The COVID-19 epidemic adversely affects the lifestyle of people. This study aimed to examine the impacts of social isolation on physical activity (PA) levels and mood states of children and adolescents and to explore the correlation between them during the COVID-19 epidemic. A total of 9979 children and adolescents (11.63 ± 1.23 years old) from Yan’an, China volunteered to participate in this study and completed online questionnaires. PA and mood states were measured by International Physical Activity Questionnaire Short Form (IPAQ-SF) and Profile of Mood States (POMS), respectively. The results showed that the mean of students’ moderate-to-vigorous PA (MVPA) was 23.19 min per day. The total mood disturbance in the moderate and high-level PA groups were significantly lower than those in the low-level PA group (p < 0.05). Additionally, boys and girls had significant differences in PA levels (p < 0.01), and the PA levels of students in different grades were also significantly different (p < 0.01). Meanwhile, boys’ mood states were worse than girls’. The Grade 4 in primary schools had the worst mood states while Grade 5 had the best mood states. The results suggested that the MVPA of students has dropped badly, compared with the results of previous studies investigated in normal times. In addition, the PA level had a significantly positive impact on the mood states of children and adolescents during the COVID-19 epidemic. Sex and grades were factors which affected the PA levels and mood states. This study can help policymakers and healthcare professionals understand PA and mood states of Chinese children and adolescents during the epidemic. We should pay attention to the changes in PA levels and mood states of children and adolescents.

Background: This study aimed to explore the characteristics of trends in physical fitness and nutritional status among school-aged students during the COVID-19 pandemic, which could help to develop targeted guidelines and policies for students (adolescents) to promote health during lockdowns resulting from public health emergencies. Methods: The physical fitness and nutritional status were measured from 2019 to 2021; the correlation between years and grade were analyzed. Results: a declining trend was found in aerobic fitness, strength fitness, speed fitness, and BMI during this lockdown. Conclusion: The changes in dietary behavior and the decrease in outdoor physical activities may be the reason for the decline. Furthermore, differences in subjects’ growth and limited space at home must be considered in the formulation of exercise and nutritional plans. According to the results of our study, exercise for aerobic fitness should receive more attention when students are enduring a pandemic lockdown. In addition, saying “no” to high-calorie foods in the form of snacking and ultra-processed food was the key to improving subjects’ nutritional status.

The topspin forehand is the most frequent and effective shot in top-level table tennis matches. The present study assesses the biomechanical differences in the topspin forehand stroke technique when the incoming ball is in different rotations. Eight national level-1 male table tennis athletes (176.6 ± 4.8 cm, 70.8 ± 6.6 kg, 20.9 ± 2.4 yr) performed two kinds of techniques—topspin forehand strokes against topspin (AT) and against backspin (AB) balls, respectively. The kinematic parameters of their bodies and rackets were calculated. Meanwhile, the force plates analyzed their lower limb moments through inverse dynamics. Paired t-test and non-parametric paired t-test mapping were used to assess the differences between the two conditions. Their center of gravity (COG) vertical distance, elbow flexion, thorax–pelvis flexion, and knee flexion angles had significant differences during the stroke phase (p < 0.05). The moment of the racket-side hip rotation and ankle dorsiflexion showed significant differences during the stroke phase (p < 0.05). The racket velocity, angle, and trajectories showed significant differences at characteristic moments (p < 0.05). This study revealed the different topspin forehand stroke techniques in table tennis, even though the two movements look similar. Compared with AT strokes, the athletes kept a straight elbow and lower center of gravity than they did during the stroke phase of AB strokes. They increased the distance of the racket trajectory and velocity to meet the incoming ball with a backspin, especially in the vertical direction. This detailed information is necessary for beginners to improve the efficiency of their forehand topspin technique, especially in strokes against incoming balls with different rotations.

Background: This research aimed to investigate the correlation between students’ physical fitness and campus-built environment, which could put forward some suggestions for the construction of a campus environment. Method: Four colleges in Xi’an were regarded as special “semi-closed” spaces. Combined with ArcGIS and SPSS, the correlation between the built environment of colleges and the students’ physical fitness test results in 2019 was analyzed (n = 1498). Results: regarding the men questioned in this research, there was a significant correlation between street connectivity and vital capacity, grip strength, 50 m running, 1000 m running, a significant correlation between land use mix and vital capacity, sit-and-reach, pull-up, grip strength, a significant correlation between green space per capita and vital capacity, grip strength, 50 m running, and a significant correlation between walk score and vital capacity, pull-up, grip strength, and 50 m running. Regarding the women questioned in this research, there was a significant correlation between street connectivity and vital capacity, grip strength, 50 m running, 800 m running, curl-up, a significant correlation between land use mix and vital capacity, sit-and-reach, curl-up, grip strength, 800 m running, a significant correlation between green space per capita and vital capacity, grip strength, curl-up, sit-and-reach, and a significant correlation between walk score and vital capacity, curl-up, grip strength, and 800 m running. Conclusion: the built environment on campus can indirectly affect the physical fitness of college students. Increasing the number of intersections and short connections of campus streets, ensuring that the green space of the campus meets the standards, and reasonably arranging the site selection of buildings are conducive to improving the physical fitness of students.

Background: This study aimed to derive the effects of walking while using a mobile phone on balance perturbation and joint movement among young adults. Methods: Sixteen healthy college students with no history of brain injury were tested. The participants were asked to walk under four different conditions: (1) walking, (2) browsing, (3) dialing, and (4) texting. Indicators related to balance control and lower limb kinematic/kinetic parameters were analyzed using the continuous relative phase and statistical nonparametric mapping methods. Results: Walking while using a mobile phone slowed participants’ gait speed and reduced the cadence, stride length, and step length. The posterior tilt angle (0–14%, 57–99%), torque of the hip flexion (0–15%, 30–35%, 75–100%), and angle of the hip flexion (0–28%, 44–100%) decreased significantly. The activation of biceps femoris and gastrocnemius, hip stiffness, and ankle stiffness increased significantly. This impact on gait significantly differed among three dual tasks: texting > browsing > dialing. Conclusion: Che overlap of walking and mobile phone use affects the gait significantly. The “hip–ankle strategy” may result in a “smooth” but slower gait, while this strategy was deliberate and tense. In addition, this adjustment also increases the stiffness of the hip and ankle, increasing the risk of fatigue. Findings regarding this effect may prove that even for young healthy adults, walking with mobile phone use induces measurable adjustment of the motor pattern. These results suggest the importance of simplifying the control of the movement.