Thermoregulation in boys and men exercising at the same heat production per unit body mass.

PURPOSE: Child-adult thermoregulatory comparisons may be biased by differences in metabolic heat production ([Formula: see text]). We compared thermoregulatory responses of boys and men exercising at two intensities prescribed to elicit either a fixed [Formula: see text] per unit body mass (BM) or a fixed absolute [Formula: see text]. METHODS: Ten boys (10-12 years) and 10 men (19-25 years) performed 4 × 20-min cycling at a fixed [Formula: see text] per BM (W kg(-1)) at 35 °C and 35 % relative humidity (MENREL). Men also cycled (MENABS) at the same absolute [Formula: see text] (in W) as the boys. RESULTS: [Formula: see text] was lower in boys compared with MENREL, but similar to MENABS (mean ± SD, 233.6 ± 38.4, 396.5 ± 72.3, 233.6 ± 34.1 W, respectively, P < 0.001). Conversely, [Formula: see text] per unit BM was similar between boys and MENREL, and lower in MENABS (5.7 ± 1.0, 5.6 ± 0.8 and 3.3 ± 0.3 W kg(-1), respectively; P < 0.001). The change in rectal temperature was similar between boys and MENREL (0.6 ± 0.2 vs. 0.7 ± 0.2 °C, P = 0.92) but was lower in MENABS (0.3 ± 0.2 °C, P = 0.004). Sweat volume was lower in boys compared to MENABS (500 ± 173 vs. 710 ± 150 mL; P = 0.041), despite the same evaporative heat balance requirement (E req) (199.1 ± 34.2 vs. 201.0 ± 32.7 W, P = 0.87). CONCLUSION: Boys and men demonstrated similar thermoregulatory responses to 80 min of exercise in the heat performed at a fixed [Formula: see text] per unit BM. Sweat volume was lower in boys compared to men, despite similarities in absolute [Formula: see text] and E req.

Mild to moderate hypohydration reduces boys' high-intensity cycling performance in the heat.

PURPOSE: To evaluate the effect of 1 and 2 % hypohydration on high-intensity cycling performance of 10- to 12-year-old boys in the heat. METHODS: In a counterbalanced order, nine boys attended three sessions in which they cycled intermittently (6 × 10-min bouts at 40-45 % [Formula: see text]) in a climate chamber. During each session, environmental conditions and water intake were individually adjusted to achieve a target hypohydration level of 0, 1 or 2 %, based on change in body weight (BW). Following 45 min of rest in thermoneutral conditions when the target hypohydration was maintained, each boy re-entered the climate chamber (35 °C and 50-55 % RH) to perform the cycling performance test at 90 % [Formula: see text] until exhaustion. Heart rate (HR) and rectal temperature (T re) were recorded continuously throughout each session. Total mechanical work (TMW) was taken as a measure of cycling performance. RESULTS: Actual hypohydration level at the start of the cycling performance test in each session was: 0.1 ± 0.0 %, 1.1 ± 0.1 % and 2.0 ± 0.1 %. With 2 % hypohydration, TMW (35.5 ± 6.8 kJ) was significantly (p < 0.05) lower than with 0 % hypohydration (49.3 ± 9.8 kJ). When expressed as a percentage of TMW with 0 % hypohydration, TMW was reduced by 15.5 and 23.3 % with 1 and 2 % hypohydration, respectively (p < 0.05 for both). At the start of the cycling performance test, HR was 13 and 15 bpm higher, and T re was 0.3 °C higher (p < 0.05 for all) with 1 and 2 % hypohydration, respectively, compared with 0 % hypohydration. CONCLUSION: Mild (~1 %) to moderate (~2 %) hypohydration reduces high-intensity cycling performance of healthy young boys in the heat.

Body weight changes in child and adolescent athletes during a triathlon competition.

