Posterior chain and core training improves pelvic posture, hamstrings-to-quadriceps ratio, and vertical jump performance.

BACKGROUND: Poor pelvic posture demonstrated through anterior pelvic tilt (APT) have been known to produce musculoskeletal imbalances involving weakness of the abdominal and pelvic musculature. While stretching and massage techniques have been reported to be effective in alleviating APT, it remains unclear if similar improvements can be elicited by posterior chain and core strength training. Therefore, the aim of this study was to examine the effect of an 8-week posterior and core strengthening program on APT, hamstrings-to-quadriceps (H:Q) strength ratio, and vertical jump performance in healthy individuals. METHODS: Ten healthy males (age = 26±12 years; mass = 87±14 kg; height = 1.8±0.1 m) and nine healthy females (age = 22±4 years; mass = 70±14 kg; heigh t = 1.7±0.1 m) performed resistance training (2×/week; 40-45 mins) involving a combination of hip extensors and abdominal strengthening exercises for 8 weeks. APT (°), vertical jump power (W), vertical jump height (m), and H:Q ratio at 60, 180, and 300°/s were assessed prior to and following the resistance training program. RESULTS: APT, vertical jump power, vertical jump height, and H:Q ratio at 60 and 180°/s, were significantly improved following 8 weeks of resistance training (all Ps<0.05). CONCLUSIONS: Our main finding was that 8 weeks of resistance training emphasizing posterior chain and core strengthening was effective in reducing APT, improving vertical jump performance and H:Q ratio in healthy individuals. Our findings have potential implications for clinicians prescribing resistance training exercises to improve pelvic posture in healthy asymptomatic individuals at risk of developing chronic low back pain and lumbar-spinal pathologies due to excessive anterior pelvic tilt.

Before-School Physical Activity Program's Impact on Social and Emotional Learning.

BACKGROUND: Despite the positive impact of social and emotional learning (SEL) on the emotional well-being of children, literature on physical activity engagement and SEL among this population has been limited. Therefore, the purpose of this study was to examine whether school students' SEL would improve after participation in a before-school physical activity program. METHODS: A total of 138 fourth and sixth grade students from 1 elementary school and 1 middle school participated in this study. Seventy-five students participated in the before-school physical activity program, while 63 students were in the control group. The physical education teachers implemented the program 3 days per week, for 3 weeks. The participants completed a 10-question adapted Devereux Student Strengths Assessment-Mini before and after the program. Repeated measures ANOVA was run to determine the effects of the program on SEL competence. RESULTS: The fourth and sixth grade students who participated in the program reported a 7 and 10% improvement in pre- versus post-intervention SEL competence, respectively. Students in the control group reported no change in their SEL competence. CONCLUSION: Considering the benefits of a before-school physical activity program on students' SEL, stakeholders should consider including more physical activity programming within school policies.

Noncircular Chainrings Do Not Influence Physiological Responses During Submaximal Cycling.

Pedal speed and mechanical power output account for 99% of metabolic cost during submaximal cycling. Noncircular chainrings can alter instantaneous crank angular velocity and thereby pedal speed. Reducing pedal speed during the portion of the cycle in which most power is produced could reduce metabolic cost and increase metabolic efficiency. PURPOSE: To determine the separate contributions of pedal speed and chainring shape/eccentricity to the metabolic cost of producing power and evaluate joint-specific kinematics and kinetics during submaximal cycling across 3 chainring eccentricities (CON = 1.0; LOW = 1.13; HIGH = 1.24). METHODS: Eight cyclists performed submaximal cycling at power outputs eliciting 30%, 60%, and 90% of their individual lactate threshold at pedaling rates of 80 rpm under each chainring condition (CON80rpm; LOW80rpm; HIGH80rpm) and at pedaling rates for the CON chainring chosen to match pedal speeds of the noncircular chainrings (CON78rpm to LOW80rpm; CON75rpm to HIGH80rpm). Physiological measures, metabolic cost, and gross efficiency were determined by indirect calorimetry. Pedal and joint-specific powers were determined using pedal forces and limb kinematics. RESULTS: Physiological and metabolic measures were not influenced by eccentricity and pedal speed (all Ps > .05). Angular velocities produced during knee and hip extension were lower with the HIGH80rpm condition compared with the CON80rpm condition (all Ps < .05), while angular velocity produced during ankle plantar flexion remained unchanged. CONCLUSIONS: Despite the noncircular chainrings imposing their eccentricity on joint angular kinematics, they did not reduce metabolic cost or increase gross efficiency. Our results suggest that noncircular chainrings neither improve nor compromise submaximal cycling performance in trained cyclists.

Children's Physical Activity Levels Following Participation in a Classroom-Based Physical Activity Curriculum.

A classroom-based physical activity curriculum offers an opportunity for students to be active during the school day to combat declining physical activity levels among this population. The effects of classroom-based physical activity curriculum on children of different weight categories is relatively unknown. Therefore, the purpose of this study was to examine the differences in physical activity levels between male and female students, and between students of different weight categories following participation in a classroom-based physical activity curriculum intervention. A total of 210 3rd to 5th grade (age = 9.1 ± 0.1) students from one U.S. elementary school participated in a 4-week intervention. Students' physical activity levels were measured using pedometers, quantified by step counts pre- and post-intervention. Results from the study indicated that students' physical activity levels increased after participation in the intervention; male students' physical activity levels were higher than female students. Additionally, there was an increase in physical activity levels regardless of weight categories, with students of healthy weight exhibiting the most increase following participation in the intervention. In view of the improvement of children's physical activity levels following their participation in a classroom-based physical activity curriculum, it is recommended that training and resources be provided for teachers to easily implement the curriculum during the school day.

Noncircular Chainrings Do Not Influence Maximum Cycling Power.

Noncircular chainrings could increase cycling power by prolonging the powerful leg extension/flexion phases, and curtailing the low-power transition phases. We compared maximal cycling power-pedaling rate relationships, and joint-specific kinematics and powers across 3 chainring eccentricities (CON = 1.0; LOWecc = 1.13; HIGHecc = 1.24). Part I: Thirteen cyclists performed maximal inertial-load cycling under 3 chainring conditions. Maximum cycling power and optimal pedaling rate were determined. Part II: Ten cyclists performed maximal isokinetic cycling (120 rpm) under the same 3 chainring conditions. Pedal and joint-specific powers were determined using pedal forces and limb kinematics. Neither maximal cycling power nor optimal pedaling rate differed across chainring conditions (all p > .05). Peak ankle angular velocity for HIGHecc was less than CON (p < .05), while knee and hip angular velocities were unaffected. Self-selected ankle joint-center trajectory was more eccentric than HIGHecc with an opposite orientation that increased velocity during extension/flexion and reduced velocity during transitions. Joint-specific powers did not differ across chainring conditions, with a small increase in power absorbed during ankle dorsiflexion with HIGHecc. Multiple degrees of freedom in the leg, crank, and pedal system allowed cyclists to manipulate ankle angular velocity to maintain their preferred knee and hip actions, suggesting maximizing extension/flexion and minimizing transition phases may be counterproductive for maximal power.