Age-Associated Changes In VO2 and Power Output - A Cross-Sectional Study of Endurance Trained New Zealand Cyclists

Age-associated changes in power and maximal oxygen consumption (VO_2max) were studied in a cross section of endurance trained cyclists. Subjects (n = 56) performed incremental cycling exercise, during which capillary blood lactate [La^-] was measured. Power output increased by 30 Watts during each 5 minutes stage, with initial power output based on individual ability. When [La^-] was >4.5 mmol·L^-1, subjects were given a 10 min recovery at a power output approximately 50% below estimated power at [La^-]_4mmol. Subjects then performed an incremental test (1 minute stages) to VO_2max. Decline in VO_2max was 0.65 ml·kg^-1·min^-1·year^-1 (r = -0.72, p < 0.01) for males, and 0.39 ml·kg^-1·min^-1·year^-1 (r = -0.54, p < 0.05) for females. Power at VO_2max decreased by 0.048 W kg^-1·year^-1 (r = -0.72, p < 0.01) in males. Power at [La^-]_4mmol decreased by 0.044 W kg^-1·year^-1 (r = -0.76, p < 0.01) in males, and by 0.019 W kg^-1·year^-1 (r = -0.53, p < 0.05) in females. Heart rate at VO_2max (HR_max) showed a weaker correlation with age in males (r = -0.36, p < 0.05). The age-associated changes in maximum aerobic power and sub-maximal power were gender- specific, thus suggesting different age-related effects on the systems which support exercise in males and females.

Key points

• VO_2max decreased with age by 0.65 ml·kg^-1·min^-1·year^-1 in male, and by 0.39 ml·kg^-1·min^-1·year^-1 in female endurance trained cyclists.
• Power at VO_2max decreased with age by 0.048 Watts·kg^-1·year^-1 in male endurance trained cyclists.
• Sub-maximal power at a blood lactate concentration of 4mmol·L^-1 decreased by 0.044 Watts·kg^-1·year^-1 in male, and by 0.019 Watts·kg^-1·year^-1 in female endurance trained cyclists.

Key words: Maximal oxygen consumption, aging, exercise, performance     

The Effects of Vibration During Maximal Graded Cycling Exercise: A Pilot Study

Whole Body Vibration training is studied and used in different areas, related to sport performance and rehabilitation. However, few studies have investigated the effects of Vibration (Vib) exposure on aerobic performance through the application of this concept to cycling exercise. A specifically designed vibrating cycloergometer, the powerBIKE^™, was used to compare the effects of Vib cycling exercise and normal cycling on different physiological parameters during maximal graded exercise test. Twelve recreationally active male adults (25 ± 4.8 yrs; 181.33 ± 5.47 cm; 80.66 ± 11.91 kg) performed two maximal incremental cycling tests with and without Vib in a block-randomized order. The protocol consisted of a 4 min warm up at 70 rev·min^-1 followed by incremental steps of 3 min each. Cycling cadence was increased at each step by 10 rev·min^-1 until participants reached their volitional exhaustion. Respiratory gases (VO₂, VCO₂), Heart Rate, Blood Lactate and RPE were collected during the test. Paired t-tests and Cor-relation Coefficients were used for statistical analysis. A significantly greater (P<0.05) response in the VO₂, HR, BLa and RPE was observed during the Vib trial compare to normal cycling. No significant differences were found in the maximal aerobic power (Vib 34.32 ± 9.70 ml·kg^-1·min^-1; no Vib 40.11 ± 9.49 ml·kg^-1·min^-1). Adding Vib to cycling exercise seems eliciting a quicker energetic demand during maximal exercise. However, mechanical limitations of the vibrating prototype could have affected the final outcomes. Future studies with more comparative setting are recommended to deeply appraise this concept.

Key points

• There is strong evidence to suggest that acute indirect vibrations act on muscle to enhance force, power, flexibility, balance and proprioception.
• There is a lack of knowledge regarding the effects of applying Vib to dynamic aerobic exercise.
• Added vibrations to cycling exercise seem producing a quicker energetic demand during maximal graded exercise when compared to traditional cycling.

Key words: Vibration, Endurance, Aerobic, Energetic demand, Cycloergometer     

Maximal Oxygen Uptake cannot be Determined in the Incremental Phase of The Lactate Minimum Test on a Cycle Ergometer

