Gross Efficiency Research Articles

An Approach to Estimating Gross Efficiency During High-Intensity Exercise

Gross efficiency (GE) is coupling power production to propulsion and is an important performance-determining factor in endurance sports. Measuring GE normally requires measuring VO(2) during submaximal exercise. In this study a method is proposed to estimating GE during high-intensity exercise. Nineteen subjects completed a maximal incremental test and 2 GE tests (1 experimental and 1 control test). The GE test consisted of 10 min cycling at 50% peak power output (PPO), 2 min at 25 W, followed by 4 min 100% PPO, 1 min at 25 W, and another 10 min at 50% PPO. GE was determined for the 50%-PPO sections and was, for the second 50%-PPO section, back-extrapolated, using linear regression, to the end of the 100%-PPO bout. Back-extrapolation of the GE data resulted in a calculated GE of 15.8% ± 1.7% at the end of the 100%-PPO bout, in contrast to 18.3% ± 1.3% during the final 2 min of the first 10-min 50%-PPO bout. Back-extrapolation seems valuable in providing more insight in GE during high-intensity exercise.

Hand-rim Forces and Gross Mechanical Efficiency at Various Frequencies of Wheelchair Propulsion

To determine the effects of push frequency changes on force application, fraction of effective force (FEF) and gross efficiency (GE) during hand-rim propulsion. 8 male able-bodied participants performed five 4-min sub-maximal exercise bouts at 1.8 ms(-1); the freely chosen frequency (FCF), followed by 4 counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMART(Wheel), measuring forces and moments. The GE was determined as the ratio of external work done and the total energy expended. Increased push frequency led to reductions in peak resultant force (P<0.05), ranging from 167 to 117 N and peak tangential force (P<0.05), ranging from 117 to 77 N. However, FEF only demonstrated a significant difference between 60% and 140% FCF (69 ± 9% and 63 ± 7, respectively; P<0.05). Work per cycle decreased significantly (P<0.05) and rate of force development increased significantly (P<0.05) with increased push frequency. GE values were significantly lower at 60%, 120% and 140% FCF than 80% and 100% FCF (P<0.05). No meaningful associations were present between FEF and GE. Under the current testing conditions, changes in push frequency are accompanied with changes in the absolute force values, albeit without changes in either the gross pattern/trend of force application or FEF. Changes in GE are not explained by different levels of force effectiveness.

INFLUENCE OF PEDALING TECHNIQUE ON METABOLIC EFFICIENCY IN ELITE CYCLISTS

Our objective was to investigate the influence of pedaling technique on gross efficiency (GE) at various exercise intensities in twelve elite cyclists ( · VO2max=75.7 ± 6.2 mL·kg -1 ·min -1 ). Each cyclist completed a · VO2max assessment, skinfold measurements, and an incremental test to determine their lactate threshold (LT) and onset of blood lactate accumulation (OBLA) values. The GE was determined during a three-phase incremental exercise test (below LT, at LT, and at OBLA). We did not find a significant relationship between pedaling technique and GE just below the LT. However, at the LT, there was a significant correlation between GE and mean torque and evenness of torque distribution (r=0.65 and r=0.66, respectively; p < 0.05). At OBLA, as the cadence frequency increased, the GE declined (r=-0.81, p < 0.05). These results suggest that exercise intensity plays an important role in the relationship between pedaling technique and GE.

Factors Affecting Gross Efficiency in Cycling

There is little standardization of how to measure cycling gross efficiency (GE). Therefore, the purposes of these studies were to evaluate the effect of: i) stage duration, ii) relative exercise intensity, iii) work capacity and iv) a prior maximal incremental test on GE. Trained subjects (n=28) performed incremental tests with stage durations of 1-, 3-, and 6-min to establish the effect of stage duration and relative exercise intensity on GE. The effect of work capacity was evaluated by correlating GE with peak power output (PPO). In different subjects (n=9), GE was measured at 50% PPO with and without a prior maximal incremental test. GE was similar in 3- and 6-min stages (19.7 ± 2.8% and 19.3 ± 2.0%), but significantly higher during 1-min stages (21.1 ± 2.7%), GE increased with relative exercise intensity, up to 50% PPO or the power output corresponding to the ventilatory threshold and then remained stable. No relationship between work capacity and GE was found. Prior maximal exercise had a small effect on GE measures; GE was lower after maximal exercise. In conclusion, GE can be determined robustly so long as steady state exercise is performed and RER ≤ 1.0.

