No effect of muscle fiber type on mechanical efficiency during cycle exercise at 1.5 Hz

The mechanical efficiency has been determined for 23 healthy young men to study possible effects of muscle fiber type on efficiency during cycle exercise. Each subject cycled for 10 min at in average 19 different powers ranging from ≈1.0 to 4.6 W kg–1 (70–370 W) while the pedalling frequency was kept constant at 1.5 Hz. The rate of energy release was determined from the steady state O2 uptake measured near the end of each 10 min exercise period. Delta efficiency was taken as the inverse of the slope of regression of O2 uptake on power (dP/dnO2). Gross efficiency at 3 W kg–1 was established, and finally, the efficiency was taken from each subject’s slope of O2 uptake versus power using a common, fixed Y-intercept. Muscle biopsies were taken from the lateral portion of the knee extensor muscle, and muscle fibers were classified as type I or type II. The proportion of type I fibers was 0.50 ± 0.13 (mean ± s), delta efficiency was 0.262 ± 0.010, and gross efficiency was 0.213 ± 0.005. There was no significant correlation between any efficiency measure and the proportion of type I fibers. A two-sided 95% confidence interval on the data suggests that if the efficiency of the two fiber types differed, the difference was less than 12%. For the same subject the efficiency did not differ more than a few percents between low powers where type II fibers may be little engaged and high powers where both fiber types are active. The data therefore support the idea that the efficiency does not differ between type I and type II fibers during cycling at 1.5 Hz

Technical modification of the Metamax II portable metabolic analyser for operation with a breathing apparatus

The O2 uptake of firefighters working in hot and polluted environment is not known. The portable Metamax II might measure the O2 uptake of firefighters using a breathing apparatus. However, the Metamax requires an inspiration signal between two expirations to work properly. When a firefighter inspires from bottles with pressurised air, the inspired air cannot readily be passed through a metabolic analyser. Expired air is on the other hand released to the surroundings and may be sampled for further analyses. In addition, the Metamax II does not tolerate heat, and gases at the scene of fire may damage its delicate sensors. We have modified the Metamax II, producing an artificial inspiration signal after every expiration. We have also protected the instrument from heat at the scene of fire. Expired air was sampled from exercising subjects using a breathing apparatus. The Metamax II instrument was run in the normal and modified modes while the instrumentʼs reported O2 uptake was recorded. Control experiments showed that without an inspiration signal, the instrument did not work reliably. In a typical experiment the reported O2 uptake was only 50% of the true value. In further experiments an artificial inspiration signal was sent to the main unit after every expiration. Then the instrument worked properly although only expired air passed through the Metamaxʼ breathing valve. With proper modifications of the Metamax II, the instrument worked well even if only expired air passed through the breathing valve. The valve may thus be mounted on the outlet of a firefighterʼs breathing mask. The instrument can readily be protected from heat at the scene of fire and thus be used to measure the O2 uptake of smoke divers during realistic exercises in hot and polluted environments

Effect of Computational Method on Accumulated O2 Deficit

The aim of this study was to examine how relationships between exercise intensity and the rate of energy release established in different ways, affect the calculated O2 deficit accumulated during strenuous exercise. Aerobic energy release is readily measured by the O2 uptake, while anaerobic energy release is by definition independent of O2. The latter is not easily measured during strenuous exercise, but it can be estimated using the accumulated O2 deficit principle. We have calculated it using nine different approaches. Thirteen moderately trained persons (three women) volunteered to serve as subjects for cycle ergometry. Their maximal O2 uptake was 2.9 ± 0.6 mmol s−1 (x¯ ± s; 3.9 ± 0.8 LSTPD min−1 ). Our reference method (M0) is based on measuring the steady state O2 uptake at the end of at least ten bouts of 10 min of exercise at constant intensity, varying between 30 and 40% of that corresponding to the maximal O2 uptake and up to a power >90% of the maximal O2 uptake, which is a rather time-consuming method. The outcomes of eight different simpler approaches have been compared with those of the reference method. The main result is that the accumulated O2 deficit calculated depends a great deal on the relationship used to calculate it. A protocol of stepwise increases in exercise intensity every 4 min appeared to work well. A gross efficiency method showed the poorest performance. Another important result is that at constant power the O2 uptake continued to increase beyond 4 min of exercise at all powers examined, also at powers well-below those corresponding to the lactate threshold. Finally, the O2 uptake during loadless pedaling was considerably higher than resting O2 uptake, and it appeared to follow a cubic function of the pedaling frequency. In conclusion, to obtain reliable values of the anaerobic energy release using the accumulated O2 deficit principle, reliable relationships between exercise intensity and O2 demand must be established

Effect of Computational Method on Accumulated O<inf>2</inf> Deficit

The aim of this study was to examine how relationships between exercise intensity and the rate of energy release established in different ways, affect the calculated O2 deficit accumulated during strenuous exercise. Aerobic energy release is readily measured by the O2 uptake, while anaerobic energy release is by definition independent of O2. The latter is not easily measured during strenuous exercise, but it can be estimated using the accumulated O2 deficit principle. We have calculated it using nine different approaches. Thirteen moderately trained persons (three women) volunteered to serve as subjects for cycle ergometry. Their maximal O2 uptake was 2.9 ± 0.6 mmol s−1 (x̄ ± s; 3.9 ± 0.8 LSTPD min−1). Our reference method (M0) is based on measuring the steady state O2 uptake at the end of at least ten bouts of 10 min of exercise at constant intensity, varying between 30 and 40% of that corresponding to the maximal O2 uptake and up to a power >90% of the maximal O2 uptake, which is a rather time-consuming method. The outcomes of eight different simpler approaches have been compared with those of the reference method. The main result is that the accumulated O2 deficit calculated depends a great deal on the relationship used to calculate it. A protocol of stepwise increases in exercise intensity every 4 min appeared to work well. A gross efficiency method showed the poorest performance. Another important result is that at constant power the O2 uptake continued to increase beyond 4 min of exercise at all powers examined, also at powers well-below those corresponding to the lactate threshold. Finally, the O2 uptake during loadless pedaling was considerably higher than resting O2 uptake, and it appeared to follow a cubic function of the pedaling frequency. In conclusion, to obtain reliable values of the anaerobic energy release using the accumulated O2 deficit principle, reliable relationships between exercise intensity and O2 demand must be established

