Effects of the time of day on repeated all-out cycle performance and short-term recovery patterns.

The effect of the time of day on repeated cycle sprint performance and short-term recovery patterns was investigated in 12 active male subjects (23+/-2 years, 76.4+/-4.2 kg, 1.80+/-0.06 m, 9.5+/-4.5 h . week (-1) of physical activity). Subjects performed ten 6-s maximal sprints inter-spaced by 30 s rest in the morning (08 : 00-10 : 00 h) and in the evening (17 : 00-19 : 00 h) on separate days. During the intermittent exercise, peak power output (P (PO), watts), total mechanical work (W, kJ), peak pedalling rate (P (PR), rev . min (-1)), and peak efficient torque (P (TCK), Nm) were recorded. The values at the 1st, the 5th, and the 10th sprints were used as mechanical indices of fatigue occurrence. Intra-aural temperature and maximal voluntary contraction of knee extensors muscles (MVC) were measured before (pre), immediately after (post) the cycle bouts and following a 5-min passive recovery period (post 5). The MVC indices were used to further confirm occurrence of neuromuscular fatigue and to assess short-term recovery patterns from all-out intermittent effort. During the MVC, electromyographic activity of the vastus lateralis muscle was recorded and analysed as its root mean square (RMS). The torque produced per unit RMS was calculated and used as index of neuromuscular efficiency (NME). A main effect for the sprint number was observed for all cycle performance parameters (p<0.05). The main effect for the time of day was not significant for any biomechanical indices of neuromuscular performance. A significant interaction effect of the time of day and the sprint repetition was demonstrated on P (TCK) ( F(2,22)=4.3, p<0.05). The decrease in P (TCK) consecutive to sprint repetition was sharper in the evening compared to the morning (sprint 10[% of sprint 1]:-9.5 % in the evening vs. - 2.2 % in the morning, p<0.05). Significant interaction effects of the time of day and the condition (i. e. pre, post, post 5) were also demonstrated for RMS ( F(2,22)=3.6, p<0.05) and NME ( F(2,22)=4.5, p<0.05) during MVC. These interactions were characterised by similar patterns of fatigue occurrence (i. e. post vs. pre condition) in the morning (+7.5 % for RMS, - 19.6 % for NME) as in the evening (+10.2 % for RMS, -19.4 % for NME) but different patterns of short-term recovery (i. e. post 5 vs. post condition; p<0.05) in the morning (-7.3 % for RMS, +13.7 % for NME) compared to the evening (+3.3 % for RMS, -1.8 % for NME). These results suggest that short-term recovery patterns of neuromuscular function are slower in the evening compared to the morning.

Effect of high-intensity intermittent cycling sprints on neuromuscular activity.

High-intensity intermittent sprints induce changes in metabolic and mechanical parameters. However, very few data are available about electrical manifestations of muscle fatigue following such sprints. In this study, quadriceps electromyographic (EMG) responses to repeated all-out exercise bouts of short duration were assessed from maximal voluntary isometric contractions (MVC) performed before and after sprints. Twelve men performed ten 6-s maximal cycling sprints, separated by 30-s rest. The MVC were performed pre-sprints ( pre), post-sprints ( post), and 5 min post-sprints ( post5). Values of root-mean-square (RMS) and median frequency (MF) of vastus lateralis (VL) and vastus medialis (VM) were recorded during each MVC. During sprints, PPO decreased significantly in sprints 8, 9, and 10, compared to sprint 1 (- 8 %, - 10 %, and - 11 %, respectively, p < 0.05). Significant decrements were found in MVC post (- 13 %, p < 0.05) and MVC post5 (- 10.5 %, p < 0.05) compared to MVC pre. The RMS value of VL muscle increased significantly after sprints (RMS pre vs. RMS post: + 15 %, p < 0.05). Values of MF decreased significantly in both VL and VM after sprints. In conclusion, our results indicate that the increase in quadriceps EMG amplitude following high-intensity intermittent short sprints was not sufficient to maintain the required force output. The concomitant decrease in frequency components would suggest a modification in the pattern of muscle fiber recruitment, and a decrease in conduction velocity of active fibers.