Inverse Relationship between V˙O2max and Gross Efficiency

The aim of this study was to identify if an inverse relationship exists between Gross Efficiency (GE) and V˙O2max in trained cyclists. In Experiment 1, 14 trained cyclist's GE and V˙O2max were recorded at 5 different phases of a cycling 'self-coached' season using an incremental laboratory test. In Experiment 2, 29 trained cyclists undertook 12 weeks of training in one of 2 randomly allocated groups (A and B). Over the first 6 weeks Group A was prescribed specific high-intensity training sessions, whilst Group B were restricted in the amount of intensive work they could conduct. In the second 6-week period, both groups were allowed to conduct high intensity training. Results of both experiments in this study demonstrate training related increases in GE, but not V˙O2max. A significant inverse within-subject correlation was evident in experiment 1 between GE and V˙O2max across the training season (r=-0.32; P<0.05). In experiment 2, a significant inverse within-subject correlation was found between changes in GE and V˙O2max in Group A over the first 6 weeks of training (r=-0.78; P<0.01). Resultantly, a training related inverse relationship between GE and V˙O2max is evident in these groups of trained cyclists.

Reliability of Cycling Gross Efficiency Using the Douglas Bag Method

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. 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. 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. 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.

Para-cycling performance was rather limited by physiological than functional factors

OPINION article Front. Physiol., 15 August 2012Sec. Exercise Physiology Volume 3 - 2012 | https://doi.org/10.3389/fphys.2012.00327

Effects of frequency on gross efficiency and performance in roller ski skating

The purpose of the present study was to examine the effect of frequency on efficiency and performance during G3 roller ski skating. Eight well-trained male cross-country skiers performed three submaximal 5-min speeds (10, 13, and 16 km/h) and a time-to-exhaustion (TTE) performance (at 20 km/h) using the G3 skating technique using freely chosen, high, and low frequency at all four speeds. All tests were done using roller skis on a large treadmill at 5% incline. Gross efficiency (GE) was calculated as power divided by metabolic rate. Power was calculated as the sum of power against frictional forces and power against gravity. Metabolic rate was calculated from oxygen consumption and blood lactate concentration. Freely chosen frequency increased from 60 to 70 strokes/min as speed increased from 10 to 20 km/h. GE increased with power. At high power (20 km/h performance test), both efficiency and performance were significantly reduced by high frequency. In regard to choice of frequency during G3 roller ski skating, cross-country skiers seems to be self-optimized both in relation to energy saving (efficiency) and performance (TTE).

Anaerobic Capacity: Effect of Computational Method

Anaerobic capacity (AnC) can be estimated by subtracting VO (2) consumed from VO (2) demand, which can be estimated from multiple submaximal exercise bouts or by gross efficiency (GE), requiring one submaximal bout. This study compares AnC using the MAOD and GE method. The precision of estimated VO (2) demand and AnC, determined by MAOD using 3 power output - VO (2) regressions, based on VO (2) from min 8-10 (10 - Y), during min 4 without (4 - Y) and with forced y-intercept (4+Y), and from GE was evaluated by the 95% confidence interval (CI). Well-trained males (n=15) performed submaximal exercise tests to establish VO (2) demand with the MAOD and GE method. To determine AnC subjects completed a constant power output trial. The 3 MAOD procedures and GE method had no significant difference for VO (2) demand and AnC. The 4+Y MAOD procedure and GE method resulted in a smaller 95% CI of VO (2) demand and AnC than the 10 - Y ( P<0.05; P<0.01) and 4 - Y ( P<0.001; P<0.01) MAOD procedures. Therefore, the 4+Y MAOD procedure and GE method are preferred for estimating AnC, but as individual differences exist, they cannot be used interchangeably.

