Fibre characteristics and enzyme levels of arm and leg muscles in elite cross-country skiers

Performance tests and measurements of maximal aerobic capacity were performed during the competition period in elite cross-country skiers. Muscle biopsies were taken in the middle of January. Histochemical fibre typing, determination of fibre areas and number of capillaries as well as assays for citrate synthetase (CS), 3-hydroxyacyl coenzyme A dehydrogenase (HAD), lactate dehydrogenase (LDH_tot and LDH_1–2) were performed on biopsies from the triceps brachii (TRI) and vastus lateralis muscles (VAS). The relative percentage of slow-twitch fibres was 51.3 and 68.6 in TRI and VAS, respectively. The FTa fibre area in TRI was significantly larger than in VAS. No differences were found in the number of capillaries per fibre in TRI (2.7) and VAS (2.5). The number of capillaries per area was significantly lower in TRI (373) as compared to VAS (422). The LDH_tot enzyme level was significantly higher in TRI than VAS, while the oxidative enzyme activities (CS and HAD) were significantly lower in TRI as compared with VAS. From all independent variables, only the maximal aerobic power was related significantly to performance time. The difference in maximal aerobic power between the skiers could explain 45% of the total variance in performance.     

Field measurements of oxygen uptake in elite orienteers during cross-country running using telemetry

Oxygen uptake (V_o2) was measured and economy calculated during running on a treadmill and during cross-country running in 14 male and 9 female orienteers using a telemetric system (K-2, Cosmed, Italy). The cross-country route comprised 3 parts: horizontal path running, horizontal running in light terrain and running in heavy terrain with obstacles and steep hills. Each subject accomplished the whole test route at a speed corresponding to 96±5% of maximal speed and at maximal speed. The running time at maximal speed was 19±3 min. The running economy was similar in treadmill and path running (211 ± 10 vs 210± 14 ml · kg⁻¹· km⁻¹), but V_o2 per km increased in light and heavy terrain to 290 ± 16 and 362±18 ml · kg⁻¹· km⁻¹, respectively. There was no difference in running economy between men and women. The elite group (5 men and 3 women) demonstrated 5% better running economy than the sub-elite (9 men and 6 women) during running in light and heavy terrain, whereas no difference was seen during treadmill and path running. In conclusion, elite orienteers have better running economy in light and heavy terrain than sub-elite orienteers.     

Influence of body weight reduction on maximal oxygen uptake in female elite athletes

The aim of this study was to investigate the effect of weight reduction on maximal oxygen uptake (O_2max and running speed in endurance-trained female elite athletes. Seven (the cases) of the 33 subjects reduced a significant amount of body weight (BW) within a period of 2 months. The cases showed a significant decrease in O_2max and running speed relative to controls during the weight reduction period (WRP). A considerable loss in BW might have prevented cases from achieving a training-induced increase in O_2max and running speed similar to controls during the WRP. Six cases maintained low BW and all 7 improved O_2max relative to controls 1 year after the WRP.     

Blood lactate and respiratory variables in elite cross-country skiing at racing speeds

The purpose of this study was to examine energy metabolism during two simulated races (skating and classical) in cross-country skiing. In each race 15 elite subjects skied a 2.75-km track 5 times. In laps 2 and 4, the skiers were told to skate without poles in the skating race and without the diagonal stride in the classical race. The total exercise time was between 42 and 50 min in the 2 races. The oxygen uptake was measured on flat and uphill terrain during each lap and blood lactate after each lap. The relative mean oxygen uptake for classical skiing was 88% (82-96) for level and 93% (87-97) for uphill terrain. The respective means for skating were 91% (85-96) for level and 91% (81-97) for uphill terrain. The mean values and range for blood lactate at race speeds were 10.6 mM (7.1-18.1) and 9.2 mM (4.8-18.8) for skating and classical, respectively. A relative steady state was achieved after the first lap, although a slight but significant blood lactate accumulation took place until finish (0.04-0.06 mM min⁻¹). The respiratory exchange ratio in both skiing styles varied between 0.88-0.90 and 0.92-0.93 for flat and uphill terrain, respectively, indicating a large lipid oxidation at these very high exercise intensities.     

