Half-marathon and full-marathon runners' hydration practices and perceptions

Context:

The behaviors and beliefs of recreational runners with regard to hydration maintenance are not well elucidated.

Objective:

To examine which beverages runners choose to drink and why, negative performance and health experiences related to dehydration, and methods used to assess hydration status.

Design:

Cross-sectional study.

Setting:

Marathon registration site.

Patients or Other Participants:

Men (n = 146) and women (n = 130) (age = 38.3 ± 11.3 years) registered for the 2010 Little Rock Half-Marathon or Full Marathon.

Intervention(s):

A 23-item questionnaire was administered to runners when they picked up their race timing chips.

Main Outcome Measure(s):

Runners were separated into tertiles (Low, Mod, High) based on z scores derived from training volume, expected performance, and running experience. We used a 100-mm visual analog scale with anchors of 0 (never) and 100 (always). Total sample responses and comparisons between tertile groups for questionnaire items are presented.

Results:

The High group (58±31) reported greater consumption of sport beverages in exercise environments than the Low (42 ± 35 mm) and Mod (39 ± 32 mm) groups (P < .05) and perceived sport beverages to be superior to water in meeting hydration needs (P < .05) and improving performance during runs greater than 1 hour (P < .05). Seventy percent of runners experienced 1 or more incidents in which they believed dehydration resulted in a major performance decrement, and 45% perceived dehydration to have resulted in adverse health effects. Twenty percent of runners reported monitoring their hydration status. Urine color was the method most often reported (7%), whereas only 2% reported measuring changes in body weight.

Conclusions:

Greater attention should be paid to informing runners of valid techniques to monitor hydration status and developing an appropriate individualized hydration strategy.     

Two different fatigue protocols and lower extremity motion patterns during a stop-jump task

Context:

Altered neuromuscular control strategies during fatigue probably contribute to the increased incidence of non-contact anterior cruciate ligament injuries in female athletes.

Objective:

To determine biomechanical differences between 2 fatigue protocols (slow linear oxidative fatigue protocol [SLO-FP] and functional agility short-term fatigue protocol [FAST-FP]) when performing a running-stop-jump task.

Design:

Controlled laboratory study.

Setting:

Laboratory.

Patients or Other Participants:

A convenience sample of 15 female soccer players (age = 19.2 ±0.8 years, height = 1.67±0.05m, mass = 61.7 + 8.1 kg) without injury participated.

Intervention(s):

Five successful trials of a running–stop-jump task were obtained prefatigue and postfatigue during the 2 protocols. For the SLO-FP, a peak oxygen consumption (V˙o₂peak) test was conducted before the fatigue protocol. Five minutes after the conclusion of the V˙o₂peak test, participants started the fatigue protocol by performing a 30-minute interval run. The FAST-FP consisted of 4 sets of a functional circuit. Repeated 2 (fatigue protocol) × 2 (time) analyses of variance were conducted to assess differences between the 2 protocols and time (prefatigue, postfatigue).

Main Outcome Measure(s):

Kinematic and kinetic measures of the hip and knee were obtained at different times while participants performed both protocols during prefatigue and postfatigue.

Results:

Internal adduction moment at initial contact (IC) was greater during FAST-FP (0.064 ±0.09 Nm/kgm) than SLO-FP (0.024±0.06 Nm/kgm) (F_1,14 = 5.610, P=.03). At IC, participants had less hip flexion postfatigue (44.7°±8.1°) than prefatigue (50.1°±9.5°) (F_1,14 = 16.229, P=.001). At peak vertical ground reaction force, participants had less hip flexion postfatigue (44.7°±8.4°) than prefatigue (50.4°±10.3°) (F_1,14 = 17.026, P=.001). At peak vertical ground reaction force, participants had less knee flexion postfatigue (−35.9°±6.5°) than prefatigue (−38.8°±5.03°) (F_1,14 = 11.537, P=.001).

Conclusions:

Our results demonstrated a more erect landing posture due to a decrease in hip and knee flexion angles in the postfatigue condition. The changes were similar between protocols; however, the FAST-FP was a clinically applicable 5-minute protocol, whereas the SLO-FP lasted approximately 45 minutes.     

A profile of glenohumeral internal and external rotation motion in the uninjured high school baseball pitcher, part I: motion

Context:

The magnitude of motion that is normal for the throwing shoulder in uninjured baseball pitchers has not been established. Chronologic factors contributing to adaptations in motion present in the thrower''s shoulder also have not been established.