Effects of different pedalling techniques on muscle fatigue and mechanical efficiency during prolonged cycling

The present study aimed to test the influence of the pedalling technique on the occurrence of muscular fatigue and on the energetic demand during prolonged constant-load cycling exercise. Subjects performed two prolonged (45 min) cycling sessions at constant intensity (75% of maximal aerobic power). In a random order, participants cycled either with their preferred technique (PT) during one session or were helped by a visual force-feedback to modify their pedalling pattern during the other one (FB). Index of pedalling effectiveness was significantly (P<0.05) improved during FB (41.4 ± 5.5%); compared with PT (36.6 ± 4.1%). Prolonged cycling induced a significant reduction of maximal power output, which was greater after PT (-15 ± 9%) than after FB (-7 ± 12%). During steady-state FB, vastus lateralis muscle activity was significantly (P<0.05) reduced, whereas biceps femoris muscles activities increased compared with PT. Gross efficiency (GE) did not significantly differ between the two sessions, except during the first 15 min of exercise (FB: 19.0 ± 1.9% vs PT: 20.2 ± 1.9%). Although changes in muscular coordination pattern with feedback did not seem to influence GE, it could be mainly responsible for the reduction of muscle fatigue after prolonged cycling.

Pedaling Technique and Energy Cost in Cycling

Because cycling is an extreme endurance sport, energy saving and therefore efficiency is of importance for performance. It is generally believed that gross efficiency (GE) is affected by pedaling technique. A measurement of pedaling technique has traditionally been done using force effectiveness ratio (FE; ratio of effective force and total force). The aim of the present study was to investigate the relationship among GE, FE, and a new technique parameter, dead center (DC) size in competitive cyclists. Twenty-one competitive cyclists cycled for 10 min at approximately 80% VO(2max) at a freely chosen cadence (FCC). GE, FE ratio, and DC size were calculated from oxygen consumption and propulsive force recordings. Mean work rate was 279 W, mean FCC was 93.1 rpm, and mean GE was 21.7%. FE was 0.47 and 0.79 after correction for inertial forces; DC was 27.3% and 25.7%, respectively. DC size correlated better with GE (r = 0.75) than with the FE ratio (r = 0.50). Multiple regressions revealed that DC size was the only significant (P = 0.001) predictor for GE. Interestingly, DC size and FE ratio did not correlate with each other. DC size is a pedaling technique parameter that is closely related to energy consumption. To generate power evenly around the whole pedal, revolution may be an important energy-saving trait.

The relationship between cadence, pedalling technique and gross efficiency in cycling.

Technique and energy saving are two variables often considered as important for performance in cycling and related to each other. Theoretically, excellent pedalling technique should give high gross efficiency (GE). The purpose of the present study was to examine the relationship between pedalling technique and GE. 10 well-trained cyclists were measured for GE, force effectiveness (FE) and dead centre size (DC) at a work rate corresponding to ~75% of VO2max during level and inclined cycling, seat adjusted forward and backward, at three different cadences around their own freely chosen cadence (FCC) on an ergometer. Within subjects, FE, DC and GE decreased as cadence increased (p < 0.001). A strong relationship between FE and GE was found, which was to great extent explained by FCC. The relationship between cadence and both FE and GE, within and between subjects, was very similar, irrespective of FCC. There was no difference between level and inclined cycling position. The seat adjustments did not affect FE, DC and GE or the relationship between them. Energy expenditure is strongly coupled to cadence, but force effectiveness, as a measure for pedalling technique, is not likely the cause of this relationship. FE, DC and GE are not affected by body orientation or seat adjustments, indicating that these parameters and the relationship between them are robust to coordinative challenges within a range of cadence, body orientation and seat position that is used in regular cycling.

