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1.
BackgroundThe biomechanics of the trunk and lower limbs during walking and running gait are frequently assessed in individuals with low back pain (LBP). Despite substantial research, it is still unclear whether consistent and generalizable changes in walking or running gait occur in association with LBP. The purpose of this systematic review was to identify whether there are differences in biomechanics during walking and running gait in individuals with acute and persistent LBP compared with back-healthy controls.MethodsA search was conducted in PubMed, CINAHL, SPORTDiscus, and PsycINFO in June 2019 and was repeated in December 2020. Studies were included if they reported biomechanical characteristics of individuals with and without LBP during steady-state or perturbed walking and running. Biomechanical data included spatiotemporal, kinematic, kinetic, and electromyography variables. The reporting quality and potential for bias of each study was assessed. Data were pooled where possible to compare the standardized mean differences (SMD) between back pain and back-healthy control groups.ResultsNinety-seven studies were included and reviewed. Two studies investigated acute pain and the rest investigated persistent pain. Nine studies investigated running gait. Of the studies, 20% had high reporting quality/low risk of bias. In comparison with back-healthy controls, individuals with persistent LBP walked slower (SMD = –0.59, 95% confidence interval (95%CI): –0.77 to –0.42)) and with shorter stride length (SMD = –0.38, 95%CI: –0.60 to –0.16). There were no differences in the amplitude of motion in the thoracic or lumbar spine, pelvis, or hips in individuals with LBP. During walking, coordination of motion between the thorax and the lumbar spine/pelvis was significantly more in-phase in the persistent LBP groups (SMD = –0.60, 95%CI: –0.90 to –0.30), and individuals with persistent LBP exhibited greater amplitude of activation in the paraspinal muscles (SMD = 0.52, 95%CI: 0.23–0.80). There were no consistent differences in running biomechanics between groups.ConclusionThere is moderate-to-strong evidence that individuals with persistent LBP demonstrate differences in walking gait compared to back-healthy controls.  相似文献   

2.
BackgroundBone stress injuries (BSIs) are common in female runners, and recurrent BSI rates are high. Previous work suggests an association between higher impact loading during running and tibial BSI. However, it is unknown whether impact loading and fatigue-related loading changes discriminate women with a history of multiple BSIs. This study compared impact variables at the beginning of a treadmill run to exertion and the changes in those variables with exertion among female runners with no history of BSI as well as among those with a history of single or multiple BSIs.MethodsWe enrolled 45 female runners (aged 18–40 years) for this cross-sectional study: having no history of diagnosed lower extremity BSI (N-BSI, n = 14); a history of 1 lower extremity BSI (1-BSI, n = 16); and diagnosed by imaging, or a history of multiple (≥3) lower extremity BSIs (M-BSI, n = 15). Participants completed a 5-km race speed run on an instrumented treadmill while wearing an Inertial Measurement Unit. The vertical average loading rate (VALR), vertical instantaneous loading rate (VILR), vertical stiffness during impact via instrumented treadmill, and tibial shock determined as the peak positive tibial acceleration via Inertial Measurement Unit were measured at the beginning and the end of the run.ResultsThere were no differences between groups in VALR, VILR, vertical stiffness, or tibial shock in a fresh or exerted condition. However, compared to N-BSI, women with M-BSI had greater increase with exertion in VALR (–1.8% vs. 6.1%, p = 0.01) and VILR (1.5% vs. 4.8%, p = 0.03). Similarly, compared to N-BSI, vertical stiffness increased more with exertion among women with M-BSI (–0.9% vs. 7.3%, p = 0.006) and 1-BSI (–0.9% vs. 1.8%, p = 0.05). Finally, compared to N-BSI, the increase in tibial shock from fresh to exerted condition was greater among women with M-BSI (0.9% vs. 5.5%, p = 0.03) and 1-BSI (0.9% vs. 11.2%, p = 0.02).ConclusionWomen with 1-BSI or M-BSIs experience greater exertion-related increases in impact loading than women with N-BSI. These observations imply that exertion-related changes in gait biomechanics may contribute to risk of BSI.  相似文献   

