Masashi Shibata

Abstract Objective Discrepancies between sleep timing on work/school and free days, also known as social jetlag (SJL), can cause health problems. These issues occur most often in individuals from adolescence to the early 20s, which is equivalent to the age of university students. This study was designed to explore the recommended level of physical activity required to minimize SJL and to examine the relationship between SJL and objective physical activity among female university students. Methods We assessed the SJL of 68 female students using the Japanese version of the Munich Chronotype Questionnaire. The objective physical activity and sleep variables of subjects were also evaluated at 3 to 4 weeks using a small triaxial accelerometer. Results A significant negative correlation was found between SJL and physical activity on both free (r = − 0.435, p < 0.001) and school days (r = − 0.341, p < 0.01). According to the linear regression analysis, physical activity of 11,174 steps on school days and 10,713 steps on free days had the lowest SJL value. Total sleep time on free days had a significant positive correlation with SJL (r = 0.399, p < 0.001) and a negative correlation with physical activity (r = − 0.520, p < 0.001). Discussion Our results suggest that substantial SJL may cause chronic fatigue and lead to a low level of physical activity in female university students. These results also imply that the recommended level of physical activity necessary to minimize SJL among these students is around 11,000 steps on both school and free days.

CONTEXT:   Soccer is the most popular junior sport in the world. In junior sports, injury analysis and injury-prevention measures for players, especially those under 12 years of age, are urgently needed. OBJECTIVE:   To prospectively study the incidence, sites, types, and mechanisms of injuries in elementary school-aged junior soccer players during games and practices. DESIGN:   Descriptive epidemiology study. SETTING:   Elementary school-aged junior soccer teams in Nagoya, Japan. PATIENTS OR OTHER PARTICIPANTS:   Eighty-nine players in 5 community-based club teams of junior soccer (U-12, age range = 11-12 years; U-11, age range = 10-11 years; U-10, age ≤10 years). MAIN OUTCOME MEASURE(S):   Data on all game and practice injuries for the 2013-2014 season were collected using an injury report form. Injury rates were calculated according to injury site, type, and mechanism. RESULTS:   The overall injury rate was 2.59/1000 athlete-hours (AHs). The game injury rate (GIR; 6.43/1000 AHs) was higher than the practice injury rate (PIR; 1.49/1000 AHs; P < .05). The most common anatomical areas of injury during games and practices were the lower limbs (62.5% and 4.02/1000 AHs versus 38.5% and 0.57/1000 AHs, respectively). Contusions (27.6%, n = 8) were the most frequent type of overall injuries. Most game injuries resulted from body contact (43.8%, 2.81/1000 AHs), whereas most practice injuries resulted from other types of contact (53.8%, 0.83/1000 AHs). CONCLUSIONS:   The GIRs were higher than the PIRs in Japanese junior soccer players. A lower overall PIR suggested that players in the U-12 age group practiced under appropriate conditions. However, the higher GIR in this age category needs to be decreased.

CONTEXT: Mini-basketball is one of the most popular junior sports in Japan. Mini-basketball-related injuries may increase because of early specialization. However, no reports have been published to date concerning basketball injuries in children younger than 12 years of age. OBJECTIVE: To prospectively study the incidence, sites, types, and mechanisms of injuries in mini-basketball teams. DESIGN: Descriptive epidemiology study. SETTING: Mini-basketball teams in Kobe, Japan. PATIENTS OR OTHER PARTICIPANTS: A total of 95 players in 7 community-based mini-basketball club teams (age range, 9 through 12 years). MAIN OUTCOME MEASURE(S): Data on all practice and game injuries for the 2013-2014 season were collected using an injury report form. Injury rates were calculated according to site, type, and mechanism. RESULTS: The overall injury rate was 3.83 per 1000 athlete-hours (AHs). The game injury rate ( 12.92/1000 AHs) was higher than the practice injury rate (3.13/1000 AHs; P < .05). The most common anatomical areas of injury during games and practices were the head and neck (36.4%, 4.70/1000 AHs) and the upper limbs (47.8%, 1.50/1000 AHs). Sprains (42.9%, n = 39) were the most common type of injuries overall, followed by contusions (29.7%, n = 27). Most game injuries resulted from body contact (45.5%, 5.87/1000 AHs), whereas most practice injuries resulted from other contact (56.5%, 1.77/1000 AHs). CONCLUSIONS: Game injury rates were higher than practice injury rates in Japanese mini-basketball players. The high practice injury rate in this study may be due to specific factors related to growth, such as individual differences in height, or to skills, such as inexperience in ball handling.

Clinical researchers do not typically assess sleep with polysomnography (PSG) but rather with observation. However, methods relying on observation have limited reliability and are not suitable for assessing sleep depth and cycles. The purpose of this methodological study was to compare a sleep analysis method based on power spectral indices of heart rate variability (HRV) data to PSG. PSG and electrocardiography data were collected synchronously from 10 healthy women (ages 20–61 years) over 23 nights in a laboratory setting. HRV was analyzed for each 60-s epoch and calculated at 3 frequency band powers (very low frequency [VLF]-hi: 0.016–0.04 Hz; low frequency [LF]: 0.04–0.15 Hz; and high frequency [HF]: 0.15–0.4 Hz). Using HF/(VLF-hi + LF + HF) value, VLF-hi, and heart rate (HR) as indices, an algorithm to categorize sleep into 3 states (shallow sleep corresponding to Stages 1 &amp; 2, deep sleep corresponding to Stages 3 &amp; 4, and rapid eye movement [REM] sleep) was created. Movement epochs and time of sleep onset and wake-up were determined using VLF-hi and HR. The minute-by-minute agreement rate with the sleep stages as identified by PSG and HRV data ranged from 32 to 72% with an average of 56%. Longer wake after sleep onset (WASO) resulted in lower agreement rates. The mean differences between the 2 methods were 2 min for the time of sleep onset and 6 min for the time of wake-up. These results indicate that distinguishing WASO from shallow sleep segments is difficult using this HRV method. The algorithm's usefulness is thus limited in its current form, and it requires additional modification.

12名の女子大学生を被検者とした.被検者は二つの異なる方法の起き上がり援助を行った.一つは一般的にこれまで用いられてきた方法(A法)であり,もう一つは力学的根拠に基づいて開発された方法(B法)であった.起き上がり援助実施時に,酸素摂取量(VO2),心拍数及び筋電図を測定し生体負担の指標とした.VO2及び心拍数はA法の方がB法に比べ有意に高かった.A法の右上腕二頭筋及び脊柱起立筋の筋電図積分値(iEMG)はB法より有意に高く,一方大腿直筋のiEMGはA法が低値を示した