Effects of Speed and Slope on Ski Skating Efficiency and Kinematics

Cross-country skiing is performed at varying speeds and slopes where a skier continuously needs to alter his technique in order to ski efficient. PURPOSE: To investigate the effects of speed and slope on gross efficiency (GE) and kinematics while treadmill roller skiing employing the skating G3 technique. METHODS: Seven male elite skiers performed nine 5-min submaximal stages. These stages were matched for low, moderate and high metabolic rates at inclinations of 2% (12, 17 and 22 km·h-1), 5% (9, 12 and 16 km·h-1) and 8% (6, 9 and 12 km·h-1), respectively. Oxygen uptake, respiratory exchange ratio and blood lactate concentration were used to determine physiological response and calculate metabolic rate. Work against gravity and friction determined work rate. GE was calculated as work rate divided by metabolic rate. Kinematics were analyzed using the Qualisys Pro Reflex system (Qualisys AB, Gothenburg, Sweden). RESULTS: A linear relationship between work rate and metabolic rate was found for each of the three different slopes (all P < 0.05). At the matched metabolic rates, work rates were always higher on steeper slopes (all P < 0.05). GE was consistently higher on steeper slopes, but increased at higher speed for all slopes, i.e, GE increased from ∼10% (at 2% inclination and 12 km·h-1) up to ∼16% (at 8% inclination and 12 km·h-1) (all P < 0.05). Cycle rate (CR) increased, whereas cycle time and cycle length decreased, both with increased speed and slope (all P < 0.05). Strong inter-individual correlations were found between GE and CR at the highest speed for all three slopes (all r = ∼0.90, P < 0.05). CONCLUSION: A linear relationship between work rate and metabolic rate, i.e., "Fenn effect", was found for cross-country skiing when treadmill roller skiing using a standardized slope and technique. Thus, GE slightly increases with speed from low to high metabolic rates. However, skiers show a higher efficiency and are able to obtain higher work rates on steeper slopes at a given metabolic rate. They do this by increasing CR, which is in contradiction with general findings in the literature. Yet, all skiers employ higher CR on steeper slopes, more efficient skiers were able to employ longer cycle lengths and lower cycle rates.

Influence of Varied Tempo Music on Wheelchair Mechanical Efficiency Following 3-Week Practice

The purpose of this study was to analyse adaptations in propulsion technique and gross efficiency in novice able-bodied subjects during the initial phase of learning hand-rim wheelchair propulsion to music. 22 able bodied participants performed wheelchair propulsion (1.1 m·s(-1)) followed by a VO(2) peak test on a wheelchair ergometer. Push frequency, gross efficiency (GE), heart rate, rating of perceived exertion and propulsion technique variables (force application and temporal characteristics) were recorded. Participants were then assigned to a 3-wk practice period listening to i) 125 beats·min(-1) tempo music (LOW); ii) 170 beats·min(-1) tempo music (HIGH); or iii) a control group (CON). Following practice, all participants repeated the pre-testing protocol whilst force application data was collected in practice trials 1 and 9. After accounting for the pre-practice differences in GE (using ANCOVA), GE was higher in LOW compared with CON (P=0.038; 6.6 vs. 6.1% respectively). The differences between CON vs. HIGH and LOW vs. HIGH (P=0.830; P=0.188) were trivial suggesting that only LOW experienced an increase in GE. Practice had a favourable effect on the perceptions of effort, work per cycle, push and cycle time in contrast to the CON group. The use of music in a rehabilitation setting warrants further investigation.

Analysis of a sprint ski race and associated laboratory determinants of world-class performance

This investigation was designed to analyze the time-trial (STT) in an international cross-country skiing sprint skating competition for (1) overall STT performance and relative contributions of time spent in different sections of terrain, (2) work rate and kinematics on uphill terrain, and (3) relationships to physiological and kinematic parameters while treadmill roller ski skating. Total time and times in nine different sections of terrain by 12 world-class male sprint skiers were determined, along with work rate and kinematics for one specific uphill section. In addition, peak oxygen uptake (VO2peak), gross efficiency (GE), peak speed (Vpeak), and kinematics in skating were measured. Times on the last two uphill and two final flat sections were correlated to overall STT performance (r = ~−0.80, P < 0.001). For the selected uphill section, speed was correlated to cycle length (r = −0.75, P < 0.01) and the estimated work rate was approximately 160% of peak aerobic power. VO2peak, GE, Vpeak, and peak cycle length were all correlated to STT performance (r = ~−0.85, P < 0.001). More specifically, VO2peak and GE were correlated to the last two uphill and two final flat section times, whereas Vpeak and peak cycle length were correlated to times in all uphill, flat, and curved sections except for the initial section (r = ~−0.80, P < 0.01). Performances on uphill and flat terrain in the latter part were the most significant determinants of overall STT performance. Peak oxygen uptake, efficiency, peak speed, and peak cycle length were strongly correlated to overall STT performance, as well as to performance in different sections of the race.