3.
PurposeThis study used downhill running as a model to investigate the repeated bout effect (RBE) on neuromuscular performance, running biomechanics, and metabolic cost of running.MethodsTen healthy recreational male runners performed two 30-min bouts of downhill running (DR1 and DR2) at a –20% slope and 2.8 m/s 3 weeks apart. Neuromuscular fatigue, level running biomechanics during slow and fast running, and running economy parameters were recorded immediately before and after the downhill bouts, and at 24 h, 48 h, 72 h, 96 h, and 168 h thereafter (i.e., follow-up days).ResultsAn RBE was confirmed by attenuated muscle soreness and serum creatine kinase rise after DR2 compared to DR1. An RBE was also observed in maximum voluntary contraction (MVC) force loss and voluntary activation where DR2 resulted in attenuated MVC force loss and voluntary activation immediately after the run and during follow-up days. The downhill running protocol significantly influenced level running biomechanics; an RBE was observed in which center of mass excursion and, therefore, lower-extremity compliance were greater during follow-up days after DR1 compared to DR2. The observed changes in level running biomechanics did not influence the energy cost of running.ConclusionThis study demonstrated evidence of adaptation in neural drive as well as biomechanical changes with the RBE after DR. The higher neural drive resulted in attenuated MVC force loss after the second bout. It can be concluded that the RBE after downhill running manifests as changes to global and central fatigue parameters and running biomechanics without substantially altering the energy cost of running.  相似文献   

4.
BackgroundAdults with obesity may display disturbed cardiac chronotropic responses during cardiopulmonary exercise testing, which relates to poor cardiometabolic health and an increased risk for adverse cardiovascular events. It is unknown whether cardiac chronotropic incompetence (CI) during maximal exercise is already present in obese adolescents and, if so, how that relates to cardiometabolic health.MethodsSixty-nine obese adolescents (body mass index standard deviation score = 2.23 ± 0.32, age = 14.1 ± 1.2 years; mean ± SD) and 29 lean adolescents (body mass index standard deviation score = –0.16 ± 0.84, age = 14.0 ± 1.5 years) performed a maximal cardiopulmonary exercise testing from which indicators for peak performance were determined. The resting heart rate and peak heart rate were used to calculate the maximal chronotropic response index. Biochemistry (lipid profile, glycemic control, inflammation, and leptin) was studied in fasted blood samples and during an oral glucose tolerance test within obese adolescents. Regression analyses were applied to examine associations between the presence of CI and blood or exercise capacity parameters, respectively, within obese adolescents.ResultsCI was prevalent in 32 out of 69 obese adolescents (46%) and 3 out of 29 lean adolescents (10%). C-reactive protein was significantly higher in obese adolescents with CI compared to obese adolescents without CI (p = 0.012). Furthermore, peak oxygen uptake and peak cycling power output were significantly reduced (p < 0.05) in obese adolescents with CI vs. obese adolescents without CI. The chronotropic index was independently related to blood total cholesterol (standardized coefficient β = –0.332; p = 0.012) and C-reactive protein concentration (standardized coefficient β = –0.269; p = 0.039).ConclusionCI is more common in the current cohort of obese adolescents, and is related to systemic inflammation and exercise intolerance.  相似文献   

5.
Purpose. We aimed to determine the effect of speed-induced changes in foot contact patterns on the vertical instantaneous loading rate (VILR). We hypothesized that transition runners, i.e. runners that shift towards a mid- (MF) or forefoot contact pattern (FF) when running speed increases, show smaller increases in VILR than non-transition runners, i.e. runners that remain with a rearfoot contact pattern (RF).

Methods. Fifty-two male and female runners ran overground at 3.2, 4.1, 5.1 and 6.2?m?s?1. Ground reaction forces, lower limb sagittal plane knee and ankle kinematics and plantar pressures were recorded. Multi-level linear regression models were used to assess differences between transition and non-transition runners.

Results. Non-transition runners experienced larger speed-induced increases in VILR (48.6?±?2.6?BW?s?1 per m?s?1) than transition runners (–1.4?±?7.6?BW?s?1 per m?s?1). Transition runners showed higher VILRs and a more flat foot touch down at the same pre-transition speed than non-transition runners.