We examined young athletes during a triathlon performed in a hot climate. Complete or partial data were available for 95 athletes competing in the National Triathlon Championship in Costa Rica. Mean ± SD for age and body weight (BW) were 13.1 ± 2.5 years and 46.3 ± 11.5 kg, respectively. Race requirements included: 500 m swimming, 15 km cycling, 3.5 km running for juniors (9-13 years); 800 m swimming, 30 km cycling, 8 km running for seniors (14-17 years). WBGT on race day was >31 °C. BW recorded pre- and post-race was available for 92 athletes and performance data were available for 83 of these. Information regarding symptoms experienced during the race was available for 95 athletes. Change in BW (%ΔBW) was calculated and ranged from +0.6 to -2.4 % for junior boys (-1.2 ± 0.9 %), +0.7 to -2.5 % for junior girls (-1.3 ± 0.9 %), 0 to -2.8 % for senior girls (-1.3 ± 0.9 %), and +0.6 to -4.5 % for senior boys (-1.7 ± 1.1 %). Eighteen participants reported no medical symptoms. Of 77 participants who reported symptoms, 42.9 % reported exhaustion/fatigue, 36.4 % reported side stitch/cramp, and 23.4 % reported dizziness. Participants reporting no medical symptoms achieved almost identical (P = 0.99) %ΔBW as those reporting at least one symptom. %ΔBW was more negative (P = 0.005) in participants who reported dizziness (-1.9 %ΔBW) compared with those who did not (-1.4 %ΔBW). %ΔBW was associated with performance in junior girls (r = 0.47, P = 0.02) and senior boys (r = 0.51, P = 0.01), with a trend in junior boys (r = 0.41, P = 0.053) but not in senior girls (r = 0.004, P = 0.99). Young athletes participating in a triathlon in a hot climate can tolerate mild to moderate levels of dehydration, without detrimental effects to self-assessed health.

Influence of pubertal stage on local sweating patterns of girls exercising in the heat.

The influence of puberty on sweating patterns of girls exercising in the heat is not known. Nine- to 17-year-old girls, representing 4 stages of breast development: T1 (n = 21); T2 (n = 22); T3 (n = 25); and T4 (n = 22), cycled for 20 min at 60% in 35 °C. The population density of heat activated sweat glands was higher in T1 vs T3 and T4 and in T2 vs T4. Sweat drop area was lower in T1 vs T3 and in T1 vs T4, T2 vs T4 and T3 vs T4. The proportion of skin covered by sweat was lower in T1 vs T4. Sweating patterns of girls exercising in the heat are influenced by pubertal stage.

Exercise capacity in pediatric patients with inflammatory bowel disease.

OBJECTIVE: To examine exercise capacity in youth with Crohn's disease (CD) and ulcerative colitis (UC). STUDY DESIGN: Eleven males and eight females with CD and six males and four females with UC participated. Patients performed standard exercise tests to assess peak power (PP) and mean power (MP) and peak aerobic mechanical power (W(peak)) and peak oxygen uptake (VO(2peak)). Fitness variables were compared with reference data and also correlated with relevant clinical outcomes. RESULTS: Pediatric patients with inflammatory bowel disease had lower PP (∼90% of predicted), MP (∼88% of predicted), W(peak) (∼91% of predicted), and VO(2peak) (∼75% of predicted) compared with reference values. When patients with CD or UC were compared separately to reference values, W(peak) was significantly lower only in the CD group. No statistically significant correlations were found between any exercise variables and disease duration (r = 0.01 to 0.14, P = .47 to .95) or disease activity (r = -0.19 to -0.31, P = .11 to .38), measured by pediatric CD activity index or pediatric ulcerative colitis activity index. After controlling for chronological age, recent hemoglobin levels were significantly correlated with PP (r = 0.45, P = .049), MP (r = 0.63, P = .003), VO(2peak) (r = 0.62, P = .004), and W(peak) (r = 0.70, P = .001). CONCLUSIONS: Pediatric patients with inflammatory bowel disease exhibit impaired aerobic and anaerobic exercise capacity compared with reference values.

The effect of pain-free treadmill training on fibrinogen, haematocrit, and lipid profile in patients with claudication.

