Validation of a commercially available markerless motion-capture system for trunk and lower extremity kinematics during a jump-landing assessment

Context: Field-based, portable motion-capture systems can be used to help identify individuals at greater risk of lower extremity injury. Microsoft Kinect-based markerless motion-capture systems meet these requirements; however, until recently, these systems were generally not automated, required substantial data postprocessing, and were not commercially available. Objective: To validate the kinematic measures of a commercially available markerless motion-capture system. Design: Descriptive laboratory study. Setting: Laboratory. Patients or Other Participants: A total of 20 healthy, physically active university students (10 males, 10 females; age ¼ 20.50 6 2.78 years, height ¼ 170.36 6 9.82 cm, mass ¼ 68.38 6 10.07 kg, body mass index ¼ 23.50 6 2.40 kg/m2). Intervention(s): Participants completed 5 jump-landing trials. Kinematic data were simultaneously recorded using Kinect-based markerless and stereophotogrammetric motion-capture systems. Main Outcome Measure(s): Sagittal- and frontal-plane trunk, hip-joint, and knee-joint angles were identified at initial ground contact of the jump landing (IC), for the maximum joint angle during the landing phase of the initial landing (MAX), and for the joint-angle displacement from IC to MAX (DSP). Outliers were removed, and data were averaged across trials. We used intraclass correlation coefficients (ICCs [2,1]) to assess intersystem reliability and the paired-samples t test to examine mean differences (a < .05). Results: Agreement existed between the systems (ICC range ¼1.52 to 0.96; ICC average ¼ 0.58), with 75.00% (n ¼ 24/ 32) of the measures being validated (P < .05). Agreement was better for sagittal- (ICC average ¼ 0.84) than frontal- (ICC average ¼ 0.35) plane measures. Agreement was best for MAX (ICC average ¼ 0.77) compared with IC (ICC average ¼ 0.56) and DSP (ICC average ¼ 0.41) measures. Pairwise comparisons identified differences for 18.75% (6/32) of the measures. Fewer differences were observed for sagittal- (0.00%; 0/15) than for frontal- (35.29%; 6/17) plane measures. Between-systems differences were equivalent for MAX (18.18%; 2/11), DSP (18.18%; 2/11), and IC (20.00%; 2/10) measures. The markerless system underestimated sagittal-plane measures (86.67%; 13/15) and overestimated frontal-plane measures (76.47%; 13/ 17). No trends were observed for overestimating or underestimating IC, MAX, or DSP measures. Conclusions: Moderate agreement existed between markerless and stereophotogrammetric motion-capture systems. Better agreement existed for larger (eg, sagittal-plane, MAX) than for smaller (eg, frontal-plane, IC) joint angles. The DSP angles had the worst agreement. Markerless motion-capture systems may help clinicians identify individuals at greater risk of lower extremity injury

Movement profile influences systemic stress and biomechanical resilience to high training load exposure

Objectives: Determine the influence of movement profile on systemic stress and mechanical loading before and after high training load exposure. Design: Cross-sectional cohort study. Methods: 43 physically active, college-aged field or court sport female athletes participated in this study. Participants were assigned to a “excellent” (n = 22; age = 20.5 ± 1.9 yrs, height = 1.67 ± 0.67 m, mass = 64.5 ± 7.8 kg) or “poor” (n = 21; age = 20.4 ± 1.3 yrs, height = 1.69 ± 0.67 m, mass = 60.9 ± 6.1 kg) movement group defined by The Landing Error Scoring System. Participants completed five cycles of high training load exercise of 5-min treadmill-running at a speed coincident with 100–120% ventilatory threshold and 10 jump-landings from a 30-cm box. Jump-landing vertical ground reaction force and serum cortisol were evaluated prior to and following exercise. Vertical ground reaction force ensemble averages and 95% confidence interval waveforms were generated for pre-exercise, post-exercise, and pre-post exercise changes. A two-way mixed model ANOVA was used to evaluate the effect of movement profile on systemic stress before and after exercise. Results: There was no significant difference in changes in serum cortisol between the poor and excellent groups (p = 0.69) in response to exercise. Overall, individuals in the poor group exhibited a higher serum cortisol level (p < 0.05, d = 0.85 [0.19,1.48]). The poor group exhibited higher magnitude vertical ground reaction force prior to (d = 1.02–1.26) and after exercise (d = 1.15) during a majority of the stance phase. Conclusions: Individuals with poor movement profiles experience greater mechanical loads compared to individuals with excellent movement profiles. A poor movement profile is associated with greater overall concentrations of circulating cortisol, representative of greater systemic stress

Trunk and lower extremity movement patterns, stress fracture risk factors, and biomarkers of bone turnover in military trainees

