Injuries of the cervical spine occur in contact sports. Generally, muscle strengthening training of the neck is performed to prevent injuries of the cervical spine. Isometric resistance training with chin-in posture exercise is recommended for strengthening the neck. However, muscle strength and electromyography(EMG)date for chin-in posture have not been reported. The purpose of this study was to validate muscle strength and EMG testing during chin-in posture. Subjects were fifteen healthy men without pathological conditions in the neck. Muscle strength date and EMG measurements were taken for maximal voluntary isometric contraction(MVIC)flexion and extension actions during normal and chin-in posture. Subjects performed MVIC using a handheld dynamometer and surface EMG was recorded sternocleidomastoid, scalenus, upper trapezius, and splenius muscles. Results of chin-in posture showed a significant increase in muscle strength and EMG of all muscles. These results indicate the beneficial effect of chin-in posture which can increase muscle strength and prevent injuries of the neck.

BACKGROUND: Happiness may help to prevent negative physiological outcomes in response to life events; however, factors contributing to happiness during the COVID-19 pandemic have not been longitudinally investigated. This study explored the predictors of happiness in mothers of young children in Japan using comparable data that were obtained before and during the COVID-19 pandemic. METHODS: We conducted the baseline survey in February 2020, and 4 months later, we also conducted the follow-up survey. Throughout all 47 prefectures in Japan, 4,700 (100 respondents/prefecture) mothers of infants and/or preschoolers (0-6 years) participated in the baseline online survey; 2,489 of these also participated in the follow-up survey. RESULTS: We performed hierarchical multiple regression analysis and our final model indicated that maternal happiness during COVID-19 pandemic was positively related to employment status (homemaker, β = 0.052, p = 0.014), levels of available social support (average, β = 0.052, p = 0.012, high, β = 0.055, p = 0.010) and happiness score before the pandemic (β = 0.467, p < 0.001), and satisfaction toward the measures against the COVID-19 at partners' workplace (average, β = 0.129, p < 0.001; high, β = 0.279, p < 0.001), preventive behavior against COVID-19 (average, β = 0.055, p = 0.002; high, β = 0.045, p = 0.015) and positive attitudes/thinking (β = 0.087, p < 0.001) during the pandemic. In contrast, poor mental health (K6 ≥5, β = -0.042, p = 0.011) before the pandemic and negative changes during the pandemic (≥3, β = -0.085, p < 0.001) were negatively related to maternal happiness during the pandemic. Our final model explained 44.9% of the variance in mothers' happiness during the COVID-19 pandemic. CONCLUSIONS Satisfaction toward the measures against the COVID-19 at partners' workplace, preventive behavior, and positive attitudes/thinking were especially important for maternal happiness during the COVID-19 pandemic. Future study is needed to consider measures against infectious diseases in the workplace that are desirable for the well-being of parents with young children, taking into account the gender perspective.
COVID-19/epidemiology* ; Child ; Child, Preschool ; Female ; Happiness ; Humans ; Japan/epidemiology* ; Mothers/psychology* ; Pandemics