Influence of physical fitness and weight status on autonomic cardiac modulation in children.

BACKGROUND: This study provides reference values for cardiovascular modulation at rest, during maximal exercise test and recovery after exercise in Caucasian children according to weight status and cardiorespiratory fitness (CRF) level. Additionally, the current study analyzed several correlations between autonomic cardiovascular modulation, cardiorespiratory performance and cardiometabolic risk. The principal goal of this study was to analyze cardiac function at rest, during maximum exercise, and during the recovery phase in children grouped according to weight status and CRF level. METHODS: One hundred and fifty-two healthy children (78 girls) 10-16 years of age were divided into three groups: soccer and basketball players (SBG), endurance group (EG), and sedentary people with overweight and obesity (OOG). A cardiac RR interval monitor recorded the cardiac data and specific software analyzed the cardiac autonomic response through heart rate (HR) and HR variability. The study analyzed resting HR (RHR), HRpeak, and HR recovery (HRR). RESULTS: OOG showed significant poorer performance in the Léger test lower V̇O2 max and higher values of blood pressure at rest and post-exercise than sport groups. The EG presented the best results in CRF and cardiometabolic risk (CMR) in relation to SBG and OOG. The OOG showed higher percentage of HR values, compatible with an unhealthy cardiovascular autonomic modulation than the sport groups, with significant differences in bradycardia, HR reserve, and HRR 5 min. CONCLUSIONS: Aerobic performance, vagal activity, blood pressure, chronotropic competence, and HRR have significant associations with CMR parameters. IMPACT: The current study presents reference values of autonomic cardiac function in Caucasian children according to weight status and cardiorespiratory fitness level. Aerobic performance, vagal activity, blood pressure, chronotropic competence, and heart rate during the recovery period after exercise have significant associations with cardiometabolic risk parameters. Children with overweight and obesity show signs of autonomic dysfunction reflected as low cardiac vagal activity and poor chronotropic competence.

Effects of a High Intensity Interval Training (HIIT) Program on Anthropomorphic and Cardiometabolic Variables in School Children with Overweight and Obesity.

The aim of this study was to assess the effects of a high intensity interval training (HIIT) program on anthropomorphic and cardiometabolic variables in schoolchildren with overweight and obesity. A total of 443 schoolchildren (age: 6.37 ± 0.65 years) took part in this study. The experimental group (EG; n = 295; age = 6.40 ± 0.64 years) was compound with children with overweight and obesity, whereas children with normoweight were included in the control group (CG; n = 148; 6.31 ± 0.67 years). The EG performed a training program based on HIIT two times per week for 28 weeks (56 sessions), whilst the CG performed their habitual physical education classes based on the national curriculum. Body mass index (BMI), waist circumference, body fat, ∑ 4 skinfold fat, waist to height ratio, waist circumference, and cardiometabolic risk were measured. The dependent variables were analysed by two-way analysis of covariance (ANCOVA 2 × 2). To analyse the percentage differences between groups, the chi-square test was used. P-value was set at p < 0.05. Significant differences were found in the EG in BMI, waist circumference, body fat, ∑ 4 skinfold fat, and waist to height ratio. In conclusion, an HIIT training program can be an effective tool for improving anthropomorphic variables and reducing cardiometabolic risk in schoolchildren with overweight and obesity.

Protective role of physical activity patterns prior to COVID-19 confinement with the severity/duration of respiratory pathologies consistent with COVID-19 symptoms in Spanish populations.

The main purpose of the present study was to determine the association of physical activity (PA) patterns prior to COVID-19 confinement with severe respiratory distress consistent with COVID-19 symptoms. Participants were recruited by sending a survey through various social network channels via the snowball method. A voluntary sample of 420 individuals consisting of 199 men and 221 women from the Spanish national territory participated in this study. Some factors, such as being overweight and obese were related to the presence of a greater number of symptoms associated with COVID-19. Interestingly, it was observed that not performing moderate or vigorous PA increased the risk of COVID-19 symptoms. Consequently, when the effect of the practise of PA was evaluated in terms of the number of practises per week and in minutes per practise per week, a protective effect was observed, where moderate PA >150 min per week reported an inverse association with hospitalization for respiratory symptoms (RR: 95%CI: 0.24, 0.05-1.04, P = 0.05). Likewise, overweight (RR: 16.3, 95%CI: 1.93-137.9, P = 0.01), obesity (RR: 19.1, 95%CI: 1.63-222.5, P = 0.019) and non-performance of moderate PA (RR: 4.12, 95%CI; 0.95-17.76, P = 0.05) reported positive associations with hospitalization for respiratory symptoms. Thus, the practise of moderate PA (>150 min per week) is a protective factor against hospitalization for respiratory symptoms consistent with COVID-19 symptoms.

