Minute Rest Period Research Articles

Effect of Capsaicinoid Ingestion on Blood Catecholamines and Markers of Lipolysis in Men and Women

BACKGROUND: Previous studies have demonstrated that capsaicinoid ingestion can increase lipolysis as measured via breath sample analysis. However, no human studies have included blood measures of catecholamines or markers of lipolysis, in particular while comparing men and women. PURPOSE: To compare blood epinephrine (EPI), norepinephrine (NE), free fatty acids (FFA) and glycerol concentrations before and after ingestion of a placebo or a taste-masked capsaicinoid supplement in men and women. METHODS: Ten men (25±1 yrs) and 10 women (24±1 yrs) ingested a placebo or a supplement (2 mg capsaicinoids) with one week separating conditions. A total of four fasting blood samples were collected from subjects during each visit; following a 30 minute rest period, immediately before placebo or supplement intake (Pre); 2 hours post intake (2 hr); immediately following the cessation of 30 minutes of exercise performed at 65% of maximal heart rate reserve (2.5 hr); 90 minutes following the cessation of exercise (4 hr). Heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure were recorded at all times. RESULTS: Although sex and time effects were noted for HR, SBP, and DBP (p<0.05; all higher for men compared to women; HR and SBP higher at 2.5 hr compared to Pre; DBP lower at 2.5 hr compared to Pre), no differences were noted in these variables between conditions (p>0.05). No condition main effects or condition interactions were noted for EPI, NE, FFA, or glycerol (p>0.05). However, a time effect was noted for all variables (p<0.0001), with values higher than Pre at 2.5 hr for EPI, FFA, and glycerol, and at 2 hr, 2.5 hr, and 4 hr for NE. A sex effect was noted for EPI (p<0.001) with men higher than women, and for FFA and glycerol (p<0.0001), for which women were higher than men. Contrast analysis indicated higher FFA at 2 hr (p=0.0003) and 2.5 hr (p=0.0001) for supplement compared to placebo when using percent change data, with only women contributing to this effect. CONCLUSION: Ingestion of a single low dose (2 mg) capsaicinoid supplement was not associated with any significant increase in EPI, NE, or glycerol compared to placebo. However, an increase in FFA (a marker of lipolysis) was noted, specifically in women. Lastly, no increase in HR, SBP, or DBP was noted with capsaicinoid supplementation. Supported by OmniActive Health Technologies

The effects of music on physiological responses and sedation scores in sedated, mechanically ventilated patients

A pilot study designed as future randomised controlled trial was carried out to determine the effects of music on physiological responses and sedation scores in sedated, mechanically ventilated patients. Mechanically ventilated ICU patients, even when receiving intravenous sedatives, may experience stress and anxiety. One possible intervention to reduce stress and anxiety is listening to music. A randomised controlled trial design with repeated measures was used. Data were collected over a six-month period in 2006. Twenty subjects were randomly assigned to either the experimental or control group. Subjects in the experimental group listened to music three times for 30 minutes over two days; subjects in the control group undertook three 30 minute rest periods. Physiological effects of music on systolic, diastolic and mean arterial blood pressure and heart and respiratory rate were assessed. Sedation scores were also measured. Physiological parameters did not show a significant difference between the groups. Patients in the experimental group showed significantly higher Ramsay (sedation) scores than patients in the control group after the first session. The higher scores indicate that patients were less responsive to external stimuli. Our results suggest that listening to music leads to higher sedation scores in sedated, mechanically ventilated ICU patients. No significant decreases in physiological parameters were observed. Listening to music showed no negative changes in the condition of these patients. Future research should focus on the use of other measures, such as stress hormones, to assess stress in sedated, mechanically ventilated ICU patients. For the sedated, mechanically ventilated ICU patient, the benefit of music may lie in the associated (deeper) level of sedation that is achieved, which in turn may make the patient less susceptible to stress and anxiety.