OBJECTIVE: To assess the effect of pain-free treadmill training on changes of plasma fibrinogen, haematocrit, lipid profile, and walking ability in patients with claudication. DESIGN: Randomized control trial. METHODS: Sixty-eight patients with peripheral obstructive arterial disease and intermittent claudication (Fontaine stage II) were randomly assigned into the treadmill training (repetitive intervals to onset of claudication pain, three times a week) or a control group (no change in physical activity) over 3 months. Both groups performed treadmill test to assess pain-free walking time (PFWT) and maximal walking time (MWT) and had blood analyses [for haematocrit, fibrinogen, triglycerides, and cholesterol: total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL)] done at baseline and after 6 and 12 weeks of the study. RESULTS: Total and LDL cholesterol levels in the training group decreased (p < 0.05) by 14.8% and 20,5%, respectively. Significant (p < 0.05) HDL cholesterol increased (14.6%) and triglycerides decreased (19%) in the training group but changes of all these lipids were insignificant in the control group over the 3 months. Haematocrit and fibrinogen changes were insignificant in both groups. PFWT was prolonged by 109% and MWT increased by 54% in the training group (p < 0.01), but not in the control group. CONCLUSION: The improvement in walking time over 3 months of pain-free treadmill training parallels with progressive normalization of lipid profiles in patients with claudication.

Temperature regulation during rest and exercise in the cold in premenarcheal and menarcheal girls.

Temperature regulation during exercise in the cold was examined in 13 adolescent female individuals, aged 13-18 yr. Six girls with established menstrual cycles comprised the eumenorrheic menarcheal (EM) group, and seven nonmenstruating girls comprised the premenarcheal (PM) group. During the first visit, maximal oxygen consumption (Vo(2 max)), height, weight, and percent body fat were measured. The second visit included a determination of metabolic rate in thermoneutrality (21 degrees C), consisting of a 10-min rest period and 20 min of cycling (30% of Vo(2 max)), and a cold test (5 degrees C, 40% humidity, <0.3 m/s air velocity) involving a 20-min rest period and 40 min of cycling (30% of Vo(2 max)). Subjects in the EM group were tested twice in the chamber: once during the follicular and once during the luteal phase. Heat production per kilogram in thermoneutrality and in the cold was significantly (P < 0.05) higher in the PM compared with the EM girls. However, the PM girls had a significantly (P < 0.05) lower core temperature in the cold than the EM group. PM girls also had a significantly higher body surface area-to-mass ratio compared with the EM girls. Although percent body fat between groups was not significantly different, within the PM group percent body fat explained 79% (P < 0.01) of the variance in the decrease of core temperature. There were no menstrual phase-related differences in temperature regulation in either the thermoneutral or cold environment. In conclusion, menstrual phase does not influence temperature regulation in female individuals during adolescence. EM girls had lower metabolic heat production but maintained their core temperature more effectively in the cold than did the PM girls. This thermoregulatory difference between PM and EM girls is mainly a function of geometric differences with maturation-related peripheral vasoconstrictive differences maybe limiting the effectiveness of the mechanism of increased heat storage in younger female individuals.

Responses of children with cerebral palsy to treadmill walking exercise in the heat.

PURPOSE: When metabolic rate during arm-cranking in the heat is equated between children and adolescents with cerebral palsy (CP) and matched controls (CON), there are no relevant intergroup differences in heat strain. The metabolic rate, however, is known to be higher in CP during treadmill walking. The purpose of this study was to determine if during treadmill walking in the heat, the higher oxygen uptake (VO2), and thus greater metabolic heat production in those with CP would result in greater heat strain compared with able-bodied, matched CON. METHODS: Ten boys and girls (10.3-16.3 yr) with spastic CP and 10 individually matched (age, body size, biological maturity, gender, race) healthy CON performed 3 x 10-min treadmill walking bouts in 35 degrees C, 50% RH. Body mass, metabolic variables, heart rate (HR), body temperatures, and rating of perceived exertion (RPE) were periodically measured. Individuals within each CP-CON pair walked at the same speed and slope (0.9 +/- 0.4 m x s(-1), 3.3 +/- 0.6%). RESULTS: Steady-state VO2 during walking, body temperatures, and HR were all higher in the CP group compared with CON. VO2 was on average 40% higher, rectal temperature was 0.4 degrees C (99% CI = 0.1-0.6 degrees C) higher and HR (during the final minute of each exercise bout) was 37 beats x min(-1) (99% CI = 19-56 beats x min(-1)) higher. There were no differences between the groups in sweating rate (as inferred from body mass changes corrected for fluid intake and output) or in RPE. CONCLUSION: The subjects with CP demonstrated greater thermal strain than CON during treadmill walking where they require more metabolic energy and thus produce more metabolic heat than CON.