I hvilken grad påvirker omvendt undervisning elevenes læ-ringsutbytte i matematikk på 9. trinn sammenlignet med tra-disjonell undervisning?

The mathematics knowledge of Norwegian students has received much attention in recent years due to the results in TIMSS- and PISA-examinations. Several studies indicate that flipped classroom-teaching provides increased learning outcomes in mathematics. In this study, a quasi-experiment (n = 269) was conducted to compare the learning outcomes of flipped classroom (n = 117) and traditional teaching (n = 152) over eight weeks. The students were tested in two sub-courses in mathematics for the ninth grade (1. surface area and volume and 2. similar shapes and pythagorean theorem). The students' mathematical knowledge was measured using a pretest-posttest design in two rounds where the student's post-pre difference (change) is used as the primary measure of the learning outcome. The students were further classified as high-, medium- or low-performing according to the final grade (respectively 5 and 6; 3 and 4 and 1 and 2 in the Norwegian grade system). A direct interpretation of the results suggests better learning outcomes from traditional teaching. A closer look at the data shows that the students who followed traditional teaching (especially middle- and high-performing students) started at a quite low level and consequently had more room for improvement. During the teaching period, these students improved more, but only up towards the level of the students who followed the flipped classroom. For both teaching programs the improvement was largest for the high-performing students and least for the low-performing ones. The results do not indicate that there is a detectable difference in the outcomes of the two teaching programs for the participants in this study.Matematikk-kunnskapene til norske elever har fått mye oppmerksomhet de siste årene på grunn av resultatene i TIMSS og PISA. Flere studier viser til at omvendt undervisning gir økt læringsutbytte i matematikk. I denne studien ble et kvasiekspriment (n = 269) gjennomført for å sammenligne læringsutbytte av omvendt undervisning (n = 117) og tradisjonell undervisning (n = 152) over åtte uker. Elever på niende trinn ble testet i to delemner i matematikk (1. overflate og volum og 2. formlikhet og pytagoras). Elevenes matematikk-kunnskap ble målt ved en pretest-posttestdesign i to omganger der elevens post–pre differanse (endring) er brukt som det primære målet på læringsutbyttet. Elevene ble videre klassifisert som høyt-, middels- og lavtpresterende etter standpunktkarakteren (henholdsvis 5 og 6; 3 og 4 og 1 og 2). En direkte tolkning av resultatene taler for større læringsutbytte ved tradisjonell undervisning. Et nærmere blikk på dataene viser at elevene som fulgte tradisjonell undervisning (særlig middels- og høyt-presterende elever), startet på et lavt nivå og har derfor hatt et større rom til forbedring. I løpet av undervisningsperioden har disse elevene forbedret seg mer, men bare opp mot nivået til de elevene som fulgte omvendt undervisning. For begge undervisningsoppleggene var det størst forbedringer for de høyt­presterende elevene og minst for de lavtpresterende. Resultatene tyder ikke på at det er en påviselig forskjell i utbyttet av de to undervisningsoppleggene for studiens elevgruppe. &nbsp; &nbsp

Acid-base status of arterial and femoral-venous blood during and after intense cycle exercise

Intense exercise depends on energy from both aerobic and anaerobic processes. These processes produce CO2 and lactate, respectively, and both metabolites affect blood's acid-base status. To examine how the acid-base status of arterial and femoral-venous blood is affected and regulated, seven healthy young men cycled for 2 min at constant power to exhaustion. Blood samples were drawn from indwelling catheters in the femoral artery and vein during exercise and for 1 h after, and the samples were analysed for lactate (La–), acid-base parameters, and plasma electrolytes (Na+, K+, Cl–, La–, HCO3–). The chloride concentration in red blood cells (cClRBC) was also determined to quantify the chloride shift. Arterial (femoral-venous, fv, mean values) blood lactate concentration rose to 13.8 mmol L–1 (fv 15.7), pH fell to 7.18 (fv 7.00), pCO2 changed to 41 hPa (fv 114), and blood bicarbonate concentration was more than halved after exercise. cClRBC rose by 5 (a) and 8 mmol L–1 blood (fv) during exercise. pCO2 and pH fell linearly by the lactate concentration. Consequently, blood bicarbonate concentration fell by 81% of the increase in blood lactate concentration, while blood base deficit rose 30% more than lactate did. Bicarbonate thus neutralised 62% of the total acid load. cClRBC rose in proportion to the amount of hydrogen ions buffered by haemoglobin, and chloride shift amounted to 31% of the total acid load. pH was lower and pCO2 and bicarbonate concentration were higher in femoral-venous than in arterial blood with the same lactate concentrations. The relationship between base deficit and blood lactate concentration did not differ between arterial and femoral-venous blood. In conclusion, after intense exercise pH falls more in femoral-venous than in arterial blood because of a lack of respiratory compensation of the metabolic acidosis