Assessment of Short-Distance Breaststroke Swimming Performance with Critical Velocity

For high-velocity running or swimming, the relationship between velocity (v) and its sustainable duration (t) can be described by a hyperbolic relationship: (v - V_crit)·t = D’, where V_crit is termed critical velocity, and D’ is defined as a curvature constant of the hyperbolic curve. The purposes of this study were to examine whether the V_crit could be applied to evaluate short-distance breaststroke swimming performance and to evaluate the relative contribution of D’ in short-distance swimming performance. Eleven male swimmers performed a series of time trials corresponding to 75, 100, and 150-m in an indoor 50-m swimming pool. The observed records were calculated into average velocities of each event to determine V_crit and D’. After the determination of V_crit and D’, all subjects performed 50-m time trial on another day. A maximal anaerobic power test using cycle ergometer was also performed in the laboratory. The average velocity of the 50-m time trial significantly correlated with the obtained V_crit, but not with D’. D’ was significantly correlated with the residual error, calculated from the regression analysis for the relationship between V_crit and the average velocities of 50-m time trial. A cluster analysis showed that most of the subjects were classified as V_crit dependency when performing 50-m time trial. Those results indicated that V_crit could be applied to evaluate short-distance swimming performance, and it determined around 80% of the short-distance breaststroke swimming performance.

Key Points

• For high-velocity running or swimming, the relationship between velocity (v) and its sustainable duration (t) can be described by a hyperbolic relationship: (v - V_crit)·t = D’, where V_crit is termed critical velocity, and D’ is defined as a curvature constant of the hyperbolic curve. The D’ contributed only around 20% of the breaststroke swimming performance even in a short-distance event.
• Critical velocity determined around 80% of 50-m breaststroke swimming performance, and it could be a useful tool for evaluating short-distance swimming performance.
• Most of the swimmers showed characteristics for critical velocity dependent physical fitness even in short-distance swimming event.

Key words: Critical swimming velocity, D’, hyperbolic curve, cluster analysis     

Neuromuscular Fatigue During 200 M Breaststroke

The aims of this study were: i) to analyze activation patterns of four upper limb muscles (duration of the active and non-active phase) in each lap of 200m breaststroke, ii) quantify neuromuscular fatigue, with kinematics and physiologic assessment. Surface electromyogram was collected for the biceps brachii, deltoid anterior, pectoralis major and triceps brachii of nine male swimmers performing a maximal 200m breaststroke trial. Swimming speed, SL, SR, SI decreased from the 1^st to the 3^rd lap. SR increased on the 4^th lap (35.91 ± 2.99 stroke·min^-1). Peak blood lactate was 13.02 ± 1.72 mmol·l^-1 three minutes after the maximal trial. The EMG average rectified value (ARV) increased at the end of the race for all selected muscles, but the deltoid anterior and pectoralis major in the 1^st lap and for biceps brachii, deltoid anterior and triceps brachii in the 4^th lap. The mean frequency of the power spectral density (MNF) decreased at the 4^th lap for all muscles. These findings suggest the occurrence of fatigue at the beginning of the 2^nd lap in the 200m breaststroke trial, characterized by changes in kinematic parameters and selective changes in upper limb muscle action. There was a trend towards a non-linear fatigue state.

Key Points

• Fatigue in the upper limbs occurs in different way as it described by 100m swimming events.
• Neuromuscular fatigue was estimated by analyzing the physiological changes (high blood lactate concentrations), biomechanical changes in the swimming stroke characteristics (decreased in swimming velocity), and by the changes in the EMG amplitude and frequency parameters at the end of the swimming bout.
• The amplitude signal of EMG provided by the ARV demonstrated an increase at the end with the respect to the beginning for all muscles under study, excepted for the muscle deltoid anterior.
• The mean frequency (MNF) in our study decrease at the end of the swimming in the 4^th lap relative to the 1^st lap for all muscles under observation, along the 200m breaststroke.