Responses of children with cerebral palsy to arm-crank exercise in the heat.

PURPOSE: In response to passive heating, adults with hemispheric brain infarction demonstrate lower skin temperatures (Tsk) and higher sweating rates (SR) on the affected side. It is unknown whether children with similar conditions demonstrate a similar response and whether this response is advantageous to defending body temperature during exercise in the heat. The purpose of this study was to determine whether children with spastic cerebral palsy (CP) demonstrate less thermal strain than healthy peers during short (10 min each) bouts of arm cranking, a mode of exercise where metabolic rate can be matched between the two groups. METHODS: Eleven young people (8.3-18.3 yr) with spastic CP and 11 individually matched (body size, age, and maturity) healthy controls (CON) performed 3 x 10-min arm-cranking bouts (40 rpm) in 35 degrees C, 50% RH. Body mass, metabolic and heart rate (HR) responses, and body temperatures were periodically measured. Individuals within each CP-CON pair worked at the same intensity (0.55 +/- 0.18 W.kg-1 body mass). Data were analyzed using a repeated measures ANOVA (alpha = 0.05). RESULTS: Subjects with CP showed no difference from CON in metabolic and HR responses, or SR (as inferred from body mass changes corrected for fluid intake and output). There were also no differences between the groups in the rectal temperature change from room temperature (21-23 degrees C). The increase in Tsk from room temperature, however, was slightly (0.6 degrees C) but significantly lower (P < 0.0001; 95% CI = 0.5-0.7 degrees C) in the subjects with CP compared with CON. CONCLUSION: Subjects with CP demonstrate thermal strain responses similar to CON during upper-body exercise at relatively low intensities for short duration in a warm climate.

Facial cooling enhances exercise-induced bronchoconstriction in asthmatic children.

PURPOSE: Exercising in cold air enhances bronchial responsiveness (BR) as compared with exercising in warm air. This may be due to intrathoracic cooling or to increased vagal activity caused by facial cooling. The purpose of this study was to compare the effects on BR of cold air inhalation and of facial exposure to cold air, as well as the combined effect of both. METHODS: Fourteen children with asthma (eight girls) performed four exercise challenge tests in a climatic chamber, under one of the following conditions: 1) inhaling warm air while the face was exposed to warm air (WW, 21 degrees C, 25% relative humidity (RH)); 2) inhaling warm air while the face was exposed to cold air (WC, 0 degrees C, 80% RH); 3) inhaling cold air while the face was exposed to cold air (CC); and 4) inhaling cold air while the face was exposed to warm air (CW). The study was analyzed, using a one- and two-way ANOVA. RESULTS: Postexercise forced expiratory volume in the first second (FEV1) and maximal mid-expiratory flow (MMEF) values as percent predicted (% pred) showed significant reductions over time (P < 0.001), significant differences among the four experimental conditions (P < 0.001) and a significant condition x time interaction (FEV1:P < 0.001, MMEF:P < 0.01). FEV1 was significantly lower for CC and WC, as compared with WW and CW at 5 and 10 min postexercise. The lowest postexercise values for FEV1 occurred in the CC and WC sessions (76% predicted in both). A similar pattern was obtained for MMEF. CONCLUSION: Facial cooling combined with either cold or warm air inhalation causes the greatest EIB, as compared with the isolated challenge with cold air inhalation. We suggest that vagal mechanisms play a major role in exercise and cold-induced bronchoconstriction.

Effects of postexercise milk consumption on whole body protein balance in youth.

