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.

目的:本研究の目的は,慢性期統合失調症患者の日中の身体活動と睡眠指標の関連を明らかにすることであった.方法:対象者は慢性期統合失調症入院患者27名(男性17名,女性10名,平均年齢58.3±11.6歳)であった.客観的睡眠指標として小型体動計を用いて,総睡眠時間(TST),入眠潜時(SL),中途覚醒時間(WASO)および睡眠効率(SE)を評価した.また,主観的睡眠指標としてピッツバーグ睡眠質問票(PSQI)を実施した.身体活動指標は歩数を採用し,一軸加速度計を用いて客観的睡眠指標とともに1週間測定した.結果:歩数は,SE(r=.629,p<.01)およびTST(r=.406,p<.05)と有意な正の関連が,またWASO(r=-.615,p<.01)と有意な負の相関関係が認められた.一方,歩数とPSQIスコアに関連は見られなかった.考察:身体活動の多い統合失調症入院患者は客観的睡眠指標が良好であり,身体活動を高めることが睡眠の改善に結びつく可能性が示唆された.(著者抄録)

Functional movement screen (FMS) has been used to establish normative data and determine potential injury risk for young adults and athletes, but there are few data in elementary school-age children. The purpose of this study was to establish fundamental values for the FMS in elementary school-age mini-basketball players. Secondary purposes were to examine relationships between functional movement patterns and age, peak height velocity (PHV), and body mass index (BMI), and to compare functional movement patterns between boys and girls and between individuals with and without a history of injury. The mean composite FMS score was 16.5 ± 2.2 (16.5 ± 2.4 for boys, 16.5 ± 1.7 for girls). The composite FMS score was positively correlated with age (r = .312) and negatively correlated with the BMI (r = - .371). However, the FMS score was not correlated with PHV or with PHV age. The FMS score was not different between boys and girls or between individuals who reported a previous injury and those who did not. However, boys in the mini-basketball teams performed better than girls on the trunk stability push-up and rotary stability tests. Age and the body mass index were significantly associated with better and poorer functional movement, respectively.

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.

本研究では,睡眠時の心拍変動(HRV)データを1分と5分間区分でMemCalc法により周波数解析してHRV指標を求め,PSGで判定した各睡眠段階におけるHRV指標についてそれぞれ比較検討した。20～44歳の女性8名から得られた16夜分のPSGおよびHRVデータを解析した。HRV解析は,超低周波数高領域(0.016～0.04Hz:VLF-hi),低周波数(0.04～0.15Hz:LF),高周波数(0.15～0.4Hz:HF)の各帯域のパワースペクトル値を算出した。LF/HF,HF/(LF+HF),HF/(VLF-hi+LF+HF),VLF-hiの4つの指標において,1分と5分間区分解析共に,REM睡眠,浅睡眠,深睡眠の各睡眠段階間に有意な差が認められた。これまでHRV周波数解析指標の算出は5分間区分が主であったが,睡眠段階の推定にはPSGの1エポック20～30秒により近似する1分間区分解析結果を用いる方が有用である可能性が示唆された。(著者抄録)

This study examined and compared the characteristics of the power spectral indices of heart rate variability (HRV) for the different stages of sleep in order to determine which indices are useful for sleep assessment. Sixteen sets of polysomnogram (PSG) and electrocardiogram data were collected synchronously from 8 healthy women (age range, 20-44 years). PSG data were analyzed in 1-min segments, while HRV data were analyzed in 1- and 5-min segments using the MemCalc method and calculated at 3 frequency band powers: higher area in very low frequency band (VLF-hi, 0.016-0.04 Hz), low frequency band (LF, 0.04-0.15 Hz), and high frequency band (HF, 0.15-0.4 Hz). Significant differences were observed in LF/HF, HF/ (LF+HF), HF/(VLF-hi+LF+HF), and VLF-hi between all sleep stages. Compared to the HRV results obtained from 5-min segments, those from the 1-min segments showed a stronger relationship with sleep stage. Although HRV analysis during sleep typically involves the use of 5-min segments, the present results imply that improvements in technology enable the detection of sleep stages at shorter 1-min segments which correspond to PSG analysis segments.

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

The purpose of this study was to determine the feasibility of estimating myocardial oxygen supply/demand relationship noninvasively for the evaluation of myocardial stress during arm and leg exercises. Seven healthy males performed arm cranking exercise (ARM) and leg cycle exercise (LEG) at each of four constant power outputs (ARM : 5,10,15,20 W, LEG :25,50,75,10O W). Electrocardiogram, phonocardiogram, carotid pulse wave and blood pressure were simultaneously recorded during the exercises. The pressure of cardiac cycle was estimated by substituting systolic blood pressure (SBP) for peak of carotid pulse wave and diastolic blood pressure (DBP) for base line of that, respectively. Potential subendcardial blood flow was also estimated from the Diastolic Pressure Time Index (DPTI) and myocardial oxygen requirments were estimated from the Tension Time Index (TTI) , respectively. The ratio DPTI/TTI, thus, provided an estimate of myocardial oxygen supply/demand relationship. Results indicated that heart rate (HR) and SBP increased more steeply in relation to work rate during ARM than LEG (HR : 1.53vs.0.41bpm・W^&lt-1&gt, SBP : 1.64vs.0.368mmHg・&lt-1&gt, p&lt0.01).Consequently,TTI increased linearly with the work rate both durirg ARM and LEG ; this increase was, however, significantly higher for ARM than LEG,i. e., TTI was higher for ARM at maximum work rate (20W) than LEG at minimum work rate (25W) (3020vs.2300mmHg・sec・min&lt-1&gt, p&lt0.01).The rate of decrease of DPTI/TTI per work rate during ARM was also significantly(p&lt0.05)greater than LEG. These results suggested that arm exercise in comparison to leg exercise is accompanied by not only higher myocardial oxygen demand but also greater myocardial stress caused by an unfavorable shift in the balance of myocardial oxygen supply and demand. Based upon these results, it seems that DPTI, TTI and DPTI/TTI determined by the noninvasive method employed in the present study may provide an effective index to the measurement of myocardial stress in various type of exercise.

Six men were studied to determine the interrelationships among blood supply, motor unit (MU) activity and lactate concentrations during intermittent isometric contractions of the hand grip muscles. The subjects performed repeated contractions at 20% of maximal voluntary contraction (MVC) for 2 s followed by 2-s rest for 4 min with either unhindered blood circulation or arterial occlusion given between the 1st and 2nd min. The simultaneously recorded intramuscular MU spikes and surface electromyogram (EMG) data indicated that mean MU spike amplitude, firing frequency and the parameters of surface EMG power spectra (mean power frequency and root mean square amplitude) remained constant during the experiment with unhindered circulation, providing no electrophysiological signs of muscle fatigue. Significant increases in mean MU spike amplitude and frequency were, however, evident during the contractions with arterial occlusion. Similar patterns of significant changes in the surface EMG spectra parameters and venous lactate concentration were also observed, while the integrated force-time curves remained constant. These data would suggest that the metabolic state of the active muscles may have played an important role in the regulation of MU recruitment and rate coding patterns during exercise.