Conclusion. When running speed increases, some runners transition towards more anterior foot contact patterns. This reduces or even eliminates the speed-induced increase in VILR. This result is especially the case for those RF runners who already have relatively high VILRs and flat foot positioning at slower running speeds.  相似文献   

6.
A two‐dimensional, dynamic bioengineering model of the lower limbs was developed in order to estimate muscle and joint forces present during running at 4.5 m s ‐1. Data were collected from four subjects using a force platform and cine film. Individual X‐rays and anthropometric data from the lower limbs were utilized to produce accurate bone models of the subjects’ legs. Electromyographic verification of the model was undertaken while a runner was undergoing treadmill running at 4.5 m s‐1. Results indicate that peak muscle forces of 22 times subject body weight (22 BW) could be present in the quadriceps muscle group and 7 BW in the gastrocnemius. The anterior shin muscles were found to be active for the first 9% of stance phase only, and compressive loads of 33 BW were found in the knee joint. The relationship between these nigh forces in the lower limbs and running related injuries is discussed.  相似文献   

7.
The effect of textured insoles on kinetics and kinematics of overground running was assessed. 16 male injury-free-recreational runners attended a single visit (age 23?±?5 yrs; stature 1.78?±?0.06 m; mass 72.6?±?9.2?kg). Overground 15-m runs were completed in flat, canvas plimsolls both with and without textured insoles at self-selected velocity on an indoor track in an order that was balanced among participants. Average vertical loading rate and peak vertical force (Fpeak) were captured by force platforms. Video footage was digitised for sagittal plane hip, knee and ankle angles at foot strike and mid stance. Velocity, stride rate and length and contact and flight time were determined. Subjectively rated plantar sensation was recorded by visual scale. 95% confidence intervals estimated mean differences. Smallest worthwhile change in loading rate was defined as standardised reduction of 0.54 from a previous comparison of injured versus non-injured runners. Loading rate decreased (?25 to ?9.3?BW?s?1; 60% likely beneficial reduction) and plantar sensation was increased (46–58?mm) with the insole. Fpeak (?0.1 to 0.14?BW) and velocity (?0.02 to 0.06?m?s?1) were similar. Stride length, flight and contact time were lower (?0.13 to ?0.01 m; ?0.02 to?0.01?s; ?0.016 to ?0.006?s) and stride rate was higher (0.01–0.07 steps?s?1) with insoles. Textured insoles elicited an acute, meaningful decrease in vertical loading rate in short distance, overground running and were associated with subjectively increased plantar sensation. Reduced vertical loading rate could be explained by altered stride characteristics.  相似文献   

8.
ABSTRACT

Loading rates have been linked to running injuries, revealing persistent impact features that change direction among three-dimensional axes in different footwear and footstrike patterns. Extracting peak loads from ground reaction forces, however, can neglect the time-varying loading patterns experienced by the runner in each footfall. Following footwear and footstrike manipulations during laboratory-based overground running, we examined three-dimensional loading rate-time features in each direction (X, Y, Z) using principal component analysis. Twenty participants (9 M, 11 F, age: 25.3 ± 3.6 y) were analysed during 14 running trials in each of two footwear (cushioned and minimalist) and three footstrike conditions (forefoot, midfoot, rearfoot). Two principal components (PC) captured the primary loading rate-time features (PC1: 42.5% and PC2: 22.8% explained variance) and revealed interaction among axes, footwear, and footstrike conditions (PC1: F (2.1, 40.1) = 5.6, p = 0.007, η 2 = 0.23; PC2: F (2.0, 38.4) = 62.3, p < 0.001, η 2 = 0.77). Rearfoot running in cushioned footwear attenuated impact loads in the vertical direction, and forefoot running in minimalist footwear attenuated impact loads in the anterior-posterior and medial-lateral directions relative to forefoot running in cushioned shoes. Loading patterns depend on footwear and footstrike interactions, which require shoes that match the runner’s footstrike pattern.  相似文献   

9.
ABSTRACT

Purpose: The present study aimed to compare the vertical ground reaction force responses during the performance of the stationary running water-based exercise with and without equipment at different cadences by elderly women. Method: Nineteen elderly women (age: 68.6 ± 5.0 years; body mass: 69.0 ± 9.5 kg; height: 154.9 ± 5.6 cm) completed one session consisting of the performance of the water-based stationary running with elbow flexion and extension immersed to the xiphoid process depth. The exercise was performed in three conditions, without equipment, with water-floating and with water-resistance equipment, at three cadences (80 b·min?1, 100 b·min?1 and maximal) in a randomized order. Peak and impulse of vertical ground reaction force were collected during the exercise using an underwater force plate. Repeated measures two-way ANOVA was used (α = 0.05). Results: Peak vertical ground reaction force (p < .001) and impulse (p ≤ 0.002) resulted in lower values for the water-floating use (0.42–0.48 BW and 0.07–0.13 N.s/BW) in comparison to the water-resistance equipment use (0.46–0.60 BW and 0.09–0.16 N.s/BW) and to the non-use of equipment (0.45–0.60 BW and 0.07–0.17 N.s/BW), except for the impulse at the maximal cadence. In addition, peak vertical ground reaction force at 80 b·min?1 (p = .002) and impulse at the maximal cadence (p < .001) showed lower values compared to the other cadences. Conclusion: The use of water-floating equipment minimizes the vertical ground reaction force during the stationary running water-based exercise performed by elderly women regardless of the cadence.  相似文献   