Objectives:

To develop a normative profile of glenohumeral rotation motion in uninjured high school baseball pitchers and to evaluate the effect of chronologic characteristics on the development of adaptations in shoulder rotation motion.

Design:

Cohort study.

Setting:

Baseball playing field.

Patients or Other Participants:

A total of 210 uninjured male high school baseball pitchers (age = 16±1.1 years, height = 1.8 + 0.1 m, mass = 77.5±11.2 kg, pitching experience = 6±2.3 years).

Intervention(s):

Using standard goniometric techniques, we measured passive rotational glenohumeral range of motion bilaterally with participants in the supine position.

Main Outcome Measure(s):

Paired t tests were performed to identify differences in motion between limbs for the group. Analysis of variance and post hoc Tukey tests were conducted to identify differences in motion by age. Linear regressions were performed to determine the influence of chronologic factors on limb motion.

Results:

Rotation motion characteristics for the population were established. We found no difference between sides for external rotation (ER) at 0° of abduction (t₂₀₉ = 0.658, P = .51), but we found side-to-side differences in ER (t₂₀₉ = −13.012, P<.001) and internal rotation (t₂₀₉ = 15.304, P<.001) at 90° of abduction. Age at the time of testing was a significant negative predictor of ER motion for the dominant shoulder (R² = 0.019, P = .049) because less ER motion occurred at the dominant shoulder with advancing age. We found no differences in rotation motion in the dominant shoulder across ages (F_4,205 range, 0.451–1.730, P>.05).

Conclusions:

This range-of-motion profile might be used to assist with the interpretation of normal and atypical shoulder rotation motion in this population. Chronologic characteristics of athletes had no influence on range-of-motion adaptations in the thrower''s shoulder.     

Active stiffness and strength in people with unilateral anterior shoulder instability: a bilateral comparison

Context:

Active muscle stiffness might protect the unstable shoulder from recurrent dislocation.

Objective:

To compare strength and active stiffness in participants with unilateral anterior shoulder instability and to examine the relationship between active stiffness and functional ability.

Design:

Cross-sectional study.

Setting:

University research laboratory.

Patients or Other Participants:

Participants included 16 males (age range, 16–40 years; height = 179.4 ± 6.1 cm; mass = 79.1 ± 6.8 kg) with 2 or more episodes of unilateral traumatic anterior shoulder instability.

Main Outcome Measure(s):

Active stiffness and maximal voluntary strength were measured bilaterally in participants. In addition, quality of life, function, and perceived instability were measured using the Western Ontario Stability Index, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, and Single Alpha Numeric Evaluation, respectively.

Results:

We found less horizontal adduction strength (t₁₅ = −4.092, P = .001) and less stiffness at 30% (t₁₄ = −3.796, P = .002) and 50% (t₁₂ = −2.341, P = .04) maximal voluntary strength in the unstable than stable shoulder. Active stiffness was not correlated with quality of life, function, or perceived instability (r range, 0.0–0.25; P > .05).

Conclusions:

The observed reduction in stiffness in the unstable shoulder warrants inclusion of exercises in the rehabilitation program to protect the joint from perturbations that might lead to dislocation. The lack of association between active stiffness and quality of life, function, or perceived instability might indicate that stiffness plays a less direct role in shoulder stability.     

Increased Immunoendocrine Cells in Intestinal Mucosa of Postinfectious Irritable Bowel Syndrome Patients 3 Years after Acute Shigella Infection - An Observation in a Small Case Control Study

Purpose

Postinfectiously irritable bowel syndrome (PI-IBS) develops in 3-30% of individuals with bacterial gastroenteritis. Recent studies demonstrated increases in inflammatory components in gut mucosa of PI-IBS patients even after complete resolution of infection. We aimed to investigate histological changes in colon and rectum of PI-IBS subjects after long term period of infection.

Materials and Methods

We recruited PI-IBS subjects who had been diagnosed IBS after complete resolution of enteritis caused by shigellosis outbreak 3 years earlier. We compared unmatched four groups, PI-IBS (n = 4), non PI-IBS (n = 7), D-IBS (n = 7, diarrhea predominant type) and healthy controls (n = 10). All of them underwent colonoscopic biopsy at three areas, including descending colon (DC), sigmoid colon (SC) and rectum, which were assessed for 5-hydroxytryptamine (5-HT)/peptide YY (PYY)-containing enterochromaffin (EC) cell, intraepithelial (IEL) and lamina propria T lymphocyte (CD3), CD8 lymphocytes, mast cells and CD68/calprotectin+ macrophages.