The aim of this study was to investigate the maximal oxygen uptake (VO_2MAX) determined using the incremental phase of the lactate minimum test (LM) on a cycle ergometer. Fifteen trained men were submitted to a graded exercise test (GXT) to evaluate the VO_2MAX and LM. The total durations of the GXT and LM were 11.2±1.8 minutes (CI95%:10.2-12.3 minutes) and 25.3±3.2 minutes (CI95%:23.5-27.0), respectively. For the variables measured at exhaustion in both the GXT and LM, the oxygen uptake (54.6 ± 8.1 ml·kg⁻¹·min⁻¹vs 50.0 ± 7.7 ml·kg⁻¹·min⁻¹), carbon dioxide production (66.1 ± 7.5 ml·kg⁻¹·min⁻¹ vs 50.4 ± 8.0 ml·kg⁻¹·min⁻¹), ventilation (153.9 ± 19.0 L·min⁻¹ vs 129.9 ± 22.9 L·min⁻¹), respiratory exchange ratio (1.22 ± 0.10 vs1.01 ± 0.05), maximal power output achieved (331.6 ± 45.8 W vs 242.4 ± 41.0 W), heart rate (183.1 ± 6.9 bpm vs175.9 ± 10.6 bpm) and lactate (10.5 ± 2.3 mmol·L⁻¹ vs 6.6 ± 2.2 mmol·L⁻¹) were statistically lower in the LM (p < 0.05). However, the values of rating of perceived exertion (17.6 ± 2.5 for GXT and 17.2 ± 2.3 for LM) did not differ (ES = 0.12 and CV = 7.8%). There was no good agreement between the values of the VO_2MAX from the GXT and VO_2PEAK from the LM, as evidenced in the Bland-Altman plot (4.7 ml·kg⁻¹·min⁻¹ and 0.34 L·min⁻¹ of mean differences, respectively), as well as the high values of the upper and lower limits of agreement. We conclude that the VO_2PEAK values obtained in the incremental phase of the LM underestimate the VO_2MAX.

Key points

• The VO_2MAX is not attained during the incremental phase of the lactate minimum test;
• The physiological responses at exhaustion during LM are not similar to physiological responses measured during GXT;
• There is a weak agreement between the peak VO₂ measured at exhaustion during LM and the VO_2MAX measured during GXT.

Key words: Maximal aerobic power, aerobic capacity, aerobic and anaerobic fitness     

A Review of Stature,Body Mass and Maximal Oxygen Uptake Profiles of U17, U20 and First Division Players in Brazilian Soccer

Investigations in the physiological demands of soccer have identified that a significant percentage of energy production in match performance is provided through the aerobic pathways. It is therefore important to assess maximal oxygen uptake (VO_2Max) of players in order to evaluate their aerobic fitness status and optimize their physical conditioning. However, it is also important to consider the variation of (VO_2Max) profiles for soccer players, with differences having been identified in terms of playing position as well as playing style. This paper reviews the academic literature between 1996 and 2006 and reports on the methodologies employed and the values obtained for stature, body mass and (VO_2Max) profiles of soccer players of different positions in professional Brazilian clubs at U-17, U-20 and First Division levels. Indirect measurements accounted for the majority of tests conducted at U-17 (70%) and U-20 (84.6%) levels whereas at First Division level almost half of the (VO_2Max) evaluations were performed by direct measurements (47.8%). The mean (VO_2Max) profiles obtained for outfield players in U-17 was 56.95 ± 3.60 ml·kg^-1·min^-1, 58.13 ± 3.21 ml·kg^-1·min^-1 for U-20 players and 56.58 ± 5.03 ml·kg^-1·min^-1 for First Division players. In Brazil, the U-20 players appear to have highest VO_2Max values, however the profiles reported for all outfield positions in U-17 and First Division levels are often lower than those reported for the same category of players from other countries. This may be a reflection of the style of play used in Brazilian soccer. This is further emphasized by the fact that the playing position with the highest VO_2Max values was the external defenders whereas most findings from studies performed in European soccer indicate that midfielders require the highest VO_2Max values.

Key points

• Physical and physiological differences exist between Brazilian soccer and European soccer.
• Players in Brazil appear to be shorter in stature, similar in body mass and have a lower overall aerobic capacity to their European equivalents
• In Brazil, there seems to be a physical development phase for players at U-20 level which prepares them for the demands at First Division level.

Key words: Soccer, maximal oxygen uptake, playing positions     

Effect of Exercise Intensity on Differentiated and Undifferentiated Ratings of Perceived Exertion During Cycle and Treadmill Exercise in Recreationally Active and Trained Women

The purpose of the study is to examine the effect of aerobic exercise intensity on components of the differentiated perceived exertion model in young women performing weight bearing and non-weight bearing aerobic exercise. Subjects were 18-25 yr old women who were recreationally active (n = 19; VO₂max = 33.40 ml·kg^-1·min^-1) and trained (N = 22; VO₂max = 43.3 ml·kg^-1·min^-1). Subjects underwent two graded exercise tests (GXT) on a treadmill and bike which were separated by 48 hours. RPE-Overall, -Legs, and -Chest, as well as oxygen uptake (VO₂) and heart rate were recorded each minute. Individual regression analyses were used to identify RPE-Overall,-Legs, and -Chest at 40, 60, 80% VO_2max/peak. Separate two factor (site (3) x intensity (3)) ANOVAs with repeated measures on site and intensity were computed for each training status. Furthermore, RPE responses were also examined with a one factor (site (3)) within subject ANOVA with repeated measure on site at the ventilatory breakpoint. For both the recreationally active and trained groups no significant differences were observed for RPE-Overall, -Legs, and -Chest during treadmill exercise. However, for cycling exercise results indicated that RPE-Legs was significantly greater at all exercise intensities than RPE-Overall and RPE-Chest for trained subjects while for recreationally active subjects RPE-Legs was only significantly higher at the highest exercise intensity. Responses at the ventilatory breakpoint during cycle exercise indicated that RPE-Legs was significantly greater than RPE-Chest and RPE-Overall for trained subjects but not for recreationally active subjects. Signal dominance was not observed at an intensity equivalent to the ventilatory breakpoint during treadmill exercise in either of the groups. In recreationally active and trained females signal dominance was demonstrated only during cycling exercise, but not during treadmill exercise. Signal integration could not be demonstrated during cycling and treadmill exercise at various intensities.