Influence of time of day and partial sleep loss on muscle strength in eumenorrheic females.

Disrupted sleep is the most common form of sleep deprivation in travellers, shift workers, athletes the night before important competitions and among parents of infants. The influence of partial sleep loss on muscle strength might differ according to the time of testing on the following day. This study was therefore designed to assess the interaction between the effects of partial sleep loss and time of day on muscle strength in females. Eight sedentary eumenorrheic females (mean +/- SD; age 30 +/- 6 years, height 1.62 +/- 0.06 m and body mass 67 +/- 5.0 kg) took part in the study, in a counterbalanced design. Measurements of muscle strength were carried out at 06:00 and 18:00 hours after the one control night (no sleep loss) and the one night of partial sleep loss, during menses. Muscle strength measures included isokinetic (at 1.05, 3.14 rad s(-1); 90 degrees range of motion) and isometric peak torque (at 60 degrees of knee flexion) of knee extensors and flexors (dominant leg). In addition, isometric force of knee extensors with super-imposed electrical twitches (50 Hz, 250 V, 200 mus pulse width) was measured using the same procedure in order to control for motivation. Rectal temperature was measured during the 30 min before muscle strength measurements. Partial sleep loss consisted of allowing 2.5 h sleep (between 03:00 and 05:30 h), whilst in the control condition (no sleep loss) subjects retired between 22:30 and 23:30 h, rising at 05:30 hours. All measurements were conducted at just one phase of the menstrual cycle (menses) to prevent any masking effect due to different phases of the menstrual cycle. In both conditions (with and without partial sleep loss) a diurnal variation was observed in peak torque of knee flexors at 1.05 (F(1,7) = 5.5, p < 0.05) and 3.14 rad s(-1) (F(1,7) = 8.0, p < 0.05); values at 18:00 hours were 4.5 and 5.9% higher than at 06:00 hours, respectively. No significant diurnal variation was observed for the other muscle strength measures. No significant effect of partial sleep loss or interaction effect (sleep x time of day) was observed for muscle strength measures. However, the performance rhythms were in phase with the circadian rhythm in rectal temperature. Partial sleep deprivation over one night did not have any adverse effect on maximal muscle strength, nor on diurnal variations of muscle strength indices. As the effect of time of day was observed with some of the muscle strength measures, it is suggested that, in designing future studies using females, the control of time of day is essential.

The isolated and combined effects of menstrual cycle phase and time-of-day on muscle strength of eumenorrheic females.

Diurnal variation in muscle performance has been well documented in the past few years, but almost exclusively in the male population. The possible effects of the menstrual cycle on human circadian rhythms have remained equivocal, particularly in the context of muscle strength. The purpose of the study was to analyze the isolated and combined effects of circamensal variation and diurnal changes on muscle strength. Eight eumenorrheic females (age 30 +/- 5 yrs, height 1.63 +/- 0.06m and body mass 66.26 +/- 4.6kg: mean +/- SD) participated in this investigation. Isokinetic peak torque of knee extensors and flexors of the dominant leg were measured at 1.05, 3.14rad.s(-1) (through 90 degrees ROM) at two times-of-day (06:00, 18:00 h) and five time points of the menstrual cycle (menses, mid-follicular, ovulation, mid-luteal, late luteal). In addition, maximum voluntary isometric contraction of knee extensors and flexors and electrically stimulated isometric contraction of the knee extensors were measured at 60 degrees of knee flexion. Rectal temperature was measured during 30min before the tests. There was a significant time-of-day effect on peak torque values for isometric contraction of knee extensors under electrical stimulation (P< 0.05). At 18:00 h, muscle force was 2.6% greater than at 06:00 h. The time-of-day effect was not significant when the tests were performed voluntarily without stimulation: effect size calculations indicated small differences between morning and evening for maximal voluntary isometric contraction and peak torque (at 1.05rad.s(-1) for the knee extensors. A circamensal variation was observed for peak torque of knee flexors at 1.05rad.s(-1), extensors at 3.14rad.s(-1), and also isometric contraction of knee flexors, values being greatest at the ovulation phase. Interaction effects between time-of-day and menstrual cycle phase were not observed in any of the indices of muscle strength studied. The phase of the menstrual cycle seemed to have a greater effect than did the time-of-day on female muscle strength in this group of subjects. The present results suggest that peripheral rather than central mechanisms (e.g., motivation) are implicated in the diurnal variation of maximal isometric strength of women.