Utilizing Age-Predicted Heart Rate Maximum to Prescribe a Minimally Invasive Cycle Ergometer HIIT Protocol in Older Adults: A Feasibility Study.

Previous research has provided evidence that aerobic HIIT exercise can induce important physiological adaptations and elicit improvements in health and fitness parameters. However, most of the research has taken place in a laboratory setting with specialized equipment and monitoring devices. It begs the question, is HIIT accessible to the general aging population? The objective of the current research was to employ an age-predicted HRmax to prescribe a minimally invasive 4x4 cycle ergometer HIIT protocol. Ten participants (age: 64.2 ± 6.1) completed a non-weight-bearing cycle ergometer protocol for 6 weeks. Significant Pearson correlations were found between %HRmax and W/kg in seven of the ten participants. Two participants showed significant correlations between RPE and W/kg. Half of the participants exhibited a significant correlation between %HRmax and RPE. Pre- to post-intervention measures demonstrated a significant increase in lower limb strength by the 10-repetition chair sit-to-stand (p = 0.004) and 30-second sit-to-stand (p = 0.021). Increased functional capacity demonstrated by TUG (p = 0.001) and SB (p = 0.034) also presented significant differences pre- to post-intervention. There was a 96% participant session completion rate. These data imply that a simple 4x4 cycle ergometer HIIT protocol prescribed using a %HRmax is effective at increasing lower-limb power/strength and can be used in the general older adult population without excessive oversight. Our intervention protocol demonstrates that 6 weeks of cycle ergometer HIIT is an adequate amount of time to result in lower limb strength and functional capacity improvements in active older adults.

Cardiac Evaluation of Exercise Testing in a Contemporary Population of Preschool Children: A New Approach Providing Reference Values.

The objective of this study was to evaluate cardiac autonomic function at rest, during maximal exercise, and in post-exercise recovery, to determine sex-specific and age-specific differences in resting heart rate (RHR), linear and spectral parameters of Heart Rate Variability (HRV), HRpeak, and heart rate recovery (HRR) after one and five minutes, in preschool children. This study involved a cohort of 167 healthy children (79 girls) aged 3 to 6 years that were selected from several schools in southern Spain. A 10 × 20 m test was conducted, and the cardiovascular response was recorded. No significant differences were found in all variables between the sexes. However, a significant reduction in RHR and an increase in HRR were found from age 4 to age 6. HRV parameters at rest were higher in older children. No associations between 10 × 20 m performance, weight status, and cardiac parameters were found. Simple linear regression analysis revealed that heart rate reserve (HRr), HRR5min, RMSSD, and HF were the variables that showed association with all HR parameters. There was also a significant correlation between HRr and HRR5min. In conclusion, cardiovascular autonomic function during rest, exercise, and recovery in Spanish preschool children was not influenced by sex, although older children showed greater cardiovascular modulation. Cardiorespiratory fitness status was not associated with HR response.

A New Approach for Evaluation of Cardiovascular Fitness and Cardiac Responses to Maximal Exercise Test in Master Runners: A Cross-Sectional Study.

The aim of this study was to analyze the cardiac autonomic function at rest, at maximum exercise, and in recovery after exercise and to determine sex-specific and age-specific values for resting heart rate (RHR), hear rate (HR)-peak, HR recovery (HRR), and HR variability at rest in master runners. Fifty endurance runners (21 women) participated in this study (43.28 ± 5.25 years). The subjects came from different athletic clubs in Andalusia (Spain), and the testing protocol was performed in-season. A 3-km running test was performed and the cardiovascular response was monitored. Regarding sex, no significant differences were found regarding cardiovascular autonomic function at rest, during exercise, and following maximal exercise, only at rest, the standard deviation of all R-R intervals and low frequency values displayed significantly (p < 0.05) lower scores in women. 46% of athletes showed an RHR < 60 bpm. Additionally, HR-peak showed a significant correlation with age (r = −0.369; p = 0.009) and HRR5min (r = 0.476, p = 0.001). Also, endurance performance was inversely associated with obesity traits and cardiometabolic risk factors. In summary, age, sex, fitness, or anthropometrics characteristics did not show a relevant influence on cardiovascular autonomic modulation in master runners. However, the 3-km performance displayed a significant negative association with several factors of cardiometabolic risk.