Results

All subjects had no structural or gross abnormalities at colonoscopy. In PI-IBS, 5-HT containing EC cells, PYY containing EC cells, IELs, CD3 lymphocytes, CD8 lymphocytes, mast cells, and CD68 + macrophages were increased compared to control (p < 0.05). In D-IBS, PYY containing EC cells, IELs, and CD3 lymphocytes were increased compared to control (p < 0.05). In PI-IBS, 5-HT containing EC cells tended to increase and PYY containing EC cells, CD8 lymphocytes, mast cells, and CD68+ macrophages were increased compared to non PI-IBS (p < 0.05). Calprotectin + marcrophages were decreased in PI-IBS, non PI-IBS and IBS compared to control.

Conclusion

The immunoendocrine cells were sporadically increased in PI-IBS, non PI-IBS and D-IBS compared with control. Our findings in a very small number of patients suggest that mucosal inflammation may play a role in long-term PI-IBS, and that other sub-groups of IBS and larger scale studies are needed to confirm this observation.     

Acupuncture for ��frequent attenders�� with medically unexplained symptoms: a randomised controlled trial (CACTUS study)

Background

Medically unexplained physical symptoms (MUPS) are common and difficult to treat.

Aim

To investigate the effectiveness of adding five-element acupuncture to usual care in ‘frequent attenders’ with MUPS.

Design and setting

Randomised controlled trial in four London general practices.

Method

Participants were 80 adults with MUPS, consulting GPs ≥8 times/year. The intervention was individualised five-element acupuncture, ≥12 sessions, immediately (acupuncture group) and after 26 weeks (control group). The primary outcome was 26-week Measure Yourself Medical Outcome Profile (MYMOP); secondary outcomes were wellbeing (W-BQ12), EQ-5D, and GP consultation rate. Intention-to-treat analysis was used, adjusting for baseline outcomes.

Results

Participants (80% female, mean age 50 years, mixed ethnicity) had high health-resource use. Problems were 59% musculoskeletal; 65% >1 year duration. The 26-week questionnaire response rate was 89%. Compared to baseline, the mean 26-week MYMOP improved by 1.0 (95% confidence interval [CI] = 0.4 to 1.5) in the acupuncture group and 0.6 (95% CI = 0.3 to 0.9) in the control group (adjusted mean difference: acupuncture versus control –0.6 [95% CI = –1.1 to 0] P = 0.05). Other between-group adjusted mean differences were: W-BQ12 4.4 (95% CI = 1.6 to 7.2) P = 0.002; EQ-5D index 0.03 (95% CI = –0.11 to 0.16) P = 0.70; consultation rate ratio 0.90 (95% CI = 0.70 to 1.15) P = 0.4; and number of medications 0.56 (95% CI = 0.47 to 1.6) P = 0.28. All differences favoured the acupuncture group. Imputation for missing values reduced the MYMOP adjusted mean difference to –0.4 (95% CI = –0.9 to 0.1) P = 0.12. Improvements in MYMOP and W-BQ12 were maintained at 52 weeks.

Conclusion

The addition of 12 sessions of five-element acupuncture to usual care resulted in improved health status and wellbeing that was sustained for 12 months.     

Heat stress and cardiovascular, hormonal, and heat shock proteins in humans

Context:

Conditions such as osteoarthritis, obesity, and spinal cord injury limit the ability of patients to exercise, preventing them from experiencing many well-documented physiologic stressors. Recent evidence indicates that some of these stressors might derive from exercise-induced body temperature increases.

Objective:

To determine whether whole-body heat stress without exercise triggers cardiovascular, hormonal, and extra-cellular protein responses of exercise.

Design:

Randomized controlled trial.

Setting:

University research laboratory.

Patients or Other Participants:

Twenty-five young, healthy adults (13 men, 12 women; age = 22.1 ± 2.4 years, height = 175.2 ± 11.6 cm, mass = 69.4 ± 14.8 kg, body mass index = 22.6 ± 4.0) volunteered.

Intervention(s):

Participants sat in a heat stress chamber with heat (73°C) and without heat (26°C) stress for 30 minutes on separate days. We obtained blood samples from a subset of 13 participants (7 men, 6 women) before and after exposure to heat stress.

Main Outcome Measure(s):

Extracellular heat shock protein (HSP72) and catecholamine plasma concentration, heart rate, blood pressure, and heat perception.