In adults, adding protein to a postexercise beverage increases muscle protein turnover and replenishes amino acid stores. Recent focus has shifted toward the use of bovine-based milk and milk products as potential postexercise beverages; however, little is known about how this research translates to the pediatric population. Twenty-eight (15 girls) pre- to early pubertal (PEP, 7-11 yr) and mid- to late-pubertal (MLP, 14-17 yr) children consumed an oral dose of [(15)N]glycine prior to performing 2 × 20-min cycling bouts at 60% V̇O(2 peak) in a warm environment (34.5°C, 47.3% relative humidity). Following exercise, participants consumed either water (W), a carbohydrate-electrolyte solution (CES), or skim milk (SM) in a randomized, cross-over fashion in a volume equal to 100% of their body mass loss during exercise. Whole body nitrogen turnover (Q), protein synthesis (S), protein breakdown (B), and whole body protein balance (WBPB) were measured over 16 h. Protein intake from SM was 0.40 ± 0.10 g/kg. Over 16 h, Q and S were significantly greater (P < 0.01) with SM than W and CES. B demonstrated a trend for a main effect for beverage (P = 0.063). WBPB was more negative (P < 0.01) with W and CES than with SM. In the SM trial, WBPB was positive in PEP, although it remained negative in MLP. Boys exhibited significantly more negative WBPB than girls (P < 0.05). Postexercise milk consumption enhances WBPB compared with W and CES; however, additional protein intake may be required to sustain a net anabolic environment over 16 h.

Effect of milk consumption on rehydration in youth following exercise in the heat.

Low-fat milk is thought to be an effective postexercise rehydration beverage in adults; however, little is known about milk's rehydration ability in children after exercising in the heat. This study tested the hypothesis that because of its electrolyte and protein content, skim milk (SM) would be more effective than both water (W) and a carbohydrate/electrolyte solution (CES) in replacing body fluid losses in children following exercise in the heat. Thirty-eight (19 females) heat-acclimated pre- to early pubertal (PEP, aged 7-11 years) and mid- to late-pubertal (MLP, aged 14-17 years) children performed 3 sessions in 34.5 °C, 47.3% relative humidity, consisting of 2 × 20-min cycling bouts at 60% peak oxygen uptake followed by consumption of either W, CES, or SM. Each beverage was consumed immediately after exercise in a volume equal to 100% of their body mass loss during exercise. Urine samples were collected before, during, and after exercise, as well as the 2-h period following beverage consumption. On average, children dehydrated 1.3% ± 0.4%. Children ingested 0.40 ± 0.11 L (PEP) and 0.74 ± 0.20 L (MLP) of fluid. The fraction of the ingested beverage retained at 2 h of recovery was greater with SM (74% ± 18%) than W (47% ± 26%) and CES (59% ± 20%, p < 0.001 for both), and greater in CES than W (p < 0.001). All participants were in a hypohydrated state after 2 h of recovery, following the pattern SM < CES < W. In both PEP and MLP children, SM is more effective than W and CES at replacing fluid losses that occur during exercise in the heat.

Design, implementation, and evaluation of a pediatric and adolescent type 2 diabetes management program at a tertiary pediatric center.

Global rates of type 2 diabetes in children and adolescents have increased significantly over the past three decades. Type 2 diabetes is a relatively new disease in this age group, and there is a dearth of information about how to structure treatment programs to manage its comorbidities and complications. In this paper, we describe the design and implementation of a personalized multidisciplinary, family-centered, pediatric and adolescent type 2 diabetes program at a tertiary pediatric center in Hamilton, Ontario, Canada. We report the process of designing and implementing such a program, and show that this multidisciplinary program led to improvement in glycated hemoglobin (n=17, 8% at baseline versus 6.4% at 1 year, 95% confidence interval (0.1-0.28), P-value <0.0001) and stabilized body mass index, with lowered C-peptide and no change in fitness or metabolic biomarkers of lipid metabolism and liver function. As type 2 diabetes becomes more prevalent in youth, the need for programs that successfully address the complex nature of this disease is central to its management and to mitigate its long-term adverse outcomes.

Voluntary fluid intake, hydration status, and aerobic performance of adolescent athletes in the heat.

