Analysis of sprint cross-country skiing using a differential global navigation satellite system

The purpose was to examine skiing velocities, gear choice (G2–7) and cycle rates during a skating sprint time trial (STT) and their relationships to performance, as well as to examine relationships between aerobic power, body composition and maximal skiing velocity versus STT performance. Nine male elite cross-country skiers performed three tests on snow: (1) Maximum velocity test (V _max) performed using G3 skating, (2) V _max test performed using double poling (DP) technique and (3) a STT over 1,425 m. Additional measurements of VO_2max during roller skiing and body composition using iDXA were made. Differential global navigation satellite system data were used for position and velocity and synchronized with video during STT. The STT encompassed a large velocity range (2.9–12.9 m s⁻¹) and multiple transitions (21–34) between skiing gears. Skiing velocity in the uphill sections was related to gear selection between G2 and G3. STT performance was most strongly correlated to uphill time (r = 0.92, P < 0.05), the percentage use of G2 (r = −0.72, P < 0.05), and DP V _max (r = −0.71, P < 0.05). The velocity decrease in the uphills from lap 1 to lap 2 was correlated with VO_2max (r = −0.78, P < 0.05). V _max in DP and G3 were related to percent of racing time using G3. In conclusion, the sprint skiing performance was mainly related to uphill performance, greater use of the G3 technique, and higher DP and G3 maximum velocities. Additionally, VO_2max was related to the ability to maintain racing velocity in the uphills and lean body mass was related to starting velocity and DP maximal speed.     

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

The present study investigated metabolic rate (MR) and gross efficiency (GE) at moderate and high work rates, and the relationships to gross kinematics and physical characteristics in elite cross-country skiers. Eight world class (WC) and eight national level (NL) male sprint cross-country skiers performed three 5-min stages using the skating G3 technique, whilst roller skiing on a treadmill. GE was calculated by dividing work rate by MR. Work rate was calculated as the sum of power against gravity and frictional rolling forces. MR was calculated using gas exchange and blood lactate values. Gross kinematics, i.e. cycle length (CL) and cycle rate (CR) were measured by video analysis. Furthermore, the skiers were tested for time to exhaustion (TTE), peak oxygen uptake (VO_2peak), and maximal speed (V _max) on the treadmill, and maximal strength in the laboratory. Individual performance level in sprint skating was determined by FIS points. WC skiers did not differ in aerobic MR, but showed lower anaerobic MR and higher GE than NL skiers at a given speed (all P < 0.05). Moreover, WC skiers skated with longer CL and had higher V _max and TTE (all P < 0.05). In conclusion, the present study shows that WC skiers are more efficient than NL skiers, and it is proposed that this might be due to a better technique and to technique-specific power.     

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

This investigation was designed to analyze the time-trial (STT) in an international cross-country skiing sprint skating competition for (1) overall STT performance and relative contributions of time spent in different sections of terrain, (2) work rate and kinematics on uphill terrain, and (3) relationships to physiological and kinematic parameters while treadmill roller ski skating. Total time and times in nine different sections of terrain by 12 world-class male sprint skiers were determined, along with work rate and kinematics for one specific uphill section. In addition, peak oxygen uptake (VO_2peak), gross efficiency (GE), peak speed (V_peak), and kinematics in skating were measured. Times on the last two uphill and two final flat sections were correlated to overall STT performance (r = ~−0.80, P < 0.001). For the selected uphill section, speed was correlated to cycle length (r = −0.75, P < 0.01) and the estimated work rate was approximately 160% of peak aerobic power. VO_2peak, GE, V_peak, and peak cycle length were all correlated to STT performance (r = ~−0.85, P < 0.001). More specifically, VO_2peak and GE were correlated to the last two uphill and two final flat section times, whereas V_peak and peak cycle length were correlated to times in all uphill, flat, and curved sections except for the initial section (r = ~−0.80, P < 0.01). Performances on uphill and flat terrain in the latter part were the most significant determinants of overall STT performance. Peak oxygen uptake, efficiency, peak speed, and peak cycle length were strongly correlated to overall STT performance, as well as to performance in different sections of the race.     