Blood profiles in elite cross-country skiers: a 6-year follow-up

Following the doping scandals at the World Championships in cross-country skiing in 2001, the International Ski Federation decided to generate individual blood profiles. From 2001 to 2007, 7081 blood samples from 1074 male and female elite cross-country skiers were collected and analyzed for hemoglobin concentration [Hb] and % reticulocytes (%rets). Data were applied to blood algorithms wherefrom blood model scores were calculated. From 1997–1999 to 2001–2002, the mean [Hb] was reduced by 0.9 g/dL to 15.3 g/dL in male skiers and by 0.4 g/dL to 13.8 in female skiers. From 2002–2003 to 2006–2007, the combination of increases in [Hb] and decreases in %rets led to pronounced increases in mean OFF-model scores. [Hb] was 0.2 g/dL higher at Olympic Games/World Championships (WOCs) than at World Cups competitions <4 weeks before and after WOCs. [Hb] and %rets increased with altitude in both genders. Since the introduction of an enlarged blood testing program, the mean [Hb] values were lowered to close to normal levels, but over the last 2–3 years there has been a small elevation and an increase in OFF-model scores, which may indicate a change in the manipulations used to elevate the [Hb].     

Maximal and submaximal oxygen uptake during running: how should body mass be accounted for?

Oxygen uptake during running, i.e., the running economy, is an important factor in determining running performance in endurance events. The relation to performance is particularly strong when the aerobic running capacity is calculated, i.e., when running economy is related to the maximal oxygen uptake. There is considerable interindividual variation in running economy, and the reason for this is only partly understood. To some extent, this may be due to the way in which the oxygen uptake during running is usually expressed. This may expecially be true when subjects with different or changing body masses are compared. Several lines of evidence, including earlier animal studies as well as more recent human studies, favor the expression of submaximal and maximal oxygen uptake during running in terms of ml · kg^−0.75· min⁻¹ rather than as ml · kg⁻¹· min^−1.     

Prolonged constant load cycling exercise is associated with reduced gross efficiency and increased muscle oxygen uptake

This study investigated the effects of prolonged constant load cycling exercise on cycling efficiency and local muscle oxygen uptake responses. Fourteen well‐trained cyclists each completed a 2‐h steady‐state cycling bout at 60% of their maximal minute power output to assess changes in gross cycling efficiency (GE) and muscle oxygen uptake (mVO₂) at time points 5, 30, 60, 90, and 120 min. Near‐infrared spatially resolved spectroscopy (NIRS) was used to continually monitor tissue oxygenation of the Vastus Lateralis muscle, with arterial occlusions (OCC) applied to assess mVO₂. The half‐recovery time of oxygenated hemoglobin (HbO₂) was also assessed pre and post the 2‐h cycling exercise by measuring the hyperemic response following a 5‐min OCC. GE significantly declined during the 2‐h cycling bout (18.4 ± 1.6 to 17.4 ± 1.4%; P < 0.01). Conversely, mVO₂ increased, being significantly higher after 90 and 120 min than at min 5 (+0.04 mlO₂/min/100 g; P = 0.03). The half‐recovery time for HbO₂ was increased comparing pre and post the 2‐h cycling exercise (+7.1 ± 19s), albeit not significantly (d: 0.48; P = 0.27). This study demonstrates that GE decreases during prolonged constant load cycling exercise and provides evidence of an increased mVO₂, suggestive of progressive mitochondrial or contractile inefficiency.     

Maximal oxygen uptake and power of lower limbs during a competitive season in triathletes

BACKGROUND: In order to study the effect of a competitive triathlon season on maximal oxygen uptake (VO2max), aerobic power (AeP) and anaerobic performance (AnP) of the lower limbs, eight triathletes performed exercise tests after: (1) a pre-competition period (Pre-COMP) (2) a competitive period (COMP), and (3) a low (volume and intensity) training period (Post-COMP). The tests were a vertical jump-and-reach test and an incremental exercise test on a cycle ergometer. Ventilatory data were collected every minute during the incremental test with an automated breath-by-breath system and the heart-rate was monitored using a telemetric system. RESULTS: No changes in VO2max were observed, whereas AeP decreased after Post-COMP compared to Pre-COMP and COMP and AnP decreased during COMP compared to Pre-COMP and Post-COMP. In addition, second ventilatory threshold (VT2) and power output at first ventilatory threshold (VT1) and VT2 decreased after Post-COMP. CONCLUSION: This study showed that six weeks of low volume and intensity of training is too long a period to preserve adaptations to training, although a stable maximal oxygen uptake throughout the triathlon season was observed. Moreover, the AnP decrease during COMP was probably in relation with the repetitive nature of the training mode and/or triathlon competitions.     