Effect Of A Dynamic Loaded Warm-Up On Vertical Jump Performance

The vertical jump is a common movement performed in several sports. Considering the importance of this movement, an optimal warm-up protocol may help athletes perform at their maximum level. The purpose of this study was to investigate the potentiating effects of different levels of external resistance (weight vest) during box jumps on vertical jump performance. Twenty resistance trained males (22.45 yrs ± 1.73,176.83 cm ± 6.67, 76.98 kg ± 8.56) participated in this study. Each subject's height, mass, and lateral femoral condyle height were measured on day one. Warm-up was performed by cycling for 5 minutes at a self selected pace. After the warm-up, subjects performed 5 jumps onto a box equivalent in height to their lateral femoral condyle. Following a 2 minute rest period, subjects performed 3 vertical jumps with the greatest height being recorded. On day one each subject performed a control condition with no external resistance to establish a baseline vertical jump height. On the following days they performed four random jump conditions with a weight vest equivalent to 5,10,15, or 20% of their bodyweight then rested for two minutes before performing 3 post-test vertical jumps. There was no significant interaction of condition by time for vertical jump height. However, there was a significant main effect for time (p < 0.05) with post-test scores (22.99 ± 3.35 inches) being greater than pre-test scores (22.69 ± 3.37 inches). Regardless of condition, post-test vertical jump performance was significantly greater than pre-test performance. Performing an active dynamic warm-up with or without a weight vest produced significantly greater post vertical jump performance. Findings from this study demonstrated that performing an active dynamic warm-up, with or without external resistance, can elicit a significant gain in vertical jump performance. This may allow athletes to perform at their maximum level in a performance environment. Future research should investigate the effects of different box heights, external loads, and volume on post vertical jump performance.

Rumination Predicts Longer Sleep Onset Latency After an Acute Psychosocial Stressor

Rumination has been linked to self-reported sleep quality. However, whether rumination is related to an objective sleep parameter has not been tested. This study examined whether rumination predicts sleep onset latency (SOL) on the night after an acute psychosocial stressor. We hypothesized that those who ruminate (assessed with both trait and stressor-specific measures) would have longer SOL (assessed with objective and subjective methods). Seventy participants delivered a 5-minute speech in front of an evaluative panel during an afternoon laboratory session. Trait rumination was assessed before the stressor. Stressor-specific rumination was captured with the frequency of task-related thoughts participants experienced during a 10-minute rest period after the stressor. Participants wore actigraphs on their wrists on the night after the laboratory session to measure objective sleep onset latency (SOL-O). Subjective sleep onset latency was estimated by participants on the subsequent morning. Consistent with hypotheses, trait and stressor-specific rumination predicted longer SOL-O and subjective sleep onset latency, respectively. In addition, trait and stressor-specific rumination interacted to predict longer SOL-O. SOL-O was longest among those who engaged in more stressor-specific rumination and had greater trait rumination scores. Neither rumination measure was related to sleep duration or wakefulness after sleep onset. The findings from this study are consistent with previous research linking rumination to subjective sleep quality. The results also suggest that post-stressor ruminative thought may predict delayed sleep onset for those with a propensity for rumination.

Exercise Recovery Hemodynamics In Overweight Vs. Obese Patients Diagnosed With Coronary Disease.

PURPOSE: To determine if blood pressures assessed during exercise recovery differ in overweight vs. obese patients diagnosed with coronary artery disease (CAD). METHODS: A group of 225 patients with CAD (N=183 males, mean age=63.5, mean BMI=30.2; N=42 females, mean age=64.0, mean BMI=30.2) underwent cycle exercise testing. Height and weight were assessed using calibrated equipment and BMI was calculated as weight (kg) / height (m) squared. All 225 test subjects were classified as either "overweight" (OW)(N=126) or "obese" (OB)(N=99) according to the National Institutes of Health guidelines. Resting systolic (SBP) and diastolic (DBP) blood pressures were taken following a 3 minute rest period. Mean arterial pressure (MAP) was estimated as [.3(SBP-DBP)]+DBP. Pressures were also assessed at 1, 3, and 5 minutes after the test. An analysis of covariance (ANCOVA) with resting pressure and body weight as covariates was used to determine if differences in recovery SBP, DBP, and estimated MAP were present at the three post-exercise recovery times (RT). RESULTS: After ACOVA adjustment, all three recovery pressures were higher in the obese group at every RT with statistical significance found at the 1 minute time point for DBP and MAP. CONCLUSION: Obese subjects with CAD demonstrate higher recovery SBP's, DBP's, and estimated MAP's than overweight subjects.Table: unadjusted means + SD, * = sig. different from OW, p<0.05