Key points

• RPE is a valid tool to track relative exercise intensity and can be applied as differentiated and undifferentiated responses regardless of training status.
• RPE-Legs dominated the signal response in trained women during cycling exercise.
• RPE-Legs, -Chest, and -Overall did not differ significantly in trained and recreationally active women during treadmill exercise.
• RPE-Legs and -Chest contribute equally to the formation of RPE-Overall during cycling and treadmill exercise.

Key words: Aerobic exercise, physical exertion, oxygen consumption, physical fitness     

Inclusion of Exercise Intensities Above the Lactate Threshold in VO2/Running Speed Regression Does not Improve the Precision of Accumulated Oxygen Deficit Estimation in Endurance-Trained Runners

The present study intended to verify if the inclusion of intensities above lactate threshold (LT) in the VO₂/running speed regression (RSR) affects the estimation error of accumulated oxygen deficit (AOD) during a treadmill running performed by endurance-trained subjects. Fourteen male endurance-trained runners performed a sub maximal treadmill running test followed by an exhaustive supra maximal test 48h later. The total energy demand (TED) and the AOD during the supra maximal test were calculated from the RSR established on first testing. For those purposes two regressions were used: a complete regression (CR) including all available sub maximal VO₂ measurements and a sub threshold regression (STR) including solely the VO₂ values measured during exercise intensities below LT. TED mean values obtained with CR and STR were not significantly different under the two conditions of analysis (177.71 ± 5.99 and 174.03 ± 6.53 ml·kg^-1, respectively). Also the mean values of AOD obtained with CR and STR did not differ under the two conditions (49.75 ± 8.38 and 45.8 9 ± 9.79 ml·kg^-1, respectively). Moreover, the precision of those estimations was also similar under the two procedures. The mean error for TED estimation was 3.27 ± 1.58 and 3.41 ± 1.85 ml·kg^-1 (for CR and STR, respectively) and the mean error for AOD estimation was 5.03 ± 0.32 and 5.14 ± 0.35 ml·kg^-1 (for CR and STR, respectively). The results indicated that the inclusion of exercise intensities above LT in the RSR does not improve the precision of the AOD estimation in endurance-trained runners. However, the use of STR may induce an underestimation of AOD comparatively to the use of CR.

Key Points

• It has been suggested that the inclusion of exercise intensities above the lactate threshold in the VO₂/power regression can significantly affect the estimation of the energy cost and, thus, the estimation of the AOD.
• However data on the precision of those AOD measurements is rarely provided.
• We have evaluated the effects of the inclusion of those exercise intensities on the AOD precision.
• The results have indicated that the inclusion of exercise intensities above the lactate threshold in the VO₂/running speed regression does not improve the precision of AOD estimation in endurance-trained runners.
• However, the use of sub threshold regressions may induce an underestimation of AOD comparatively to the use of complete regressions.

Key Words: Methodology, linear regression, estimation error, lactate threshold     

Cycling Efficiency in Trained Male and Female Competitive Cyclists

The aim of this study was to examine differences in cycling efficiency between competitive male and female cyclists. Thirteen trained male (mean ± SD: 34 ± 8 yr, 74.1 ± 6.0 kg, Maximum Aerobic Power (MAP) 414 ± 40 W, VO₂max 61.3 ± 5.4 ml·kg^-1·min^-1) and 13 trained female (34 ± 9 yr, 60.1 ± 5.2 kg, MAP 293 ± 22 W, VO₂max 48.9 ± 6.1 ml·kg^-1·min^-1) competitive cyclists completed a cycling test to ascertain their gross efficiency (GE). Leg and lean leg volume of all cyclists was also measured. Calculated GE was significantly higher in female cyclists at 150W (22.5 ± 2.1 vs 19.9 ± 1. 8%; p < 0.01) and 180W (22.3 ± 1.8 vs 20.4 ± 1.5%; p = 0.01). Cadence was not significantly different between the groups (88 ± 6 vs 91 ± 5 rev·min^-1). Lean leg volume was significantly lower for female cyclists (4.04 ± 0.5 vs 5.51 ± 0.8 dm³; p < 0.01) and was inversely related to GE in both groups at 150 and 180W (r = -0.59 and -0.58; p < 0.05). Lean leg volume was shown to account for the differences in GE between the males and females. During an “unloaded ”pedalling condition, male cyclists had a significantly higher O₂ cost than female cyclists (1.0 ± 0.1 vs 0.7 ± 0.1 L·min^-1; p < 0.01), indicative of a greater non-propulsive cost of cycling. These results suggest that differences in efficiency between trained male and female cyclists can be partly accounted for by sex-specific variation in lean leg volume.