We determined whether beverage flavoring and composition would stimulate voluntary drink intake, prevent dehydration, and maintain exercise performance in heat-acclimated adolescent males running in the heat. Eight adolescent (age, 13.7 ± 1.1 years) runners (peak oxygen uptake, 59.5 ± 4.0 mL·kg-1·min-1) underwent at least four 80-min exercise heat-acclimation sessions before completing 3 experimental sessions. All sessions were performed at 30 °C and 60%-65% relative humidity. Each experimental session consisted of five 15-min treadmill runs at a speed eliciting 65% peak oxygen uptake, with a 5 min rest prior to each run. Ten minutes after the final run, a time to exhaustion test was performed at a speed eliciting 90% peak oxygen uptake. Counterbalanced experimental sessions were identical, except for fluid intake, which consisted of tap water (W), flavored water (FW), and FW with 6% carbohydrate and 18 mmol·L-1 NaCl (CNa) consumed ad libitum. Fluid intake and body weight were monitored to calculate dehydration. Voluntary fluid intake was similar to fluid losses in W (1032 ± 130 vs. 1340 ± 246 g), FW (1086 ± 86 vs. 1451 ± 253 g), and CNa (1259 ± 119 vs. 1358 ± 234 g). As a result, significant dehydration was avoided in all trials (-0.45% ± 0.68% body weight in W, -0.66% ± 0.50% body weight in FW, and -0.13% ± 0.71% body weight in CNa). Core temperature increased by ~1 °C during exercise, but was not different between trials. Time to exhaustion was not different between trials and averaged 8.8 ± 1.7 min. Under exercise conditions more closely reflecting real-life situations, heat-acclimatized adolescent male runners can appropriately gauge fluid intake regardless of the type of beverage made available, resulting in consistency in exercise performance.

Voluntary drinking and hydration in trained, heat-acclimatized girls exercising in a hot and humid climate.

This study examined the effects of beverage composition on the voluntary drinking pattern, body fluid balance and body temperature responses of heat-acclimatized trained girls exercising intermittently in outdoor conditions (WBGT = 30.9 +/- 0.2 degrees C). Twelve trained, heat-acclimatized girls (age = 10.6 +/- 0.2 years) performed three 3-h sessions, each consisting of four 20-min cycling bouts at 60% VO2max, alternating with 25-min rest. One of three beverages was assigned: unflavored water (W), flavored water (FW) or flavored water plus 6% carbohydrate and 18 mmol/l NaCl (CNa). Drinking was ad libitum. Total intake was similar among conditions (W = 953.3 +/- 107.8 ; FW = 1026.5 +/- 138.1; CNa = 906.4 +/- 107.5 g). A mild hypohydration occurred during the three conditions (W = -1.12%; FW = -0.95%; CNa = -0.74% BW, P > 0.05). Sweat loss, higher than previously reported for sedentary girls, was not different among conditions (W = 1,051.5 +/- 90.8; FW = 979.9 +/- 72.8; CNa = 1,052.7 +/- 52.6 g). The average amount of urine produced (W = 269.8 +/- 85.9; FW = 320.8 +/- 87.2; CNa = 85.6 +/- 9.3 g) was 73 and 68% lower [corrected] during CNa compared to [corrected] FW and W, respectively, [corrected] (CNa vs. FW, P < 0.05), CNa vs W, P = 0.06) [corrected] The increase in rectal temperature, heart rate and all perceptual variables did not differ among conditions. In conclusion, flavoring of the water and addition of 6% carbohydrate plus 18 mmol/l NaCl do not prevent mild hypohydration in trained, heat-acclimatized girls with high sweating rates. However, there is a tendency towards a greater fluid retention with the CNa beverage.

Voluntary drinking and hydration in non-acclimatized girls exercising in the heat.