Spring-mass Leg Stiffness Is Not Affected By Brief Static Or Dynamic Stretching

Stretching has had a longstanding use in the development of flexibility, prevention of injury, and preparation for exercise. Recent research has demonstrated a loss of muscle power following an acute bout of prolonged static stretching. However studies using briefer periods of stretch or dynamic stretching have provided equivocal results. PURPOSE: To investigate the effect of brief static and non task-specific dynamic stretching on spring-mass leg stiffness in a vertical bouncing task. METHODS: 37 physically active male volunteers completed the study. Subjects were randomly assigned to one of two groups (natural bouncing [NAT], n= 20; maximal bouncing [MAX], n=17). NAT bounced at their self-selected stiffness and MAX were instructed to bounce as stiffly as possible. Bouncing was controlled at a frequency of 2.2 Hz (± 5%). After each of four treatment conditions, subjects completed three × 30 s bouts (separated by 2 minute rest periods) of vertical bouncing, in a counterbalanced crossover design. Treatment conditions were: no stretch (NO); single 30 s stretch (SS); repeated (4 ×) 30 s stretch (RS) and dynamic stretch (DY). Stretches were carried out on the gluteals, hamstrings, quadriceps and calves and did not involve any direct replication or rehearsal of the movements used in the bouncing task. Spring-mass leg stiffness was calculated as the ratio of peak vertical force to vertical displacement during ground contact. Data was collected via a piezoelectric force plate (1000 Hz) and vertical displacement calculated from the second integral of the acceleration curve. RESULTS: Three-factor ANOVA (group × treatment × bout) with repeated measures indicated that the MAX group were predictably stiffer than the NAT group (31162 ± 10080 vs 17324 ± 4871 N·m-1; F = 35.8; p < 0.001), the NAT group scores being similar to those elsewhere in the literature. There were no significant effects of treatment (F = 0.46; p = 0.71), bout (F = 0.05; p = 0.95), or interactions (p > 0.05) on leg stiffness scores. CONCLUSIONS: Relative to control (NO), the results of this study showed that brief static stretching or non task-specific dynamic stretching does not affect spring-mass leg stiffness during vertical bouncing.

Comparison of Methods to Quantify Volume During Resistance Exercise

The purpose of this investigation was to compare 4 different methods of calculating volume when comparing resistance exercise protocols of varying intensities. Ten Appalachian State University students experienced in resistance exercise completed 3 different resistance exercise protocols on different days using a randomized, crossover design, with 1 week of rest between each protocol. The protocols included 1) hypertrophy: 4 sets of 10 repetitions in the squat at 75% of a 1-repetition maximum (1RM) (90-second rest periods); 2) strength: 11 sets of 3 repetitions at 90% 1RM (5-minute rest periods); and 3) power: 8 sets of 6 repetitions of jump squats at 0% 1RM (3-minute rest periods). The volume of resistance exercise completed during each protocol was determined with 4 different methods: 1) volume load (VL) (repetitions [no.] x external load [kg]); 2) maximum dynamic strength volume load (MDSVL) (repetitions [no.] x [body mass--shank mass (kg) + external load (kg)]); 3) time under tension (TUT) (eccentric time +milliseconds] + concentric time +milliseconds]); and 4) total work (TW) (force [N] x displacement [m]). The volumes differed significantly (p , 0.05) between hypertrophy and strength in comparison with the power protocol when VL and MDSVL were used to determine the volume of resistance exercise completed. Furthermore, significant differences in TUT existed between all 3 resistance exercise protocols. The TW calculated was not significantly different between the 3 protocols. These data imply that each method examined results in substantially different values when comparing various resistance exercise protocols involving different levels of intensity.

Abstract P76: Assessment of Resuscitation Skills in Foundation Year 1 Hospital Doctors in Northern Ireland

