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     

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     

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     

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     

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     

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     

Physiological Demands of Simulated Off-Road Cycling Competition

The purpose of the study was to measure the demands of off-road cycling via portable spirometry, leg-power output (PO), heart rate (HR) and blood lactate (BLa) concentration. Twenty-four male competitive cyclists (age: 29±7.2 yrs, height: 1.79 ± 0.05 m, body mass: 70.0 ± 4.9 kg, VO_2peak: 64.9 ± 7.5 ml·kg^-1·min^-1) performed simulated mountain bike competitions (COMP) and laboratory tests (LabT). From LabT, we determined maximal workload and first and second ventilatory thresholds (VT1, VT2). A high-performance athlete (HPA) was used for comparison with three groups of subjects with different sport-specific performance levels. Load profiles of COMP were also investigated during uphill, flat and downhill cycling. During the COMP, athletes achieved a mean oxygen uptake (VO_2COMP) of 57.0 ± 6.8 ml·kg^-1·min^-1 vs. 71.1 ml·kg^-1·min^-1 for the HPA. The PO_COMP was 2.66±0.43 W·kg^-1 and 3.52 W·kg^-1 for the HPA. PO_COMP, VO_2COMP and HR_COMP were compared to corresponding variables at the VT2 of LabT. LabT variables correlated with racing time (RT_COMP) and PO_COMP (p < 0.01 to <0.001; r-0.59 to -0.80). The VO_2peak (LabT) accounted for 65% of variance of a single COMP test. VO_2COMP, PO_COMP and also endurance variables measured from LabTs were found as important determinants for cross-country performance. The high average VO_2COMP indicates that a high aerobic capacity is a prerequisite for successful COMP. Findings derived from respiratory gas measures during COMPs might be useful when designing mountain bike specific training.

Key points

• Cross- country cycling is characterized by high oxygen costs due to the high muscle mass simultaneously working to fulfill the demands of this kind of sports.
• Heart rate and blood lactate concentration measures are not sensitive enough to assess the energy requirements of COMP. Therefore, respiratory gas and power output measures are helpful to provide new information to physiological profile of cross- country cycling.
• An excellent cycling-specific capacity is a prerequisite for successful off-road cycling.
• Data determined from LabT might be utilized to describe semi-specific abilities of MB- athletes on a cycle ergometer, while data originating from COMP might be useful when designing a mountain bike specific training.

Key words: Off-road cycling, mountain biking, oxygen uptake, power output, lactate, heart rate     

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     

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     

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     

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     

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     

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     

Prior Knowledge of Trial Number Influences the Incidence of Plateau at VO2max

The purpose of this study was to assess the VO₂max plateau response at VO₂max during a series of pre-determined trials. METHODS: Ten male well-trained athletes (age, 23.0 ± 3.2; height, 183.3 ± 5.5 cm; mass 77.5 ± 11.1 Kg; VO₂max 66.5 ± 5.0 ml^.kg^-1,min^-1), but who were VO₂max testing naïve and with prior-knowledge of trial number completed four incremental tests to volitional exhaustion, separated by ~72-h for the determination of VO₂max and gas exchange threshold. Throughout all trials VO₂max was recorded on a breath-by-breath basis using a pre-calibrated metabolic cart, using a plateau criterion of Δ VO₂ ≤1.5 ml^.kg^-1.min^-1 over the final 2 consecutive 30 s sampling periods. A significant difference was observed between trial-1 and trial-4 for plateau incidence (p = 0.0285) rising from 20% in trial-1 to a 70% response rate in trial-4. Furthermore a significant difference was observed for VO_2dif (difference between criterion value and Δ VO₂) in trial-1, 1.02 ± 1.69 ml^.kg^-1.min^-1 (p = 0.038), with non-significant differences observed for all other trials, despite a non-significant difference for VO₂max across all trials (p > 0.05). Finally, a significant difference was observed for effort perception (RPE) at volitional exhaustion between trial-1 (17.7 ± 1.3) and trial-4 (19.0 ± 1.4) (p = 0.0052). These data indicate that prior-knowledge of trial number can influence the manifestation of the VO₂ plateau in a group of well-trained male athletes, thereby suggesting that a form of effort control is established in order to preserve the finite anaerobic capacity.

Key points

• In well-trained athletes the incidence of plateau at VO_2max increases in conjunction with an increase in trial number and the associated sensations of pain and fatigue.
• By informing the participant of the number of trials to be completed a closed-loop condition is developed whereby effort in all trials is compared to a perceptually developed template.
• Closed-loop condition leads to a sparing of the finite anaerobic capacity during incremental tests when the number of trials to be completed is known.

