James G. Hopker

Changes in cycling efficiency during a competitive season

PURPOSE To monitor training-related changes in gross efficiency (GE) over the course of a competitive cycling season. METHODS Fourteen trained cyclists (mean +/- SD: 34 + 8 yr, 74.3 +/- 7.4 kg, Wmax = 406 +/- 43 W, V O2max = 59.5 +/- 3.8 mL x kg x min) with at least 3 yr competitive experience completed five laboratory tests during a competitive cycling season. The tests measured lactate threshold (LT), onset of blood lactate accumulation (OBLA), maximal oxygen uptake (V O2max), maximal minute power (Wmax), and GE. The data were analyzed using repeated-measures ANOVA and Pearsons product-moment correlation coefficient. RESULTS GE changed significantly over the course of the competitive cycling season (P < 0.05), increasing over the precompetition phase of the season (19.6% vs 20.6%; P < 0.05). GE was maintained during the main competitive phase of the season (20.6% vs 20.3%; P > 0.05) and then decreased during the postcompetitive phase to 19.4% (P < 0.05). The precompetition changes in GE were related to the total time spent training and the time spent above OBLA intensity (r = 0.84 and 0.80, respectively). Riders who spent the most time training between LT and OBLA intensities (r = 0.87; P < 0.05) were better able to maintain GE. A significant inverse relationship was also identified between the changes in GE and the percentage change in training below LT over the competitive phase of the season. CONCLUSION GE changes over the course of a competitive cycling season and is related to the volume and intensity of training conducted.

Controversies in the physiological basis of the ‘anaerobic threshold’ and their implications for clinical cardiopulmonary exercise testing

This article reviews the notion of the ‘anaerobic threshold’ in the context of cardiopulmonary exercise testing. Primarily, this is a review of the proposed mechanisms underlying the ventilatory and lactate response to incremental exercise, which is important to the clinical interpretation of an exercise test. Since such tests are often conducted for risk stratification before major surgery, a failure to locate or justify the existence of an anaerobic threshold will have some implications for clinical practice. We also consider alternative endpoints within the exercise response that might be better used to indicate a patient’s capacity to cope with the metabolic demands encountered both during and following major surgery.

Validity and reliability of the Wattbike cycle ergometer.

The purpose of this study was to assess the validity and reliability of the Wattbike cycle ergometer against the SRM Powermeter using a dynamic calibration rig (CALRIG) and trained and untrained human participants. Using the CALRIG power outputs of 50-1 250  W were assessed at cadences of 70 and 90  rev x min(-1). Validity and reliability data were also obtained from 3 repeated trials in both trained and untrained populations. 4 work rates were used during each trial ranging from 50-300  W. CALRIG data demonstrated significant differences (P<0.05) between SRM and Wattbike across the work rates at both cadences. Significant differences existed in recorded power outputs from the SRM and Wattbike during steady state trials (power outputs 50-300  W) in both human populations (156±72  W vs. 153±64  W for SRM and Wattbike respectively; P<0.05). The reliability (CV) of the Wattbike in the untrained population was 6.7% (95%CI 4.8-13.2%) compared to 2.2% with the SRM (95%CI 1.5-4.1%). In the trained population the Wattbike CV was 2.6% (95%CI 1.8-5.1%) compared to 1.1% with the SRM (95%CI 0.7-2.0%). These results suggest that when compared to the SRM, the Wattbike has acceptable accuracy. Reliability data suggest coaches and cyclists may need to use some caution when using the Wattbike at low power outputs in a test-retest setting.