Different Effect of Cadence on Cycling Efficiency between Young and Older Cyclists

We investigated the difference in the cadence-efficiency relationship between young and older competitive cyclists. Eight young (24.3 ± 5.3 yr) and eight older (65.6 ± 2.8 yr) competitive cyclists participated in two laboratory sessions. The first consisted of an incremental maximal cycling test to determine the freely chosen pedal cadence and the maximal power output at VO2max and the second for the determination of gross efficiency (GE), calculated as the ratio of external work and energy expenditure (VO2). The latter test consisted of 6-min cycling exercise bouts at 40% and 60% of maximal power output and at a cadence of 40, 60, 80, 100, and 120 rpm. GE was lower in older cyclists than that in young cyclists at all cadences considered and at both levels of power output (P < 0.01). Peak efficiency was reached at 60 rpm in young cyclists (21.2% ± 1.9%), whereas in older cyclists this was observed already at 40 rpm and was not different from that at 60 rpm (18.3% ± 0.6%). The decline in GE with the increase in cadence was more pronounced in older than in young cyclists (P < 0.01) and was mitigated by the increase in power output more in the latter than in the former. These observations were in line with a lower freely chosen cadence recorded during the maximal test in older than that in young (P < 0.01). The present data indicate that the effect of cadence on cycling efficiency is different between young and older cyclists and that it seems more disadvantageous for the latter to use high cadences. This may help explain why our older cyclists chose to pedal at lower cadences than the younger.

Interaction Between Intermittent Hypoxia and Sprint Interval Training on Efficiency and Economy

VO2max, efficiency and economy play important roles in endurance performance. These improvements have been elicited separately through endurance and sprint interval training (SIT) and intermittent hypoxic exposure (IHE). However, there is limited data of the interaction of SIT and IHE on endurance performance. PURPOSE: To compare the effects of IHE, SIT, and a combination of IHE/SIT on VO2max and submaximum energy costs. METHODS: 20 healthy male subjects (age: 26 ± 4yrs, ht: 179 ± 7cm, wt: 85 ± 18kg, VO2max: 52.32±14.32ml/kg/min) were split into 4 groups for a 2 wk training study. The 4 groups consisted of a normoxic control group (NC) (n=5), a normoxic training group (NST) (n=5), an intermittent hypoxic control group (IHC) (n=5) and an intermittent hypoxic training group (IHST) (n=5). All volunteers spent ∼ 10 days within 12 day period in a hypoxic enclosure. The IHE and normoxic conditions were blinded to the participants. The intermittent hypoxic and normoxic groups were exposed for 3 hours to a simulated altitude of 90.34 ± 1.35 mmHg and ∼149 mmHg PiO2, respectively. The training groups performed 6 SIT sessions on a cycle ergometer over a 2 wk period. Each SIT session included 4-7 × 30 second all out sprints with a resistance of 7.5% of body weight. Hypoxic or normoxic exposure was conducted immediately after each SIT session. Pre and post maximal (1min incremental ramp) and submaximal cycle ergometer tests (60 min @ 10% below ventilatory threshold) were conducted 1 wk before and after the last IHE or normoxic exposure. The following variables were measured: VO2max, gross efficiency (GEF), net efficiency (NEF) and economy (EC). A mixed model repeated measures ANOVA was used to analyze the differences between IHE, SIT and IHST. RESULTS: Post intervention, there were no significant effects between the 4 groups for VO2max (p=0.307), GEF (p=0.207), NEF (p=0.349), and EC (p=0.349). CONCLUSION: Two weeks of IHE, SIT or IHST does not have a significant effect on VO2max, GEF, NEF or EC. Therefore, 2 wks of IHE to a simulated altitude of ∼4000 m nor 2 wks of sprint interval training; or a combination of the two training interventions are ineffective in improving VO2max or submaximum energy costs in males with above average fitness.