High-dose inhaled salbutamol has no acute effects on aerobic capacity or oxygen uptake kinetics in healthy trained men

The prevalence of asthma is higher among elite athletes than in the general population. This has resulted in the frequent use of anti-asthmatic medication such as beta2-agonists among asthmatic athletes. Beta2-agonists are on the prohibited list of WADA. The use of the beta2-agonist salbutamol is only permitted in therapeutic inhaled doses. Most studies have reported the lack of ergogenic effects of therapeutic doses of inhaled beta2-agonists measured in maximal oxygen uptake. No previous studies have examined any possible effects of high-dose inhaled salbutamol on oxygen uptake kinetics. We enrolled nine healthy well-trained men in a randomized, blinded, placebo-controlled crossover study. Subjects were randomized to inhalation of 40 puffs of 0.2 mg salbutamol or two placebo tablets and performed an incremental test to exhaustion and three submaximal tests at 75% of peak power to determine oxygen uptake kinetics. During the incremental test, there were no effects of inhaled salbutamol on VO(2max) in absolute or relative terms, and no effect on peak power and lactate threshold. During the submaximal test, we found no effects on the time constant, time delay, the mean response time or O(2) deficit related to oxygen uptake kinetics. In conclusion, no ergogenic effect of a high dose of salbutamol on aerobic capacity was found.     

A two-kilometer walking test: effect of walking speed on the prediction of maximal oxygen uptake

A 2-km walking test was developed previously to predict maximal oxygen uptake (Vo_2max) in field conditions. The prediction is based on the time required for the 2-km fast walk, heart rate at the end of the walk, age and body mass index. This study examined the effects of the walking speed on the prediction of Vo_2max in 111 moderately to highly active 35- to 55-year-old adults. The Vo_2max was determined in an uphill walk-run on a treadmill. Five 2-km walking tests were conducted on a flat outdoor course. The first two were performed at the maximal speed and the remaining at submaximal speeds of 60%, 70% and 80% of the maximal heart rate. All tests underpre-dicted the measured Vo_2max. A walking speed corresponding to 80% of the maximal heart rate or more resulted in the most accurate prediction of maximal aerobic power.     

5‐week block periodization increases aerobic power in elite cross‐country skiers

The purpose of this study was to compare the effect of two different methods of organizing endurance training in elite cross‐country skiers approaching the competition period. During the 5‐week intervention period, one group performed block periodization (BP; n = 10) with 5 and 3 high‐intensity sessions (HIT) during the first and third training week. One HIT was performed during the remaining weeks in BP, while the group performing traditional training organization (TRAD, n = 9) performed two weekly HIT except during the third week where they performed three HIT. HIT were interspersed with low‐intensity training (LIT) and both groups performed similar total amount of both HIT and LIT during the intervention. BP achieved a larger relative increase in peak power output and power output at a blood lactate concentration of 4 mmol/L than TRAD (4 ± 4 vs ?3 ± 6% and 11 ± 10 vs 2 ± 4%, respectively, both P < 0.01). BP also increased maximal oxygen uptake by 2 ± 2% (P < 0.05), while no changes occurred in TRAD. The effect sizes of the relative improvement in these measurements revealed moderate effects of BP vs TRAD training. The present study suggests that block periodization of endurance training have superior effects on several endurance and performance indices compared with traditional organization.     

Gender differences in endurance performance by elite cross‐country skiers are influenced by the contribution from poling

Greater gender differences have been found in exercise modes where the upper body is involved. Therefore, the present study investigated the influence of poling on gender differences in endurance performance by elite cross‐country skiers. Initially, the performance of eight male and eight female sprint skiers was compared during four different types of exercise involving different degrees of poling: double poling (DP), G3 skating, and diagonal stride (DIA) techniques during treadmill roller skiing, and treadmill running (RUN). Thereafter, DP was examined for physiological and kinematic parameters. The relative gender differences associated with the DP, G3, DIA and RUN performances were approximately 20%, 17%, 14%, and 12%, respectively. Thus, the type of exercise exerted an overall effect on the relative gender differences (P < 0.05). In connection with DP, the men achieved 63%, 16%, and 8% higher VO_2peak than the women in absolute terms and with normalization for total and fat‐free body mass (all P < 0.05). The DP VO_2peak in percentage of VO_2max in RUN was higher in men (P < 0.05). The gender difference in DP peak cycle length was 23% (P < 0.05). In conclusion, the present investigation demonstrates that the gender difference in performance by elite sprint skiers is enhanced when the contribution from poling increases.     