Key Words: Swimming, Kinematics, EMG, Mean frequency     

Relationship between Fat Oxidation and Lactate Threshold in Athletes and Obese Women and Men

The first aim of this study was to determine the exercise intensity that elicited the highest rate of fat oxidation in sedentary, obese subjects (OB; n=10 men, n=10 women) compared with endurance athletes (AT; n=10 men, n=10 women). The second aim was to investigate the relationship between VO₂ at the intensity eliciting the highest rate of fat oxidation and the corresponding VO₂ at the lactate threshold. Peak oxygen consumption (VO_2peak) was determined in 20 AT and 20 OB using an incremental exercise protocol on a cycle ergometer. Based on their VO_2peak values, subjects completed a protocol requiring them to exercise for 20 min at three different workloads (55, 65 and 75% VO_2peak), randomly assigned on two separate occasions. The oxidation rates of fat and carbohydrate were measured by indirect calorimetry. The highest rates of fat oxidation were at 75 % VO_2peak (AT), and at 65 % VO_2peak (OB). The rate of fat oxidation was significantly higher in AT (18.2 ± 6.1) compared with OB women (10.6 ± 4.5 kJ min^-1·kg^-1) (p < 0.01). There was no significant difference in the rate of fat oxidation for the men (AT 19.7 ± 8.1 vs. OB 17.6 ± 8.2 kJ min^-1·kg^-1). AT reached LT at a significantly (p < 0.01) higher exercise intensity expressed in VO_2peak than obese subjects (AT women 76.4 ± 0.1, men 77.3 ± 0.1 vs. OB women, 49.7 ± 0.1, men 49.5 ± 0.1% VO_2peak). A significant correlation was found between VO₂ at LT and VO₂ (L·min^-1) eliciting the maximal rate of fat oxidation in athletes (women; r = 0.67; p = 0.03; men: r = 0.75; p = 0.01) but not in the obese. In summary, we observed higher rates of fat oxidation at higher relative work rates in AT compared with OB. A significant correlation was found between LT and the exercise intensity eliciting a high rate of fat oxidation in AT (r=0.89; p < 0.01) but not in OB. Cardiorespiratory fitness, defined as VO_2peak, seems to be important in defining the relationship between a high rate of fat oxidation and LT.

Key Points

• Within the tested intensities of 55, 65 and 75% VO_2peak athletes reached higher rates of fat oxidation at higher relative work rates compared with obese subjects.
• We found in obese women and men the intensity of the highest rate of fat oxidation at 65% VO_2peak.
• Between the lactate threshold and the intensity eliciting a high rate of fat oxidation a significant correlation was found in athletes but not in obese subjects.

Key words: Exercise intensity, substrate utilization, obesity, lactate threshold     

An Approach to Identifying the Effect of Technique Asymmetries on Body Alignment in Swimming Exemplified by a Case Study of a Breaststroke Swimmer

Despite the importance of maintaining good alignment to minimize resistive drag in swimming there is a paucity of literature relating to the effect of technique asymmetries on rotations of the body about a vertical axis (yaw). The purpose of this paper was to present an approach to analyzing the effect of technique asymmetries on rotations in swimming, exemplifying the process with a case study of a breaststroke swimmer. The kinematics and angular kinetics of an elite female international breaststroke swimmer performing a ‘fatigue set’ of four 100m swims were derived from digitized three-dimensional video data using a 13 segment body model. Personalised anthropometric data required to quantify accurately segment and whole body centres of mass and segmental angular momentum were obtained by the elliptical zone method. Five episodes of torques producing yaw occurred in the stroke cycle sampled for each 100m swim of this swimmer. These torques were linked to bilateral differences in upper limb kinematics during 1) out-sweep; 2) in-sweep; 3) upper limb recovery; and lower limb kinematics during 4) Lower limb recovery and 5) the kick. It has been shown that by quantifying whole body torques, in conjunction with the kinematic movement patterns, the effect of technique asymmetries on body alignment can be assessed. Assessment of individual swimmers in this manner provides a solid foundation for planning interventions in strength, flexibility, and technique to improve alignment and performance.

Key points

• A unique (not been attempted previously) study of yaw in breaststroke swimming that yields new knowledge of how technique and strength asymmetries affects body alignment.
• Establishes an approach to investigation of yaw in swimming using 3D videography and inverse dynamics.
• Exemplifies the approach with a case study. The case study illustrated the potential of the approach to enable detailed assessment of yaw and to explain how the yaw is produced in terms of the asymmetries in speed and magnitude of the swimming actions.
• This procedure should be used to identify and quantify asymmetries that might impair performance.