Aims: To assess Foundation Year 1 (F1) doctors’ ability to perform effective cardiopulmonary resuscitation (CPR) using different chest compression:ventilation ratios. Methods: All forty F1 doctors working in a major teaching hospital were asked to participate in the study. Thirty four doctors participated, eighteen male and sixteen female. BMI was recorded in each case. They were asked to perform two, three minute sessions of CPR on a skills reporter manikin separated by a five minute rest period. Half of the doctors started using a ratio of 15:2 and half used 30:2. After a five minute rest the alternate ratio was performed. Their performance was assessed both objectively, by measuring the rate and depth of chest compressions, and subjectively by a panel of five advanced life support (ALS) instructors who reviewed tracings of each CPR session. Results: Mean compression rate per minute was sixty five while performing 15:2 and ninety one at 30:2. Chest compressions were effective if &gt;38mm. Twenty three doctors (67.7%) achieved &gt;80% effective chest compressions at a ratio of 15:2, compared with nineteen doctors (55.9%) at 30:2. At 15:2, males were 89% effective compared to 44% of females. At 30:2 males were 83 % effective compared to 25% of females. At 15:2 82% of compressions were effective in BMI&gt;24 group compared with 50% of BMI&lt;24. At 30:2 BMI&gt;24 achieved 76% effective compared with 35% in BMI&lt;24 group. Outcome measures shown in table 1 show no statistical difference between 15:2 and 30:2. Subjectively, 41% of doctors were deemed effective at 15:2 compared with 35% at 30:2. Conclusions: A significant number of F1 doctors are unable to perform effective CPR. Objectively, F1 doctors performed better at 15:2 than 30:2 but no statistical significance was noted. Subjectively, ALS instructors favoured the 15:2 regieme. CPR was performed better by males and doctors with BMI&gt;24. F1 doctors’ should be carefully assessed before they act as first responders at in-hospital cardiac arrests. Mean difference between 15:2 and 30:2

Abstract P93: Heart Rate Variability Analysis using Wavelet Transform to Predict Hemorrhage Severity

Introduction: The Pulse Initiative on resuscitation identified the need to develop biosensing for detection of critical limitations of blood flow. The ability to rapidly detect the severity of hemorrhage based on heart rate has been limited. Use of heart rate variability (HRV) is problematic. We used a number of new defined ECG features based on discrete wavelet transformation (DWT) that may be used to estimate blood loss severity. The features are defined based on the energy of detail coefficients of Daubecies DWT. Methods: The performance of DWT was tested using ECG data from a human model of hemorrhage using lower body negative pressure (LBNP). LBNP consisted of a 5-minute rest period (0 mm Hg) followed by 5 minutes of chamber decompression of the lower body to −15, −30, −45, and −60 mm Hg and additional increments of −10 mm Hg every 5 minutes until the onset of cardiovascular collapse. These levels were divided into 3 classes (mild: −15 to −30 mmHg; moderate: −45 to −60 mmHg; severe: over −60 mmHg). These levels correspond to estimated blood losses of 400 –550 cc, 500 –1000 cc and greater than 1000 cc respectively. The ECG DWT features of subjects were used for classification of each ECG recording during volume loss levels. Before classification in order to eliminate redundancy among the features, principal component analysis is applied to the feature set. Machine learning algorithms (SVM, AdaBoost, C4.5) were then applied to analyze the processed features and predict the severity of blood loss. Results: A 219 sample set was used to classify groups by using machine learning algorithms with 10-fold cross validation. C4.5 outperformed other algorithms with a prediction accuracy of 74.4%. The average precision and recall (sensitivity) for the three classes were 77.4% and 76.1%, respectively. In particular, 30 out of 39 cases in the severe class were correctly classified by C4.5. These results required sampling rates of only 125 Hz. Conclusion: This is the first reported use of an ECG analysis method to classify volume loss. The DWT method described may have the ability to rapidly determine the degree of volume loss from hemorrhage providing for more rapid triage and decision making. This may be particularly helpful for remote monitoring of war fighters or for mass casualty care.

Rumination and Cortisol Responses to Laboratory Stressors

For some, a stressor's psychological and physiological influence ceases on removal; for others, the effects may persist through rumination. These repetitive, intrusive thoughts might prolong physiological stress responses. Previous studies produced mixed results, indicating a need to clarify the relationship between rumination and cortisol responses. The current study investigated whether a laboratory speech task is sufficient to elicit rumination and whether those who ruminated in response to the speech task have elevated cortis of responses. Additionally, whether trait depressive rumination follows a similar pattern was examined. It was hypothesized that those delivering speeches in a social-evaluative context would experience more posttask rumination and that greater posttask rumination would predict elevated cortisol responses. Eighty-nine participants performed a speech in front of an evaluative panel (SET) or in one of two nonexplicitly evaluative conditions. Participants indicated the frequency of the thoughts they experienced during a 10-minute rest period after the speech as a measure of posttask rumination. Salivary cortisol was collected at five time points throughout the session. The SET condition elicited more posttask rumination than the nonexplicitly evaluative conditions. Posttask rumination was associated with amplified and prolonged elevations in cortisol across all conditions. Trait depressive rumination was associated with blunted cortisol responses in the SET condition. There was no association between trait depressive rumination and cortisol responses in the nonexplicitly evaluative conditions. Results suggest that the nature of the relationship between cortisol activation and rumination may be contingent on how rumination is conceptualized and measured.