Training effects of cross-country skiing and running on maximal aerobic cycle performance and on blood lipids

Summary Two experiments were carried out to compare the cardiorespiratory and metabolic effects of cross-country skiing and running training during two successive winters. Forty-year-old men were randomly assigned into skiing (n = 15 in study 1,n = 16 in study 2), running (n = 16 in study 1 andn = 16 in study 2) and control (n = 17 in study 1 andn = 16 in study 2) groups. Three subjects dropped out of the programme. The training lasted 9–10 weeks with 40-min exercise sessions three times each week. The training intensity was controlled at 75%–85% of the maximal oxygen consumption (VO_2max) using portable heart rate metres and the mean heart rate was 156–157 beats·min^–1 in the training groups. In the pooled data of the two studies the mean increase in theVO_2max (in ml·min^–1·kg^–1) on a cycle ergometer was 17% for the skiing group, 13% for the running group and 2% for the control group. The increase inVO_2max was highly significant in the combined exercise group compared to the control group but did not differ significantly between the skiing and running groups. The fasting serum concentrations of lipoproteins and insulin did not change significantly in any of the groups. These results suggested that training by cross-country skiing and running of the same duration and intensity at each session for 9–10 weeks improved equally the cardiorespiratory fitness of untrained middle-aged men.     

Maximal oxygen uptake,anaerobic threshold and running economy in women and men with similar performances level in marathons

Sex differences in running economy (gross oxygen cost of running, C_R), maximal oxygen uptake (VO_2max), anaerobic threshold (Th_an), percentage utilization of aerobic power (% VO_2max), and Th_an during running were investigated. There were six men and six women aged 20–30 years with a performance time of 2 h 40 min over the marathon distance. The VO_2max, Th_an, and CR were measured during controlled running on a treadmill at 1° and 3° gradient. From each subject's recorded time of running in the marathon, the average speed (v _M) was calculated and maintained during the treadmill running for 11 min. The VO_{2 max} was inversely related to body mass (m _b), there were no sex differences, and the mean values of the reduced exponent were 0.65 for women and 0.81 for men. These results indicate that for running the unit ml·kg^–0.75·min^–1 is convenient when comparing individuals with different m _b. The VO_2max was about 10% (23 ml·kg^–0.75·min^–1) higher in the men than in the women. The women had on the average 10–12 ml·kg^–0.75·min^–1 lower VO₂ than the men when running at comparable velocities. Disregarding sex, the mean value of C_R was 0.211 (SEM 0.005) ml·kg^–1·m^–1 (resting included), and was independent of treadmill speed. No sex differences in Th_an expressed as % VO_2max or percentage maximal heart rate were found, but Than expressed as VO₂ in ml·kg^–0.75·min^–1 was significantly higher in the men compared to the women. The percentage utilization of f _emax and concentration of blood lactate at v _M was higher for the female runners. The women ran 2 days more each week than the men over the first 4 months during the half year preceding the marathon race. It was concluded that the higher VO_2max and Th_an in the men was compensated for by more running, superior C_R, and a higher exercise intensity during the race in the performance-matched female marathon runners.     

Age-related changes in cardio-respiratory responses and muscular performance following an Olympic triathlon in well-trained triathletes

The aim of the present study was to compare the maximal isometric torque and cardio-respiratory parameters in well-trained young and master triathletes prior to and following an Olympic distance triathlon. One day before and 24 h following the event, participants performed three maximum voluntary isometric knee extensions and flexions and an incremental running test on a treadmill to determine the maximal isometric torque, maximal oxygen uptake ( [(V)\dot]\textO_2max ) \left( {\dot{V}{\text{O}}_{2\max } } \right) , speed at [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } (vVO₂max), speed at ventilatory thresholds (VT1 and VT2) and submaximal running economy. Prior to the event [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } , vVO₂max, speed at ventilatory thresholds and running economy were significantly lower in master athletes, but maximal voluntary torque was similar between the groups. 24 h following the race, a similar significant decrease in [(V)\dot]\textO_2max \dot{V}{\text{O}}_{2\max } (−3.1% in masters, and −6.2% in young, p < 0.05), and vVO₂max (−9.5% in masters, and −5.6% in young, p < 0.05) was observed in both the groups. The speed at VT2 significantly decreased only in master athletes (−8.3%, p < 0.05), while no change was recorded in maximal voluntary torque or submaximal running economy following the event. The results indicate that for well-trained subjects, the overall relative exercise intensity during an Olympic distance triathlon and the fatigue 24 h following the event seem to be independent of age.     