Key points

• Differences in GE exist between male and female cyclists.
• Males have a higher oxygen cost of “unloaded ”cycling, as predicted by the intercept of the O2 cost-power output relationship
• This suggests that in addition to work rate, leg volume/mass may be an important determinant of observed differences in oxygen cost and therefore GE, between male and female competitive cyclists.

Key words: Gross efficiency, endurance performance, sex-related differences, power output, leg volume     

Physiological Responses and Predictors of Performance in a Simulated Competitive Ski Mountaineering Race

Competitive ski mountaineering (SKIMO) has achieved great popularity within the past years. However, knowledge about the predictors of performance and physiological response to SKIMO racing is limited. Therefore, 21 male SKIMO athletes split into two performance groups (elite: VO_2max 71.2 ± 6.8 ml· min^-1· kg^-1 vs. sub-elite: 62.5 ± 4.7 ml· min^-1· kg^-1) were tested and analysed during a vertical SKIMO race simulation (523 m elevation gain) and in a laboratory SKIMO specific ramp test. In both cases, oxygen consumption (VO₂), heart rate (HR), blood lactate and cycle characteristics were measured. During the race simulation, the elite athletes were approximately 5 min faster compared with the sub-elite (27:15 ± 1:16 min; 32:31 ± 2:13 min; p < 0.001). VO₂ was higher for elite athletes during the race simulation (p = 0.046) and in the laboratory test at ventilatory threshold 2 (p = 0.005) and at maximum VO₂ (p = 0.003). Laboratory maximum power output is displayed as treadmill speed and was higher for elite than sub-elite athletes (7.4 ± 0.3 km h^-1; 6.6 ± 0.3 km h^-1; p < 0.001). Lactate values were higher in the laboratory maximum ramp test than in the race simulation (p < 0.001). Pearson’s correlation coefficient between race time and performance parameters was highest for velocity and VO₂ related parameters during the laboratory test (r > 0.6). Elite athletes showed their superiority in the race simulation as well as during the maximum ramp test. While HR analysis revealed a similar strain to both cohorts in both tests, the superiority can be explainable by higher VO₂ and power output. To further push the performance of SKIMO athletes, the development of named factors like power output at maximum and ventilatory threshold 2 seems crucial.Key points

• VO₂ measurements in the laboratory and the field confirm the high involvement of the aerobic system in SKIMO
• Elite athletes showed their supremacy in the laboratory test and the simulated vertical race
• Relative heart rate, relative VO₂ and lactate values indicate the same emphasized strain for elite and sub-elite athletes during SKIMO vertical racing.
• Peak speed, peak lactate and VO_2max were the highest in lab predictors of outdoor SKIMO vertical race performance.

Key words: Performance diagnosis, predictors of performance, oxygen uptake, competition simulation, winter sports physiology, ski mountaineering     

Oxygen Uptake Kinetics During Incremental- and Decremental-Ramp Cycle Ergometry

The pulmonary oxygen uptake (VO₂) response to incremental-ramp cycle ergometry typically demonstrates lagged-linear first-order kinetics with a slope of ~10-11 ml·min^-1·W^-1, both above and below the lactate threshold (θ_L), i.e. there is no discernible VO₂ slow component (or “excess” VO₂) above θ_L. We were interested in determining whether a reverse ramp profile would yield the same response dynamics. Ten healthy males performed a maximum incremental -ramp (15-30 W·min^-1, depending on fitness). On another day, the work rate (WR) was increased abruptly to the incremental maximum and then decremented at the same rate of 15-30 W.min^-1 (step-decremental ramp). Five subjects also performed a sub-maximal ramp-decremental test from 90% of θ_L. VO₂ was determined breath-by-breath from continuous monitoring of respired volumes (turbine) and gas concentrations (mass spectrometer). The incremental-ramp VO₂-WR slope was 10.3 ± 0.7 ml·min^-1·W^-1, whereas that of the descending limb of the decremental ramp was 14.2 ± 1.1 ml·min^-1·W^-1 (p < 0.005). The sub-maximal decremental-ramp slope, however, was only 9. 8 ± 0.9 ml·min^-1·W^-1: not significantly different from that of the incremental-ramp. This suggests that the VO₂ response in the supra-θ_L domain of incremental-ramp exercise manifest not actual, but pseudo, first-order kinetics.

Key points

• The slope of the decremental-ramp response is appreciably greater than that of the incremental.
• The response dynamics in supra-θ_L domain of the incremental-ramp appear not to manifest actual first-order kinetics.
• The mechanisms underlying the different dynamic response behaviour for incremental and decremental ramps are presently unclear.

Key words: Oxygen uptake-work rate gain, incremental-ramp exercise, decremental-ramp exercise, system linearity.     