The between and within day variation in gross efficiency.

Before the influence of divergent factors on gross efficiency (GE) [the ratio of mechanical power output (PO) to metabolic power input (PI)] can be assessed, the variation in GE between days, i.e. the test–retest reliability, and the within day variation needs to be known. Physically active males (n = 18) performed a maximal incremental exercise test to obtain VO2max and PO at VO2max (PVO2max), and three experimental testing days, consisting of seven submaximal exercise bouts evenly distributed over the 24 h of the day. Each submaximal exercise bout consisted of six min cycling at 45, 55 and 65% PVO2max, during which VO2 and RER were measured. GE was determined from the final 3 min of each exercise intensity with: GE = (PO/PI) × 100%. PI was calculated by multiplying VO2 with the oxygen equivalent. GE measured during the individually highest exercise intensity with RER <1.0 did not differ significantly between days (F = 2.70, p = 0.08), which resulted in lower and upper boundaries of the 95% limits of agreement of 19.6 and 20.8%, respectively, around a mean GE of 20.2%. Although there were minor within day variations in GE, differences in GE over the day were not significant (F = 0.16, p = 0.99). The measurement of GE during cycling at intensities approximating VT is apparently very robust, a change in GE of ~0.6% can be reliably detected. Lastly, GE does not display a circadian rhythm so long as the criteria of a steady-state VO2 and RER <1.0 are applied.

Effects of Sprint Interval Training Combined with Intermittent Hypoxia: A Case Study

INTRODUCTION: The benefits of hypoxic exposure in conjunction with endurance training on exercise performance at sea level have been studied extensively. However, limited research on the interaction of sprint interval training (SIT) and intermittent hypoxic exposure (IHE) has been conducted. Research suggests separately, SIT and IHE may increase performance. PURPOSE: To investigate the effects of SIT followed by IHE on sea level performance. METHODS: A healthy male subject (age: 23yrs, ht: 180.5cm, wt: 83.7kg) with excellent cardiovascular fitness (VO2 = 51.3 mL/kg/min) participated in a 2 week training study consisting of 6 sessions of 30 second all out sprints and 9 days of IHE (12.68% O2, 14,025ft). Each SIT session included 4-7 thirty second all out effort with a load weight of 7.5% of the subject's body weight. Each IHE session consisted of 3 hrs and was conducted immediately after the SIT on training days. Pre and post maximal and sub maximal tests were conducted looking at the following variables: VO2max, peak power at VO2max (PPO(w)), gross efficiency (GEF), net efficiency (NEF) and economy (EC). RESULTS:TABLECONCLUSION: While other research has shown significant increases in sea level performance after SIT or IHE alone, this study indicates that pairing SIT and IHE may produce greater increases in VO2max, PPO, GEF, NEF and EC than SIT or IHE alone.

Metabolic rate and gross efficiency at high work rates in world class and national level sprint skiers

The present study investigated metabolic rate (MR) and gross efficiency (GE) at moderate and high work rates, and the relationships to gross kinematics and physical characteristics in elite cross-country skiers. Eight world class (WC) and eight national level (NL) male sprint cross-country skiers performed three 5-min stages using the skating G3 technique, whilst roller skiing on a treadmill. GE was calculated by dividing work rate by MR. Work rate was calculated as the sum of power against gravity and frictional rolling forces. MR was calculated using gas exchange and blood lactate values. Gross kinematics, i.e. cycle length (CL) and cycle rate (CR) were measured by video analysis. Furthermore, the skiers were tested for time to exhaustion (TTE), peak oxygen uptake (VO(2peak)), and maximal speed (V(max)) on the treadmill, and maximal strength in the laboratory. Individual performance level in sprint skating was determined by FIS points. WC skiers did not differ in aerobic MR, but showed lower anaerobic MR and higher GE than NL skiers at a given speed (all P < 0.05). Moreover, WC skiers skated with longer CL and had higher V(max) and TTE (all P < 0.05). In conclusion, the present study shows that WC skiers are more efficient than NL skiers, and it is proposed that this might be due to a better technique and to technique-specific power.