Results:

After 30 minutes of heat stress, body temperature measured via rectal sensor increased by 0.8°C. Heart rate increased linearly to 131.4 ± 22.4 beats per minute (F_6,24 = 186, P < .001) and systolic and diastolic blood pressure decreased by 16 mm Hg (F_6,24 = 10.1, P < .001) and 5 mm Hg (F_6,24 = 5.4, P < .001), respectively. Norepinephrine (F_1,12 = 12.1, P = .004) and prolactin (F_1,12 = 30.2, P < .001) increased in the plasma (58% and 285%, respectively) (P < .05). The HSP72 (F_1,12 = 44.7, P < .001) level increased with heat stress by 48.7% ± 53.9%. No cardiovascular or blood variables showed changes during the control trials (quiet sitting in the heat chamber with no heat stress), resulting in differences between heat and control trials.

Conclusions:

We found that whole-body heat stress triggers some of the physiologic responses observed with exercise. Future studies are necessary to investigate whether carefully prescribed heat stress constitutes a method to augment or supplement exercise.     

Limb blood flow after class 4 laser therapy

Context:

Laser therapy is purported to improve blood flow in soft tissues. Modulating circulation would promote healing by controlling postinjury ischemia, hypoxia, edema, and secondary tissue damage. However, no studies have quantified these responses to laser therapy.

Objective:

To determine a therapeutic dose range for laser therapy for increasing blood flow to the forearm.

Design:

Crossover study.

Setting:

Controlled laboratory setting.

Patients or Other Participants:

Ten healthy, college-aged men (age = 20.80 ± 2.16 years, height = 177.93 ± 3.38 cm, weight = 73.64 ± 9.10 kg) with no current history of injury to the upper extremity or cardiovascular conditions.

Intervention(s):

A class 4 laser device was used to treat the biceps brachii muscle. Each grid point was treated for 3 to 4 seconds, for a total of 4 minutes. Each participant received 4 doses of laser therapy: sham, 1 W, 3 W, and 6 W.

Main Outcome Measure(s):

The dependent variables were changes in blood flow, measured using venous occlusion plethysmography. We used a repeated-measures analysis of variance to analyze changes in blood flow for each dose at 2, 3, and 4 minutes and at 1, 2, 3, 4, and 5 minutes after treatment. The Huynh-Feldt test was conducted to examine differences over time.

Results:

Compared with baseline, blood flow increased over time with the 3-W treatment (F_3,9 = 3.468, P < .011) at minute 4 of treatment (2.417 ± 0.342 versus 2.794 ± 0.351 mL/min per 100 mL tissue, P = .032), and at 1 minute (2.767 ± 0.358 mL/min per 100 mL tissue, P < .01) and 2 minutes (2.657 ± 0.369 mL/min per 100 mL tissue, P = .022) after treatment. The sham, 1-W, and 6-W treatment doses did not change blood flow from baseline at any time point.

Conclusions:

Laser therapy at the 3-W (360-J) dose level was an effective treatment modality to increase blood flow in the soft tissues.     

Comparison of recovery strategies on maximal force-generating capacity and electromyographic activity level of the knee extensor muscles

Context:

With regard to intermittent training exercise, the effects of the mode of recovery on subsequent performance are equivocal.

Objective:

To compare the effects of 3 types of recovery intervention on peak torque (PT) and electromyographic (EMG) activity of the knee extensor muscles after fatiguing isokinetic intermittent concentric exercise.

Design:

Crossover study.

Setting:

Research laboratory.

Patients or Other Participants:

Eight elite judo players (age = 18.4 ± 1.4 years, height = 180 ± 3 cm, mass = 77.0 ± 4.2 kg).

Interventions :

Participants completed 3 randomized sessions within 7 days. Each session consisted of 5 sets of 10 concentric knee extensions at 80% PT at 120°/s, with 3 minutes of recovery between sets. Recovery interventions were passive, active, and electromyostimulation. The PT and maximal EMG activity were recorded simultaneously while participants performed isokinetic dynamometer trials before and 3 minutes after the resistance exercise.

Main Outcome Measure(s):

The PT and maximal EMG activity from the knee extensors were quantified at isokinetic velocities of 60°/s, 120°/s, and 180°/s, with 5 repetitions at each velocity.

Results:

The reduction in PT observed after electromyo-stimulation was less than that seen after passive (P < .001) or active recovery (P < .001). The reduction in PT was less after passive recovery than after active recovery (P < .001). The maximal EMG activity level observed after electromyostimulation was higher than that seen after active recovery (P < .05).

Conclusions:

Electromyostimulation was an effective recovery tool in decreasing neuromuscular fatigue after high-intensity, intermittent isokinetic concentric exercise for the knee extensor muscles. Also, active recovery induced the greatest amount of neuromuscular fatigue.     