Block training periodization in alpine skiing: effects of 11-day HIT on VO2max and performance

Attempting to achieve the high diversity of training goals in modern competitive alpine skiing simultaneously can be difficult and may lead to compromised overall adaptation. Therefore, we investigated the effect of block training periodization on maximal oxygen consumption (VO_2max) and parameters of exercise performance in elite junior alpine skiers. Six female and 15 male athletes were assigned to high-intensity interval (IT, N = 13) or control training groups (CT, N = 8). IT performed 15 high-intensity aerobic interval (HIT) sessions in 11 days. Sessions were 4 × 4 min at 90–95% of maximal heart rate separated by 3-min recovery periods. CT continued their conventionally mixed training, containing endurance and strength sessions. Before and 7 days after training, subjects performed a ramp incremental test followed by a high-intensity time-to-exhaustion (tlim) test both on a cycle ergometer, a 90-s high-box jump test as well as countermovement (CMJ) and squat jumps (SJ) on a force plate. IT significantly improved relative VO_2max by 6.0% (P < 0.01; male +7.5%, female +2.1%), relative peak power output by 5.5% (P < 0.01) and power output at ventilatory threshold 2 by 9.6% (P < 0.01). No changes occurred for these measures in CT. tlim remained unchanged in both groups. High-box jump performance was significantly improved in males of IT only (4.9%, P < 0.05). Jump peak power (CMJ −4.8%, SJ −4.1%; P < 0.01), but not height decreased in IT only. For competitive alpine skiers, block periodization of HIT offers a promising way to efficiently improve VO_2max and performance. Compromised explosive jump performance might be associated with persisting muscle fatigue.     

The energetics of ultra-endurance running

Our objective was to determine the effects of long-lasting endurance events on the energy cost of running (C _r), and the role of maximal oxygen uptake (VO_2max), its fractional utilisation (F) and C _r in determining the performance. Ten healthy runners (age range 26–59 years) participated in an ultra-endurance competition consisting of three running laps of 22, 48 and 20 km on three consecutive days in the North–East of Italy. Anthropometric characteristics and VO_2max by a graded exercise test on a treadmill were determined 5 days before and 5 days after the competition. In addition, C _r was determined on a treadmill before and after each running lap. Heart rate (HR) was recorded throughout the three laps. Results revealed that mean C _r of the individual laps did not increase significantly with lap number (P = 0.200), thus ruling out any chronic lap effect. Even so, however, at the end of lap 3, C _r was 18.0% (P < 0.001) greater than before lap 1. In addition, a statistically significant acute lap effect on C _r was observed at the end of the second and third laps (by 11.4 and 7.2%, respectively). The main factors determining performance were VO_2max, F, as estimated from the average HR, and the average C _r-mean throughout the three laps; the grand average speed over the three laps being described by v _end-mean = F × VO_2max × C _r-mean⁻¹. We concluded that (1) the substantial increase of C _r-mean during the competition yields to marked worsening of the performance, and (2) the three variables F, VO_2max and C _r-mean combined as described above explaining 87% of the total competition time variance.     

Sprint running performance: comparison between treadmill and field conditions

We investigated the differences in performance between 100-m sprints performed on a sprint treadmill recently validated versus on a standard track. To date, studies comparing overground and treadmill running have mainly focused on constant and not maximal “free” running speed, and compared running kinetics and kinematics over a limited number of steps, but not overall sprint performance. Eleven male physical education students including two sprinters performed one 100-m on the treadmill and one on a standard athletics track in a randomized order, separated by 30 min. Performance data were derived in both cases from speed–time relationships measured with a radar and with the instrumented sprint treadmill, which allowed subjects to run and produce speed “freely”, i.e. with no predetermined belt speed imposed. Field and treadmill typical speed–distance curves and data of maximal and mean speed, 100-m time and acceleration/deceleration time constants were compared using t tests and field–treadmill correlations were tested. All the performance parameters but time to reach top speed and deceleration time constant differed significantly, by about 20% on average, between field and treadmill (e.g. top speed of 8.84 ± 0.51 vs. 6.90 ± 0.39 m s⁻¹). However, significant correlations were found (r > 0.63; P < 0.05) for all the performance parameters except time to reach top speed. Treadmill and field 100-m sprint performances are different, despite the fact that subjects could freely accelerate the belt. However, the significant correlations found make it possible to investigate and interpret inter-individual differences in field performance from treadmill measurements.     