Effect of inertia on performance and fatigue pattern during repeated cycle sprints in males and females.

The effect of recovery duration on performance and fatigue pattern during short exercises was studied including and excluding the flywheel inertia. Subjects (11 males and 11 females) performed a force-velocity test to determine their optimal force (f (opt)). On the following day, subjects performed randomly 4 series of two 8-s sprints against f (opt), with 15 s (R (15)), 30 s (R (30)), 60 s (R (60)), and 120 s (R (120)) recovery between sprints. The cycle (Monark 824 E, Stockholm, Sweden) was equipped with an optical sensor to calculate the revolution velocity of the pedal. For each sprint, peak power (P (peak)), mechanical work (W) and time to reach P (peak) (t (Ppeak)) were calculated including (I) and excluding (NI) the acceleration of the flywheel. For a given sprint, P (peak) and W were greater and t (Ppeak) was lower in I compared to NI condition (p < 0.05). Differences averaged 13 % for P (peak), 20 % for W, 34 % for t (Ppeak), and remained constant between sprints 1 and 2. In sprint 2, P (peak) and W were significantly reduced compared to sprint 1 only after R (15) and R (30) in I and NI (p < 0.05), and no gender differences occurred. In each sprint, P (peak) and W were higher (p < 0.001) and t (Ppeak) was shorter (p < 0.05) in males than in females, and gender differences were the same including or excluding the flywheel inertia. In conclusion, values excluding inertia underestimated mechanical performance and consequently the total energy supply. However, the pattern of fatigue and gender differences in performance and fatigue remained unchanged whatever the condition (I or NI). This result may have practical implications when the flywheel inertia can not be taken into account in the calculation of mechanical work and power output.

Circular myotomy of the distal esophageal stump for long gap esophageal atresia.

PURPOSE: The aim of this work is to report the utility of the distal esophageal stump's circular myotomy in case of a long gap esophageal atresia repair. METHODS: Between 1972 and 1999 the authors treated 192 patients who had esophageal atresia (EA). Among them, 6 patients with EA long gap underwent both a distal and proximal stump circular myotomy. Five cases were Gross type C, and 1 case was Gross type A. The gap (average 4.5 cm) did not permit a simple and direct end-to-end anastomosis. RESULTS: One patient died 6 days after the operation because of a cardiac malformation. There was no mucosal tear during the myotomies or any anastomotic stricture later. Five patients survived. Three of them needed an antireflux procedure (60% of surviving patients). None of the 5 patients showed any mucosal outpouching, and their esophageal motility and swallowing were not different clinically compared with the patients who underwent an EA repair without a myotomy. CONCLUSIONS: Distal circular myotomy is a very useful, however, delicate, procedure that can help solve the problem given by long gap EA. It is mandatory not to tear the mucosa during the myotomy to avoid the shortening of the stump caused by its repair, which would lead to an increase in the size of the gap. J Pediatr Surg 36:855-857.

Decreased submaximal oxygen uptake during short duration oral contraceptive use: a randomized cross-over trial in premenopausal women.