Adjunctive Cilostazol versus High Maintenance Dose of Clopidogrel in Patients with Hyporesponsiveness to Chronic Clopidogrel Therapy

Purpose

Whether addition of cilostazol is superior to increasing dose of clopidogrel in patients with hyporesponsiveness to chronic clopidogrel therapy is unknown.

Materials and Methods

We studied 73 patients with hyporesponsiveness to clopidogrel on standard dual antiplatelet therapy for more than 2 weeks. Clopidogrel hyporesponsiveness was defined as percent inhibition of P2Y12 reaction units (PRU) <30% on VerifyNow P2Y12 assay. Patients were randomly assigned to increased dose of clopidogrel (aspirin 100 mg+clopidogrel 150 mg daily: group A, n=38) or to receiving additional cilostazol (aspirin 100 mg+clopidogrel 75 mg+cilostazol 100 mg bid daily: group B, n=35).

Results

Baseline percent inhibition of PRU and PRU was similar between 2 groups (13.0±10.2% versus 11.8±9.7%, p=0.61, and 286.3±54.7 versus 295.7±53.7, p=0.44, respectively). At follow-up, percent inhibition of PRU was higher and PRU was lower significantly in group B than in group A (38.5±17.9% versus 28.3±16.6%, p=0.02, and 207.3±68.2 versus 241.3±76.7, p=0.050, respectively). Among those still showing hyporesponsiveness to clopidogrel at follow-up (21 patients in group A, 10 patients in group B), 12 patients completed further crossover study. Compared to the baseline, magnitude of change in percent inhibition of PRU and PRU showed an improved tendency after the crossover (from 2.7±8.7% to 15.8±18.4%, p=0.08, and from -18.6±58.0 to -61.9±84.3, p=0.08).

Conclusion

Adjunctive cilostazol improved clopidogrel responsiveness better than the higher maintenance dose of clopidogrel in hyporesponsive patients with chronic clopidogrel therapy.     

A profile of glenohumeral internal and external rotation motion in the uninjured high school baseball pitcher, part II: strength

Context:

A database describing the range of normal rotator cuff strength values in uninjured high school pitchers has not been established. Chronologic factors that contribute to adaptations in strength also have not been established.

Objectives:

To establish a normative profile of rotator cuff strength in uninjured high school baseball pitchers and to determine whether bilateral differences in rotator cuff strength are normal findings in this age group.

Design:

Cohort study.

Setting:

Baseball playing field.

Patients or Other Participants:

A total of 165 uninjured male high school baseball pitchers (age = 16 ± 1 years, height = 1.8 ± 0.1 m, mass = 76.8 ± 10.1 kg, pitching experience = 7 ± 2 years).

Main Outcome Measure(s):

Isometric rotator cuff strength was measured bilaterally with a handheld dynamometer. We calculated side-to-side differences in strength (external rotation [ER], internal rotation [IR], and the ratio of ER:IR at 90° of abduction), differences in strength by age, and the influence of chronologic factors (participant age, years of pitching experience) on limb strength.

Results:

Side-to-side differences in strength were found for ER, IR, and ER:IR ratio at 90° of abduction. Age at the time of testing was a significant but weak predictor of both ER strength (R² = 0.032, P = .02) and the ER:IR ratio (R² = 0.051, P = .004) at 90° of abduction.

Conclusions:

We established a normative profile of rotator cuff strength for the uninjured high school baseball pitcher that might be used to assist clinicians and researchers in the interpretation of muscle strength performance in this population. These data further suggested that dominant-limb adaptations in rotator cuff strength are a normal finding in this age group and did not demonstrate that these adaptations were a consequence of the age at the time of testing or the number of years of pitching experience.     

Dexmedetomidine for the prevention of shivering during spinal anesthesia

PURPOSE:

The aim of this study was to evaluate the effect of dexmedetomidine on shivering during spinal anesthesia.

METHODS:

Sixty patients (American Society of Anesthesiologists physical status I or II, aged 18-50 years), scheduled for elective minor surgical operations under spinal anesthesia with hyperbaric bupivacaine, were enrolled. They were administered saline (group C, n = 30) or dexmedetomidine (group D, n = 30). Motor block was assessed using a Modified Bromage Scale. The presence of shivering was assessed by a blinded observer after the completion of subarachnoid drug injection.