10.
ABSTRACT

Running-related injuries have been associated with excessive foot pronation and high vertical loading rates. Traditional plaster-molded (TPM) foot orthoses are commonly prescribed to minimize these atypical biomechanical patterns. Recently, 3D printed (3DP) orthoses have become popular, yet the functional difference between these two types of orthoses remains unknown. Therefore, this study compared running biomechanics and perceived comfort during treadmill running in three orthotic conditions: 3DP orthoses, TPM orthoses, and a no-orthoses control condition (CON). Thirteen female asymptomatic runners with excessive foot pronation were recruited. Rearfoot eversion angle and velocity (at initial contact and peak) during stance, vertical loading rates, and perceived comfort were compared. Results showed lower peak rearfoot eversion angles during running with TPM (p=0.001, d=0.38) or 3DP orthoses (p=0.002, d=0.24) than CON. No differences were observed in other biomechanical parameters among the three conditions (p>0.05). Running with TPM (p≤0.001, d=1.74–1.82) and 3DP orthoses (p<0.003, d=1.06–1.34) resulted in better perceived comfort in “medial-lateral control” and “heel cushioning” than CON. There were no statistical differences in all parameters between TPM and 3DP orthoses. The present findings indicate improved comfort during running with TPM or 3DP orthoses, which hinted 3DP orthoses could be a viable alternative to TPM orthoses for clinical practice.  相似文献   

11.
BackgroundThere is controversial evidence regarding the effect of acute resistance exercise (ARE) on heart rate variability (HRV) parameters, which indicates the activities of the cardiac autonomic nervous system. The aim of this study was to perform a systematic review and meta-analysis of the literature on the effect of ARE on HRV parameters and identify its possible moderating factors.MethodsThe PubMed–Medline, Web of Science, SPORTDiscus, and Cochrane Library databases were searched. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) declaration was followed, and the methodological quality of the studies was evaluated. The level of significance was set at p ≤ 0.05. Twenty-six studies met the inclusion criteria. Main effect analyses between pre- and post-test interventions demonstrated an increase in normalized units low frequency (p < 0.001; standardized mean difference (SMD) = 0.78; 95% confidence interval (95%CI): 0.46?1.11) and low frequency/high frequency ratio (p < 0.001; SMD = 0.82; 95%CI: 0.64?0.99) and a decrease in standard deviation of the normal-to-normal (NN) interval (p < 0.001; SMD = –0.58; 95%CI: –0.85 to –0.30), root mean square of the successive differences (p < 0.001; SMD = –1.01; 95%CI: –1.29 to –0.74), and normalized units high frequency (p < 0.001; SMD: –1.08; 95%CI: –1.43 to –0.73) following ARE in healthy individuals range: 15 ± 1 to 48 ± 2 years; mean ± SD).ResultsThere were differences between the subgroups in the number of sets used in an exercise (p = 0.05) for root mean square of the successive differences, as well as for exercise intensity (p = 0.01) and rest between sets (p = 0.05) for normalized units high frequency. Interestingly, there were differences between the subgroups in training volume for root mean square of the successive differences (p = 0.01), normalized units high frequency (p = 0.003) and normalized units low frequency (p = 0.02).ConclusionOverall, there was a withdrawal of cardiac parasympathetic and activation of cardiac sympathetic modulations following ARE, and these changes were greater with higher training volume ～30 min after ARE in healthy individuals. Furthermore, the number of sets, intensity, and rest between sets affected HRV parameters. However, gender, body mass index, and training status did not influence the changes in HRV parameters as a response to ARE.  相似文献   