Context: Military service members commonly sustain lower extremity stress fractures (SFx). How SFx risk factors influence bone metabolism is unknown. Understanding how SFx risk factors influence bone metabolism may help to optimize risk-mitigation strategies. Objective: To determine how SFx risk factors influence bone metabolism. Design: Cross-sectional study. Setting: Military service academy. Patients or Other Participants: Forty-five men (agepre ¼ 18.56 6 1.39 years, heightpre ¼ 176.95 6 7.29 cm, masspre ¼ 77.20 6 9.40 kg; body mass indexpre ¼ 24.68 6 2.87) who completed Cadet Basic Training (CBT). Individuals with neurologic or metabolic disorders were excluded. Intervention(s): We assessed SFx risk factors (independent variables) with (1) the Landing Error Scoring System (LESS), (2) self-reported injury and physical activity questionnaires, and (3) physical fitness tests. We assessed bone biomarkers (dependent variables; procollagen type I amino-terminal propeptide [PINP] and cross-linked collagen telopeptide [CTx-1]) via serum. Main Outcome Measure(s): A markerless motion-capture system was used to analyze trunk and lower extremity biomechanics via the LESS. Serum samples were collected post-CBT; enzyme-linked immunosorbent assays determined PINP and CTx-1 concentrations, and PINP: CTx-1 ratios were calculated. Linear regression models demonstrated associations between SFx risk factors and PINP and CTx-1 concentrations and PINP: CTx-1 ratio. Biomarker concentration mean differences with 95% confidence intervals were calculated. Significance was set a priori using a ≤ .10 for simple and a ≤ .05 for multiple regression analyses. Results: The multiple regression models incorporating LESS and SFx risk factor data predicted the PINP concentration (R2 ¼ 0.47, P ¼ .02) and PINP: CTx-1 ratio (R2 ¼ 0.66, P ¼ .01). The PINP concentration was increased by foot internal rotation, trunk flexion, CBT injury, sit-up score, and pre- to post-CBT mass changes. The CTx-1 concentration was increased by heel-to-toe landing and post-CBT mass. The PINP: CTx-1 ratio was increased by foot internal rotation, lower extremity sagittal-plane displacement (inversely), CBT injury, sit-up score, and pre- to post-CBT mass changes. Conclusions: Stress fracture risk factors accounted for 66% of the PINP: CTx-1 ratio variability, a potential surrogate for bone health. Our findings provide insight into how SFx risk factors influence bone health. This information can help guide SFx risk-mitigation strategies

Exercise training biomarkers: Influence of short-term diet modification on the blood lactate to rating of perceived exertion (La:RPE) ratio

This study examined the effect of dietary consumption of carbohydrates (CHO) on the blood lactate to rating of perceived exertion (La:RPE) ratio during an intense micro-cycle of exercise training. This ratio is a proposed biomarker of exercise training stress and potential indicator for under- or overtraining in athletes. Sixteen male athletes were randomly assigned into two groups; high CHO (H-CHO; 60% of daily caloric intake) and low CHO (L-CHO; 30% of daily caloric intake). Diets were controlled the day before and for the three days of the micro-cycle. The micro-cycle consisted of three successive days of 60 minutes of intense cycling (∼70% of VO2peak). Blood samples were obtained immediately before and after exercise (post) on each day of exercise training (D1, D2, D3) and were analyzed for blood lactate. Rating of perceived exertion (RPE) scores were taken at the end of each exercise session and combined with the post exercise lactate value to form the La:RPE ratio. An analysis of variance (ANOVA) showed a significant difference between the La:RPE ratio for the H-CHO and L-CHO groups at D3 even though the exercise intensity was not significantly different between the groups. Specifically, the ratio was significantly (p < 0.02) lower on D3 in the L-CHO group (∼31% lower) than in the H-CHO group. From these findings it is recommended that diet needs to be monitored when using the La:RPE ratio as an exercise training biomarker to determine whether an athlete is truly under-training or overtraining. Athletes or coaches that use the La:RPE ratio as a training biomarker, but do not monitor dietary CHO intake need to interpreted their findings carefully

Characterization of the cortisol response to incremental exercise in physically active young men

This study examined the cortisol response to incremental exercise; specifically to see if there was an increase in blood cortisol levels at low intensity exercise (i.e., <60% VO2 intensity threshold) and determine whether a linear relationship existed between the blood cortisol responses and exercise of increasing workloads (i.e., intensity). Healthy, physically active young men (n=11) completed exercise tests involving progressive workload stages (3 min) to determine peak oxygen uptake responses (VO2). Blood specimens were collected at rest and at the end of each stage and analyzed for cortisol. Results showed cortisol was significantly increased from resting levels at the end of the first exercise stage (80 W; 41.9±5.4% peak VO2) and remained significantly elevated from rest until the exercise ended. Interestingly, however, the cortisol concentrations observed at 80 W through 200 W did not significantly differ from one another. Thereafter, during the final two stages of exercise the cortisol concentrations increased further (p<0.01). The subjects exceeded their individual lactate thresholds over these last two stages of exercise. Regression modeling to characterize the cortisol response resulted in significant regression coefficients (r=0.415 [linear] and r=0.655 [3 rd order polynominal], respectively; p<0.05). Comparative testing (Hotelling test) between the two regression coefficents revealed the polynominal model (sigmoidal curve) was the significantly stronger of the two (p=0.05). In conclusion, the present findings refute the concept that low intensity exercise will not provoke a significant change in blood cortisol levels and suggest the response to incremental exercise involving increasing exercise workloads (i.e., intensities) are not entirely linear in nature. Specifically, a sigmoid curve more highly accurately characterizes the cortisol response to such exercise