Differences in efficiency between trained and recreational cyclists

Controversy still exists in the literature as to whether cycling experience affects gross mechanical efficiency (GME). The aim of this study was to identify differences in efficiency between trained and untrained cyclists. Thirty-two participants, 16 trained (mean+/-SD: age, 33+/-4 y; height, 1.76+/-0.05 m; mass 75+/-10 kg; Wmax, 421+/-38 W; maximal oxygen uptake, 62.6+/-7.30 mL.kg(-1).min(-1)) and 16 untrained (22+/-3 y, 175+/-0.06 m, 76+/-10 kg, 292+/-34 W, 42.6+/-7.80 mL.kg(-1).min(-1)), performed two tests of cycling efficiency. One was at the relative workloads of 50% and 60% Wmax and the other was at a fixed workload of 150 W using an electrically braked cycle ergometer. Cadence was maintained at the cyclists preferred rate throughout. All workloads lasted 10 min with data sampling in the final 3 min. GME was calculated from the gas data. GME was found to be significantly higher in the trained cyclists across all workloads (+1.4%; p=0.03). At workloads of 60% Wmax GME was significantly lower than work at 150 W (-0.8%; p=0.04), but not significantly different from 50% Wmax. These results show that differences do exist between trained and untrained cyclists, illustrating that training experience is a factor that warrants further investigation.

Reliability of Cycling Gross Efficiency Using the Douglas Bag Method

Book review of Eric Schaefers edited collection Sex Scene: Media and the Sexual Revolution published in the journal Film Studies as part of the special issue Sex and the Cinema.PURPOSE The aim of this study was to establish the reliability of gross efficiency (GE) measurement (the ratio of mechanical power input to metabolic power output, expressed as a percentage) using the Douglas bag method. METHODS The experiment was conducted in two parts. Part 1 examined the potential for errors in the Douglas bag method arising from gas concentration analysis, bag residual volume, and bag leakage or gas diffusion rates. Part 2 of this study examined the within-subject day-to-day variability of GE in 10 trained male cyclists using the Douglas bag method. Participants completed three measurements of GE on separate days at work rates of 150, 180, 210, 240, 270, and 300 W. RESULTS The results demonstrate that the reliability of gas sampling is high with a coefficient of variation (CV) <0.5% for both O2 and CO2. The bag residual volume CV was ∼15%, which amounts to +0.4 L. This could cause the largest error, but this can be minimized by collecting large gas sample volumes. For part 2, a mean CV of 1.5% with limits of agreement of +0.6% in GE units, around a mean GE of 20.0%, was found. CONCLUSIONS The Douglas bag method of measuring expired gases and GE was found to have very high reliability and could be considered the gold-standard approach for evaluating changes in GE. Collecting larger expired gas samples minimizes potential sources of error.

Controversies in the physiological basis of the ‘anaerobic threshold: Implications for cardiopulmonary exercise testing

This article reviews the notion of the ‘anaerobic threshold’ in the context of cardiopulmonary exercise testing. Primarily, this is a review of the proposed mechanisms underlying the ventilatory and lactate response to incremental exercise, which is important to the clinical interpretation of an exercise test. Since such tests are often conducted for risk stratification before major surgery, a failure to locate or justify the existence of an anaerobic threshold will have some implications for clinical practice. We also consider alternative endpoints within the exercise response that might be better used to indicate a patient’s capacity to cope with the metabolic demands encountered both during and following major surgery.

The influence of training status, age, and muscle fiber type on cycling efficiency and endurance performance

The purpose of this study was to assess the influence of age, training status, and muscle fiber-type distribution on cycling efficiency. Forty men were recruited into one of four groups: young and old trained cyclists, and young and old untrained individuals. All participants completed an incremental ramp test to measure their peak O2 uptake, maximal heart rate, and maximal minute power output; a submaximal test of cycling gross efficiency (GE) at a series of absolute and relative work rates; and, in trained participants only, a 1-h cycling time trial. Finally, all participants underwent a muscle biopsy of their right vastus lateralis muscle. At relative work rates, a general linear model found significant main effects of age and training status on GE (P < 0.01). The percentage of type I muscle fibers was higher in the trained groups (P < 0.01), with no difference between age groups. There was no relationship between fiber type and cycling efficiency at any work rate or cadence combination. Stepwise multiple regression indicated that muscle fiber type did not influence cycling performance (P > 0.05). Power output in the 1-h performance trial was predicted by average O2 uptake and GE, with standardized β-coefficients of 0.94 and 0.34, respectively, although some mathematical coupling is evident. These data demonstrate that muscle fiber type does not affect cycling efficiency and was not influenced by the aging process. Cycling efficiency and the percentage of type I muscle fibers were influenced by training status, but only GE at 120 revolutions/min was seen to predict cycling performance.