Reliability and Validity of Physiological Data Obtained Within a Cycle-Run Transition Test in Age-Group Triathletes

This study examined the validity and reliability of a sequential “Run-Bike-Run” test (RBR) in age-group triathletes. Eight Olympic distance (OD) specialists (age 30.0 ± 2.0 years, mass 75.6 ± 1.6 kg, run VO_2max 63.8 ± 1.9 ml· kg^-1· min^-1, cycle VO_2peak 56.7 ± 5.1 ml· kg^-1· min^-1) performed four trials over 10 days. Trial 1 (TRVO_2max) was an incremental treadmill running test. Trials 2 and 3 (RBR₁ and RBR₂) involved: 1) a 7-min run at 15 km· h^-1 (R₁) plus a 1-min transition to 2) cycling to fatigue (2 W· kg^-1 body mass then 30 W each 3 min); 3) 10-min cycling at 3 W· kg^-1 (B_submax); another 1-min transition and 4) a second 7-min run at 15 km· h^-1 (R₂). Trial 4 (TT) was a 30-min cycle - 20-min run time trial. No significant differences in absolute oxygen uptake (VO₂), heart rate (HR), or blood lactate concentration ([BLA]) were evidenced between RBR₁ and RBR₂. For all measured physiological variables, the limits of agreement were similar, and the mean differences were physiologically unimportant, between trials. Low levels of test-retest error (i.e. ICC <0.8, CV<10%) were observed for most (logged) measurements. However [BLA] post R₁ (ICC 0.87, CV 25.1%), [BLA] post B_submax (ICC 0.99, CV 16.31) and [BLA] post R₂ (ICC 0.51, CV 22.9%) were least reliable. These error ranges may help coaches detect real changes in training status over time. Moreover, RBR test variables can be used to predict discipline specific and overall TT performance. Cycle VO_2peak, cycle peak power output, and the change between R₁ and R₂ (deltaR₁R₂) in [BLA] were most highly related to overall TT distance (r = 0.89, p < 0. 01; r = 0.94, p < 0.02; r = 0.86, p < 0.05, respectively). The percentage of TR VO_2max at 15 km· h^-1, and deltaR₁R₂ HR, were also related to run TT distance (r = -0.83 and 0.86, both p < 0.05).

Key points

• It is extremely important to ensure that the measurements made as part of research or athlete support work are adequately reliable and valid.
• The modified Millet triathlete “Run-Bike-Run” (RBR) test allows both for important physiological variables that are normally obtained from isolated tests (such as cycle VO_2peak and peak power output) to be determined, and for measurement of the extent to which an athlete adapts to a cycle-run transition (T2).
• The data reported in this paper regarding the test-retest reliability of the modified RBR, and its validity relative to cycle-run time-trial performance in male age-group triathletes, may help coaches determine the extent to which changes on test measures are likely due to training adaptation rather than to measurement error.

Key words: Multi-discipline, reproducibility, time-trial, test, adaptation     

Comparison of Oxygen Uptake Kinetics and Oxygen Deficit in Severely Overweight and Normal Weight Adolescent Females

The purpose of this study was to determine if differences in oxygen uptake kinetics and oxygen deficit existed between normal weight and severely overweight adolescent girls. Subjects included 10 normal weight and 8 severely overweight girls. The participants performed a leg cycling VO₂ peak test and a constant load leg cycling test at 80% of the ventilatory threshold (T-vent). In the constant workload test O₂ kinetics as indicated by Phase I (VO₂ L at 20 sec) and Phase II time constants (t) were determined. Also, the O₂ deficit (VO₂ L) was measured. As expected significant differences were noted in body composition and VO₂ peak relative to mass with normal weight body mass averaging 55.3 ± 7.0 kg, severely overweight 90.5 ± 18.0 kg, % fat normal weight 27.3 ± 3.9%, severely overweight 49.7 ± 4.9% and VO₂ peak (ml·kg^-1·min^-1) normal weight 32.0 ± 2.7 and severely overweight 22.0 ± 5.3. VO₂ peak (l·min^-1) and T-vent (%VO₂ max) were similar between groups. Results revealed similar O₂ kinetic responses between groups; phase I kinetics normal weight 0.72 ± 0.15 L; severely overweight 0.75 ± 0.13L, phase II (t) normal weight 41.5 ± 21.3 sec; severely overweight 33.9 ± 22.7 sec. However, the O₂ deficit was significantly higher in the severely overweight (0.75 ± 0.15L) when compared to the normal weight group (0.34 ± 0.13L). Correlations ranged from r = -0.15 to 0.51 between VO₂ peak (L·min^-1) or fat weight and phase I, t and O₂ deficit. These data generally support previous research concerning the independence of O₂ uptake response and body size.

