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.     

Rewarming of feet by lower and upper body exercise

Summary The capacity of different types of exercise to rewarm the body, especially the feet, was studied. Six healthy male subjects wearing winter clothing (2.4 clo, 0.37° C·m²·W^–1) were exposed on three occasions to –15° C for 120 min. For the first 60 min the subjects were cooled while sitting motionless and for the latter 60 min they were submitted to cycle ergometer exercise (CE), arm ergometer exercise (AE) or step exercise (ST). The rate of work in CE (about 350 W) served as a reference value for AE and ST. The cooling resulted in an average 1.7 (SEM 0.03) °C decrease in mean body temperature (T _b) corresponding to a 425 (SEM 9) kJ heat debt. The ST increased most effectively mean skin, rectal and lower body skin temperatures as well as dry heat loss. The ST increased T _b by 0.83 (SEM 0.16) °C, CE by 0.10 (SEM 0.11) °C and AE by only 0.07 (SEM 0.12) °C. At the end of the exercise the foot temperature was approximately 6°C higher in ST than in CE. The superior rewarming by ST was apparently due to its low mechanical efficiency. Because the increase in T _b could not explain all the changes in foot temperatures, increased circulation and metabolism of the feet would also appear to have been involved.     

Power output and work in different muscle groups during ergometer cycling

Summary The aim of this study was to calculate the magnitude of the instantaneous muscular power output at the hip, knee and ankle joints during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at 120 watts (W) and 60 revolutions per minute (rpm). The subjects were filmed with a cine camera, and pedal reaction forces were recorded from a force transducer mounted in the pedal. The muscular work at the hip, knee and ankle joint was calculated using a model based upon dynamic mechanics described elsewhere. The mean peak concentric power output was, for the hip extensors, 74.4 W, hip flexors, 18.0 W, knee extensors, 110.1 W, knee flexors, 30.0 W and ankle plantar flexors, 59.4 W. At the ankle joint, energy absorption through eccentric plantar flexor action was observed, with a mean peak power of 11.4 W and negative work of 3.4 J for each limb and complete pedal revolution. The energy production relationships between the different major muscle groups were computed and the contributions to the total positive work were: hip extensors, 27%; hip flexors, 4%; knee extensors, 39%; knee flexors, 10%; and ankle plantar flexors 20%.     

An ergometer bicycle controlled by heart rate

Bicycling, which involves large groups of muscles at work, is a good way of measuring work capacity. Normally in ergometer tests the load is set and the subject's heart rate (HR) is brought into a steady-state value, which might be dangerous for the person. To simplify and unify the test procedure and, in addition, decrease the risk of overloading the subject, a heart-rate-controlled ergometer was constructed. Besides the necessary feedback system, the ergometer is equipped with an automatic readout of the test result.     

潘生丁食管心房调搏复合试验诊断冠心病的实用价值

本文设计了潘生丁食管心房调搏复合试验（ＤＴＴ），并对８０例受检者先后作踏车试验（ＥＴ）、潘生丁试验（ＤＰＴ）、食管心房调搏负荷试验（ＴＥＡＰＴ）、潘生丁踏车复合试验（ＤＥＴ），进行对比分析。结果表明：ＤＴＴ的敏感性及准确性分别高达９０．９％和９１．３％，明显优于ＴＥＡＰＴ、ＤＰＴ和ＥＴ（Ｐ〈０．０５）。     

Zur ObjektivitÄt,ValiditÄt und ReliabilitÄt der Bestimmung von Erholungsdauern nach Erschöpfungsversuchen bei schwerer dynamischer Muskelarbeit aus Zeitreihen der Herzschlagfrequenz