Long-term oral contraceptive (OC) use is known to be associated with changes in haemostasis, cardiovascular dynamics, and carbohydrate and lipid metabolism. Less well documented are the short-term variations in cardiorespiratory responses to exercise during the menstrual cycle of OC users. In this study the short-term effects of the usage of OC on cardiorespiratory and ventilatory responses to submaximal exercise were examined. Ten women (age = 23 +/- 3 years) on monophasic OC were tested at three different times during their 'cycle': during menstruation, off OC use (off OC: days 2-4), early on OC use (EOC: days 7 - 9) and late on OC use (LOC: days 19 - 21). Times of testing were assigned randomly. On each occasion participants performed a continuous 12-min run exercise on a treadmill at three submaximal intensities (averaging 7, 8 and 9 km h(-1)), each for 4 min. Heart rate, ventilation (VE), oxygen uptake (VO2), carbon dioxide output (VCO2), respiratory exchange ratio and running economy were assessed in the last minute of each stage of exercise. No significant variations were observed between the different times for heart rate, VE, and VCO2 irrespective of the stage of exercise (p > 0.05). Using two-way analysis of variance (ANOVA) with repeated measures on both factors (three stages and three times), VO2 (ml kg(-1) min(-1)) was lower by 3% to 5.8% when participants were on early and late OC use compared to off OC regardless of the stage of the exercise (F(2,18) = 6.3; p = 0.008). Running economy (ml O2 kg(-1) km(-1)) was significantly improved (lower values) when women were on late OC use compared to off OC regardless of the stage of exercise. No significant interaction effect between stage of exercise and time of pill usage was demonstrated in any of the parameters studied. Results suggest that oral contraceptive users may expect lower VO2 and better running economy during the pill ingestion phase and consequently have implications for exercise performances.

Influence of the menstrual cycle phase and menstrual symptoms on maximal anaerobic performance.

PURPOSE: This study was designed to analyze the effect of the menstrual cycle phase on maximal anaerobic performance during short-term anaerobic tests. METHODS: Seven eumenorrheic women (NOC) and 10 women using monophasic oral contraceptives (OC) performed three anaerobic tests (force-velocity, multi-jump, and squatting jump tests) during menstruation (M: between days 1 and 4), the midfollicular phase (F: between days 7 and 9), and the midluteal phase (L: between days 19 and 21) of the ovarian cycle. Follicular and luteal phases were confirmed by serum progesterone levels. The order of testing sessions was randomly assigned and a 15-min standardized warm-up preceded each testing session. Rectal temperatures were taken before (Trec(b)) and after (Trec(a)) warm-up. RESULTS: No significant differences were observed among M, F, and L in Trec(b), Trec(a) maximal cycling power (Pmax(c)), maximal jumping power (Pmax(j)), or maximal height of jump (h(j)) in either NOC or OC. Ten of the women suffered premenstrual or menstrual symptoms (MS); the other seven did not report any premenstrual or menstrual discomfort (NMS). Presence or absence of symptoms was not correlated with oral contraceptive use. No significant differences were observed among the three stages of the menstrual cycle in Pmax(c), Pmax(j), or h(j) in NMS. In MS, only Pmax(j) decreased by 8% in M compared with that in F (P < 0.05). CONCLUSIONS: Although there were no significant differences in maximal anaerobic performance during different menstrual cycle phases, results of this study suggest that the presence or absence of premenstrual or menstrual syndrome symptoms may have an effect, possibly through an action on the stretch-shortening cycle of tendons and ligaments.

Diurnal variations in ventilatory and cardiorespiratory responses to submaximal treadmill exercise in females.

Diurnal variations in ventilatory and cardiorespiratory responses to submaximal treadmill exercise were analysed in 11 eumenorrhoeic women and in 10 women using monophasic oral contraceptives. Subjects performed submaximal treadmill exercise at three intensities averaging 7, 8, and 9 km x h(-1), each for 4 min at 0800, 1300 and 1700 hours, assigned randomly on 3 separate days. Rectal temperature was measured before (T(rec(b))) and after (T(rec(a))) exercise. Cardiac frequency (f(c)), ventilation (V(E)), oxygen uptake (VO(2)), carbon dioxide output (VCO(2)), and respiratory exchange ratio (R) were assessed in the last minute of each stage of the exercise. Both T(rec(b)) and T(rec(a)) increased from 0800 to 1700 hours (P < 0.001). For a given submaximal work rate, VO(2) and VCO(2) were higher in the afternoon compared to the morning. Similarly, R was increased at 1700 hours compared to 0800 hours during the recovery period following exercise (P < 0.05). However, V(E) did not vary significantly during the day at any of the running intensities. No significant interactions (group x time of day) were observed in any of the studied parameters. In contrast to ventilation, the VO(2) and VCO(2) of the females during submaximal exercise were both affected by the time of day, without any differences between eumenorrhoeic women and users of oral contraceptives.