Aerobic fitness and field test performance in elite Spanish soccer referees of different ages

The major aim of this study was to examine the physical fitness of elite Spanish soccer referees in relation to their age. A secondary aim was to assess the population criterion validity of the 12 min running test (12 MRT) against aerobic-fitness laboratory tests. Participants were 45 soccer referees (age 35.5 ± 4.4 years, height 178.3 ± 5.0 cm, body mass 75.1 ± 6.6 kg, body fat 11.3 ± 2.15%, VO_2max 54.9 ± 3.9 ml kg⁻¹ min⁻¹) who were enrolled in the Referees Technical Committee of the Royal Spanish Soccer Federation. They were divided into three age groups: young (Y, 27–32 years, n = 15), average (A, 33–38 years, n = 17) and old (O, 39–45 years, n = 13). No age-related effects were observed for VO_2max, 12 MRT or 200 m sprint performance in either the pooled or grouped data. However, age-related performance decrements were observed for 50 m sprint performance and the ventilatory threshold (VT) running speed. Twelve MRT performance was moderately related to VO_2max (r = 0.46, P = 0.002), VT (km h⁻¹) (r = 0.49, P < 0.001), and peak treadmill velocity (PTV) (r = 0.60, P < 0.001). The results showed that older elite-level referees may be able to limit the expected age-related performance decrements in both aerobic and anaerobic performance usually reported for sedentary people. Additionally, these results show that older referees are able to reach physical fitness levels that have been suggested to be appropriate for coping with match demands.     

Effects of training on functional performance in 65, 75 and 85 year-old women: experiences deriving from community based studies in Odense,Denmark

The aim of the Odense training studies is to elucidate if regular physical training influences the expected decline in physical functional ability in order to assess capacity for postponing dependence in old age. All participants were healthy community-dwelling women representing three different age-cohorts of 65, 75 and 85 year-old subjects. The 65 and 85 year-old participants of the training group took part in physical class-based exercises for eight months with one session of 60 min a week, whereas the 75 year-old women trained twice a week over eight months. The multicomponent training consisted of various exercises typically involving body awareness, rhythm, aerobic performance (walking), muscle strength and muscle endurance, flexibility, reaction and balance exercises. Physical ability was measured as physical performance test (PPT), isometric muscle strength of the trunk, hip and leg, aerobic capacity and walking speed. This shows that regular training can significantly improve physical ability of elderly women with regard to PPT, maximal oxygen uptake and maximal walking speed, suggesting that both young-old and old-old women are able to benefit from regular tailored exercise training. Thus, physical training of old community-dwelling women appears to represent a prophylactic remedy that merits further research aimed at evaluating the preliminary findings of the present studies in larger, less selective groups of participants.     

Salmeterol and physical performance at -15°C in hghly trained nonasthmatic cross-country skiers

The aim of this double-blind. placebo-controlled, cross-over study was to investigate possible improvement in physical performance at an ambient temperature of −15°C by an inhaled dose of 50 μg salmeterol in 8 highly trained nonasthmatic cross-country skiers. FEV₁ was measured before, during and after the treadmill exercise protocol, which consisted of a warm-up run. runs of 10 min at 90%, and 5 min at 80% V O_2max, followed by a timed run to exhaustion. Despite a significant improvement in FEV₁, salmeterol did not have a beneficial effect on heart rate, blood lactate concentration, respiratory exchange ratio, oxygen uptake or minute ventilation during the exercise protocol. Running time to exhaustion was not significantly different from placebo. This lack of enhancement of exercise performance in healthy endurance athletes further supports the recent approval of salmeterol for prophylactic use by asthmatic athletes during training and competition.     