Anaerobic Speed Reserve, Sprint Force-Velocity Profile, Kinematic Characteristics, and Jump Ability among Elite Male Speed- and Endurance-Adapted Milers.

This study aimed to compare sprint, jump performance, and sprint mechanical variables between endurance-adapted milers (EAM, specialized in 1500-3000-m) and speed-adapted milers (SAM, specialized in 800-1500 m) and to examine the relationships between maximal sprint speed (MSS), anaerobic speed reserve (ASR), sprint, jump performance, and sprint mechanical characteristics of elite middle-distance runners. Fifteen participants (8 EAM; 7 SAM) were evaluated to obtain their maximal aerobic speed, sprint mechanical characteristics (force-velocity profile and kinematic variables), jump, and sprint performance. SAM displayed greater MSS, ASR, horizontal jump, sprint performance, and mechanical ability than EAM (p < 0.05). SAM also showed higher stiffness in the 40-m sprint (p = 0.026) and a higher ratio of horizontal-to-resultant force (RF) at 10 m (p = 0.003) and RFpeak (p = 0.024). MSS and ASR correlated with horizontal (r = 0.76) and vertical (r = 0.64) jumps, all sprint split times (r ≤ -0.85), stiffness (r = 0.86), and mechanical characteristics (r ≥ 0.56) during the 100-m sprint, and physical qualities during acceleration (r ≥ 0.66) and sprint mechanical effectiveness from the force-velocity profile (r ≥ 0.69). Season-best times in the 800 m were significantly correlated with MSS (r = -0.86). Sprint ability has a crucial relevance in middle-distance runners' performance, especially for SAM.

Seasonal Changes in the Sprint Acceleration Force-Velocity Profile of Elite Male Soccer Players.

ABSTRACT: Jiménez-Reyes, P, Garcia-Ramos, A, Párraga-Montilla, JA, Morcillo-Losa, JA, Cuadrado-Peñafiel, V, Castaño-Zambudio, A, Samozino, P, and Morin, J-B. Seasonal changes in the sprint acceleration force-velocity profile of elite male soccer players. J Strength Cond Res 36(1): 70-74, 2022-This study aimed to describe the seasonal changes in the sprint force-velocity (Fv) profile of professional soccer players. The sprint Fv profile of 21 male soccer players competing in the first division of the Spanish soccer league was evaluated 6 times: preseason 1 (September 2015), in-season 1 (November 2015), in-season 2 (January 2016), in-season 3 (March 2016), in-season 4 (May 2016), and preseason 2 (August 2016). No specific sprint capabilities stimuli other than those induced by soccer training were applied. The following variables were calculated from the velocity-time data recorded with a radar device during an unloaded sprint: maximal force (F0), maximal velocity (v0), Fv slope, maximal power (Pmax), decrease in the ratio of horizontal-to-resultant force (DRF), and maximal ratio of horizontal-to-resultant force (RFpeak). F0 (effect size [ES] range = 0.83-0.93), Pmax (ES range = 0.97-1.05), and RFpeak (ES range = 0.56-1.13) were higher at the in-seasons 2 and 3 compared with both preseasons (p ≤ 0.006). No significant differences were observed for v0, Fv slope, and DRF (p ≥ 0.287). These results suggest that relevant Fv profile variables may be compromised (F0 more compromised than v0) toward the end of the competitive season when specific sprint stimuli are not systematically applied.

Comprehensive cardiac evaluation to maximal exercise in a contemporary population of prepubertal children.