Continuous heart rate monitoring over 1 week in teenagers aged 11-16 years.

Heart rate (HR) was monitored in 66 French pubertal boys (B, n = 28) and girls (G, n = 38) aged 11-16 years to evaluate habitual physical activity (HPA) over a 1-week period in the winter. The HR and the percentage of heart rate reserve (%HRR) were taken to be indexes of the metabolic activity for the whole day and for the different parts of the day. The HPA was evaluated from the time spent each day below 50%HRR, between 50%-70%HRR and above 70%HRR, which related to the time spent in no or low physical activity (NLPA), moderate physical activity (MPA) and vigorous physical activity (VPA), respectively. No sex differences were observed in the average %HRR each day [%HRRmean, [B 30 (SD 4)%; G 32 (SD 4)%]] or in NLPA [B 715 (SD 61) min, G 711 (SD 81) min] and VPA [B 19 (SD 16) min, G 21 (SD 21) min] throughout the week. During school days, daily %HRRmean was 7% smaller in 14-16 year olds compared to 11-13 year olds. This was linked to a decrease in MPA and a concomitant increase in NLPA (P < 0.05). Daily %HRRmean varied significantly during the week (range: 28-34% HRR). There were significant differences among the periods of the day (P < 0.05). The HR was the greatest during physical education lessons [128 (SD 11) beats x min(-1)], recreation [113 (SD 15) beats x min(-1)] and lunch break [108 (SD 12) beats x min(-1)] and the lowest during the evening [94 (SD 10) beats x min(-1)]. It was only during the lunch breaks that %HRRmean was greater (P < 0.05) on school days than on free days. Of all the teenagers studied 32% were considered active during the week.

Time-of-day effects in maximal anaerobic leg exercise.

Time of day variations in maximal anaerobic leg exercise were studied in 23 men mean age 23 (SD 3) years. All the subjects performed two anaerobic tests (force-velocity and multi-jump tests) and those familiar with sprinting ran an additional 50-m dash (n = 16). The maximal anaerobic powers for cycling and jumping (Pcycling and Pjump) and maximal anaerobic velocity (vpeak) were performed consecutively in the same order for all tests. The force-velocity and force-power relationships were established to determine Pcycling. The flight time (tf) and the ground contact time (tc) were recorded from five consecutive jumps on a jump-ergometer to calculate Pjump. The vpeak was measured between the 35th and the 45th m during the dash-run. The test schedules were at 0900, 1400 and 1800 hours on separate days in random order. Rectal temperatures (Tre) and body mass (mb) were measured before each test. The Tre increased significantly from 0900 to 1800 hours (P < 0.001) but mb did not vary during the day (P > 0.05). The Pcycling and Pjump were higher at 1400 and 1800 hours than at 0900 hours. The differences between the morning and the afternoon reached 3% (P < 0.05) for Pcycling and 5%-7% for Pjump (P < 0.01). The time-of-day effect was significant for tf (P < 0.05) but not for tc. During the dash-run tests, the differences almost reached significance for vpeak between 0900 and 1800 hours (P = 0.0544). No significant variations were observed between 1400 and 1800 hours for cycling, jumping and running tests. A time-of-day effect in the maximal anaerobic power of cycle and multi-jump tests existed. Such variations would have pronounced effects when expressed in competitions.

Relationships between oxygen consumption and heart rate in transitory and steady states of exercise and during recovery: influence of type of exercise.