RESULTS:

Hypothermia was observed in 21 patients (70%) in group D and in 20 patients (66.7%) in group C (p = 0.781). Three patients (10%) in group D and 17 patients (56.7%) in group C experienced shivering (p = 0.001). The intensity of shivering was lower in group D than in group C (p = 0.001). Time from baseline to onset of shivering was 10 (5-15) min in group D and 15 (5-45) min in group C (p = 0.207).

CONCLUSION:

Dexmedetomidine infusion in the perioperative period significantly reduced shivering associated with spinal anesthesia during minor surgical procedures without any major adverse effect during the perioperative period. Therefore, we conclude that dexmedetomidine infusion is an effective drug for preventing shivering and providing sedation in patients during spinal anesthesia.     

Sex differences, hormone fluctuations, ankle stability, and dynamic postural control

Context:

Hormonal fluctuation as a risk factor in anterior cruciate ligament injury has been investigated with conflicting results. However, the influence of hormone fluctuations on ankle laxity and function has not been thoroughly examined.

Objective:

To examine the potential hormone contributions to ankle laxity and dynamic postural control during the preovulatory and postovulatory phases of the menstrual cycle using an ankle arthrometer and the Star Excursion Balance Test in healthy women. The cohort group consisted of male control participants.

Design:

Cohort study.

Setting:

Research laboratory.

Patients or Other Participants:

Twenty healthy women (age = 23.8 ± 6.50 years, height = 163.88 ± 8.28 cm, mass = 63.08 ± 12.38 kg) and 20 healthy men (age = 23.90 ± 4.15 years, height = 177.07 ± 7.60 cm, mass = 80.57 ± 12.20 kg).

Intervention(s):

Ankle stability was assessed with anterior-posterior and inversion-eversion loading. Dynamic postural control was assessed with the posteromedial reaching distance of the Star Excursion Balance Test.

Main Outcome Measure(s):

Female participants used ovulation kits for 3 months to determine the time of ovulation; during their preovulatory and postovulatory phases, they were tested in the laboratory with an ankle arthrometer and the Star Excursion Balance Test. Male participants were tested on similar dates as controls. For each dependent variable, a time by side by sex repeated-measures analysis of variance was performed. Statistical significance was set a priori at P < .05.

Results:

For anterior-posterior laxity, a side main effect was noted (F_1,38 = 10.93, P = .002). For inversion-eversion laxity, a sex main effect was seen (F_1,38 = 10.75, P = .002). For the posteromedial reaching task, a sex main effect was demonstrated (F_1,38 = 8.72, P = .005). No influences of time on the dependent variables were evident.

Conclusions:

Although women presented with more ankle inversion-eversion laxity and less dynamic postural control, hormonal fluctuations during the menstrual cycle (preovulatory compared with postovulatory) did not affect ankle laxity or dynamic postural control, 2 factors that are associated with ankle instability.     

Short-term diabetes attenuates left ventricular dysfunction and mortality rates after myocardial infarction in rodents

OBJECTIVES:

To investigate the effects of hyperglycemia on left ventricular dysfunction, morphometry, myocardial infarction area, hemodynamic parameters, oxidative stress profile, and mortality rate in rats that had undergone seven days of myocardial infarction.

INTRODUCTION:

Previous research has demonstrated that hyperglycemia may protect the heart against ischemic injury.

METHODS:

Male Wistar rats were divided into four groups: control-sham, diabetes-sham, myocardial infarction, and diabetes + myocardial infarction. Myocardial infarction was induced 14 days after diabetes induction. Ventricular function and morphometry, as well as oxidative stress and hemodynamic parameters, were evaluated after seven days of myocardial infarction.

RESULTS:

The myocardial infarction area, which was similar in the infarcted groups at the initial evaluation, was reduced in the diabetes + myocardial infarction animals (23±3%) when compared with the myocardial infarction (42±7%, p<0.001) animals at the final evaluation. The ejection fraction (22%, p = 0.003), velocity of circumferential fiber shortening (30%, p = 0.001), and left ventricular isovolumetric relaxation time (26%, p = 0.002) were increased in the diabetes + myocardial infarction group compared with the myocardial infarction group. The diabetes-sham and diabetes + myocardial infarction groups displayed increased catalase concentrations compared to the control-sham and myocardial infarction groups (diabetes-sham: 32±3; diabetes + myocardial infarction: 35±0.7; control-sham: 12±2; myocardial infarction: 16±0.1 pmol min^-1 mg^-1 protein). The levels of thiobarbituric acid-reactive substances were reduced in the diabetes-sham rats compared to the control-sham rats. These positive adaptations were reflected in a reduced mortality rate in the diabetes + myocardial infarction animals (18.5%) compared with the myocardial infarction animals (40.7%, p = 0.001).