BACKGROUND: Heart rate (HR) is a biomarker used to measure physiological function, health status and cardiovascular autonomic function. The purpose of this study was to determine sex- and age-specific reference values for cardiac autonomic function at rest, during maximal exercise and the recovery phase in prepubertal children. METHODS: Five hundred and twelve healthy children 7-11 years of age performed a Léger test. A heart RR-interval monitor recorded the heart data and a specific software analysed the cardiac autonomic response through HR and HR variability (HRV). It analysed HR before the test (resting HR, RHR), during the test (HRpeak) and HR recovery (HRR) in the first minute (HRR1) and the fifth minute (HRR5). The values are mean ± SD. RESULTS: Collectively, 91.2% of girls and 92.3% of boys were within the recommended ranges regarding RHR. The average HRpeak was 199 ± 10.83 b.p.m. and 96.8% of girls and 95.3% of boys were within the minimum threshold value recommended (180 b.p.m.). Boys showed lower values of RHR than girls (p < 0.001) and larger values of HRR 1 and HRR5 (p < 0.001). CONCLUSIONS: This study comprehensively provides a reference set of data for the most important HR variables that can be obtained during exercise testing in prepubertal children regarding age and sex and in a field setting. IMPACT: This is the first study to provide reference values of autonomic cardiac function at rest, during maximal exercise and during the recovery period in prepubertal children aged 7-11 years. Despite the early age of participants, cardiorespiratory fitness, RHR and HRR are different according to sex. Aerobic performance and HRpeak have a negative correlation with body mass index and cardiometabolic risk.

Effect of COVID-19 confinement on physical activity patterns in relation to sociodemographic parameters in Spanish population.

BACKGROUND: The main purpose of the present study was to determine the sociodemographic parameters associated to physical activity (PA) patterns changes during the COVID-19 lockdown in the Spanish population. METHODS: Participants were recruited by sending a survey through various social network channels via the snowball method. A voluntary sample of 2430 individuals consisting of 1203 men and 1227 women (aged between 18 to 73 years old) from the Spanish national territory participated in this study. An online survey was performed to collect the information, which was tested through ad hoc analysis with different sociodemographic variables. Participants were a median of 34 years old (18-73 years old) with a mean BMI of 23.6 kg/m2. RESULTS: The risk factors associated with the change in PA hours during confinement showed that to do sports (ß=-56.88, 95% CI: -79.35 to -34.40, P<0.001), male sex (ß -34.78, 95%CI;-54.02 to -15.52, P<0.001) and the educational level (i.e., elementary school category) (ß=-54.21, 95%CI;-89.10 to -19.32, P=0.002) reported negative changes with hours of PA during confinement. By the contrary, the employment status (passive work) and to be student reported positive association (i.e., increase PA hours per week). CONCLUSIONS: The COVID-19 lockdown led to a reduction PA patterns in Spanish population. Mostly men showed a drastic decrease in hours of PA compared to the women's group. Likewise, the groups of people with elementary and high education showed a decrease in hours of weekly PA, as well as unemployed people.

Association between Creativity and Memory with Cardiorespiratory Fitness and Lifestyle among Chilean Schoolchildren.

The objective was to investigate the association between creativity and memory with cardiorespiratory fitness (CRF; i.e., CFR classification and V˙O2max); lifestyle parameters (i.e., physical activity (PA), sleep duration, screen time (ST), and food habits); and anthropometric measures (i.e., body mass index (BMI), waist circumference (WC)) among Chilean schoolchildren. A total of 248 schoolchildren (137 boys, 111 girls, 11.80 ± 1.17 and 11.58 ± 1.09 years, respectively) participated in the cross-sectional study. Creativity, memory, concentration, and selective attention and lifestyle (PA, ST, sleep duration, and Mediterranean diet (MD) adherence) were measured using a standard questionnaire. CRF (measured by the 20 m shuttle run test and expressed as maximum oxygen consumption (V˙O2max) and anthropometric measures (BMI and WC) were also included. Creativity showed a positive association with V˙O2max (mL/kg/min) (ß; 0.209, 95% CI; 0.02-0.40, p = p < 0.05) and MD Adherence (score) (ß; 0.206, 95% CI; 0.01; 0.74, p = p < 0.05). Long-term memory reported a positive association with CRF (ß; 1.076, 95% CI; 0.02-2.13, p = p < 0.05). An increase in CRF levels, together with healthy food habits and normal nutritional status, should be a target for community- and school-based interventions to promote cognitive development in creativity and memory among schoolchildren.

Influence of Resistance Training on Gait & Balance Parameters in Older Adults: A Systematic Review.