Key words: Maximal oxygen uptake, effort control, anaerobic capacity, experience     

Individual versus Standardized Running Protocols in the Determination of VO2max

The purpose of this study was to determine whether an individually designed incremental exercise protocol results in greater rates of oxygen uptake (VO_2max) than standardized testing. Fourteen well-trained, male runners performed five incremental protocols in randomized order to measure their VO_2max: i) an incremental test (INC_S+I) with pre-defined increases in speed (2 min at 8.64 km·h⁻¹, then a rise of 1.44 km·h⁻¹ every 30 s up to 14.4 km·h⁻¹) and thereafter inclination (0.5° every 30 s); ii) an incremental test (INC_I) at constant speed (14.4 km·h⁻¹) and increasing inclination (2° every 2 min from the initial 0°); iii) an incremental test (INC_S) at constant inclination (0°) and increasing speed (0.5 km·h⁻¹ every 30 s from the initial 12.0 km·h⁻¹); iv) a graded exercise protocol (GXP) at a 1° incline with increasing speed (initially 8.64 km·h⁻¹ + 1.44 km·h⁻¹ every 5 min); v) an individual exercise protocol (INDXP) in which the runner chose the inclination and speed. VO_2max was lowest (-4.2%) during the GXP (p = 0.01; d = 0.06-0.61) compared to all other tests. The highest rating of perceived exertion, heart rate, ventilation and end-exercise blood lactate concentration were similar between the different protocols (p < 0.05). The time to exhaustion ranged from 7 min 18 sec (INC_S) to 25 min 30 sec (GXP) (p = 0.01).The VO_2max attained by employing an individual treadmill protocol does not differ from the values derived from various standardized incremental protocols.

Key points

• The mean maximum oxygen uptake during the GXP was lower than for all other tests.
• Differences in the maximum rate of oxygen uptake between the various protocols exhibited considerable inter-individual variation.
• From the current findings, it can be concluded that well trained athletes are able to perform an individually designed treadmill running protocol.

Key words: Maximum oxygen uptake, aerobic power, treadmill running, ramp test, treadmill protocol     

Oxygen Uptake Kinetics in Endurance Trained Youth and Adult Cyclists

Previous studies reported faster pulmonary oxygen uptake kinetics at the onset of exercise in untrained youth compared with adults. Whether or not these differences are identical for trained groups have not been examined. The purpose of this study was to compare ˙VO₂ kinetics of youth and adult cyclists at moderate and heavy-intensity exercise. Thirteen adult (age: 23.2 ± 4.8 years; ˙VO_2peak 68.4 ± 6.8 mL·min^-1.kg^-1) and thirteen youth cyclists (age: 14.3 ± 1.5 years; ˙VO_2peak 61.7 ± 4.3 mL·min^-1.kg^-1) completed a series of 6-min square wave exercises at moderate and heavy-intensity exercise at 90 rev·min^-1. A two-way repeated-measure ANOVA was conducted to identify differences between groups and intensities. The time constant, time delay and the mean response time were not significantly different between youth and adult cyclists (p > 0.05). We found significant differences between intensities, with a faster time constant during moderate than heavy-intensity exercise in youth (24.1 ± 7.0 s vs. 31.8 ± 5.6 s; p = 0.004) and adults (22.7 ± 5.6 s vs. 28.6 ± 5.7 s; p < 0.001). The present data suggest that the effect of training history in adult cyclists compensate for the superior primary response of the oxygen uptake kinetics typically seen in youth compared to adults. Furthermore, the ˙VO₂ response is dependent of work rate intensity in trained youth and adult cyclists.Key points

• No differences in the primary response between youth and adult cyclists at moderate and heavy-intensity exercise
• This suggests that adaptations to long-term training have a high potential as an influencing factor on the response of oxygen uptake kinetics
• Oxygen uptake kinetics are influenced by work rate in both youth and adult cyclists with a slower response at higher work rates.