Key words: Asymmetry, human swimming, hydrodynamic drag, yaw     

Physiological Responses to 90 s All Out Isokinetic Sprint Cycling in Boys and Men

The purpose of this study was to compare the VO₂ kinetic and mechanical power responses of boys and men to all out 90 s sprint cycle exercise. Eight boys (14.6 ± 0.3 y) and eight men (33.8 ± 6.5 y) volunteered to participate and completed a ramp test (to determine VO_2peak and ventilatory threshold, VT) and then on subsequent days, two 90 s all out cycle sprints on an isokinetic cycle ergometer. During each test, breath-by-breath pulmonary gas exchange and power output were measured. Parameters from the power output profiles were derived from the average response of the two tests including peak power (PP, highest power output in 1 s), end power (EP_60-90, power over the last 30 s), and mean power over the 90 s (MP₉₀). Independent pairwise and dependent t-tests were used to compare the data from tests between adults and boys subject groups. Significant differences between adults and boys were found for absolute PP (881.4 ± 60.7 vs 533.6 ± 50.7 W), EP_60-90 (288.6 ± 25.7 vs 134.3 ± 17.6 W) and MP₉₀ (434.5 ± 27.4 vs 238.4 ± 17.3 W, p =0.001) respectively. Relative to body mass significant differences between adults and boys were found for EP_60-90, MP₉₀ and total work (p < 0.002). The boys attained 90 s VO₂ values that were closer to VO_2peak than their adult counterparts (93.3 ± 2.6 vs 84.9 ± 2.3 %, p = 0.03). They also demonstrated faster VO₂ kinetics (10.8 ± 1.5 vs 17.6 ± 1.0 s, p < 0.01). In conclusion, during all out 90 s cycle sprinting boys were able to attain VO₂ values that were closer to VO_2peak and a faster time constant than adult men. These findings provide insight into the contribution and speed of response of the aerobic system during an ‘anaerobic’ test.

Key Points

• The results of this study confirm the significant contributions of the aerobic energy systems during so called ‘anaerobic tests’.
• Boys were able to attain VO₂ values from an all out 90 s sprint cycle that were closer to their aerobic VO₂ peak test than adults. More detailed studies are required to investigate the limiting factors that prevent VO₂ peak being reached in an all out sprint cycle.
• All out tests of a duration > 30 s and coupled with gas and power analyses offer paediatric physiologists considerable scope to examine the contributions of the anaerobic and aerobic energy systems until more ethically viable methods are found.

Key Words: VO_2peak, anaerobic, kinetics, aerobic, ergometry     

Searching for Criteria in Evaluating the Monofin Swimming Turn from the Perspective of Coaching and Improving Technique

This study aims to analysise the selected kinematic parameters of the monofin swimming turn. The high complexity of performing turns is hindered by the large surface of the monofin, which disturbs control and sense of the body in water. A lack of objective data available on monofin swimming turns has resulted in field research connected with the specification of parameters needed for the evaluation of the technique. Therefore, turns observed in elite swimmers contain underlying conclusions for objective criteria, ensuring the highest level of coaching and the improving of turns in young swimmers. Six, high level, male swimmers participated in the study. The subject of the analysis was the fastest turn, from one out of three trial turns made after swimming a distance of 25 m. Images of the turns were collected from two cameras located under water in accordance with the procedures of the previous analyses of freestyle turns. The images were digitized and analysed by the SIMI^®- Movement Analysis System. The interdependency of the total turn time and the remaining recorded parameters, constituted the basis for analysis of the kinematic parameters of five turn phases. The interdependency was measured using r- Pearson’s correlation coefficients. The novel character of the subject covered in this study, forced interpretation of the results on the basis of turn analyses in freestyle swimming. The results allow for the creation of a diagram outlinig area of search for an effective and efficient monofin swimming turn mechanism. The activities performed from the moment of wall contact until the commencement of stroking seem to be crucial for turn improvement. A strong belief has resulted that, the correct monofin swimming turn, is more than just a simple consequence of the fastest performance of all its components. The most important criteria in evaluating the quality of the monofin swimming turn are: striving for the optimal extension of wall contact time, push-off time and glide time.

Key points

• Short time and large surface of the monofin additionally hinders complexity of the turn performance by disturbance in sensing and controlling body in water. Availability of no objective data on monofin swimming turns resulted in research in the field connected with specifying parameters needed for the technique evaluation.
• Correct turn technique may help to improve swimming race results.
• The diagram constructed on the basis of the interdependency of the total turn time and the remaining recorded kinematic parameters should establish the areas of searching for mechanism of effective and efficient monofin swimming turn.
• The most crucial, from the coaching and improving point of view, seem to be activities which take place from the moment of feet wall contact till the first propulsive movements. Therefore, the high quality of the monofin swimming turn technique is not just a simple consequence of the fastest performance of all its component parts.
• The most important criteria of the quality in the monofin swimming turn technique are: striving for extending in the optimum scope of wall contact time, the time of the push-off phase and the glide time.