CONCLUSIONS:

These data suggest that short-term hyperglycemia initiates compensatory mechanisms, as demonstrated by increased catalase levels, which culminate in improvements in the ventricular response, infarcted area, and mortality rate in diabetic rats exposed to ischemic injury.     

Self-paced exercise performance in the heat after pre-exercise cold-fluid ingestion

Context:

Precooling is the pre-exercise reduction of body temperature and is an effective method of improving physiologic function and exercise performance in environmental heat. A practical and effective method of precooling suitable for application at athletic venues has not been demonstrated.

Objective:

To confirm the effectiveness of pre-exercise ingestion of cold fluid without fluid ingestion during exercise on pre-exercise core temperature and to determine whether pre-exercise ingestion of cold fluid alone without continued provision of cold fluid during exercise can improve exercise performance in the heat.

Design:

Randomized controlled clinical trial.

Setting:

Environmental chamber at an exercise physiology laboratory that was maintained at 32°C, 60% relative humidity, and 3.2 m/s facing air velocity.

Patients or Other Participants:

Seven male recreational cyclists (age = 21 ± 1.5 years, height = 1.81 ± 0.07 m, mass = 78.4 ± 9.2 kg) participated.

Intervention(s):

Participants ingested 900 mL of cold (2°C) or control (37°C) flavored water in 3 300-mL aliquots over 35 minutes of pre-exercise rest.

Main Outcome Measure(s):

Rectal temperature and thermal comfort before exercise and distance cycled, power output, pacing, rectal temperature, mean skin temperature, heart rate, blood lactate, thermal comfort, perceived exertion, and sweat loss during exercise.

Results:

During rest, a greater decrease in rectal temperature was observed with ingestion of the cold fluid (0.41 ± 0.16°C) than the control fluid (0.17 ± 0.17°C) over 35 to 5 minutes before exercise (t₆ = −3.47, P = .01). During exercise, rectal temperature was lower after ingestion of the cold fluid at 5 to 25 minutes (t₆ range, 2.53–3.38, P ≤ .05). Distance cycled was greater after ingestion of the cold fluid (19.26 ± 2.91 km) than after ingestion of the control fluid (18.72 ± 2.59 km; t₆ = −2.80, P = .03). Mean power output also was greater after ingestion of the cold fluid (275 ± 27 W) than the control fluid (261 ± 22 W; t₆ = −2.13, P = .05). No differences were observed for pacing, mean skin temperature, heart rate, blood lactate, thermal comfort, perceived exertion, and sweat loss (P > .05).

Conclusions:

We demonstrated that pre-exercise ingestion of cold fluid is a simple, effective precooling method suitable for field-based application.     

Acute lower extremity running kinematics after a hamstring stretch

Context:

Limited passive hamstring flexibility might affect kinematics, performance, and injury risk during running. Pre-activity static straight-leg raise stretching often is used to gain passive hamstring flexibility.

Objective:

To investigate the acute effects of a single session of passive hamstring stretching on pelvic, hip, and knee kinematics during the swing phase of running.

Design:

Randomized controlled clinical trial.

Setting:

Biomechanics research laboratory.

Patients or Other Participants:

Thirty-four male (age = 21.2 ± 1.4 years) and female (age = 21.3±2.0 years) recreational athletes.

Intervention(s):

Participants performed treadmill running pretests and posttests at 70% of their age-predicted maximum heart rate. Pelvis, hip, and knee joint angles during the swing phase of 5 consecutive gait cycles were collected using a motion analysis system. Right and left hamstrings of the intervention group participants were passively stretched 3 times for 30 seconds in random order immediately after the pretest. Control group participants performed no stretching or movement between running sessions.

Main Outcome Measure(s):

Six 2-way analyses of variance to determine joint angle differences between groups at maximum hip flexion and maximum knee extension with an α level of .008.

Results:

Flexibility increased between pretest and post-test in all participants (F_1,30 = 80.61, P<.001). Anterior pelvic tilt (F_1,30 = 0.73, P=.40), hip flexion (F_1,30 = 2.44, P=.13), and knee extension (F_1,30 = 0.06, P=.80) at maximum hip flexion were similar between groups throughout testing. Anterior pelvic tilt (F_1,30 = 0.69, P=.41), hip flexion (F_1,30 = 0.23, P=.64), and knee extension (F_1,30 = 3.38, P=.62) at maximum knee extension were similar between groups throughout testing. Men demonstrated greater anterior pelvic tilt than women at maximum knee extension (F_1,30 = 13.62, P=.001).