Key words: Adolescents, endurance training, exercise physiology, physical performance, trained athletes     

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     

Higher Precision of Heart Rate Compared with VO2 to Predict Exercise Intensity in Endurance-Trained Runners

The aim of the present study was to assess the precision of oxygen uptake with heart rate regression during track running in highly-trained runners. Twelve national and international level male long-distance road runners (age 30.7 ± 5.5 yrs, height 1.71 ± 0.04 m and mass 61.2 ± 5.8 kg) with a personal best on the half marathon of 62 min 37 s ± 1 min 22 s participated in the study. Each participant performed, in an all-weather synthetic track five, six min bouts at constant velocity with each bout at an increased running velocity. The starting velocity was 3.33 m·s^-1 with a 0.56 m·s^-1 increase on each subsequent bout. VO₂ and heart rate were measured during the runs and blood lactate was assessed immediately after each run. Mean peak VO₂ and mean peak heart rate were, respectively, 76.2 ± 9.7 mL·kg^-1·min^-1 and 181 ± 13 beats·min^-1. The linearity of the regressions between heart rate, running velocity and VO₂ were all very high (r > 0.99) with small standard errors of regression (i.e. Sy.x < 5% at the velocity associated with the 2 and 4 mmol·L^-1 lactate thresholds). The strong relationships between heart rate, running velocity and VO₂ found in this study show that, in highly trained runners, it is possible to have heart rate as an accurate indicator of energy demand and of the running speed. Therefore, in this subject cohort it may be unnecessary to use VO₂ to track changes in the subjects’ running economy during training periods.

Key points

• Heart rate is used in the control of exercise intensity in endurance sports.
• However, few studies have quantified the precision of its relationship with oxygen uptake in highly trained runners.
• We evaluated twelve elite half-marathon runners during track running at various intensities and established three regressions: oxygen uptake / heart rate; heart rate / running velocity and oxygen uptake / running velocity.
• The three regressions presented, respectively, imprecision of 4,2%, 2,75% and 4,5% at the velocity associated with the 4 mmol·L^-1 threshold.
• The results of the present study show that, in highly trained runners, it is possible to use heart rate as an accurate index of the external work rate during sub maximal running speeds.

Key words: Running velocity, internal load, relationships, standard error     

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     

Cardiorespiratory Characteristics and Cholesterol Responses to a Single Session of Heavy Leg Press Exercise

The effect of resistance exercise on blood lipids is not clear yet. The purpose of this study was to examine the cholesterol responses to a heavy resistance leg press exercise emphasizing on the eccentric movement 24 and 48 hours following exercise and to quantify the cardiorespiratory responses of the exercise bout in an attempt to clarify the exercise characteristics that may be responsible for the effects of heavy resistance exercise on blood lipids. Nine healthy, untrained male volunteers aged 27.2 ± 1.1 yrs (76.2 ± 2.5 kg, 1.79 ± 0.02 m) performed a session of heavy RE emphasizing on the eccentric movement consisting of eight sets of inclined leg presses at six repetition maximum with 3-min rest intervals. Venous blood samples were obtained at rest (control) and 24 and 48 hours following exercise. Average VO₂ at rest was 4.0 ± 0.4 ml·min⁻¹·kg⁻¹, during exercise 19.6 ± 0.2 ml·min⁻¹·kg⁻¹ and during the 180 sec recovery period between sets 12.5 ± 0.2 ml·min⁻¹·kg⁻¹. RER values decreased with the progression of the exercise and were significantly lower during the last four sets compared with the first four sets of the exercise session. Resting heart rate was 67 ± 2 bpm, and maximum heart rate during exercise was 168 ± 1 bpm. Serum creatine kinase was significantly elevated on day 1 (1090 ± 272 U·L⁻¹, p < 0.03) and peaked on day 2 (1230 ± 440 U·L⁻¹ p < 0. 01). Total cholesterol, HDL cholesterol and calculated LDL cholesterol concentration did not change significantly following with exercise. This protocol of heavy resistance exercise has no effect on TC or cholesterol sub-fraction concentration 24 and 48 hours following exercise which may be due to the low energy expenditure of the exercise and/or to the gender of the participants.

Key points

• Repeated sets of heavy resistance exercise significantly increase oxygen uptake both during exercise and the following recovery period.
• Even though exercise was of low volume (8 sets x 6 repetitions) the elevated oxygen uptake during the rest intervals in combination with the total exercise session duration (26 min) resulted in aerobic energy expenditure that is equivalent to low to moderate intensity cycling.
• Leg press resistance exercise emphasizing on the eccentric movement that caused muscle damage had no effect on total cholesterol, HDL-C and LDL-C during the two days following exercise in young healthy male subjects.

Key words: Muscle damage, energy expenditure, total cholesterol, HDL, oxygen uptake.