12.
Runners often experience delayed onset muscle soreness (DOMS), especially of the knee extensors, following prolonged running. Sagittal knee joint biomechanics are altered in the presence of knee extensor DOMS but it is unclear how muscle soreness affects lower limb biomechanics in other planes of motion. The purpose of this study was to assess the effects of knee extensor DOMS on three-dimensional (3D) lower limb biomechanics during running. Thirty-three healthy men (25.8?±?6.8 years; 84.1?±?9.2?kg; 1.77?±?0.07?m) completed an isolated eccentric knee extensor damaging protocol to elicit DOMS. Biomechanics of over-ground running at a set speed of 3.35?m?s?1±5% were measured before eccentric exercise (baseline) and, 24?h and 48?h following exercise in the presence of knee extensor DOMS. Knee flexion ROM was reduced at 48?h (P?=?0.01; d?=?0.26), and peak knee extensor moment was reduced at 24?h (P?=?0.001; d?=?0.49) and 48?h (P?<?0.001; d?=?0.68) compared to baseline. Frontal and transverse plane biomechanics were unaffected by the presence of DOMS (P?>?0.05). Peak positive ankle and knee joint powers and, peak negative knee joint power were all reduced from baseline to 24?h and 48?h (P?<?0.05). These findings suggest that knee extensor DOMS greatly influences sagittal knee joint angular kinetics and, reduces sagittal power production at the ankle joint. However, knee extensor DOMS does not affect frontal and transverse plane lower limb joint biomechanics during running.  相似文献   

13.
PurposeThe purpose of this study was to compare the effects of intermittent sprint training and plyometric training on endurance running performance.MethodsFourteen moderately trained male endurance runners were allocated into either the intermittent sprint training group (n = 7) or the plyometric training group (n = 7). The preliminary tests required subjects to perform a treadmill graded exercise test, a countermovement jump test for peak power measurement, and a 10-km time trial. Training included 12 sessions of either intermittent sprint or plyometric training carried out twice per week. On completion of the intervention, post-tests were conducted.ResultsBoth groups showed significant reduction in weekly training mileage from pre-intervention during the intervention period. There were significant improvements in the 10-km time trial performance and peak power. There was also significant improvement in relative peak power for both groups. The 10-km time trial performance and relative peak power showed a moderate inverse correlation.ConclusionThese findings showed that both intermittent sprint and plyometric training resulted in improved 10-km running performance despite reduction in training mileage. The improvement in running performance was accompanied by an improvement in peak power and showed an inverse relationship with relative peak power.  相似文献   

14.
There are differences in ground reaction force when wearing soccer boots compared with training shoes on a natural turf surface. Two natural-turf-covered force platforms, located outdoors in a field, allowed comparison of performance when six-studded soccer boots and soccer training shoes were worn during straight fast running (5.4 m s-1 ± 0.27 m s-1) and slow running (4.4 ms-1 ± 0.22 m s-1). Six male soccer players (mean age: 25 ± 4.18 years; mean mass 79.7 ±9.32 kg) struck the first platform with the right foot and the second platform with the left foot. In fast running, the mean vertical impact peak was significantly greater in soccer boots (2.706 BW) than in training shoes (2.496 BW) when both the right and left foot were considered together and averaged (P = 0.003). Similarly, the mean vertical impact peak loading rate was greater when wearing soccer boots at 26.09 BWs-1 compared to training shoes (21.32 BWs-1;P = 0.002). Notably, the mean vertical impact peak loading rate of the left foot (boots: 28.07 BWs-1; shoes: 22.52 BWs-1) was significantly greater than the right foot (boots: 24.11 BWs-1; shoes: 20.11 BWs-1) in both boots and shoes (P = 0.018). The braking force was greater for the left foot (P = 0.013). In contrast, mean peak vertical propulsion forces were greater for the right foot (P > 0.001) when either soccer boots or training shoes were considered. Similar significant trends were evident in slow running, and, notably, in both soccer boots and training shoes medial forces were greater for the left foot (P = 0.008) and lateral forces greater for the right foot (P = 0.011). This study showed the natural turf ground reaction force measurement system can highlight differences in footwear in an ecological environment. Greater forces and impact loading rates occurred during running activity in soccer boots than in training shoes, with soccer boots showing reduced shock attenuation at impact. Such findings may have implications for impact-related injuries with sustained exposure, especially on harder natural-turf surfaces. There were differences in the forces occurring at the right and left feet with the ground, thus suggesting the use of bipedal monitoring of ground reaction forces.  相似文献   