Key Points

• VO₂ (L·min^-1 ) similar between the severely overweight and normal weight female youth
• Phase I and II O₂ kinetic responses similar between severely overweight and normal weight female youth
• O₂ deficit was significantly greater in the severely overweight participants

Key words: O₂ kinetics, O₂ deficit, severely overweight, female, youth     

Lactate and Ventilatory Thresholds Reflect the Training Status of Professional Soccer Players Where Maximum Aerobic Power is Unchanged

The aim of this study was to investigate maximum aerobic power (VO₂ max) and anaerobic threshold (AT) as determinants of training status among professional soccer players. Twelve professional 1st team British male soccer players (age: 26.2 ± 3.3 years, height: 1.77 ± 0.05 m, body mass: 79.3 ± 9.4 kg) agreed to participate in the study and provided informed consent. All subjects completed a combined test of anaerobic threshold (AT) and maximum aerobic power on two occasions: Test 1) following 5 weeks of low level activity at the end of the off-season and Test 2) immediately following conclusion of the competitive season. AT was assessed as both lactate threshold (LT) and ventilatory threshold (V_T). There was no change in VO₂ max between Test 1 and Test 2 (63.3 ± 5.8 ml·kg^-1·min^-1 vs. 62.1 ± 4.9 ml·kg^-1·min^-1 respectively), however, the duration of exercise tolerance (ET) at VO₂ max was significantly extended from Test 1 to Test 2 (204 ± 54 vs. 228 ± 68 s respectively) (P<0.01). LT oxygen consumption was significantly improved in Test 2 versus Test 1 (P<0.01) V_T was also improved (P<0.05). There was no significant difference in VO₂ (ml·kg^-1·min^-1) corresponding to LT and V_T. The results of this study show that VO₂ max is a less sensitive indicator to changes in training status in professional soccer players than either LT or V_T.Key words: VO₂ max, anaerobic threshold, lactate threshold, ventilatory threshold     

Comparing Fat Oxidation in an Exercise Test with Moderate-Intensity Interval Training

This study compared fat oxidation rate from a graded exercise test (GXT) with a moderate-intensity interval training session (MIIT) in obese men. Twelve sedentary obese males (age 29 ± 4.1 years; BMI 29.1 ± 2.4 kg·m^-2; fat mass 31.7 ± 4.4 %body mass) completed two exercise sessions: GXT to determine maximal fat oxidation (MFO) and maximal aerobic power (VO_2max), and an interval cycling session during which respiratory gases were measured. The 30-min MIIT involved 5-min repetitions of workloads 20% below and 20% above the MFO intensity. VO_2max was 31.8 ± 5.5 ml·kg^-1·min^-1 and all participants achieved ≥ 3 of the designated VO_2max test criteria. The MFO identified during the GXT was not significantly different compared with the average fat oxidation rate in the MIIT session. During the MIIT session, fat oxidation rate increased with time; the highest rate (0.18 ± 0.11 g·min^{- 1}) in minute 25 was significantly higher than the rate at minute 5 and 15 (p ≤ 0.01 and 0.05 respectively). In this cohort with low aerobic fitness, fat oxidation during the MIIT session was comparable with the MFO determined during a GXT. Future research may consider if the varying workload in moderate-intensity interval training helps adherence to exercise without compromising fat oxidation.

Key Points

• Fat oxidation during interval exercise is not com-promised by the undulating exercise intensity
• Physiological measures corresponding with the MFO measured during the GXT correlated well to the MIIT
• The validity of exercise intensity markers derived from a GXT to reflect the physiological responses during MIIT.

Key Words: Interval exercise, FAT_max, maximal fat oxidation, obesity     

Indirect Calorimetry During Ultradistance Running: A Case Report

The purpose was to determine the energy expenditure during ultradistance trail running. A portable metabolic unit was carried by a male subject for the first 64.5 km portion of the Western States 100 running race. Calibrations were done with known gases and volumes at ambient temperature, humidity and pressure (23-40.5 °C and 16-40% respectively). Altitude averaged 1692.8 ± 210 m during data collection. The male subject (36 yrs, 75 kg, VO₂max of 67.0 ml·kg^-1·min^-1) had an average (mean ± SD) heart rate of 132 ± 9 bpm, oxygen consumption of 34.0 ± 6.8 ml·kg^-1·min^-1, RER of 0.91 ± 0.04, and V_E of 86.0 ± 14.3 L·min^-1 during the 21.7 km measuring period. This represented an average of 51% VO₂max and 75% heart rate maximum. Energy expenditure was 12.6 ± 2.5 kcals·min^-1, or 82.7 ± 16.6 kcals·km^-1 (134 ± 27 kcals·mile^-1) at 68.3 ± 12.5% carbohydrate. Extrapolation of this data would result in an energy expenditure of >13,000 kcals for the 160 km race, and an exogenous carbohydrate requirement of >250 kcal·hr^-1. The energy cost of running for this subject on separate, noncompetitive occasions ranged from 64.9 ± 8.5 to 74.4 ± 5.5 kcals·km^-1 (105 ± 14 to 120 ± 9 kcals·mile^-1). Ultradistance trail running increases energy expenditure above that of running on nonundulating terrain, which may result in underestimating energy requirements during these events and subsequent undernourishment and suboptimal performance.

Key Points

• The energy cost of running is elevated during ultradistance trail races compared to normal running conditions.
• This elevated energy cost results in a ~12% increase in energy expenditure for a given distance.
• Ad libitum energy intake may grossly underestimate the demand of ultradistance running in the conditions investigated in this paper, thus jeopardizing race performance.

Key words: Energy expenditure, caloric expenditure, running economy     

Can Aerobic and Anaerobic Power be Measured in a 60-Second Maximal Test?

