The modified Chrispin-Norman radiography score (CNS) is used in evaluation of radiographic changes in children with cystic fibrosis (CF). We evaluated the correlation of modified CNS with peak exercise capacity (Wpeak) and ventilatory efficiency (reflected by breathing reserve index—BRI) during progressive cardiopulmonary exercise testing (CPET). Thirty-six children aged 8–17 years were stratified according to their CNS into 3 groups: mild (<10), moderate (10–15), and severe (>15). CPET was performed on a cycle ergometer. Lung function tests included spirometry and whole-body plethysmography. Patients with higher CNS had lower FEV1 (p < .001), Wpeak predicted (%; p = .01) and lower mean peak oxygen consumption (VO2peak/kg; p = .014). The BRI at the anaerobic threshold and at Wpeak was elevated in patients with the highest CNS values (p < .001). The modified CNS correlates moderately with Wpeak (R = −0.443; p = .007) and BRI (R = −0.419; p = .011). Stepwise multiple linear regression showed that RV/TLC was the best predictor of Wpeak/pred (%; B = −0.165; b = −0.494; R2 = .244; p = .002). Children with CF who have high modified CNS exhibit decreased exercise tolerance and ventilatory inefficacy during progressive effort.
Aleksandar Sovtic, Predrag Minic, Jovan Kosutic, Gordana Markovic-Sovtic and Milan Gajic
Richard B. Kreider, Gary W. Miller, Deborah Schenck, Charles W. Cortes, Victor Miriel, C. Thomas Somma, Pam Rowland, Caroll Turner and Dawn Hill
Six trained male cyclists and triathletes participated in a double blind study to determine the effects of phosphate loading on maximal and endurance exercise performance. Subjects ingested either 1 gm of tribasic sodium phosphate or a glucose placebo four times daily for 3 days prior to performing either an incremental maximal cycling test or a simulated 40-km time trial on a computerized race simulator. They continued the supplementation protocol for an additional day and then performed the remaining maximal or performance exercise test. Subjects observed a 17-day washout period between testing sessions and repeated the experiment with the alternate supplement regimen in identical fashion. Metabolic data were collected at 15-sec intervals while venous blood samples and 2D-echocardiographic data were collected during each stage of exercise during the maximal exercise test and at 8-km intervals during the 404cm time trial. Results indicate that phosphate loading attenuated anaerobic threshold, increased myocardial ejection fraction and fractional shortening, increased maximal oxidative capacity, and enhanced endurance performance in competitive cyclists and triathletes.
Hichem Souissi, Hamdi Chtourou, Anis Chaouachi, Mohamed Dogui, Karim Chamari, Nizar Souissi and Mohamed Amri
The aim of this study was to assess the effect of time-of-day-specific training on the diurnal variations of short-term performances in boys. Twenty-four boys were randomized into a morning-training-group (07:00–08:00h; MTG), an evening training-group (17:00–18:00h; ETG) and a control-group (CG). They performed four tests of strength and power (unilateral isometric maximal voluntary contraction of the knee extensor muscles, Squat-Jump, Counter-Movement-Jump and Wingate tests) at 07:00 and 17:00h just before (T0) and after 6 weeks of resistance training (T1). In T0, the results revealed that short-term performances improved and oral temperature increased significantly from morning to afternoon (amplitudes between 2.36 and 17.5% for both oral temperature and performances) for all subjects. In T1, the diurnal variations of performances were blunted in the MTG and persisted in the ETG and CG. Moreover, the training program increase muscle strength and power especially after training in the morning hours and the magnitude of gains was greater at the time-of-day-specific training than at other times. In conclusion, these results suggest that time-of-day-specific training increases the child’s anaerobic performances specifically at this time-of-day. Moreover, the improvement of these performances was greater after morning than evening training.
Hans Luttikholt, Lars R. McNaughton, Adrian W. Midgley and David J. Bentley
There is currently no model that predicts peak power output (PPO) thereby allowing comparison between different incremental exercise test (EXT) protocols. In this study we have used the critical power profile to develop a mathematical model for predicting PPO from the results of different EXTs.
The purpose of this study was to examine the level of agreement between actual PPO values and those predicted from the new model.
Eleven male athletes (age 25 ± 5 years, VO2max 62 ± 8 mL · kg–1 · min–1) completed 3 laboratory tests on a cycle ergometer. Each test comprised an EXT consisting of 1-minute workload increments of 30 W (EXT30/1) and 3-minute (EXT25/3) and 5-minute workload increments (EXT25/5) of 25 W. The PPO determined from each test was used to predict the PPO from the remaining 2 EXTs.
The differences between actual and predicted PPO values were statistically insignificant (P > .05). The random error components of the limits of agreement of ≤30 W also indicated acceptable levels of agreement between actual and predicted PPO values.
Further data collection is necessary to confirm whether the model is able to predict PPO over a wide range of EXT protocols in athletes of different aerobic and anaerobic capacities.
Ildus I. Ahmetov, Olga L. Vinogradova and Alun G. Williams
The ability to perform aerobic or anaerobic exercise varies widely among individuals, partially depending on their muscle-fiber composition. Variability in the proportion of skeletal-muscle fiber types may also explain marked differences in aspects of certain chronic disease states including obesity, insulin resistance, and hypertension. In untrained individuals, the proportion of slow-twitch (Type I) fibers in the vastus lateralis muscle is typically around 50% (range 5–90%), and it is unusual for them to undergo conversion to fast-twitch fibers. It has been suggested that the genetic component for the observed variability in the proportion of Type I fibers in human muscles is on the order of 40–50%, indicating that muscle fiber-type composition is determined by both genotype and environment. This article briefly reviews current progress in the understanding of genetic determinism of fiber-type proportion in human skeletal muscle. Several polymorphisms of genes involved in the calcineurin–NFAT pathway, mitochondrial biogenesis, glucose and lipid metabolism, cytoskeletal function, hypoxia and angiogenesis, and circulatory homeostasis have been associated with fiber-type composition. As muscle is a major contributor to metabolism and physical strength and can readily adapt, it is not surprising that many of these gene variants have been associated with physical performance and athlete status, as well as metabolic and cardiovascular diseases. Genetic variants associated with fiber-type proportions have important implications for our understanding of muscle function in both health and disease.