15.
Purpose:We aimed to perform a systematic review and meta-analysis of the effects of training to muscle failure or non-failure on muscular strength and hypertrophy.Methods:Meta-analyses of effect sizes(ESs)explored the effects of training to failure vs.non-failure on strength and hypertrophy.Subgroup meta-analyses explored potential moderating effects of variables such as training status(trained vs.untrained),training volume(volume equated vs.volume non-equated),body region(upper vs.lower),exercise selection(multi-vs.single-joint exercises(only for strength)),and study design(independent vs.dependent groups).Results:Fifteen studies were included in the review.All studies included young adults as participants.Meta-analysis indicated no significant difference between the training conditions for muscular strength(ES=-0.09,95%confidence interval(95%CI):-0.22 to 0.05)and for hypertrophy(ES=0.22,95%CI:-0.11 to 0.55).Subgroup analyses that stratified the studies according to body region,exercise selection,or study design showed no significant differences between training conditions.In studies that did not equate training volume between the groups,the analysis showed significant favoring of non-failure training on strength gains(ES=-0.32,95%CI:-0.57 to-0.07).In the subgroup analysis for resistance-trained individuals,the analysis showed a significant effect of training to failure for muscle hypertrophy(ES=0.15,95%CI:0.03-0.26).Conclusion:Training to muscle failure does not seem to be required for gains in strength and muscle size.However,training in this manner does not seem to have detrimental effects on these adaptations,either.More studies should be conducted among older adults and highly trained individuals to improve the generalizability of these findings.  相似文献   

16.
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17.
BackgroundRegular physical activity (PA) has been postulated to improve, or at least maintain, immunity across the life span. However, the link between physical (in)activity and coronavirus disease 2019 (COVID-19) remains to be established. This small-scale prospective cohort study is nested within a randomized controlled trial aimed to investigate the possible associations between PA levels and clinical outcomes among hospitalized patients with moderate to severe COVID-19.MethodsHospitalized patients with COVID-19 (mean age: 54.9 years) were recruited from the Clinical Hospital of the School of Medicine of the University of Sao Paulo (a quaternary referral teaching hospital) and from Ibirapuera Field Hospital, both located in Sao Paulo, Brazil. PA level was assessed using the Baecke Questionnaire of Habitual Physical Activity. The primary outcome was hospital length of stay. The secondary outcomes were mortality, admission to the intensive care unit (ICU), and mechanical ventilation requirement.ResultsThe median hospital length of stay was 7.0 ± 4.0 days, median ± IQR; 3.3% of patients died, 13.8% were admitted to the ICU, and 8.6% required mechanical ventilation. Adjusted linear regression models showed that PA indices were not associated with hospital length of stay (work index: β = –0.57 (95% confidence interval (95%CI): –1.80 to 0.65), p = 0.355; sport index: β = 0.43 (95%CI: –0.94 to 1.80), p = 0.536; leisure-time index: β = 1.18 (95%CI: –0.22 to 2.59), p = 0.099; and total activity index: β = 0.20 (95%CI: –0.48 to 0.87), p = 0.563). None of the PA indices were associated with mortality, admission to the ICU, or mechanical ventilation requirement (all p > 0.050).ConclusionAmong hospitalized patients with COVID-19, PA did not independently associate with hospital length of stay or any other clinically relevant outcomes. These findings should be interpreted as meaning that, among already hospitalized patients with more severe forms of COVID-19, being active is a potential protective factor likely outweighed by a cluster of comorbidities (e.g., type 2 diabetes, hypertension, weight excess) and older age, suggesting that the benefit of PA against the worsening of COVID-19 may vary across stages of the disease.  相似文献   