Relationships between percentage of maximal oxygen consumption (%VO2max) and percentage of maximal heart rate reserve (%f(cr)) were compared during steady states of exercise (S), transitory states of exercise (T) and a 5-min recovery period (R). Male adults [mean age 27 (SD 10) years] were studied exercising on a treadmill (TR, n = 26), cycle ergometer (CE, n = 14) and arm traction bench (ATB, n = 14). The exercise intensity was adjusted according to the subjects in order to reach exhaustion in 4-5 steps of 2 min (ATB) or 3 min (TR, CE). The 1st min of each stage was considered as T and the last minute of each stage as S. The oxygen consumption (VO2) and heart rate (f(c)) were recorded simultaneously. Significant correlations were observed for each type of exercise and for each state between %f(cr) and %VO2max (r range 0.87-1.00). During T and R, the %VO2max versus %f(cr) relationships were laterally shifted, suggesting a resetting of f(c) control mechanisms. In S, the intercept was greater than in T and R; in T, the slope was greater than in S and R. The VO2 could be predicted from individual %VO2max versus %f(cr) relationships during T and R as is usually done in S using specific equations. Taking into consideration the average relationships established on the three ergometers, the standard error of the predicted VO2 during S and T reached 10%-20% and 22%-38% in R. During exercise, the higher the intensity the better was the prediction of VO2 from f(c) (r range 0.46-0.60, P < 0.001). Therefore except at high exercise intensities, it was found that individual relationships had to be used to obtain an accurate estimation of VO2.

[Renal ectopia in childhood. Experience in 13 cases]. / Ectopia renale in età pediatrica. Esperienza su 13 casi.

Renal ectopy is a rare congenital malformation related to an abnormal migration of the kidney from the sacral to the lumbar region. Three possibilities are present: absent migration (pelvic ectopia), excessive (intrathoracic ectopia) or to the opposite side (crossed ectopia). During the last 10 years in the Department of Pediatric Surgery of the Niguarda Hospital 13 cases of renal ectopy have been observed. Five patients had a crossed ectopy (4 with fusion) and eight had a simple ectopy (1 intrathoracic, 7 pelvic). Female were more affected than males (9 cases) and the right side was involved in 8 cases, the left in 4 cases and both kidneys in 1 case. Associated anomalies were present in 7 patients: 6 cases with exclusively genito-urinary malformations while 1 patient only was polimalformed (cloacal exstrophy, MMC, bilateral TEV). Correct diagnosis was obtained during urologic screening in 5 cases (1 suspected antenatally), while in 7 cases was related to the associated symptoms (UTI, hematuria, abdominal pain). Seven patients were surgically treated for the associated urologic abnormalities while in the remaining six cases no treatment was required.

[Infections of the urinary tract persisting in successful outcome of vesico-ureteral reimplants for primary reflux]. / Infezioni delle vie urinarie persistenti in esiti favorevoli di reimpianto vescico-ureterale per reflusso primitivo.

Persistence of urinary tract infections after successful ureteric reimplantation for vesico-ureteric reflux has been reported with an incidence varying between 20-30% according to different series. The Authors analyze their own experience with 99 patients successfully operated for primary VUR during a five year period. In 22 patients (22.2%) there was evidence of persistent UTI, which were almost exclusively low and asymptomatic (91%) and occurring within 6-12 months after the antireflux surgery. A single UTI was documented in over 60% of the patients. There was strong female prevalence (21 patients) and 50% were more than 6 years old. No significant relationship was found between grade of VUR, renal scarring, type of germ and number of preoperative infections and incidence of post-operative UTI. On the other end, voiding and continence disorders and cystoscopic evidence of cystitis cystica would both indicate to be predisposing factors. In these specific cases it is mandatory an accurate pre-operative evaluation of the voiding habits, in order to better define the treatment strategy, not only limited to the surgical correction of the associated reflux.

[Perforated appendicitis in a newborn infant associated with Down's syndrome. Review of the literature]. / Appendicite perforata in un neonato con associata sindrome di Down. Revisione della letteratura.

A seven days old male newborn with associated Down's syndrome suddenly presented with symptoms suggestive of intestinal obstruction. At laparotomy a perforated appendix with generalized peritonitis was discovered. This is the first case reported in the literature in association with the Down's syndrome.

[Congenital intrapericardial diaphragmatic hernia associated with an omphalocele in a newborn infant]. / L'ernia diaframmatica intrapericardica congenita associata ad onfalocele nel neonato.

The authors present a case of congenital intraperichardic diaphragmatic hernia and omphalocele, diagnosed on post birth day 11. The patient underwent an emergency procedure with evidenced an abdomino-perichardic hernia with perichardic sca due to the presence of a "breach gap" in the central-anterior region of the diaphragm. This rare malformation could be related to a development anomaly of the septum trasversum.