Key words: Monofin, turn, kinematics, technique evaluation     

The Effects of Intermittent Exercise on Physiological Outcomes in an Obese Population: Continuous Versus Interval Walking

This study compared the effects of 12 weeks of caloric restriction and interval exercise (INT) and caloric restriction and continuous aerobic exercise (CON) on physiological outcomes in an obese population. Forty-four individuals (BMI ≥ 30 kg·m^-2) were randomised into the INT or CON group. Participant withdrawal resulted in 12 and 14 participants in the INT and CON groups, respectively. All participants were on a strict monitored diet. Exercise involved two 15-min bouts of walking performed on five days per week. Interval exercise consisted of a 2:1 min ratio of low-intensity (40-45% VO_2peak) and high- intensity (70-75% VO_2peak) exercise, while the CON group exercised between 50-55% VO_2peak. Exercise duration and average intensity (%VO_2peak) were similar between groups. There were no significant differences (p > 0.05) between the two groups for any variable assessed apart from very low density lipoprotein (VLDL-C), which significantly decreased over time in the INT group only (p < 0.05, d = 1.03). Caloric restriction and interval exercise compared to caloric restriction and continuous aerobic exercise resulted in similar outcome measures apart from VLDL-C levels, which significantly improved in the INT group only.

Key points

• Twelve weeks of interval exercise and caloric restriction resulted in significant improvement in very low density lipoprotein cholesterol in an obese population, as compared to continuous aerobic exercise and caloric restriction.
• Twelve weeks of either interval exercise or continuous exercise resulted in similar improvements in aerobic fitness in an obese population.

Key words: Interval training, body fat, fitness, metabolism     

A Self-Paced Intermittent Protocol on a Non-Motorised Treadmill: A Reliable Alternative to Assessing Team-Sport Running Performance

This study assessed the reliability of a ‘self-paced’ 30-min, team-sport running protocol on a Woodway Curve 3.0 non-motorised treadmill (NMT). Ten male team-sport athletes (20.3 ± 1.2 y, 74.4 ± 9.7 kg, VO_2peak 57.1 ± 4.5 ml·kg^-1·min^-1) attended five sessions (VO_2peak testing + familiarisation; four reliability trials). The 30-min protocol consisted of three identical 10-min activity blocks, with visual and audible commands directing locomotor activity; however, actual speeds were self-selected by participants. Reliability of variables was estimated using typical error ± 90% confidence limits expressed as a percentage [coefficient of variation (CV)] and intraclass correlation coefficient. The smallest worthwhile change (SWC) was calculated as 0.2 × between participant standard deviation. Peak/mean speed and distance variables assessed across the 30-min protocol exhibited a CV < 5%, and < 6% for each 10-min activity block. All power variables exhibited a CV < 7.5%, except walking (CV 8.3-10.1%). The most reliable variables were maximum and mean sprint speed (CV < 2%). All variables produced a CV% greater than the SWC. A self-paced, team-sport running protocol performed on a NMT produces reliable speed/distance and power data. Importantly, a single familiarisation session allowed for adequate test-retest reliability. The self-paced design provides an ecologically-valid alternative to externally-paced team-sport running simulations.

Key points

• Self-paced team-sport running protocols on a curved NMT that closely match the locomotor demands of competition deliver reliable test-retest measures of speed, distance and power.
• Such protocols may be sensitive to changes in running profile following an intervention that may not be detectable during externally-paced protocols.
• One familiarisation session is adequate to ensure test-retest reliability.