Upper body power as a determinant of classical cross-country ski performance

The purpose of this study was to evaluate the relationship between short (≤60 s) and long duration (4–12 min) measures of upper body power (UBP) and mass start classical cross-country ski performance. Several experienced skiers (eight men, five women) completed three separate tests of UBP on a double poling ergometer: two tests of highest average power output for 10 s (UBP₁₀) and 60 s (UBP₆₀), and an incremental test to exhaustion to measure peak oxygen uptake (VO_2PEAK) and peak power output (UBP_PEAK). Lastly, subjects competed in a 10-km classical cross-country ski race from which race speed (RS) was computed. RS correlated highly with UBP₁₀ (r = 0.93; P < 0.05), UBP₆₀ (r = 0.92; P < 0.05), and UBP_PEAK (r = 0.94; P < 0.05); the correlation was lower but still significant for VO_2PEAK (r = 0.88; P < 0.05). These findings suggest that both short and long duration measures of UBP are important determinants of mass start classical ski race performance.     

Prediction of <Emphasis Type="Italic">V</Emphasis>O<Subscript>2max</Subscript> with daily step counts for Japanese adult women

The purpose of the study was to develop a new non-exercise VO_2max prediction model using a physical activity (PA) variable determined by pedometer-determined step counts (SC, steps day⁻¹) in Japanese women aged 20–69 years old. Eighty-seven and 102 subjects were used to develop the prediction model, and to validate the new model, respectively. VO_2max was measured using a maximal incremental test on a bicycle ergometer. SC was significantly related to VO_2max (partial correlation coefficient r = 0.40, P < 0.001) after adjusting for BMI (kg m⁻²) and age (years). When the new prediction equation developed by multiple regression to estimate VO_2max from age, BMI, and SC (R = 0.71, SEE = 5.3 ml kg⁻¹ min⁻¹, P < 0.001) was applied to the Validation group, predicted VO_2max correlated well with measured VO_2max (r = 0.81, P < 0.001), suggesting that SC is a useful PA variable for non-exercise prediction of VO_2max in Japanese women.     

Are fixed-rate step tests medically safe for assessing physical fitness?

Maximal oxygen uptake (VO_2max) can be predicted by fixed-rate step tests. However, it remains to be analyzed as to what exercise intensities are reached during such tests to address medical safety. In this study, we compared the physiological response to a standardized fixed-rate step test with maximal cardiopulmonary exercise testing (CPET). One hundred and thirteen healthy adults executed a maximal CPET on bike, followed by a standardized fixed-rate step test 1 week later. During these tests, heart rate (HR) and VO₂ were monitored continuously. From the maximal CPET, the ventilatory threshold (VT) was calculated. Next, the physiological response between maximal CPET and step testing was compared. The step test intensity was 85 ± 24% CPET VO_2max and 88 ± 11% CPET HR_max (VO_2max and HR_max were significantly different between CPET and step testing; p < 0.01). In 41% of the subjects, step test exercise intensities >95% CPET VO_2max were noted. A greater step testing exercise intensity (%CPET VO_2max) was independently related to higher body mass index, and lower body height, exercise capacity (p < 0.05). Standardized fixed-rate step tests elicit vigorous exercise intensities, especially in small, obese, and/or physically deconditioned subjects. Medical supervision might therefore be required during these tests.     