Criterion validity of a two-kilometer walking test for predicting the maximal oxygen uptake of moderately to highly active middle-aged adults

This work examined whether prediction models based on a 2-km walking test are valid for predicting the Vo_2max of middle-aged, healthy, moderately to highly physically active adults. Sixty-seven 35- to 45-year-old moderately active men and women and 44 35- to 55-year-old healthy men who participated regularly in marathon-long sports competitions were studied. Vo_2max was determined in an uphill walk-run on a treadmill. The 2-km walking test was conducted on a flat outdoor course. The subjects walked the distance as fast as they could. Walking time, heart rate at the end of the walk, age and body mass index were entered in the prediction formulas as established in the original study. The total errors of prediction and the correlation coefficients between the measured and predicted Vo_2max (ml-kg⁻¹ min⁻¹) for the moderately active women and men and for the competitors were 5.2, 5.7 and 7.7 ml kg⁻¹ min⁻¹ and 0.55, 0.79 and 0.60, respectively. The measured relative Vo_2max was slightly underpredicted in all groups. The results suggest that the 2-km walk test is a reasonably valid test of maximal aerobic power for moderately fit men and women, but less valid for very fit individuals.     

A multi-stage shuttle run as a predictor of running performance and maximal oxygen uptake in adults.

The aim of this study was to assess the validity of a 20 metre multi-stage shuttle run (20-MST) as both a field test of cardiorespiratory endurance and as a predictor of competitive performance in a 10 kilometre (10 km) race. Nine male subjects (age 35.4 +/- 5.8 years) (mean +/- SD) underwent a laboratory test of maximum oxygen uptake on a treadmill (VO2 max 59.0 +/- 9.9 ml.kg.-1min-1), completed the 20-MST (score 105 +/- 23.7 laps/11.4 +/- 2.7 paliers) and competed in a 10 km race (finishing time 41.8 +/- 7.3 minutes). Analysis using Pearson's Product Moment Coefficient revealed high correlations between these variables (20-MST vs. VO2 max, r = 0.93; 20-MST vs. 10 km, r = -0.93; VO2 max vs. 10 km, r = -0.95). These results confirm that the 20-MST is a valid field test of cardio-respiratory endurance and suggest that it can additionally be used to predict relative running performance over 10 km.     

Lung function, arterial saturation and oxygen uptake in elite cross country skiers: influence of exercise mode

Arterial desaturation during exercise is common in endurance-trained athletes, a phenomenon often more pronounced when the muscle mass engaged in the exercise is large. With this background, the present study monitored seven international-level cross country skiers performing on a treadmill while running (RUN), double poling (DP; upper body exercise) and diagonal skiing (DIA; arm and leg exercise). Static and dynamic lung function tests were performed and oxygen uptake was measured during submaximal and maximal exercise. Lung function variables (including the diffusion capacity) were only 5-20% higher than reported in sedentary men. Vital capacity was considerably lower than expected from the skiers' maximal oxygen uptake (VO(2max)), but the maximal ventilation followed a linear relationship with VO(2max). None or only a mild desaturation was observed in DP, RUN and DIA. Blood lactate concentration was slightly higher in DIA than in DP but not different from RUN. In DIA, VO(2max) was 6.23 +/- 0.47 L/min (mean +/- SD), which was 3.8% and 13.9% higher than in RUN and DP, respectively, with similar peak heart rates for the three exercise modes. No relationships were present either between the degree of desaturation and pulmonary functions tests, or with peak oxygen uptakes. The low blood lactate accumulation during the exhaustive efforts contributed to the arterial oxygen saturation being mild in spite of the very high oxygen uptake observed in these skiers.     

Aerobic fitness in young Norwegian men: a comparison between 1980 and 2002

The purpose of this study was to compare the maximal oxygen uptake (VO2max) in 18-19-year-old Norwegian men from 1980 to 1985 and 2002. In addition, we investigated the relationship between VO2max and education and smoking habits in the sample from 2002. From 1980 to 1985, VO2max was predicted using the Astrand-Rhyming bicycle test for 183 610 eighteen-year-old Norwegian men (91% of the male Norwegian population in this age group). In 2002, the same test was performed on a representative sample of the same age population (N=1028). VO2max (mL x kg(-1)x min(-1)), decreased by 8%, body weight increased by 7% and body mass index (BMI) increased by 6% over the approximately 20-year period (P<0.01). Results from the 2002 sample revealed that smokers had a lower VO2max than non-smokers and vocational students had a lower VO2max than academic students (P<0.05). The average reduction in VO2max was because of an increased number of men with low or very low VO2max, and a reduced number of men with high VO2max values. This is of particular concern since the prevalence of lifestyle-related diseases is higher in groups with low VO2max.