Key words: Exercise test, athletic performance, running, reproducibility of results     

Exertion During Uphill,Level and Downhill Walking With and Without Hiking Poles

This study examined the effects of poles when walking on the rate of perceived exertion (RPE), physiological and kinematics parameters, and upon the mean ratio between locomotor and respiratory rhythms. Twelve healthy male and female volunteers, aged 22 to 49 years old, completed on a motorized treadmill in a counterbalanced randomized order 12 walking trials for 10 min at an individually preferred walking speed, with three grades (horizontal level, uphill or downhill with a slope of 15%), with and without hiking poles and a load carriage of 15% of body mass. During all testing sessions, heart rate (HR), oxygen consumption (VO₂), ventilation (V_E), tidal volume (V_T), breathing frequency (Bf), and stride frequency were recorded continuously during the last 5-min of each trial. At the end of each trial, subjects were asked to give RPE. Energy cost (EC) and V_E increased significantly with the grade (-15% < 0% < +15%) and with the carrying load. V_T was significantly less important with hiking poles, while Bf was significantly more elevated. VO₂ and EC increased (p < 0.05) with the use of the hiking poles only during the downhill trials. No significant effect of poles was observed on HR, RPE, and preferred walking speed. The average ratio between the locomotor and respiratory frequencies was significantly influenced by the three experimental factors tested. There was a significant relationship between average ratio of leg movement per breath and EC of walking among all conditions (r = 0.83, n = 12). These results suggest that the use of the hiking poles had a significant influence on the respiratory and energetic responses only during downhill walking.

Key points

• Energetic cost, respiratory responses, stride rate, respiratory to cycle rate ratio were significantly influenced by the use of hiking poles according to the grade at self-selected walking speed.
• Hiking poles induced an increase in respiratory frequency, VE and energetic cost during downhill, while little changes were observed during level and uphill terrain.
• The original results obtained in downhill necessitate supplementary studies in the field in order to confirm these first tendencies on treadmill.

Key words: Energy cost, grades, hiking poles, respiration, nordic-walking     

Effects of High Intensity Training and Continuous Endurance Training on Aerobic Capacity and Body Composition in Recreationally Active Runners

The aim of the study was to examine the effects of two different training programs (high-intensity-training vs. continuous endurance training) on aerobic power and body composition in recreationally active men and women and to test whether or not participants were able to complete a half marathon after the intervention period. Thirty-four recreational endurance runners were randomly assigned either to a Weekend-Group (WE, n = 17) or an After-Work- Group (AW, n = 17) for a 12 week-intervention period. WE weekly completed 2 h 30 min of continuous endurance running composed of 2 sessions on the weekend. In contrast, AW performed 4 30 min sessions of high intensity training and an additional 30 min endurance run weekly, always after work. During an exhaustive treadmill test aerobic power was measured and heart rate was continuously recorded. Body composition was assessed using bio-impedance. Following the intervention period all subjects took part in a half-marathon. AW significantly improved peak oxygen uptake (VO₂ peak) from 36.8 ± 4.5 to 43.6 ± 6.5 [mL.min^-1.kg^-1], velocity at lactate threshold (V_LT) from 9.7 ± 2.2 to 11.7 ± 1.8 [km.h^-1] and visceral fat from 5.6 ± 2.2 to 4.7 ± 1.9 In WE VO₂ peak signifi-cantly increased from 38.8 ± 5.0 to 41.5 ± 6.0 [mL.min^-1.kg^-1], V_LT from 9.9 ± 1.3 to 11.2 ± 1.7 [km.h^-1] and visceral fat was reduced from 5.7 ± 2.1 to 5.4 ± 1.9 (p < 0.01). Only the improvements of VO₂ peak were significantly greater in AW compared with WE (pre/post group interaction: F=15.4, p = 0.01, η² = 0.36). Both groups completed a half marathon with no significant differences in performance (p = 0.63). Short, intensive endurance training sessions of about 30 min are effective in improving aerobic fitness in recreationally active runners.

Key points

• Continuous endurance training and high intensity training lead to significant improvements of aerobic capacity and body composition
• Both training methods enable recreationally active runners to finish a half-marathon
• High intensity training is favorable to improve VO₂ peak

Key words: Aerobic power, lactate threshold, VO₂ peak, endurance running, aerobic training     