Trunk sway analysis to quantify the warm-up phenomenon in myotonia congenita patients

Objective:Patients with autosomal recessive myotonia congenita display myotonia and transient paresis that diminish with repetitive muscle contractions (warm-up phenomenon). A new approach is presented to quantify this warm-up phenomenon under...

The Effect of Warm-Up on High-Intensity, Intermittent Running Using Nonmotorized Treadmill Ergometry

The aim of this study was to investigate the effect of previous warming on high-intensity intermittent running using nonmotorized treadmill ergometry. Ten male soccer players completed a repeated sprint test (10 x 6-second sprints with 34-second recovery) on a nonmotorized treadmill preceded by an active warm-up (10 minutes of running: 70% VO2max; mean core temperature (Tc) 37.8 +/- 0.2 degrees C), a passive warm-up (hot water submersion: 40.1 +/- 0.2 degrees C until Tc reached that of the active warm-up; 10 minutes +/- 23 seconds), or no warm-up (control). All warm-up conditions were followed by a 10-minute static recovery period with no stretching permitted. After the 10-minute rest period, Tc was higher before exercise in the passive trial (38.0 +/- 0.2 degrees C) compared to the active (37.7 +/- 0.4 degrees C) and control trials (37.2 +/- 0.2 degrees C; p < 0.05). There were no differences in pre-exercise oxygen consumption and blood lactate concentration; however, heart rate was greater in the active trial (p < 0.05). The peak mean 1-second maximum speed (MxSP) and group mean MxSP were not different in the active and passive trials (7.28 +/- 0.12 and 7.16 +/- 0.10 m x s(-1), respectively, and 7.07 +/- 0.33 and 7.02 +/- 0.24 m x s(-1), respectively; p > 0.05), although both were greater than the control. The percentage of decrement in performance fatigue was similar between all conditions (active, 3.4 +/- 1.3%; passive, 4.0 +/- 2.0%; and control, 3.7 +/- 2.4%). We conclude that there is no difference in high-intensity intermittent running performance when preceded by an active or passive warm-up when matched for post-warm-up Tc. However, repeated sprinting ability is significantly improved after both active and passive warm-ups compared to no warm-up.

The Effects of an Acute Bout of Plyometrics on Muscle Fatigue in Female Athletes

It is often presumed that after performing plyometric exercises muscle fatigue and delayed onset muscle soreness occur resulting in an overall decline in athletic performance. For this reason many coaches do not employ plyometric training within 24 hours of competition, however, very little of the plyometric research has been performed on plyometrically trained athletes. PURPOSE: To evaluate muscle fatigue in female athletes accustomed to plyometric training immediately after and 24 hours after an acute bout of plyometric exercises. METHODS: Twenty-three females aged 18-22 years (165± 2.59 cm; 65.9± 10.53 kg) from the Syracuse University soccer and field hockey teams participated in this study. The subjects completed 10 plyometric exercises consisting of various forms of squat jumps, lateral jumps, box jumps and skipping with one minute rest periods between exercises. Force production of the knee extensors (KE) and knee flexors (KF), vertical jump height, and the Illinois Agility Test were used to assess muscle fatigue and athletic performance. Additionally, surface electromyogram (EMG) signals were collected from the thigh muscles and analyzed for root mean square (RMS) alterations during maximal and submaximal contractions. These tests were completed prior to, immediately after and 24 hours after the plyometric exercises. RESULTS: KE and KF force production decreased 14 and 10% respectively immediately after the exercise (p=0.000 and p=0.001) and KE force remained 7% lower than pre-exercise at 24-hours post exercise (p=0.032). During the submaximal contractions, RMS EMG was significantly elevated immediately after the exercise in the rectus femoris (p=0.026) and vastus medialis (p=0.001)muscles only. Immediately after the exercise the time to complete the Illinois Agility Test increased 3% (p=0.006) and vertical jump ability declined 6% (p=0.18). CONCLUSIONS: Decrements in performance were seen immediately after exercise indicating that fatigue had occurred, but most measurements (with the exception of KE strength) returned to pre-exercise values at 24-hours after exercise. An intense bout of plyometrics should not be performed the day before competition because muscle strength may not be fully recovered the following day.