Zusammenfassung VerlÄufe der Herzschlagfrequenz nach 152 grö\tenteils mehrstündigen Erschöpfungsversuchen von drei mÄnnlichen Versuchspersonen am Fahrrad- und Kurbelergometer werden von drei erfahrenen Beurteilern im Hinblick auf die Bestimmung eines Endes der Erholungsphase beurteilt. Die daraus ermittelten Inter-Rater-ReliabilitÄtskoeffizienten der Erholungszeiten erreichten Werte von 0,87–0,97, je nach dem gewÄhlten mathematisch-statistischen Ermittlungsverfahren. Ein Identifizierungsalgorithmus für das Erholungsende in Angleichung an die Rater-Urteile wird entwickelt, wobei an den Herzfrequenzverlauf angeglichene e-Funktionen und Potenzfunktionen, Steigungskriterien und Streuungskriterien des Zeitverlaufs in die Entwicklung einbezogen werden. Der ausgewÄhlte Algortihmus kombiniert ein Streuungskriterium mit einem Steigungskriterium und erreicht eine Rater-ReliabilitÄt von r=0,9 zu den mittleren Expertenurteilen. Durch eine schrittweise multiple Regressionsrechnung wird geprüft, durch was die Erholungsdauer bestimmt ist: Dominierende Einflu\grö\e (63,8% erklÄrter Varianz) ist die Beanspruchungshöhe bei Arbeitsende/Erschöpfung, quantifiziert durch die Arbeits-Herz-schlagfrequenz und die Bedingungen in der Erholungsphase (18,6% erklÄrte Varianz). Der Einflu\ von Belastungsart (10,6% erklÄrte Varianz) und Belastungshöhe (20% erklÄrte Varianz) ist vergleichsweise geringer. Unterschiede in den Ergebnissen zu bisher in der Literatur vorhandenen werden auf die Unterschiedlichkeit von gesetzten Kriterien der Ermüdung und Erholung im Sinne von Grenzwerten und Grenzbedingungen auch physiologisch diskutierend zurückgeführt.Herrn Prof. Dr. H.-G. Wenzel zum 60. Geburtstag gewidmet     

Prediction of uphill time-trial bicycling performance in humans with a scaling-derived protocol

The present study sought to create a scaling-derived cycle ergometer protocol (SDP) that was derived theoretically and would correlate highly with actual uphill time-trial (TT) cycling performance. Local competitive cyclists each completed the SDP (an incremental test to exhaustion) using their own bicycle mounted on a stationary trainer, together with either a short (6.2 km, 2.9% grade; n=8 men and 5 women) or long-course (12.5 km, 2.7% grade; n=8 men) uphill TT. Maximal power output and power at the ventilatory threshold were determined from the SDP results, as well as maximal oxygen uptake , using standard indirect calorimetry procedures. Actual TT speed correlated very highly with both SDP completion time (r=0.97–0.98) and relative (watts per kilogram; r=0.92–0.97) for both uphill TT races. Correlations between TT speed and more demanding measurements were generally lower and more variable (r=0.54–0.97). These results would indicate that two non-laboratory dependent measurements (SDP completion time and relative ) derived from the SDP are valid markers for predicting actual uphill TT performance. This protocol may be useful to cycling coaches and athletes in identifying talented cyclists or for tracking changes in cycling performance outside of the sports science laboratory environment. Electronic Publication     

Diagnostic Values of Venous Peak Lactate,Lactate-to-pyruvate Ratio,and Fold Increase in Lactate from Baseline in Aerobic Exercise Tests in Patients with Mitochondrial Diseases

Objective Although aerobic exercise tests on cycle ergometry have long been used for initial assessments of cases of suspected mitochondrial disease, the test parameters in patients with final diagnoses of other diseases via the widely used 15 W for 15 minutes exercise protocol have not been fully characterized. Methods We retrospectively reviewed all patients who underwent the test at our institution. We classified the patients with genetic diagnoses or those who met previously reported clinical criteria as having mitochondrial diseases and those with a final diagnosis of another disease as having other diseases. Results were available from 6 patients with mitochondrial disease and 15 with other diseases. Results During the test, elevated venous peak lactate above the upper normal limit of healthy controls at rest [19.2 mg/dL (2.13 mM)] was observed in 3 patients with mitochondrial diseases (50.0%) and 5 with other diseases (33.3%). In the group of patients with elevated venous peak lactate, a lactate-to-pyruvate ratio of >20 was observed in all 3 patients with mitochondrial disease but in only 1 of the 5 with other diseases. More than a 2-fold increase in venous lactate from baseline was observed in 4 patients with mitochondrial disease (66.7%) and 1 with another disease (6.7%). Conclusion Elevated venous peak lactate levels were observed in patients with final diagnoses of other diseases, even under a low 15-minute workload at 15 W. The lactate-to-pyruvate ratio and increase in lactate level from baseline may add diagnostic value to venous peak lactate levels alone.