In this work we aimed to perform a systematic review of randomized controlled trials within an aging population that investigated the general impacts of a resistance training (RT) protocol on key outcome measures relating to gait and/or balance. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement guidelines, two electronic databases (PubMed, and Scopus) were searched for randomized controlled trials that measured at least one key outcome measure focusing on gait and/or balance in older adults. 3794 studies were identified, and after duplicates were removed, 1913 studies remained. 1886 records were removed due to the abstract not meeting the inclusion criteria. 28 full-text articles were assessed further, and 20 of the articles were identified as meeting the criteria for inclusion. The remaining 20 studies were assessed for quality using the Physiotherapy Evidence Database (PEDro) scale; 12 studies remained and were included in this systematic review. Our review suggests that RT has a positive effect on both gait and balance in an elderly population. RT improves gait, specifically straight-line walking speed in older adults. RT is an adequate training method to improve balance in an aging population. Improvements in strength, attributed to RT, may allow for greater autonomy and independence to carry out activities of daily living as we age.

Analysis of dynamic balance in preschool children through the balance beam test: A cross-sectional study providing reference values.

BACKGROUND: dynamic balance (DB) is a complex ability at an early age and balance deficits are related to numerous disorders. There are several balance measures but wide variation in their use has restricted the capacity to synthesise references values. The main purpose of this study was to analyse the performance of the Balance beam test (BBT) in preschool children, according to age and sex providing BBT reference values, and also to analyse its reliability and validity. RESEARCH QUESTION: could the BBT be a reliable test for measuring dynamic balance in preschool children? METHODS: 593 preschool children (3-6 years) participated in this study. The BBT was used to evaluate DB by measuring distance reached, time spent, and number of steps. Differences between sex and age groups were analysed using the Mann-Whitney U and Kruskal-Wallis tests. Test-retest reliability analysis was performed using intraclass correlation coefficients and the Bland-Altman graphic. Convergent validity was investigated with the Stork Balance stand test (SBST). RESULTS: no significant differences were found for sex in any components of the BBT. Age had positive effects on BBT performance in distance (χ2 = 63.474, p < 0.001), time (χ2 = 46.441, p < 0.001), and step numbers (χ2 = 40.967, p < 0.001). Younger children performed more poorly than older children. No significant interactions between age groups and sex were found. The BBT showed adequate validity and reliability. SIGNIFICANCE: the reference values established for Spanish preschool children in the current study could be used to monitor DB development. It is necessary to take into account distance reached, time spent, and the steps taken to obtain a more precise measure of DB in this population.

Comparison of High-Intensity Interval Training to Moderate-Intensity Continuous Training in Older Adults: A Systematic Review.

High-intensity interval training (HIIT) is emerging as a safe and effective means to combat chronic diseases. The objective of this work was to perform a systematic review of the effect of HIIT interventions in an aging population. Three electronic databases were searched for randomized trials comparing the effect of HIIT and moderate-intensity continuous training in older adults. After a thorough screening process, 15 articles were identified as meeting the inclusion criteria. All studies expressed a comparable or superior effect of HIIT in cardiorespiratory fitness measures. No studies reported a lessened effect of HIIT in comparison with moderate-intensity continuous training. This systematic review demonstrates that HIIT is a useful exercise regimen, which can be used in older adults to increase cardiorespiratory fitness. More research is needed to determine the effects of HIIT in an aging, predominately female population.

Effects of a functional training program in patients with fibromyalgia: A 9-year prospective longitudinal cohort study.

There are evidences that physical exercise is an effective instrument for improving physical fitness, health, and quality of life and causes beneficial effects on the symptoms of patients with fibromyalgia. The purpose of this study was to analyze effects of a functional training program on pain, fitness, and quality of life in patients with fibromyalgia in a 9-year prospective longitudinal cohort study. Forty women with fibromyalgia participated in this study; 24 received an exercise program and were called the active group; and 16 were the control group. Tender points, visual analogical scale (VAS) of pain, physical fitness, Fibromyalgia Impact Questionnaire (FIQ), and Short-Form Health Survey 36 (SF-36) were analyzed. The active group experienced significant improvements in FIQ, TP, and VAS (P < .001), whereas the control group showed significant worsening in the FIQ scale (P = .004). Moreover, the active group experienced significant improvements in leg strength (P < .001), balance (P = .033), cardiorespiratory fitness (P < .001), emotional role (P = .024), and mental health (P = .025); whereas the control group significantly worsened on handgrip strength (P = .017), balance (P = .043), cardiorespiratory fitness (P = .020), and in general health (P < .001). A Pearson correlation analysis revealed a significant relationship between the improvement in physical fitness variables and the improvements in FIQ, TP, and VAS. In conclusion, a regular practice of moderate-intensity physical activity shows a positive effect long-term on fitness, pain, the impact of the disease, and the quality of life in women with fibromyalgia.