Exercise and Training Effects on Appetite-Regulating Hormones in Individuals with Obesity

International audienceThe prevalence of obesity in the world is increasing rapidly, and the associated morbidity and mortality require crucial need for non-pharmacological and therapeutic intervention to reduce alteration of appetite, food intake, and gut hormones. The effectiveness of this non-pharmacological intervention for weight management is due to probable alteration in gut hormones which regulating appetite and food intake. There are several types of hormones that control an individual’s appetite. In this study, researchers focused on major hormones of appetite regulation, ghrelin, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), cholecystokinin (CCK), leptin, and oxyntomodulin (OXN). Obese individuals were believed to have lower energy expenditure (EE) rates compared to normal and overweight ones. As such it is important to increase EE through exercise. The decrease in energy expenditure is partly due to a reduction in lean mass, the component of the body responsible for most of the energy expenditure of rest, which is found during diet. In addition, adaptive responses to weight loss are associated with many hormonal changes, including a decrease in leptin, insulin, intestinal peptide PYY, and sympathetic nervous system activity, with an increase in tissue sensitivity to insulin and circulating levels of ghrelin. Studies have shown that aerobic or resistance training resulted in slightly higher or no changes in circulating levels of these hormones, while other studies in normal-weight or overweight individuals found an interesting result about more intense physical exercise. They suggested that this type of exercise could affect ghrelin by decreasing the secretion of this peptide and stimulating that of another gastrointestinal peptide antagonist, the PYY. Intense physical exercise decreases energy intake in normal-weight and overweight individual. Further studies are required to confirm those results in obese individual. © 2020, Springer Nature Switzerland AG

Competition effects on physiological responses to exercise: Performance, cardiorespiratory and hormonal factors

The purpose of this study was to explore the mechanisms for increased exercise performance in conditions of competition. Endurance trained subjects (n=14) performed incremental treadmill running to exhaustion in control laboratory conditions (non-competition) and in conditions of simulated competition to assess performance (running duration). Heart rate and respiration gases were monitored continuously through each exercise condition. Blood lactate, cortisol, growth hormone and testosterone concentrations were also determined at pre- (rest) and postexercise in each condition. Results indicated competition exercise performance was significantly increased 4.2% (+49 sec; p0.05). These findings support that in competitive situations the affective state (motivation) experienced by athletes can enhance performance in exercise events, and lead to an increased peak oxygen uptake. The magnitude of the improvement is of a substantial nature and of a level seen with some training programs. Competitive conditions also augment the cortisol response to exercise, suggesting that enhanced sympatho-adrenal system activation occur in such situations which may be one of the key “driving forces” to performance improvement

Effects of preterm birth and fetal growth retardation on life-course cardiovascular risk factors among schoolchildren from Colombia: The FUPRECOL study

Background Both fetal growth restriction and prematurity have been associated with cardiometabolic risk in youth and adults, however, data on their combined effects on cardiometabolic health in youth are scarce. Aims This study aimed at assessing the effects of birth weight and gestational age combined on life-course cardiovascular risk factors and obesity among schoolchildren from Colombia. Study design A cross-sectional study. Subjects Participants comprised 2510 Colombian schoolchildren (54.8% girls) aged 9–17.9 years. Outcome measures Four groups were created according to WHO criteria: those born at term with an appropriate birth weight (? 2500 g to ? 4000 g) for gestational age (term AGA); those born preterm ( less than  37 to less than  42 completed weeks) with an appropriate birth weight for gestational age (preterm AGA); those born at term with low birth weight for gestational age (term SGA); and those born preterm with low birth weight for gestational age (preterm SGA). Anthropometric markers (body mass, height, waist circumference, and body mass index), blood pressure, lipids profile, fasting glucose, and pubertal stage were assessed. The prevalence of metabolic syndrome was determined by de Ferranti definition. Results There were differences between the 4 groups for calendar age (p = 0.011), body mass (p = 0.001), height (p = 0.001), and body mass index (p = 0.027). Overall, preterm SGA group had a greater risk for having elevated fasting glucose and metabolic syndrome (total sample and in boys) compared with term AGA group (p  less than  0.05). For other cardiovascular risk factors, no significant relationships were observed based on birth characteristics. Conclusions School-age children and adolescents with combined fetal growth restriction and prematurity exhibited an increased prevalence of glucose risk and metabolic syndrome. © 201