Mike D. Quinn
A mathematical model based on a differential equation of motion is used to simulate the 400-m hurdles race for men and women. The model takes into account the hurdler’s stride pattern, the hurdle clearance, and aerobic and anaerobic components of the propulsive force of the athlete, as well as the effects of wind resistance, altitude of the venue, and curvature of the track. The model is used to predict the effect on race times of different wind conditions and altitudes. The effect on race performance of the lane allocation and the efficiency of the hurdle clearance is also predicted. The most favorable wind conditions are shown to be a wind speed no greater than 2 m/s assisting the athlete in the back straight and around the second bend. The outside lane (lane 8) is shown to be considerably faster than the favored center lanes. In windless conditions, the advantage can be as much as 0.15 s for men and 0.12 s for women. It is shown that these values are greatly affected by the wind conditions.
Eric C. Haakonssen, David T. Martin, Louise M. Burke and David G. Jenkins
Body composition in a female road cyclist was measured using dual-energy X-ray absorptiometry (5 occasions) and anthropometry (10 occasions) at the start of the season (Dec to Mar), during a period of chronic fatigue associated with poor weight management (Jun to Aug), and in the following months of recovery and retraining (Aug to Nov). Dietary manipulation involved a modest reduction in energy availability to 30–40 kcal · kg fat-free mass−1 · d−1 and an increased intake of high-quality protein, particularly after training (20 g). Through the retraining period, total body mass decreased (−2.82 kg), lean mass increased (+0.88 kg), and fat mass decreased (−3.47 kg). Hemoglobin mass increased by 58.7 g (8.4%). Maximal aerobic- and anaerobic-power outputs were returned to within 2% of preseason values. The presented case shows that through a subtle energy restriction associated with increased protein intake and sufficient energy intake during training, fat mass can be reduced with simultaneous increases in lean mass, performance gains, and improved health.
Melinda M. Manore, Janice Thompson and Marcy Russo
This study presents the diet and exercise strategies of a world-class bodybuilder during an 8-week precompetition period. Weighed food records were kept daily, and body fat, resting metabolic rate (RMR),
Giorgos P. Paradisis, Athanassios Bissas and Carlton B. Cooke
This study examined the effects of sprint running training on sloping surfaces (3°) on selected kinematic and physiological variables.
Fifty-four sport and physical education students were randomly allocated to one of two training groups (combined uphill–downhill [U+D] and horizontal (H)) and a control group (C). Pre- and post training tests were performed to examine the effects of 8 wk of training on the maximum running speed (MRS), step rate, step length, step time, contact time, eccentric and concentric phase of contact time (EP, CP), fight time, selected posture characteristics of the step cycle, and 6-s maximal cycle sprint test.
MRS, step rate, contact time, and step time were improved significantly in a 35-m sprint test for the U+D group (P < .01) after training by 4.3%, 4.3%, -5.1%, and -3.9% respectively, whereas the H group showed smaller improvements, (1.7% (P < .05), 1.2% (P < .01), 1.7% (P < .01), and 1.2% (P < .01) respectively). There were no significant changes in the C group. The posture characteristics and the peak anaerobic power (AWT) performance did not change with training in any of the groups.
The U+D training method was significantly more effective in improving MRS and the kinematic characteristics of sprint running than a traditional horizontal training method.
Colin Wilborn, Lem Taylor, Chris Poole, Cliffa Foster, Darryn Willoughby and Richard Kreider
The purpose of this study was to determine the effects of an alleged aromatase and 5-α reductase inhibitor (AI) on strength, body composition, and hormonal profiles in resistance-trained men. Thirty resistance-trained men were randomly assigned in a double-blind manner to ingest 500 mg of either a placebo (PL) or AI once per day for 8 wk. Participants participated in a 4-d/wk resistance-training program for 8 wk. At Weeks 0, 4, and 8, body composition, 1-repetition-maximum (1RM) bench press and leg press, muscle endurance, anaerobic power, and hormonal profiles were assessed. Statistical analyses used a 2-way ANOVA with repeated measures for all criterion variables (p ≤ .05). Significant Group × Time interaction effects occurred over the 8-wk period for percent body fat (AI: –1.77% ± 1.52%, PL: –0.55% ± 1.72%; p = .048), total testosterone (AI: 0.97 ± 2.67 ng/ml, PL: –2.10 ± 3.75 ng/ml; p = .018), and bioavailable testosterone (AI: 1.32 ± 3.45 ng/ml, PL: –1.69 ± 3.94 ng/ml; p = .049). Significant main effects for time (p ≤ .05) were noted for bench- and leg-press 1RM, lean body mass, and estradiol. No significant changes were detected among groups for Wingate peak or mean power, total body weight, dihydrotestosterone, hemodynamic variables, or clinical safety data (p > .05). The authors concluded that 500 mg of daily AI supplementation significantly affected percent body fat, total testosterone, and bioavailable testosterone compared with a placebo in a double-blind fashion.