Inspiratory Muscle Fatigue Following Moderate-Intensity Exercise in the Heat

Heavy exercise has been shown to elicit reductions in inspiratory muscle strength in healthy subjects. Our purpose was to determine the combined effects of moderate-intensity endurance exercise and a thermal load on inspiratory muscle strength in active subjects. Eight active, non heat-acclimatized female subjects (23.5 ± 1.4 yr; VO₂max = 39.8 ± 2.4 ml.kg^-1.min^-1) randomly performed two 40 min endurance exercise bouts (60% VO₂max) in either a thermo-neutral (22°C/21% RH) or hot (37°C/33% RH) environment on separate days. Maximal sustained inspiratory mouth pressure (PI_max) was obtained pre and post exercise as an index of inspiratory muscle strength. Additional variables obtained every 10 min during the endurance exercise bouts included: rectal temperature (T_RE), heart rate (HR), minute ventilation (V_E), oxygen uptake (VO₂), tidal volume (V_T), breathing frequency (F_b), and ratings of perceived exertion and dyspnea (RPE/RPD). Data were analyzed with repeated measures ANOVA. PI_max was significantly reduced (p < 0.05) after exercise in the hot environment when compared to baseline and when compared to post exercise values in the thermo-neutral environment. PI_max was unchanged from baseline following exercise in the thermo-neutral environment. HR and T_RE were significantly higher (p < 0.05) in the hot compared to the thermo-neutral environment. V_E and VO₂ were not significantly different between conditions. V_T was unchanged between conditions whereas F_b was higher (p < 0.05) in the hot condition compared to thermo-neutral. RPE was not significantly different between conditions. RPD was significantly higher (p < 0.05) in the hot compared to the thermo-neutral environment. We conclude that moderate-intensity endurance exercise (60% VO₂max) in a hot environment elicits significant reductions in inspiratory muscle strength in unfit females. This finding is novel in that previous studies conducted in a thermo-neutral environment have shown that an exercise intensity of >80% VO₂max is required to elicit reductions in inspiratory muscle strength. In addition, dyspnea perception during exercise is greater in a hot environment, compared to thermo-neutral, at a similar level of V_E and VO₂.

Key Points

• The combined effects of a heat load and exercise on inspiratory muscle strength were investigated in untrained female subjects.
• Previous studies have shown that a very high exercise intensity (> 80% VO₂max) is required to elicit reductions in inspiratory muscle strength.
• Prolonged submaximal exercise (40-min/60% VO₂max) in a hot environment significantly reduced inspiratory muscle strength in untrained females whereas the same intensity in a thermo-neutral environment had no effect on inspiratory muscle function.
• These reductions in inspiratory muscle strength may be related to competition for blood flow among the locomotor, inspiratory, and cutaneous circulations.

Key Words: Control of breathing, endurance, respiratory function, thermal load     

Lack of Agreement Between Gas Exchange Variables Measured by Two Metabolic Systems

The purpose of this study was to assess the agreement and consistency between gas exchange variables measured by two online metabolic systems during an incremental exercise test. After obtaining local ethics approval and informed consent, 15 healthy subjects performed an incremental exercise test to volitional fatigue using the Bruce protocol. The Innocor (Innovision, Denmark) and CardiO₂ (Medical Graphics, USA) systems were placed in series, with the Innocor mouthpiece attached to the pneumotach of the CardiO₂. Metabolic data were analysed during the last 30 seconds of each stage and at peak exercise. There were non- significant differences (p > 0.05) between the two systems in estimation of oxygen consumption (VO₂) and in minute ventilation (V_E). Mean Cronbach’s alpha for VO₂ and V_E were 0.88 and 0.92. The Bland-Altman analysis revealed that limits of agreement were -0.52 to 0.55 l.min^-1 for VO₂, and -8.74 to 10.66 l.min^-1 for V_E. Carbon dioxide production (VCO₂) and consequently respiratory exchange ratio (RER) measured by the Innocor were significantly lower (p < 0.05) through all stages. The CardiO₂ measured fraction of expired carbon dioxide (FeCO₂) significantly higher (p < 0.05). The limits of agreement for VO₂ and V_E are wide and unacceptable in cardio-pulmonary exercise testing. The Innocor reported VCO₂ systematically lower. Therefore the Innocor and CardiO₂ metabolic systems cannot be used interchangeably without affecting the diagnosis of an individual patient. Results from the present study support previous suggestion that considerable care is needed when comparing metabolic data obtained from different automated metabolic systems.

Key points

• There is general concern regarding the limited knowledge available about the accuracy of a number of commercially available systems.
• Demonstrated limits of agreement between key gas exchange variables (oxygen consumption and minute ventilation) as measured by the two metabolic systems were wide and unacceptable in cardio-pulmonary exercise testing.
• Considerable care is needed when comparing metabolic data obtained from different automated metabolic systems.