Validation Of The Cosmed K4 b2 Portable Metabolic System In Measuring STEADY-STATE Walking Energy Expenditure

PURPOSE: The purpose of this study was to assess the accuracy of the Cosmed k4b2 portable metabolic analyzer (Cosmed, Rome, Italy) against the Medgraphics D-Series gas exchange system (Medical Graphics Corporation, St Paul, MN) during steady state, submaximal walking exercise. METHODS: Nineteen men and women (9 women, 10 men) with an average age of 39.8 years (± 13.8) completed two consecutive 400 meter walk tests, separated by a 10 minute rest period, at a constant, self-selected pace on a treadmill. Oxygen consumption (VO2) and carbon dioxide production (VCO2) from the steady state portion of each 400m walk were analyzed. RESULTS: All subjects (N=19) successfully completed both tests. Intraclass Correlation Coefficient (ICC) and Pearson values between the two machines for VO2 (ml/kg/min), VO2 (ml/min), and VCO2 (ml/min) indicate high correlation.Table: Caption not availableA comparison of the average values obtained using the Cosmed and Medgraphics analyzers using paired t-tests indicate no significant difference for VO2 (ml/kg/ min) overall (p=0.27), or by gender (p=0.28 females, p=0.58 males). Results were not significantly different for VO2 (ml/min) or VCO2 (ml/min) over all participants (p=0.12, p=.11, respectively), or when stratified by gender (VO2: p=0.42 males, p=0.11 females; VCO2: p=.15 males, p=0.53 females). There was a trend towards lower VO2 values and higher CO2 values with the Cosmed unit, however the difference was not significant at the p = 0.05 level. CONCLUSION: These results indicate that the Cosmed k4b2 portable metabolic analyzer is acceptable for measuring VO2 and VCO2 during steady state, submaximal exercise.

Substrate Utilization during Sub-Maximal Exercise in Lean and Overweight Children

PURPOSE: To examine the rates of substrate utilization in lean and overweight children during sub-maximal exercise. METHODS: Seventeen (10 boys/7 girls) overweight [BMI >85th percentile] and twenty (10 boys/10 girls) lean children aged 7–10 years participated. Aerobic fitness was assessed by maximal oxygen consumption (VO2max) test using the Bruce protocol. The exercise session consisted of subjects performing 3 separate 8-minute bouts of treadmill walking: 1.7mph, 0%grade; 2.5mph, 0%grade; and 3.4mph, 0%grade. Each 8-minute, exercise workload was followed by a 5-minute rest period. Carbohydrate (CHOox) and fat (FATox) oxidization rates were calculated from oxygen uptake and carbon dioxide output for each minute during the steady-state sub-maximal exercise bouts using the stochiometric equations of Frayn (1983). RESULTS: Overweight children had significant lower VO2max values (37.8±3.8 vs. 45.9±5.1 mL. kg-1.min-1; P<0.0001) and exercise time (464±57 vs. 539±65 s; P<0.001) when compared to lean children. No differences were observed for FATox rate between groups at any sub-maximal exercise workload. Overweight children had a significantly greater CHOox rate during each exercise bout when compared to lean children (1.7mph = 0.42±0.13 vs. 0.31±0.09 g.min-1, P<0.01; 2.5mph = 0.50±0.12 vs. 0.39±0.11 g.min-1, P<0.005; 3.4mph = 0.81±0.19 vs. 0.57±0.14 g.min-1, P<0.0005). Finally, energy expenditure was greater for the overweight children at each exercise workload when compared to lean children (1.7mph = 2.47±0.50 vs. 1.92±0.22 kcal. min-1, P<0.0001; 2.5mph = 2.99±0.59 vs. 2.30±0.29 kcal.min-1, P<0.0001; 3.4mph = 4.17±0.78 vs. 3.17±0.43 kcal.min-1, P<0.0001). CONCLUSIONS: The differences for substrate utilization between lean and overweight children may be attributed to higher relative exercise intensities in the overweight children during the exercise trial. Future investigations should examine substrate utilization rate in lean and overweight children at the same percentage of aerobic fitness.