The intent of this study was to assess the influence of drink flavor and composition on voluntary drinking and hydration status in girls exercising intermittently in the heat (35 +/- 1 degrees C, 45-50% relative humidity). Twelve physically active, nonacclimatized girls (9-12 years) performed three 3 h identical sessions, each consisting of four 20 min cycling bouts at 50% (VO(2max)), separated by 25 min of rest. One of the three beverages (chilled to 8-10 degrees C) was assigned to each session: unflavored water (W), grape-flavored water (FW) and grape-flavored water plus 6% carbohydrate and 18 mmol l(-1) NaCl (CNa). Drinking was ad libitum. Body weight (BW), drink intake (DI), heart rate, rectal and skin temperatures, and perceptions of thirst and stomach fullness were monitored periodically. Total DI was 759, 940, 1,045 g in W, FW and CNa, respectively (P < 0.05 for CNa-W and FW-W). BW changes were -0.15, 0.16, and 0.45% in W, FW and CNa, respectively, but only the difference between CNa and W was significant (P < 0.05). Other physiological and perceptual variables were not different between trials. In conclusion, beverage flavoring regardless if its combination with carbohydrate and NaCl, mildly enhanced voluntary drinking in young non-acclimatized girls. In contrast to previous research in young boys, euhydration was maintained in the girls by an adequate intake of unflavored water.

Self-efficacy and perceived exertion of girls during exercise.

BACKGROUND: An important national goal in Healthy People 2010 is to reduce the high prevalence of sedentary lifestyles and resultant overweight and obesity among girls. OBJECTIVES: The purpose of the present study was threefold: (a) to determine if pre-exercise self-efficacy predicted girls' perceptions of exertion during exercise, (b) to determine if these perceptions, in turn, influenced postexercise self-efficacy, and (c) to assess if exercise self-efficacy increased following completion of an exercise task. METHODS: A sample of 103 girls, 8 to 17 years of age, pedaled 20 minutes on a cycle ergometer at 60% of their predetermined peak VO2 in a climatic chamber (90 degrees F, 50% relative humidity). Ratings of perceived exertion were obtained every 4 minutes. Exercise self-efficacy was assessed before and after the exercise session. RESULTS: Controlling for peak VO2 and percent body fat, pre-exercise efficacy exerted an independent effect on perception of exertion during exercise with girls high on pre-exercise self-efficacy reporting lower perceived exertion during exercise, than girls low on self-efficacy. Both pre-exercise efficacy and perceived exertion explained postexercise efficacy. Exercise self-efficacy increased significantly from pre- to postexercise. CONCLUSIONS: Pre-exercise efficacy is an important factor influencing girls' perceptions of exertion during exercise and their postexercise efficacy. Increased exercise self-efficacy of girls following successful completion of an exercise challenge suggests possible strategies to increase physical activity.

Anaerobic muscle performance of children after long-term recovery from Guillain-Barré syndrome.

The aim of this study was to evaluate anaerobic muscle performance in children after long-term recovery from Guillain-Barré syndrome (GBS). Participants were recruited from all children and adolescents with GBS admitted to The Hospital for Sick Children, University of Toronto, Canada, between 1988 and 1995. We assessed 17 children (nine males, eight females; mean age at GBS diagnosis 7 years 11 months, SD 4 years 2 months; mean age at testing 14 years 1 month) more than two years after acute GBS. Participants completed the Wingate anaerobic test to evaluate mean and peak muscle power. For mean arm muscle power (mean 47.5% [SD 17.4%] of normal), only two participants were in the normal range. For mean leg muscle power (mean 83% [SD 28.3%] of normal), 15 participants were in the normal range. For arm peak power (mean 92.6% [SD 20.7%] of normal), 12 participants were in the normal range. For leg peak power (mean 116.3% of normal, SD 15.8%), all participants were in the normal range. Detailed manual muscle testing with the modified Medical Research Council scale was done on 34 muscle groups. Data were pooled to give a mean arm and leg muscle strength score (9.7, SD 0.30 and 9.4, SD 0.50 respectively). Pearson's correlations of muscle endurance with arm and leg strength were not significant. Children with GBS have excellent long-term recovery of peak muscle power. Muscle endurance, measured by mean muscle power, was normal in the legs but markedly low in the arms. Pediatric rehabilitation programs after GBS should specifically target endurance of arm muscles.