The Effects of Training on Gross Efficiency in Cycling: A Review

There has been much debate in the recent scientific literature regarding the possible ability to increase gross efficiency in cycling via training. Using cross-sectional study designs, researchers have demonstrated no significant differences in gross efficiency between trained and untrained cyclists. Reviewing this literature provides evidence to suggest that methodological inadequacies may have played a crucial role in the conclusions drawn from the majority of these studies. We present an overview of these studies and their relative shortcomings and conclude that in well-controlled and rigorously designed studies, training has a positive influence upon gross efficiency. Putative mechanisms for the increase in gross efficiency as a result of training include, muscle fibre type transformation, changes to muscle fibre shortening velocities and changes within the mitochondria. However, the specific mechanisms by which training improves gross efficiency and their impact on cycling performance remain to be determined.

The Self-Paced VO2max Test to Assess Maximal Oxygen Uptake in Highly Trained Runners

PURPOSE The novel self-paced maximal-oxygen-uptake (VO2max) test (SPV) may be a more suitable alternative to traditional maximal tests for elite athletes due to the ability to self-regulate pace. This study aimed to examine whether the SPV can be administered on a motorized treadmill. METHODS Fourteen highly trained male distance runners performed a standard graded exercise test (GXT), an incline-based SPV (SPVincline), and a speed-based SPV (SPVspeed). The GXT included a plateau-verification stage. Both SPV protocols included 5×2-min stages (and a plateau-verification stage) and allowed for self-pacing based on fixed increments of rating of perceived exertion: 11, 13, 15, 17, and 20. The participants varied their speed and incline on the treadmill by moving between different marked zones in which the tester would then adjust the intensity. RESULTS There was no significant difference (P=.319, ES=0.21) in the VO2max achieved in the SPVspeed (67.6±3.6 mL·kg(-1)·min(-1), 95%CI=65.6-69.7 mL·kg(-1)·min(-1)) compared with that achieved in the GXT (68.6±6.0 mL·kg(-1)·min(-1), 95%CI=65.1-72.1 mL·kg(-1)·min(-1)). Participants achieved a significantly higher VO2max in the SPVincline (70.6±4.3 mL·kg(-1)·min(-1), 95%CI=68.1-73.0 mL·kg(-1)·min(-1)) than in either the GXT (P=.027, ES=0.39) or SPVspeed (P=.001, ES=0.76). CONCLUSIONS The SPVspeed protocol produces VO2max values similar to those obtained in the GXT and may represent a more appropriate and athlete-friendly test that is more oriented toward the variable speed found in competitive sport.

Inter- and intra-session reliability of muscle activity patterns during cycling

The aim of this study was to determine the inter- and intra-session reliability of the temporal and magnitude components of activity in eight muscles considered important for the leg cycling action. On three separate occasions, 13 male non-cyclists and 11 male cyclists completed 6 min of cycling at 135, 150, and 165 W. Cyclists completed two additional 6-min bouts at 215 and 265 W. Surface electromyography was used to record the electrical activity of tibialis anterior, soleus, gastrocnemius medialis, gastrocnemius lateralis, vastus medialis, vastus lateralis, rectus femoris, and gluteus maximus. There were no differences (P > 0.05) in the muscle activity onset and offset or in the iEMG of any muscles between visits. There were also no differences (P > 0.05) between cyclists and non-cyclists in the variability of these parameters. Overall, standard error of measurement (SEM) and intra-class correlation analyses suggested similar reliability of both inter- and intra-session muscle activity onset and offset. The SEM of activity onset in tibialis anterior and activity offset in soleus, gastrocnemius lateralis and rectus femoris was markedly higher than in the other muscles. Intra-session iEMG was reliable (coefficient of variation (CV) = 5.3-13.5%, across all muscles), though a CV range of 15.8-43.1% identified low inter-session iEMG reliability. During submaximal cycling, the temporal components of muscle activity exhibit similar intra- and inter-session reliability. The magnitude component of muscle activity is reliable on an intra-session basis, but not on an inter-session basis.