Sex differences in performance-matched marathon runners

Summary Six male and six female runners were chosen on the basis of age (20–30 years) and their performance over the marathon distance (mean time = 199.4, SEM 2.3 min for men and 201.8, SEM 1.8 min for women). The purpose was to find possible sex differences in maximal aerobic power (VO_2max), anaerobic threshold, running economy, degree and utilization of VO_2max (when running a marathon) and amount of training. The results showed that performance-matched male and female marathon runners had approximately the same VO_2max (about 60 ml·kg^–1·min^–1). For both sexes the anaerobic threshold was reached at an exercise intensity of about 83% of VO_2max, or 88%–90% of maximal heart rate. The females' running economy was poorer, i.e. their oxygen uptake during running at a standard submaximal speed was higher (P<0.05). The heart rate, respiratory exchange ratio and blood lactate concentration also confirmed that a given running speed resulted in higher physiological. strain for the females. The percentage utilization of VO_2max at the average marathon running speed was somewhat higher for the females, but the difference was not significant. For both sexes the oxygen uptake at average speed was 93%–94% of the oxygen uptake corresponding to the anaerobic threshold. Answers to a questionnaire showed that the females' training programme over the last 2 months prior to running the actual marathon comprised almost twice as many kilometres of running per week compared to the males (60 and 33 km, respectively). The better state of training of the females was also confirmed by a 10% higher VO_2max, in relation to lean body mass than that of the male runners. Apart from the well-known variation in height and differences in the percentage of fat, the difference between performance-matched male and female marathon runners seemed primarily to be found in running economy and amount of training.     

The between and within day variation in gross efficiency

Before the influence of divergent factors on gross efficiency (GE) [the ratio of mechanical power output (PO) to metabolic power input (PI)] can be assessed, the variation in GE between days, i.e. the test–retest reliability, and the within day variation needs to be known. Physically active males (n = 18) performed a maximal incremental exercise test to obtain VO_2max and PO at VO_2max (PVO_2max), and three experimental testing days, consisting of seven submaximal exercise bouts evenly distributed over the 24 h of the day. Each submaximal exercise bout consisted of six min cycling at 45, 55 and 65% PVO_2max, during which VO₂ and RER were measured. GE was determined from the final 3 min of each exercise intensity with: GE = (PO/PI) × 100%. PI was calculated by multiplying VO₂ with the oxygen equivalent. GE measured during the individually highest exercise intensity with RER <1.0 did not differ significantly between days (F = 2.70, p = 0.08), which resulted in lower and upper boundaries of the 95% limits of agreement of 19.6 and 20.8%, respectively, around a mean GE of 20.2%. Although there were minor within day variations in GE, differences in GE over the day were not significant (F = 0.16, p = 0.99). The measurement of GE during cycling at intensities approximating VT is apparently very robust, a change in GE of ~0.6% can be reliably detected. Lastly, GE does not display a circadian rhythm so long as the criteria of a steady-state VO₂ and RER <1.0 are applied.     

Changes in performance, muscle metabolites, enzymes and fibre types after short sprint training

In contrast to endurance training, little research has been carried out to investigate the effects of short (<10?s) sprint training on performance, muscle metabolism and fibre types. Nine fit male subjects performed a mean of 16 outdoor sprint running training sessions over 6 weeks. Distances sprinted were 30–80?m at 90–100% maximum speed and between 20 and 40 sprints were performed in each session. Endurance (maximal oxygen consumption; V˙O_{2 max}), sprint (10?m and 40?m times), sustained sprint (supramaximal treadmill run) and repeated sprint (6?×?40?m sprints, 24?s recovery between each) performance tests were performed before and after training. Muscle biopsy samples (vastus lateralis) were also taken to examine changes in metabolites, enzyme activities and fibre types. After training, significant improvements were seen in 40?m time (P?P?P?V˙O_{2 max} (P?P?P?P?相似文献   

Optimising high-intensity treadmill training using the running speed at maximal O(2) uptake and the time for which this can be maintained