Acute and Delayed Effects of a Resistance Training Session Leading to Muscular Failure on Mechanical, Metabolic, and Perceptual Responses.

Párraga-Montilla, JA, García-Ramos, A, Castaño-Zambudio, A, Capelo-Ramírez, F, González-Hernández, JM, Cordero-Rodríguez, Y, and Jiménez-Reyes, P. Acute and delayed effects of a resistance training session leading to muscular failure on mechanical, metabolic, and perceptual responses. J Strength Cond Res 34(8): 2220-2226, 2020-This study explored the acute and delayed (24 and 48 hours after exercise) effects of a resistance training session leading to muscular failure. Eleven resistance-trained men completed a training session consisting on 3 sets of repetitions to failure during the back-squat exercise performed at the maximum possible speed with a load equivalent to a mean propulsive velocity (MPV) of 1 m·s (≈60% of 1 repetition maximum). A number of mechanical (number of repetitions and starting MPV of the set, MPV achieved against the 1MPV load, countermovement jump [CMJ] height, and handgrip strength), metabolic (lactate, uric acid, and ammonia concentrations), and perceptual (OMNI-RES perceived exertion) variables were measured. The results revealed (a) a decrease of 38.7% in set 2 and 54.7% in set 3 of the number of repetitions performed compared with the first set (p < 0.05), (b) a reduction in the MPV of the repetitions and an increase in lactate concentration and OMNI-RES values with the succession of sets (p < 0.05), (c) comparable decrements in CMJ height after the 3 sets (25-32%), (d) a decrease in CMJ height (p < 0.05; 6.7-7.9%) and in the MPV attained against the 1MPV load (p < 0.05; 13-14%) after 24 and 48 hours of completing the training session, but no significant changes were observed in handgrip strength (p > 0.05; <2%), and (e) uric acid and ammonia concentrations above the basal levels (p < 0.05). The large decrements in mechanical performance together with the high metabolic stress discourage the frequent use of resistance training sessions leading to muscular failure.

Kinematic alterations after two high-intensity intermittent training protocols in endurance runners.

PURPOSE: This study aimed to evaluate running kinematic characteristics during the early and late stages of 2 high-intensity intermittent training (HIIT) protocols with similar external load but different average running pace, as well as to compare the fatigue-induced changes during both HIIT protocols at a kinematic level. METHODS: Eighteen endurance runners were tested on a track on 2 occasions: 10 runs of 400 m with 90-120 s recovery between running bouts (10 × 400 m), and 40 runs of 100 m with 25-30 s recovery between running bouts (40 × 100 m). Heart rate was monitored during both protocols; blood lactate accumulation and rate of perceived exertion were recorded after both exercises. A high-speed camera was used to measure sagittal-plane kinematics at the first and last runs during both HIIT protocols. The dependent variables were spatial-temporal parameters (step length and contact and flight time), joint angles during support (relative angles of the hip, knee, and ankle), and foot strike pattern. RESULTS: High levels of exhaustion were reached by the athletes during both workouts (blood lactate accumulation >12 mmol/L, rate of perceived exertion >15; peak heart rate (HRpeak) > 176 bpm). A within-protocol paired t test (first vs. last run) revealed no significant changes (p ≥ 0.05) in kinematic variables during any of the HIIT sessions. A between-protocol comparison with the first run of each protocol revealed the effect of running speed on kinematics: +2.44 km/h during the 40 × 100 m: shorter contact and flight time (p ≤ 0.01) and longer step length (p = 0.001); greater hip flexion (p = 0.031) and ankle extension (p = 0.001) at initial contact; smaller knee and ankle flexion (p < 0.001) at midstance; and greater hip extension at toe-off (p < 0.001). CONCLUSION: HIIT sessions including runs for 15-90 s and performed at intensity above the velocity associated with maximal oxygen uptake did not consistently perturb the running kinematics of trained endurance runners.

Agreement between the spatiotemporal gait parameters from two different wearable devices and high-speed video analysis.

