The correlation between pregnancy-related low back pain and physical fitness evaluated by an index system of maternal physical fitness test.

To investigate incidence of pregnancy-related low back pain (LBP), evaluate physical fitness objectively during pregnancy and analyze the correlation between LBP and physical fitness of pregnant women, 180 pregnant women including 101 in mid-gestation (14-28 gestational weeks) and 79 in late-gestation (28-37 gestational weeks) were recruited and self-reported their LBP. The aerobic ability such as cardiorespiratory fitness and anaerobic ability including strength, endurance, speed, flexibility, and balance were evaluated by a novel materal physical fitness test system. The correlation between LBP and each component in physical fitness test system was analyzed in SPSS. As the results, 135 out of 180 participants (75% of total) had pregnancy-related LBP. Physical fitness of participants in late-gestation was significantly weaker including weaker back strength (p<0.05), less resistance band pullbacks in 30s (p<0.01), less stretching in sit-and-reach test (p<0.001), shorter duration in left legged blind balance test (p<0.05) and weaker bird dog balance(p<0.05) than those in mid-gestation. Correlation analysis indicated that LBP was negatively associated with standing heel raises in 20s (p<0.01) and standing glute kickbacks in 30s (left p<0.01, right p<0.05). Thus, it is concluded that LBP is in high prevalence throughout the entire pregnant course. The pregnant women are prone to have weakened strength of core muscle groups and poorer flexibility and balance along the pregnancy. In addition, their LBP was negatively correlated to strength of back muscle groups of lower limbs.

Upper limb isokinetic muscle strength predicts the performance in cross-country sit-skiing.

The double poling (DP) technique in cross-country sit-skiing is primarily considered as an upper-body exercise. The upper limb muscle strength and motion economy are important factors accounting for DP performance in cross-country sit-skiing. The present study investigates how upper limb muscle strength predicts DP performance in cross-country sit-skiing. A total of 19 female non-disabled college students (age 23.2 ± 0.8 years, BMI 20.4 ± 2.2) performed 30-s and 3-min DP performance tests using a sit-skiing ergometer. Isokinetic muscle strength of the shoulder and elbow extensor were measured at the angular velocity of 30°/s, 60°/s, and 120°/s with an ISOMED2000 isokinetic system. A medium correlation was found between DP output power and isokinetic upper limb muscle strength (shoulder strength at all speeds, r = 0.39-0.74, p ≤ 0.1). Multiple regression analyses which were employed to predict power production in the 30-s and 3-min tests showed that shoulder extension strength at 60°/s accounted for 34% of the variation in the 30-s test, and 40% of the variance in the 3-min test. Muscle strength and biomechanical analysis of DP process indicated that upper limb extensor muscle strength and muscle coordination were important factors for the power output generation in sit-skiing DP. These results may use to guide special physical fitness training for paralympic cross-country sit-skiing.

First on-sky demonstration of the piezoelectric adaptive secondary mirror.

We propose using a piezoelectric adaptive secondary mirror (PASM) in the medium-sized adaptive telescopes with a 2-4 m aperture for structure and control simplification by utilizing the piezoelectric actuators in contrast with the voice-coil adaptive secondary mirror. A closed-loop experimental setup was built for on-sky demonstration of the 73-element PASM developed by our laboratory. In this Letter, the PASM and the closed-loop adaptive optics system are introduced. High-resolution stellar images were obtained by using the PASM to correct high-order wavefront errors in May 2016. To the best of our knowledge, this is the first successful on-sky demonstration of the PASM. The results show that with the PASM as the deformable mirror, the angular resolution of the 1.8 m telescope can be effectively improved.