The aim of this study was to compare the effects of two high-intensity, treadmill interval-training programs on 3000-m and 5000-m running performance. Maximal oxygen uptake (V˙O_2max), the running speed associated with V˙O_2max (vV˙O_2max), the time for which vV˙O_2max can be maintained (T _max), running economy (RE), ventilatory threshold (VT) and 3000-m and 5000-m running times were determined in 27 well-trained runners. Subjects were then randomly assigned to three groups; (1) 60% T _max, (2) 70% T _max and (3) control. Subjects in the control group continued their normal training and subjects in the two T _max groups undertook a 4-week treadmill interval-training program with the intensity set at vV˙O_2max and the interval duration at the assigned T _max. These subjects completed two interval-training sessions per week (60% T _max=six intervals/session, 70% T _max group=five intervals/session). Subjects were re-tested on all parameters at the completion of the training program. There was a significant improvement between pre- and post-training values in 3000-m time trial (TT) performance in the 60% T _max group compared to the 70% T _max and control groups [mean (SE); 60% T _max=17.6 (3.5) s, 70% T _max =6.3 (4.2) s, control=0.5 (7.7) s]. There was no significant effect of the training program on 5000-m TT performance [60% T _max=25.8 (13.8) s, 70% T _max=3.7 (11.6) s, control=9.9 (13.1) s]. Although there were no significant improvements in V˙O_2max, vV˙O_2max and RE between groups, changes in V˙O_2max and RE were significantly correlated with the improvement in the 3000-m TT. Furthermore, VT and T _max were significantly higher in the 60% T _max group post- compared to pre-training. In conclusion, 3000-m running performance can be significantly improved in a group of well-trained runners, using a 4-week treadmill interval training program at vV˙O_2max with interval durations of 60% T _max. Electronic Publication     

Effect of sprint interval training on circulatory function during exercise in sedentary, overweight/obese women

Very high-intensity, low-volume, sprint interval training (SIT) increases muscle oxidative capacity and may increase maximal oxygen uptake ( [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} ), but whether circulatory function is improved, and whether SIT is feasible in overweight/obese women is unknown. To examine the effects of SIT on [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} and circulatory function in sedentary, overweight/obese women. Twenty-eight women with BMI > 25 were randomly assigned to SIT or control (CON) groups. One week before pre-testing, subjects were familarized to [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} testing and the workload that elicited 50% [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} was calculated. Pre- and post-intervention, circulatory function was measured at 50% of the pre-intervention [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} , and a GXT was performed to determine [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} . During the intervention, SIT training was given for 3 days/week for 4 weeks. Training consisted of 4–7, 30-s sprints on a stationary cycle (5% body mass as resistance) with 4 min active recovery between sprints. CON maintained baseline physical activity. Post-intervention, heart rate (HR) was significantly lower and stroke volume (SV) significantly higher in SIT (−8.1 and 11.4%, respectively; P < 0.05) during cycling at 50% [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} ; changes in CON were not significant (3 and −4%, respectively). Changes in cardiac output ( [(\textQ)\dot] {\dot{\text{Q}}} ) and arteriovenous oxygen content difference [(a − v)O₂ diff] were not significantly different for SIT or CON. The increase in [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} by SIT was significantly greater than by CON (12 vs. −1%). Changes by SIT and CON in HR_max (−1 vs. −1%) were not significantly different. Four weeks of SIT improve circulatory function during submaximal exercise and increases [(V)\dot]\textO _{2 \textmax} {\dot{V}\text{O}}_{{ 2 {\text{max}}}} in sedentary, overweight/obese women.     

Regulating intensity using perceived exertion during extended exercise periods

The present study was undertaken to examine the validity of using the OMNI scale of perceived exertion to regulate intensity during extended exercise periods. Forty-eight subjects (24 male, 24 female) were recruited and each subject completed a maximal graded exercise test (GXT) and two 20-min submaximal exercises. During the GXT, ratings of perceived exertion (RPE) as well as oxygen uptake (V˙O₂) and heart rate (HR) equivalent to 50 and 70% of maximum V˙O₂ (V˙O_2max) were estimated. During each submaximal exercise, subjects were instructed to produce and maintain a workload equivalent to the RPE estimated at 50 or 70% V˙O_2max, and V˙O₂ and HR were measured every 5 min throughout the exercise. Of the 48 subjects, 12 (6 male and 6 female) performed both the estimation and production trials on a treadmill (TM/TM), 12 (6 male and 6 female) performed both the estimation and production trials on a cycle ergometer (C/C), 12 (6 male and 6 female) performed the estimation trial on a treadmill and the production trial on a cycle ergometer (TM/C), and 12 (6 male and 6 female) performed the estimation trial on a cycle ergometer and the production trial on a treadmill (C/TM). No differences in V˙O₂ between the estimation and any 5 min of the production trial were observed at either intensity in TM/TM and C/C. No differences in HR between the estimation and any 5 min of the production trial were also observed at 50% V˙O_2max in TM/TM and at both 50 and 70% V˙O_2max in C/C. However, HR was higher at 20th min of the production trial at 70% V˙O_2max in TM/TM. Both the V˙O₂ and HR were generally lower in TM/C and higher in C/TM. However, these differences diminished when values were normalized using V˙O_2max of the same mode that other groups had attained. These data suggest that under both intra- and intermodal conditions, using the OMNI perceived exertion scale is effective not only in establishing the target intensity at the onset of exercise, but also in maintaining the intensity throughout a 20-min exercise session. Electronic Publication     