Conclusions:

A single session of 3 straight-leg raise hamstring stretches did not change pelvis, hip, or knee running kinematics.     

Whey protein addition to a carbohydrate-electrolyte rehydration solution ingested after exercise in the heat

Context:

Many active people finish exercise hypohydrated, so effective rehydration after exercise is an important consideration.

Objective:

To determine the effects of a rehydration solution containing whey protein isolate on fluid balance after exercise-induced dehydration.

Design:

Randomized controlled clinical trial.

Setting:

University research laboratory.

Patients or Other Participants:

Twelve healthy men (age = 21 ± 1 years, height = 1.82 ± 0.08m, mass = 82.71 ± 10.31 kg) participated.

Intervention(s):

Participants reduced body mass by 1.86% ± 0.07% after intermittent exercise in the heat and re-hydrated with a volume of drink in liters equivalent to 1.5 times their body mass loss in kilograms of a solution of either 65 g/L carbohydrate (trial C) or 50 g/L carbohydrate and 15 g/L whey protein isolate (trial CP). Solutions were matched for energy density and electrolyte content. Urine samples were collected before and after exercise and for 4 hours after rehydration.

Main Outcome Measure(s):

We measured urine volume, drink retention, net fluid balance, urine osmolality, and subjective responses. Drink retention was calculated as the difference between the volume of drink ingested and urine produced. Net fluid balance was calculated from fluid gained through drink ingestion and fluid lost through sweat and urine production.

Results:

Total cumulative urine output after rehydration was not different between trial C (1173 ± 481 mL) and trial CP (1180 ± 330 mL) (F₁ = 0.002, P = .96), and drink retention during the study also was not different between trial C (50% ± 18%) and trial CP (49% ± 13%) (t₁₁ = −0.159, P = .88). At the end of the study, net fluid balance was negative compared with base-line for trial C (−432 ± 436 mL) (t₁₁ = 3.433, P = .03) and trial CP (−432 ± 302 mL) (t₁₁ = 4.958, P = .003).

Conclusions:

When matched for energy density and electrolyte content, a solution of carbohydrate and whey protein isolate neither increased nor decreased rehydration compared with a solution of carbohydrate.     

Craniofacial Phenotyping in Obstructive Sleep Apnea – A Novel Quantitative Photographic Approach

Study Objectives:

To compare the craniofacial morphological phenotype of subjects with and without obstructive sleep apnea (OSA) using a quantitative photographic analysis technique.

Design:

Case-control study; subgroup matched for body mass index (BMI) and sex.

Setting:

Sleep investigation unit in a university teaching hospital.

Patients:

114 subjects (93% Caucasian) with OSA (apnea-hypopnea index [AHI] ≥ 10/h) and 66 controls (AHI < 10/h).

Interventions:

Standardized frontal-profile craniofacial photographic imaging performed prior to polysomnography. Photographs were analyzed for the computation of linear, angular, area and polyhedral volume measurements representing dimensions and relationships of the various craniofacial regions.

Measurements and Results:

Photographic craniofacial phenotypic differences were demonstrated between OSA and control subjects, including a range of measurements of the face, mandible, maxilla, eyes, nose, head and neck. After 1-for-1 subgroup matching for BMI and sex (51 subjects in each group), mandibular length 1 (6.21 ± 0.08 [mean ± SEM] vs 6.58 ± 0.08 cm, P = 0.006), mandibular-nasion angle 1 (35.0 ± 0.48 vs 36.7 ± 0.37 degrees, P = 0.006) and anterior neck space area (10.2 ± 0.53 vs 12.2 ± 0.52 cm², P = 0.01) remained smaller in the OSA group. Mandibular width-length angle (88.0 ± 0.75 vs 85.3 ± 0.54 degrees, P = 0.005) and face width-midface depth angle (72.3 ± 0.44 vs 70.7 ± 0.39 degrees, P = 0.01) remained larger in the OSA group, whereas mandibular triangular area (39.2 ± 0.63 vs 41.7 ± 0.74 cm², P = 0.01) was smaller.

Conclusions:

Craniofacial phenotypic differences in OSA in Caucasian subjects can be demonstrated using a photographic analysis technique.

Citation:

Lee RWW; Chan ASL; Grunstein RR; Cistulli PA. Craniofacial phenotyping in obstructive sleep apnea – a novel quantitative photographic approach. SLEEP 2009;32(1):37–45.