The primary objective of this study was to assess the efficacy of measuring both aerobic and anaerobic power in a 60-second, maximal effort test. It was hypothesized that oxygen consumption increases rapidly during maximal effort and maximal oxygen consumption (VO₂ max) may be reached in one minute. Fifteen United States Cycling Federation competitive cyclists performed the following tests: 1) practice 60-second maximal exertion test; 2) standard incremental workload VO₂ max test; 3) Wingate anaerobic power test (WAT); 4) VO₂ measured during 60-second maximal exertion test (60-SEC); and 5) VO₂ measured during 75-second maximal exertion test (75-SEC). All tests were performed on an electrically-braked cycle ergometer. Hydrostatic weighing was performed to determine percent body fat. Peak oxygen consumption values for the 60-SEC (53.4 ml·kg^-1·min^-1, 92% VO₂ max), and 75-SEC (52.6 ml·kg^-1·min^-1, 91% VO₂ max) tests were significantly lower than VO₂ max (58.1 ml·kg^-1·min^-1). During the 75-SEC test, there was no significant difference in percentage VO₂max from 30 seconds to 75 seconds, demonstrating a plateau effect. There were no significant differences in peak power or relative peak power between the Wingate, 60-SEC, and 75 SEC tests while, as expected, mean power, relative mean power, and fatigue index were significantly different between these tests. Power measures were highly correlated among all three tests. It was concluded that VO₂ max was not attained during either the 60-SEC nor 75-SEC tests. Furthermore, high correlations in power output for WAT, 60-SEC, and 75-SEC precludes the necessity for anaerobic tests longer than the 30-second WAT.Key Words: Maximal oxygen consumption, Wingate     

Oxygen Cost During Treadmill Walking with Hip and Knee Immobilised

The aim of this study was to determine the effect of immobilising the knee and hip on the oxygen cost (ml·kg^-1·min^-1) to velocity relationship during treadmill walking. The study was a prospective experimental conducted in a Rehabilitation centre. Ten healthy individuals, five men and five women, with no gait abnormality participated. Following familiarisation five men and five women walked on a treadmill and selected their own, free “comfortable walking velocity ”(SSWS). Subjects then performed an incremental test at -60 to +60% of SSWS. Individuals later repeated the test with the knee and hip of one limb immobilised. Samples of expired air were measured at each velocity and the oxygen cost (ml·kg^-1·min^-1) to Froude number (Fr) relationship plotted (where calculation of Fr normalizes for subjects of differing leg length and acts as an index of velocity). There was a higher oxygen cost, and lower Fr at SSWS during immobilised (0.21 ± 0.03 ml·kg^-1·min^-1; Fr = 0.12 ± 0. 03) compared with free walking (0.16 ± 0.02 ml·kg^-1·min^-1; Fr = 0.18 ± 0.04) (p < 0. 01). Statistical analysis demonstrated that during immobilised walking an inverse fit (y = β₀ + β₁/x) and for free walking a cubic fit (y = β₀ + β₁x + β₂x² + β₃x³) best fitted the data. Hip and knee immobilisation increased the oxygen cost at SSWS and altered the oxygen cost to Fr relationship. The results have implications in selecting optimal walking velocities in individuals with impairments affecting mobility such as hemiplegic gait.

Key Points

• Walking with one limb immobilised requires greater energy cost than normal free walking.
• This has clinical implications when developing rehabilitation strategies for patients who mobility problems such as those with hemi paretic gait.

Key words: Froude number, oxygen cost, immobilisation, hip, knee, walking, hemiplegic gait     

Season-to-Season Variations of Physiological Fitness Within a Squad of Professional Male Soccer Players

The purpose of this study was to examine season-to-season variations in physiological fitness parameters among a 1^st team squad of professional adult male soccer players for the confirmatory purposes of identifying normative responses (immediately prior to pre-season training (PPS), mid-season (MID), and end-of-season (EOS)). Test-retest data were collected from a student population on the primary dependent variables of anaerobic threshold (AT) and maximal aerobic power (VO₂ max) to define meaningful measurement change in excess of test-retest technical error between test-to-test performances. Participants from a pool of 42 professional soccer players were tested over a set sequence of tests during the 3-year period: 1) basic anthropometry, 2) countermovement jump (CMJ) tests 3) a combined AT and VO₂ max test. Over the 3-year period there were no test-to-test changes in mean VO₂ max performance exceeding pre-defined limits of test agreement (mean of eight measures: 61.6 ± 0.6 ml·kg^-1·min^-1). In contrast, VO₂ at AT was significantly higher at the MID test occasion in seasons 2 (+4.8%; p = 0.04, p < 0.05) and 3 (+6.8%; p = 0.03, p < 0.05). The CMJ tests showed a test-to-test improvement of 6.3% (best of 3 jumps) (p = 0.03, p < 0.05) and 10.3% (20-s sustained jumping test) (p = 0.007, p < 0.01) between PPS2 and MID2 and thereafter remained stable. Anthropometrics were unaffected. In summary, despite some personnel changes in the elite cohort between test-to-test occasions, VO₂ max values did not vary significantly over the study which supports previous short-term observations suggesting a general ‘elite’ threshold of 60 ml·kg^-1 min. Interestingly, AT significantly varied where VO₂ max was stable and these variations also coincided with on- and off-seasons suggesting that AT is a better indication of acute training state than VO₂ max.