Neuromuscular factors determining 5 km running performance and running economy in well-trained athletes

This study investigated the effects of the neuromuscular and force–velocity characteristics in distance running performance and running economy. Eighteen well-trained male distance runners performed five different tests: 20 m maximal sprint, running economy at the velocity of 4.28 m s⁻¹, 5 km time trial, maximal anaerobic running test (MART), and a treadmill test to determine VO_2max. The AEMG ratio was calculated by the sum average EMG (AEMG) of the five lower extremity muscles during the 5 km divided by the sum AEMG of the same muscles during the maximal 20 m sprinting. The runners’ capacity to produce power above VO_2max (MART VO_2gain) was calculated by subtracting VO_2max from the oxygen demand of the maximal velocity in the MART (V _MART). Velocity of 5 km (V _5K) correlated with V _MART (r=0.77, p<0.001) and VO_2max (r=0.49, p<0.05). Multiple linear regression analysis showed that MART VO_2gain and VO_2max explained 73% of the variation in V _5K. A significant relationship also existed between running economy and MART VO_2gain (r=0.73, p<0.01). A significant correlation existed between V _5K and AEMG ratio during the ground contact phase at the 3 km (r=0.60, p<0.05) suggesting that neural input may affect distance running performance. The results of the present study support the idea that distance running performance and running economy are related to neuromuscular capacity to produce force and that the V _MART can be used as a determinant of distance-running performance.     

Effectiveness of intermittent training in hypoxia combined with live high/train low

Elite athletes often undertake altitude training to improve sea-level athletic performance, yet the optimal methodology has not been established. A combined approach of live high/train low plus train high (LH/TL+TH) may provide an additional training stimulus to enhance performance gains. Seventeen male and female middle-distance runners with maximal aerobic power ( [(V)\dot]\textO_{2 max} ) \left( {\dot{V}{\text{O}}_{{2{ \max }}} } \right) of 65.5 ± 7.3 mL kg⁻¹ min⁻¹ (mean ± SD) trained on a treadmill in normobaric hypoxia for 3 weeks (2,200 m, 4 week⁻¹). During this period, the train high (TH) group (n = 9) resided near sea-level (~600 m) while the LH/TL+TH group (n = 8) stayed in normobaric hypoxia (3,000 m) for 14 hours day⁻¹. Changes in 3-km time trial performance and physiological measures including [(V)\dot]\textO_{2 max} , \dot{V}{\text{O}}_{{2{ \max }}} , running economy and haemoglobin mass (Hb_mass) were assessed. The LH/TL+TH group substantially improved [(V)\dot]\textO_{2 max} \dot{V}{\text{O}}_{{2{ \max }}} (4.8%; ±2.8%, mean; ±90% CL), Hb_mass (3.6%; ±2.4%) and 3-km time trial performance (−1.1%; ±1.0%) immediately post-altitude. There was no substantial improvement in time trial performance 2 weeks later. The TH group substantially improved [(V)\dot]\textO_{2 max} \dot{V}{\text{O}}_{{2{ \max }}} (2.2%; ±1.8%), but had only trivial changes in Hb_mass and 3-km time-trial performance. Compared with TH, combined LH/TL+TH substantially improved [(V)\dot]\textO_{2 max} \dot{V}{\text{O}}_{{2{ \max }}} (2.6%; ±3.2%), Hb_mass (4.3%; ±3.2%), and time trial performance (−0.9%; ±1.4%) immediately post-altitude. LH/TL+TH elicited greater enhancements in physiological capacities compared with TH, however, the transfer of benefits to time-trial performance was more variable.