This study aimed to evaluate the concurrent validity of two different inertial measurement units for measuring spatiotemporal parameters during running on a treadmill, by comparing data with a high-speed video analysis (VA) at 1,000 Hz. Forty-nine endurance runners performed a running protocol on a treadmill at comfortable velocity (i.e., 3.25 ± 0.36 m.s-1). Those wearable devices (i.e., Stryd™ and RunScribe™ systems) were compared to a high-speed VA, as a reference system for measuring spatiotemporal parameters (i.e. contact time [CT], flight time [FT], step frequency [SF] and step length [SL]) during running at comfortable velocity. The pairwise comparison revealed that the Stryd™ system underestimated CT (5.2%, p < 0.001) and overestimated FT (15.1%, p < 0.001) compared to the VA; whereas the RunScribe™ system underestimated CT (2.3%, p = 0.009). No significant differences were observed in SF and SL between the wearable devices and VA. The intra class correlation coefficient (ICC) revealed an almost perfect association between both systems and high-speed VA (ICC > 0.81). The Bland-Altman plots revealed heteroscedasticity of error (r2 = 0.166) for the CT from the Stryd™ system, whereas no heteroscedasticity of error (r2 < 0.1) was revealed in the rest of parameters. In conclusion, the results obtained suggest that both foot pods are valid tools for measuring spatiotemporal parameters during running on a treadmill at comfortable velocity. If the limits of agreement of both systems are considered in respect to high-speed VA, the RunScribe™ seems to be a more accurate system for measuring temporal parameters and SL than the Stryd™ system.

How Does Power During Running Change when Measured at Different Time Intervals?

This study aimed to examine how the power output changes while running at a continuous comfortable velocity on a motorized treadmill by comparing running power averaged during different time intervals. Forty-nine endurance runners performed a running protocol on a treadmill at self-selected comfortable velocity. Power output (W) was estimated with the Stryd™ power meter, and it was examined over six recording intervals within the 3-min recording period: 0-10 s, 0-20 s, 0-30 s, 0-60 s, 0-120 s and 0-180 s. The ANOVAs showed no significant differences in the magnitude of the power output between the recording intervals (p=0.276, F=1.614, partial Eta 2 =0.155). An almost perfect association was also observed in the magnitude of the power output between the recording intervals (ICC≥0.999). Bland-Altman plots revealed no heteroscedasticity of error for the power output in any of the between-intervals comparisons (r 2<0.1), although longer recording intervals yield smaller systematic bias, random errors, and narrower limits of agreement for power output. The results show that power data during running, as measured through the Stryd™ system, is a stable metric with negligible differences, in practical terms, between shorter (i. e., 10, 20, 30, 60 or 120 s) and longer recording intervals (i. e., 180 s).

How does the slope gradient affect spatiotemporal parameters during running? Influence of athletic level and vertical and leg stiffness.

BACKGROUND: The current evidence leaves certain questions unanswered, including whether well-trained athletes adapt to different slope gradients in the same way as amateurs, and whether stiffness influences spatiotemporal adaptations during uphill running. RESEARCH QUESTION: This study aimed to determine the effect of different slope gradients (0%-11%) on spatiotemporal gait characteristics during running, taking into account the influence of athletic level, vertical and leg stiffness. METHODS: Male endurance runners (12 amateurs, 10 highly-trained) performed a running test on a motorized treadmill. The running velocity was set at 12 km/h, and participants completed six different running conditions (0, 3, 5, 7, 9 and 11% gradients). Spatiotemporal parameters were measured using the OptoGait system. Vertical (Kvert) and leg (Kleg) stiffness were calculated according to the sine-wave method. RESULTS: A 2 (amateur; highly-trained) × 6 (running conditions) ANOVA found no significant between-group differences in spatiotemporal parameters at any gradient (P ≥ 0.05); however, significant Kvert and Kleg differences (P < 0.05) were found within both groups with increasing gradients. Stepwise linear regression analysis showed that Kleg was strongly associated with contact time (R2 = 0.797, P < 0.001), whereas Kvert was associated with spatiotemporal adaptations to different slope gradients (R2 = 0.547, P = 0.002). SIGNIFICANCE: An increased slope gradient (0-11%) at a given running velocity (12 km.h-1) caused spatiotemporal adaptations (i.e., increased CT and SF and decreased FT, SL and SA) regardless of the athletic level of the runner, although a non-significant trend differentiated the adaptations between the amateur and highly-trained groups. The results also indicated that leg stiffness plays a key role in the characteristics of spatiotemporal gait during level running, whereas vertical stiffness is strongly associated with spatiotemporal adaptations when running uphill.