Post-Exercise Hyperemic Response Adds to Muscle Microvascular Flow Changes during Lower Body Pressure

Exercise increases muscle microvascular flow via vasodilation from both endothelial dependent and independent mechanisms. Altered transmural pressure also affects blood flow in muscle. For example, lower body negative pressure decreases and lower body positive pressure increases blood flow. PURPOSE: To determine muscle microvascular blood flow (MBF) during post-exercise hyperemia at negative and positive lower body pressure (LBP). It was hypothesized that the post-exercise hyperemic response would not be present at increased levels of positive LBP. METHODS: Eight healthy subjects (6 male, 2 female; ages 21–41) were placed supine in a LBP chamber that was sealed at the waist. Photoplethysmography was used to noninvasively measure MBF of the tibialis anterior muscle and skin microvascular blood flow (SBF) of overlying skin during exposure to a series of LBP levels (−30, −20, −10, 0, 10, 20, 30mmHg) with and without dorsiflexion exercise. At each pressure level MBF was allowed to stabilize for one minute prior to a one minute baseline data collection. Subjects then performed a one minute isometric dorsiflexion at a resistance of 41N and MBF was recorded for one minute following dorsiflexion. Subjects were given a 5 minute rest period between pressure levels to ensure MBF return to baseline. All microvascular flow data were normalized to the control value obtained at ambient pressure without exercise and presented as percentages (mean±SE) to compare between conditions. Data were analyzed using two-way repeated measures ANOVA to determine exercise effect and pressure effect on MBF. RESULTS: MBF and SBF increased at all LBP levels with exercise compared to no exercise (p=0.001 and p=0.005). MBF significantly decreased with negative pressure and increased with positive pressure (p=0.003 and p<0.001). The lowest MBF was at −30mmHg (52±9% w/o exercise, 61±9% w/ exercise) and the highest was at 10mmHg (137±15% w/o exercise, 145±12% w/ exercise). CONCLUSION: Post exercise hyperemia occurs at all lower body pressure levels studied. Elevation of microvascular flow after isometric exercise adds to changes measured at different levels of LBP. Regimens for exercise training and post-injury rehabilitation may benefit from exercise at low levels of positive LBP. Supported by NIH Training Grant 2 T32AR07484-22 to GCM.

Efeitos hemodinâmicos da intoxicação aguda com bupivacaína e a mistura enantiomérica: estudo experimental em suínos

Racemic bupivacaine has been the local anaesthetic of choice in regional blocks due to quality and duration of anesthesia. However its cardiovascular toxicity has been a source of concern and research has been made for lesser impact drugs. One choice is its levogyre isomer, levobupivacaine, apparently less cardiotoxic due a lower affinity to the heart sodium channels. In Brazil, a drug containing 75% of levogyre isomer and 25% of dextrogyre isomer, called enantiomeric excess mixture, is available. This study intends to evaluate haemodynamic effects of the intravascular injection of a toxic dose of both agents in swine. Large White pigs were anaesthetized with thiopental, intubated and placed on mechanical ventilation. Haemodynamic monitoring was performed with an invasive blood pressure and Swan-Ganz catheter on a pulmonary artery. After a 30 minute rest period, animals were randomly divided in two groups and the intoxication was performed on a double-blind method with 4 mg.kg-1 of one of the drugs. Haemodynamic parameters were then evaluated at 1, 5, 10, 15, 20 and 30 minutes. The enantiomeric excess mixture caused greater haemodynamic effects than the racemic bupivacaine. These results diverge from those found in humans with levogyre isomer but are similar to recent results reported in animals. Care should be taken when extrapolating data obtained in swine to humans and further research is necessary. When high doses are injected in swine, the enantiomeric excess mixture was more toxic than the racemic bupivacaine.

