cr of some subjects when running uphill. Thus, a short graded (5min at 12.5%) running test should be performed at a submaximal velocity (around 40% of level vVO2max) to enhance understanding of an endurance runner's uphill capability. Key pointsIn elite endurance mountain runners, there is no difference in VO2max values between level and uphill running.In a homogeneous group of mountain runners, uphill Cr is not associated with level Cr.To assess performance potential of endurance mountain runners, a standardized uphill running protocol should be performed.

Peak torque and rate of torque development influence on repeated maximal exercise performance: contractile and neural contributions.

Rapid force production is critical to improve performance and prevent injuries. However, changes in rate of force/torque development caused by the repetition of maximal contractions have received little attention. The aim of this study was to determine the relative influence of rate of torque development (RTD) and peak torque (T(peak)) on the overall performance (i.e. mean torque, T(mean)) decrease during repeated maximal contractions and to investigate the contribution of contractile and neural mechanisms to the alteration of the various mechanical variables. Eleven well-trained men performed 20 sets of 6-s isokinetic maximal knee extensions at 240° · s(-1), beginning every 30 seconds. RTD, T(peak) and T(mean) as well as the Rate of EMG Rise (RER), peak EMG (EMG(peak)) and mean EMG (EMG(mean)) of the vastus lateralis were monitored for each contraction. A wavelet transform was also performed on raw EMG signal for instant mean frequency (if(mean)) calculation. A neuromuscular testing procedure was carried out before and immediately after the fatiguing protocol including evoked RTD (eRTD) and maximal evoked torque (eT(peak)) induced by high frequency doublet (100 Hz). T(mean) decrease was correlated to RTD and T(peak) decrease (R(²) = 0.62; p<0.001; respectively ß=0.62 and ß=0.19). RER, eRTD and initial if(mean) (0-225 ms) decreased after 20 sets (respectively -21.1 ± 14.1, -25 ± 13%, and ~20%). RTD decrease was correlated to RER decrease (R(²) = 0.36; p<0.05). The eT(peak) decreased significantly after 20 sets (24 ± 5%; p<0.05) contrary to EMG(peak) (-3.2 ± 19.5 %; p=0.71). Our results show that reductions of RTD explained part of the alterations of the overall performance during repeated moderate velocity maximal exercise. The reductions of RTD were associated to an impairment of the ability of the central nervous system to maximally activate the muscle in the first milliseconds of the contraction.

Potential role of optimal velocity as a qualitative factor of physical functional performance in women aged 72 to 96 years.

OBJECTIVE: To assess the relationship of maximal leg power and its corresponding determinants (eg, optimal velocity and optimal torque) measured during maximal voluntary knee extension to physical functional performance of older women. DESIGN: Descriptive. SETTING: Community retirement homes. PARTICIPANTS: Women (N=39) aged 72 to 96 years. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Volunteers performed in sitting position maximal knee extensions on an Ergopower dynamometer to calculate maximal leg power, optimal velocity, and optimal torque. Three standardized tests were also performed to evaluate physical performance: walking speed over 6m, time taken to rise 5 times from a chair, and time to climb 6 stairs. RESULTS: On multiple regression analysis, leg power (mean, 1.37+/-0.80 W/kg) significantly correlated with physical performance as measured by 6-m walking speed (mean, .85+/-.40 m/s), chair-stand time (mean, 16.3+/-7.7s), and stair-climb time (mean, 7+/-4s), describing 16% to 33% of the variance. Optimal velocity (mean, 1.79+/-1.20 rad/s) also significantly correlated with 6-m walking speed, chair-stand time, and stair-climb time, describing 46% to 89% of the variance. Optimal torque (50.8+/-16.9 Nm) did not correlate with physical performance. CONCLUSIONS: Maximal power and moreover optimal velocity were thus found to be determinants of physical performance, both appearing as significant mobility factors in older adults. This may provide more focus on velocity-oriented training as a means of improving functional status.