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City bike-share programs can result in more people bicycling while also lowering the risk of crashes between cars and cyclists, a study in the June issue of AJPH finds. Researchers [...]

The purpose of the present study was to assess the reliability and validity of fatigue measures, as derived from 4 separate formulae, during tests of repeat sprint ability. On separate days over a 3-week period, 2 groups of 7 recreationally active men completed 6 trials of 1 of 2 maximal (20 x 5 seconds) intermittent cycling tests with contrasting recovery periods (10 or 30 seconds). All trials were conducted on a friction-braked cycle ergometer, and fatigue scores were derived from measures of mean power output for each sprint. Apart from formula 1, which calculated fatigue from the percentage difference in mean power output between the first and last sprint, all remaining formulae produced fatigue scores that showed a reasonably good level of test-retest reliability in both intermittent test protocols (intraclass correlation range: 0.78-0.86; 95% likely range of true values: 0.54-0.97). Although between-protocol differences in the magnitude of the fatigue scores suggested good construct validity, within-protocol differences highlighted limitations with each formula. Overall, the results support the use of the percentage decrement score as the most valid and reliable measure of fatigue during brief maximal intermittent work. KEY WORDS. reliability, multiple sprints, intermittent exercise

We modeled the 2003 Tour de France bicycle race using stage profile data for which elevations at various points in each stage are known. Each stage is modeled as a series of inclined planes. We accounted for the forces on a bicycle-rider combination such as aerodynamic drag and rolling resistance and calculated the winning stage times for an assumed set of bicycle and rider parameters. The calculated total race time differed from the sum of all actual winning stage times by only 0.03%.

The aims of the present study were: (a) to determine the number of familiarization trials required to establish a high degree of reliability in measures of power output during maximal intermittent cycling; and (b) to examine the reliability of those same measures after familiarization had been established. On separate days over a 3-week period, 2 groups of 7 recreationally active men completed 8 trials of 1 of 2 maximal (20 x 5-second) intermittent cycling tests with contrasting recovery periods (10-seconds or 30-seconds). Significant (p < 0.05) between-trial differences were detected in post-hoc tests involving trials 1 and 2 only. Within-subject test-retest reliability was therefore assessed across trials 3-8. Apart from values of maximum power output in Protocol 1 (10-second recovery periods), all remaining measures of power output showed high degrees of within-subject test-retest reliability (coefficient of variation: 2.4-3.7%). The results of the present study indicate that in subjects unfamiliar with maximal intermittent cycling, high degrees of reliability in many performance measures can be achieved following the completion of 2 familiarization trials. Key Words: familiarization, test-retest reliability, multiple sprints, intermittent exercise

Intramuscular triglycerides (IMTG) are assumed to form an important substrate source during prolonged endurance exercise in trained males. This study investigated the effects of endurance exercise and recovery diet on IMTG content in vastus lateralis muscle. Nine male cyclists were provided with a standardized diet for 3 days, after which they performed a 3-h exercise trial at a 55% maximum workload. Before and immediately after exercise and after 24 and 48 h of recovery, magnetic resonance spectroscopy (MRS) was performed to quantitate IMTG content. Muscle biopsies were taken after 48 h of recovery to determine IMTG content by using quantitative fluorescence microscopy. The entire procedure was performed two times; in one trial, a normal diet containing 39% energy (En%) as fat was provided (NF) and in the other a typical carbohydraterich athlete's diet (LF: 24 Eh% fat) was provided. During exercise, IMTG content decreased by 21.4 [+ or -] 3.1%. During recovery, IMTG content increased significantly in the NF trial only, reaching preexercise levels within 48 h. In accord with MRS, fluorescence microscopy showed significantly higher IMTG content in the NF compared with the LF trial, with differences restricted to the type I muscle fibers (2.1 [+ or -] 0.2 vs. 1.4 [+ or -] 0.2% area lipid staining, respectively). In conclusion, IMTG content in the vastus lateralis muscle declines significantly during prolonged endurance exercise in male cyclists. When a normal diet is used, IMTG contents are subsequently repleted within 48 h of postexercise recovery. In contrast, IMTG repletion is impaired substantially when a typical, carbohydrate-rich athlete's diet is used. Data obtained by quantitative fluorescence microscopy correspond well with MRS results, implying that both are valid methods to quantify IMTG content. muscle; nuclear magnetic resonance; [sup.1]H magnetic resonance spectroscopy; oil red O; exercise; intramyocellular lipid; diet

The effect of altered hip orientation angle ([HOA] angle of hip joint center to bottom bracket relative to horizontal) on Wingate anaerobic test results and cycling technique while maintaining a constant body configuration angle (included angle between torso, hip, and bottom bracket) and maximum hip-to-pedal distance was examined. Nineteen recreational cyclists, all men, with no recent recumbent cycling experience completed 30-second Wingate tests in 3 recumbent positions (HOA = -20[degrees], -10[degrees], and 0[degrees]) and the standard cycling position (SCP) (HOA = 75[degrees]). Peak, average, and minimum power output, as well as fatigue index, were not significantly different across all positions (p < 0.01). Average hip and knee extension angles increased slightly, and ankle angle did not change as HOA increased. These findings indicate that although HOA does have a small effect on cycling kinematics, these effects are not large enough to alter short-term power output. Therefore, anaerobic power output may be evaluated and compared in the recumbent positions and the SCP. Key Words: anaerobic power, cycling kinematics, recumbent

The objective of this study was to evaluate the performance of different multivariate optimization algorithms by solving a 'tracking' problem using a forward dynamic model of pedaling. The tracking problem was defined as solving for the muscle controls (muscle stimulation onset, offset, and magnitude) that minimized the error between experimentally collected kinetic and kinematic data and the simulation results of pedaling at 90 rpm and 250 W. Three different algorithms were evaluated: a downhill simplex method, a gradient-based sequential quadratic programming algorithm, and a simulated annealing global optimization routine. The results showed that the simulated annealing algorithm performed far superior to the conventional routines by converging more rapidly and avoiding local minima.