Relationships between adrenocorticotropic hormone and cortisol are altered during clustered nursing care in preterm infants born at extremely low gestational age

Background Little is known about the effects of clustered nursing care on hypothalamic pituitary axis (HPA) responses in preterm infants in the neonatal intensive care unit. Aims To examine facial responses, adrenocorticotropic hormone (ACTH) and cortisol levels, and the relationship between ACTH and cortisol in preterm infants in two gestational age groups (extremely low gestational age [ELGA: ≤ 28 weeks]; very low gestational age [VLGA: 29–31 weeks]) under basal conditions and in response to routine nursing procedures. Study design Within subjects' cross-over design in random order. Subjects Ninety preterm infants with no postnatal steroid exposure were studied at 32 ± 1 weeks postconceptional age. Outcome measures Facial actions, ACTH and cortisol levels were measured after a 30 minute rest period and in response to routine clustered nursing care (CC). Changes in facial actions were analyzed using repeated measures ANOVA. MANOVA or Mann–Whitney U tests were used to determine differences in ACTH and cortisol between gestational age groups. Spearman rank correlations were used to examine relationships between perinatal variables and facial, ACTH and cortisol levels. Results All infants had significantly increased facial responses to CC ( p = 0.001). Infants having experienced higher numbers of skin breaking procedures 24 h before basal assessment had higher basal cortisol levels ( r = 0.30, p = 0.01). In response to CC, ELGA infants showed no correlation between ACTH and cortisol levels; VLGA infants showed a strong, positive correlation ( r = 0.62, p = 0.02). Conclusion The pattern of relationship between ACTH and cortisol differs depending on gestational age at birth in response to clustered nursing care. Prior pain alters responsiveness and HPA dysregulation is apparent in ELGA infants.

High‐repetition cyclic loading is a risk factor for a lumbar disorder

Epidemiological data suggest that prolonged exposure to cyclic lumbar flexion elicits a chronic neuromuscular disorder and disability in workers. This study provides a physiological and biomechanical assessment of various repetitions of cyclic lumbar flexion sessions as a risk factor for development of an acute neuromuscular disorder. An in vivo feline model was subjected to 10 minutes of cyclic (0.25-HZ) loading, followed by a 10-minute rest period, repeated three times in one experimental group, six times in a second group, and nine times in the third group, followed by rest for 7 hours. Displacement of the lumbar viscoelastic tissue and reflex electromyographic (EMG) activity from the lumbar multifidus muscle were monitored. Creep developed and accumulated during each load/rest period and partially recovered during the subsequent rest. Loading periods were characterized by a decrease in reflex EMG activity with superimposed spasms. In the 7-hour recovery period, initial hyperexcitability was present in all groups, whereas only the six- and nine-repetition groups displayed significant delayed hyperexcitability, indicating the presence of acute inflammation. The mathematical model developed fit the data reasonably well, as the R2 values were generally near 0.90. It was concluded that the resulting delayed muscular hyperexcitability constitutes an acute neuromuscular disorder associated with exposure to many repetitions of cyclic lumbar flexion. The acute disorder can become chronic if not allowed sufficient rest to resolve itself. Workers engaged in cyclic lumbar flexion (e.g., loading/unloading, assembly workers) should avoid long-term exposure in order to prevent the development of a chronic neuromuscular condition known as cumulative trauma disorder.

The Effects of Glucose Consumption and 8 Hours of Submaximal Exercise on Heart Rate Variability in Trained Males

PURPOSE: The purpose of this study was to determine the effects of consuming a glucose beverage on heart rate variability (HRV) measures in trained males across 8 hours of submaximal exercise. METHODS: Subjects (n=8) completed two 8-hour bouts of exercise (Carbohydrate (CHO), placebo) alternating between 25-minute portions of cycling and treadmill walking with 5-minute rest periods. During each 25-minute interval, subjects exercised at varying moderate to hard workloads that were based on ventilatory threshold. For the CHO trial, 15 g of CHO in a 10% solution glucose beverage was provided every 15 minutes. Supine 4-minute HRV measurements were collected pre and post-exercise. Measurements included standard deviation of R-R interval (SDNN), low frequency (LF), and high frequency (HF). Data were collected with a Polar S-810i heart rate monitor and analyzed with Fourier Transform software. A 2-way, within subjects, repeated measures ANO VA was used for statistical analysis to assess effects of time and feeding strategy. RESULTS: Overall, SDNN was lower post-exercise (pre=69.94±32.32 versus post=47.39±23.09 ms, p < 0.05). No significant main effect changes occurred in LF or HF measurements. There was no treatment (CHO versus placebo) effect for any HRV measurement. CONCLUSIONS: These data demonstrate that 8 hours of exercise decreases SDNN, showing a decreased overall variability in heart rate, but this variability was not identified as specifically LF or HF. Consumption of a 12% solution glucose beverage throughout an 8-hour exercise regimen of cycling and treadmill walking does not affect any heart rate variability measurements.