18.
PurposeTo evaluate the potential of a year-round school calendar (180-day school year distributed across 12 months) as an intervention compared to a traditional school calendar (180-day school year distributed across 9 months) for mitigating children's weight gain and fitness loss via a natural experiment.MethodsHeight, weight, and cardiorespiratory fitness (CRF) (i.e., Fitnessgram Progressive Aerobic Cardiovascular Endurance Run) were measured in children (5–12 years old) in 3 schools (2 traditional, 1 year-round, n = 990 students, age = 8.6 ± 2.4 years, 53.1% male, 68.9% African American) from 1 school district. Structure (represented by the presence of a school day) was the independent variable. Changes in body mass index (BMI), age- and sex-specific BMI z-scores (zBMI), BMI percentile, percent of overweight or obese children, and CRF (Progressive Aerobic Cardiovascular Endurance Run laps completed) were assessed for summer 2017 (May–August 2017), school year 2017/2018 (August 2017–May 2018), and summer 2018 (May–August 2018). Primary analyses examined the overall change in weight and CRF from summer 2017 until summer 2018 via multilevel mixed effects regression, with group (traditional vs. year-round calendar), time, and a group-by-time interaction as the independent variables. Secondary regression analyses estimated differences in change within and between groups during each time period, separately.ResultsYear-round students gained less BMI (difference in ∆ = –0.44, 95% confidence interval (CI): –0.67 to –0.03) and less CRF (difference in ∆ = –1.92, 95%CI: –3.56 to –0.28) than students attending a traditional school overall. Compared with traditional students, during both summers, year-round students gained less BMI (summer 2017 difference in ∆ = –0.15, 95%CI: –0.21 to –0.08; summer 2018 difference in ∆ = –0.16, 95%CI: –0.24 to –0.07) and zBMI (summer 2017 difference in ∆ = –0.032, 95%CI: –0.050 to –0.010; summer 2018 difference in ∆ = –0.033, 95%CI: –0.056 to –0.009), and increased CRF (summer 2017 difference in ∆ = 0.40, 95%CI: 0.02–0.85; summer 2018 difference in ∆ = 0.23, 95%CI: –0.25 to 0.74). However, the opposite was observed for the school year, with traditional students gaining less BMI and zBMI and increasing CRF compared with year-round students (difference in BMI ∆ = 0.05, 95%CI: 0.03–0.07; difference in zBMI ∆ = 0.012, 95%CI: 0.005–0.019; difference in Progressive Aerobic Cardiovascular Endurance Run laps ∆ = –0.43, 95%CI: –0.58 to –0.28).ConclusionThe year-round school calendar had a small beneficial impact on children's weight status but not CRF. It is unclear if this benefit to children's weight would be maintained because gains made in the summer were largely erased during the school year. Trajectories of weight and CRF gain/loss were consistent with the structured days hypothesis.  相似文献   

19.
BackgroundTibial stress fracture (TSF) is an overuse running injury with a long recovery period. While many running studies refer to biomechanical risk factors for TSF, only a few have compared biomechanics in runners with TSF to controls. The aim of this systematic review and meta-analysis was to evaluate biomechanics in runners with TSF compared to controls.MethodsElectronic databases PubMed, Web of Science, SPORTDiscus, Scopus, Cochrane, and CINAHL were searched. Risk of bias was assessed and meta-analysis conducted for variables reported in 3 or more studies.ResultsThe search retrieved 359 unique records, but only the 14 that compared runners with TSF to controls were included in the review. Most studies were retrospective, 2 were prospective, and most had a small sample size (5–30 per group). Many variables were not significantly different between groups. Meta-analysis of peak impact, active, and braking ground reaction forces found no significant differences between groups. Individual studies found larger tibial peak anterior tensile stress, peak posterior compressive stress, peak axial acceleration, peak rearfoot eversion, and hip adduction in the TSF group.ConclusionMeta-analysis indicated that discrete ground reaction force variables were not statistically significantly different in runners with TSF compared to controls. In individual included studies, many biomechanical variables were not statistically significantly different between groups. However, many were reported by only a single study, and sample sizes were small. We encourage additional studies with larger sample sizes of runners with TSF and controls and adequate statistical power to confirm or refute these findings.  相似文献   

20.
A two-dimensional, dynamic bioengineering model of the lower limbs was developed in order to estimate muscle and joint forces present during running at 4.5 m s-1. Data were collected from four subjects using a force platform and cine film. Individual X-rays and anthropometric data from the lower limbs were utilized to produce accurate bone models of the subjects' legs. Electromyographic verification of the model was undertaken while a runner was undergoing treadmill running at 4.5 m s-1. Results indicate that peak muscle forces of 22 times subject body weight (22 BW) could be present in the quadriceps muscle group and 7 BW in the gastrocnemius. The anterior shin muscles were found to be active for the first 9% of stance phase only, and compressive loads of 33 BW were found in the knee joint. The relationship between these high forces in the lower limbs and running related injuries is discussed.  相似文献   

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