Key points

• Maximal aerobic power remains fairly stable across inter- and intra-season measurements.
• Anaerobic threshold appears more sensitive of training state confirming our earlier observations.
• The professional players tended to attain optimal performances at the mid-season interval over the 3 seasons, presumably prior to the development of accumulative fatigue.

Key words: Aerobic power, anaerobic threshold, countermovement jump, elite athletes     

The Effects of Hypobaric Hypoxia on Erythropoiesis,Maximal Oxygen Uptake and Energy Cost of Exercise Under Normoxia in Elite Biathletes

The aim of the present study was to evaluate the effects of 3 weeks altitude training according to the HiHiLo (live high-base train high-interval train low) procedure as described by Chapman et al. (1998), on erythropoiesis, maximal oxygen uptake and energy cost of exercise under normoxia in elite biathletes. Fifteen male elite biathletes randomly divided into an experimental (H) group (n = 7; age 27.1 ± 4.6 years; maximal oxygen uptake (VO_2max) 66.9 ± 3.3 ml·kg^–1·min^–1; body height (BH) 1.81 ± 0.06 m; body mass (BM) 73.1 ± 5.4kg), and a control (C) group (n = 8; age 23.2 ± 0.9 years; VO_2max 68.2 ± 4.1 ml·kg^–1·min^–1; BH 1.75 ± 0.03 m; BM 63.1 ± 1.5 kg) took part in the study. The H group stayed for 3 weeks at an altitude of 2015 m and performed endurance training on skis four times per week at 3000 m. Additionally, the training protocol included three high-intensity interval sessions at an altitude of 1000 m. The C group followed the same training protocol with skirollers in normoxia at an altitude of 600 m. The HiHiLo protocol applied in our study did not change VO_2max or maximal workload (WRmax) significantly during the incremental treadmill test in group H. However, the energy cost for selected submaximal workloads in group H was significantly (p < 0.01) reduced compared to group C (-5.7%, -4.4%, -6% vs. -3.5%, -2.1%, -2.4%). Also a significant (p < 0.001) increase in serum EPO levels during the first two weeks of HiHiLo training at 2015 m was observed, associated with a significant (p < 0.05) increase in hemoglobin mass, number of erythrocytes, hematocrit value and percent of reticulocytes compared with initial values (by 6.4%, 5%, 4.6% and 16,6%, respectively). In group C, changes in these variables were not observed. These positive changes observed in our study led to a conclusion that the HiHiLo training method could improve endurance in normoxia, since most of the biathlon competitions are performed at submaximal intensities.

Key points

• The observed results suggests that the 3-weeks HiHiLo protocol is an effective training means for improving energy cost during submaximal exercise at sea level.
• The 3-weeks HiHiLo protocol increased the rate of erythropoiesis and improved most haematological variables.
• However, the positive changes in the athletes haematological variables after the HiHiLo protocol did not contribute to the improvement of VO_2max values.

Key words: Altitude training, erythropoiesis, aerobic capacity, biathlon     

Muscle Fatigue Increases Metabolic Costs of Ergometer Cycling without Changing VO2 Slow Component

The aim of the present study was to investigate effects of muscle fatigue on oxygen costs of ergometer cycling and slow component of pulmonary oxygen uptake (VO₂) kinetics. Seven young men performed 100 drop jumps (drop height of 40 cm) with 20 s of rest after each jump. After the subsequent hour of rest, they cycled at 70, 105, 140 and 175 W, which corresponded to 29.6 ± 5.4, 39.4 ± 7.0, 50.8 ± 8.4 and 65.8 ± 11.8 % of VO_2peak, respectively, for 6 min at each intensity with 4-min intervals of rest in between the exercise bouts. The VO₂ response to cycling after the exercise (fatigue condition) was compared to ergometer cycling without prior exercise (control condition). From 3rd to 6th min of cycling at 105, 140 and 175 W, VO₂ was higher (p < 0.05-0.01) when cycling in the fatigue compared to the control condition. Slow component of VO₂ kinetics was observed when cycling at 175 W in the control condition (0.17 ± 0.09, l·min^-1, mean ± SD), but tended to decrease in the fatigue condition (0.13 ± 0.15 l·min^-1). In summary, results of the study are in agreement with the hypothesis that muscle fatigue increases oxygen costs of cycling exercise, but does not affect significantly the slow component of pulmonary oxygen uptake (VO₂) kinetics.

Key Points

• Repetitive fatiguing exercise induce an increase in metabolic costs of ergometer cycling exercise.
• It is argued that muscle pain, muscle temperature, elevated pulmonary ventilation and heart rate, shift towards from carbohydrate to fat metabolism are of minor importance in this phenomenon.
• Increased recruitment of type II fibres and impaired force transmission between muscle fibres due to damage of structural proteins appear to play the major role in reducing efficiency of ergometer cycling.

Key Words: Muscle fatigue, energy cost, oxygen uptake, oxygen consumption slow component