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Biomedical subjects

N H Secher

Publications and source records attributed to N H Secher.

239 records · Page 14Linked to original sources
PubMed1977

Central and regional circulatory effects of adding arm exercise to leg exercise.

7 young, healthy, male subjects performed exercise on bicycle ergometers in two 20 min periods with an interval of 1 h. The first 10 min of each 20 min period consisted of arm exercise (38--62% of Vo2 max for arm exercise) or leg exercise (58--78% of Vo2 max for leg exercise). During the last 10 min the subjects performed combined arm and leg exercise (71--83% of Vo2 max for this type of exercise). The following variables were measured during each type of exercise: oxygen uptake, heart rate, mean arterial blood pressure, cardiac output, leg blood flow (only during leg exercise and combined exercise), arterio-venous concentration differences for O2 and lactate at the levels of the axillary and the external iliac vessels. Superimposing a sufficiently strenuous arm exercise (oxygen uptake for arm exercise greater than 40% of oxygen uptake for combined exercise) on leg exercise caused a reduction in blood flow and oxygen uptake in the exercising legs with unchanged mean arterial blood pressure. Superimposing leg exercise on arm exercise caused a decrease in mean arterial blood pressure and an increased axillary arterio-venous oxygen difference. These findings indicate that the oxygen supply to one large group of exercising muscles may be limited by vasoconstriction or by a fall in arterial pressure, when another large group of muscles is exercising simultaneously.

Adult↗
PubMed1976

The aerobic demands of rowing in two Olympic rowers.

The relationship between rowing speed and Vo2 was determined on two Olympic oarsmen while rowing the single, double and coxless pair shells. The speeds covered ranged from 120 to approximately 300 meters/min and resulted in oxygen demands from 1.2 to 6.45 1 O2/min. First order regression equations described the speed/Vo2 relationship for each shell. Rowing at racing speed in either shell required an aerobic expenditure of 5.8-6.0 1 O2/min.

Adult↗
PubMed1975

Isometric rowing strength of experienced and inexperienced oarsmen.

The significance of isometric muscle strength for rowing performance was studied. The questions investigated were: A) Is the isometric rowing strength (IRS) of oarsmen which is two to three times the dynamic force applied on the oar at maximal power rowing, a ratio which is equivalent to the maximal efficiency of Hill's force/velocity relationship? B) Is IRS higher among successful oarsmen that among those less so? C) Is isometric strength of individual muscle groups correlated to IRS? From measurments on 40 oarsmen the results showed: a) IRS among the most successful oarsmen was 2.6 times the dynamic force indicated in literature; b) IRS was 21 kp higher in the 7 international competitive oarsmen than in 22 national oarsmen, and 42 kp higher than IRS of 11 club oarsmen; and c) of eight other strength determinations only hand grip strength was correlated to IRS. It is suggested that IRS, but not isometric strength of individual muscle groups limits rowing performance.

Adult↗
PubMedDate not supplied

Adaptation of skeletal muscles to training.

Based on the myosin ATPase reaction, human skeletal muscles are composed of two main fibre types, named slow (ST) and fast (FT) twitch fibres, respectively. With few exceptions, ST and FT fibres are evenly represented in the muscles, however with a large interindividual variation. Endurance athletes tend to have a predominance of ST fibres while sprinters have a predominance of FT fibres. The ST fibres are surrounded by 3-4 capillaries, and they have the largest potential for terminal oxidation and the smallest for glycolysis. Of the FT fibres, two subtypes may be distinguished (a and b), of which no FTb fibres are seen in the endurance trained muscles of athletes. Training also results in an increase in the number of capillaries for all fibre types. FTa fibres have a metabolic potential which is intermediate to that of the ST and FTb fibres. With endurance training, the potential for terminal oxidation increases, resulting in a larger ability to use fat as a fuel during submaximal exercise and in a reduced production of lactate. Thus, training has a glycogen sparing effect and endurance increases. Human intercostal muscles appear to have approximately 60% ST fibres. In the external intercostal muscles, the number of capillaries and the occurrence of FTb fibres is similar to the findings in untrained muscles. In contrast, the internal intercostal muscles placed in the mid-axillary line have no FTb fibres and relatively many capillaries. Thus, these (expiratory) muscles appear to be extensively used.

Adenosine Triphosphatases↗