Key words: Metabolic system, oxygen consumption, minute ventilation, carbon dioxide production, Bruce 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     

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     

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     

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     

Longitudinal Study in Male Swimmers: A Hierachical Modeling of Energetics and Biomechanical Contributions for Performance

The aim of this study was to assess the pooled and individual response of male swimmers over two consecutive years of training and identify the energetic and biomechanical factors that most contributed for the final performance. Nine competitive swimmers (20.0 ± 3.54 years old; 10.1 ± 3.41 years of training experience; 1.79 ± 0.07 m of height; 71.34 ± 8.78 kg of body mass; 22.35 ± 2.02 kg·m^-2 of body mass index; 1.86 ± 0.07 m of arm span; 116.22 ± 4.99 s of personal record in the 200 m long course freestyle event) performed an incremental test in six occasions to obtain the velocity at 4 mmol of blood lactate (V₄) and the peak blood lactate concentrations (La_peak) as energetics, and the stroke frequency (SF), stroke length (SL), stroke index and swim efficiency as biomechanical variables. Performance was determined based on official time’s lists of 200 m freestyle event. Slight non-significant improvements in performance were determined throughout the two season period. All energetic and biomechanical factors also presented slight non-significant variations with training. Swimmers demonstrat-ed high inter-individual differences in the annual adaptations. The best performance predictors were the V₄, SF and SL. Each unit of change V₄, SF and SL represented an enhancement of 0.11 s, 1.21 s and 0.36 s in performance, respectively. The results show that: (i) competitive male swimmers need at least two consecutive seasons to have slight improvements in performance, energetics and biomechanical profiles; (ii) major improvements in competition performance can be accomplished by improving the V₄, SF and SL based on the individual background.

Key Points

• Elite swimmers are able to demonstrate slight changes in performance, energetic and biomechanical characteristics at least during two seasons of training;
• Additional improvements in competition performance can be accomplished by manipulating the V₄, SF and SL based on the individual background.
• Each unit of change V₄, SF and SL represent an enhancement of 0.11 s, 1.21 s and 0.36 s in performance, respectively.

Key words: Male swimmers, tracking, training, testing, annual changes     

The Contribution of "Resting" Body Muscles to the Slow Component of Pulmonary Oxygen Uptake During High-Intensity Cycling

Oxygen uptake (VO₂) kinetics during moderate constant-workrate (WR) exercise (>lactate-threshold (θL)) are well described as exponential. AboveθL, these kinetics are more complex, consequent to the development of a delayed slow component (VO₂sc), whose aetiology remains controversial. To assess the extent of the contribution to the VO₂sc from arm muscles involved in postural stability during cycling, six healthy subjects completed an incremental cycle-ergometer test to the tolerable limit for estimation of θL and determination of peak VO₂. They then completed two constant-WR tests at 90% of θL and two at 80% of ∆ (difference between θL and VO_2peak). Gas exchange variables were derived breath-by-breath. Local oxygenation profiles of the vastus lateralis and biceps brachii muscles were assessed by near-infrared spectroscopy, with maximal voluntary contractions (MVC) of the relevant muscles being performed post-exercise to provide a frame of reference for normalising the exercise-related oxygenation responses across subjects. Above supra-θL, VO₂ rose in an exponential-like fashion ("phase 2), with a delayed VO₂sc subsequently developing. This was accompanied by an increase in [reduced haemoglobin] relative to baseline (∆[Hb]), which attained 79 ± 13 % (mean, SD) of MVC maximum in vastus lateralis at end-exercise and 52 ± 27 % in biceps brachii. Biceps brachii ∆[Hb] was significantly correlated with VO₂ throughout the slow phase. In contrast, for sub- L exercise, VO₂ rose exponentially to reach a steady state with a more modest increase in vastus lateralis ∆[Hb] (30 ± 11 %); biceps brachii ∆[Hb] was minimally affected (8 ± 2 %). That the intramuscular O₂ desaturation profile in biceps brachii was proportional to that for VO₂sc during supra-θL cycle ergometry is consistent with additional stabilizing arm work contributing to the VO₂sc.

Key points

• The source(s) of the "slow component" component of pulmonary oxygen uptake kinetics (VO₂sc) associated with high-intensity exercise remains the source of debate.
• Noninvasive interrogation techniques of the biceps brachii muscle during cycle ergometry suggest that "resting" muscles, such as those of the arms and shoulder girdle, may contribute to the VO₂sc, through stabilising actions (e.g. more forceful pulling on the ergometer handlebars).
• The quantitative contribution of such extra "resting"-muscle work awaits precise determination.

Key words: Muscle oxygenation, near infrared spectroscopy, oxygen uptake kinetics, arm exercise     

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