Harald E. Refsum

High density lipoprotein cholesterol, total cholesterol and triglycerides in serum after a single exposure to prolonged heavy exercise

Serum high density lipoprotein (HDL) cholesterol, total serum cholesterol and triglycerides were determined in twenty men before, immediately after, and 1, 2 and 4 days after a 70 km cross-country ski race. HDL cholesterol increased by 12% of the pre-race level immediately after the race, rose further to 17% above the initial level on the following day, and was still elevated 4 days after the race. LDL + VLDL cholesterol, however, showed a tendency to decrease immediately after the race and was reduced by 17% and 11% of the pre-race level on the following 2 days. Triglycerides were reduced by 30% of the initial level immediately after the race, were still low on the following day, but were restored to normal 2 days after the race. It is concluded that a single exposure to prolonged heavy exercise induces changes in the HDL metabolism, showing that the physical exercise per se plays an important role for the increased HDL level seen in well-trained athletes.

Changes in plasma amino acid distribution and urine amino acids excretion during prolonged heavy exercise

Venous plasma and urine amino acids and urea were measured in ten well-trained men, aged 23--45 years, in connection with a 70 km cross-country ski race, lasting 4.39--6.04 h, leading to slight dehydration. The estimated urea production rate during the race was of the order 7.6 mumol/min, kg b.wt, i.e. twice the rate for such men on ordinary protein intake, during ordinary activity, thus suggesting increased protein catabolism. The race led to a fall of the total plasma amino acid concentration to about 60% of the pre-race level. In particular, the branched chain amino acids (valine, iso-leucine, leucine) and alanine were markedly reduced, whereas the S-containing amino acids (taurine, cystine, methionine) and the aromatic (phenylalanine, tyrosine, trytophan, histidine) and glutamine/glutamate were increased, unchanged or only moderately reduced. It is concluded that prolonged heavy exercise is accompanied by increased protein catabolism and changes in the plasma amino acid concentrations similar to those observed during prolonged starvation, but differing from those seen at heavy exercise of less than 2 h duration or prolonged exercise of moderate intensity.

Serum thyroxine, triiodothyronine and thyroid stimulating hormone after prolonged heavy excerise

Serum thyroxine (T4), triiodothyronine (T3) and thyroid stimulating hormone (TSH) was measured before, immediately after and on the following days after a 70 km cross-country ski race in two groups of ten well-trained men, one aged 21--29 years, taking 5.01--7.03 h, and one aged 51--57 years, taking 6.07--7.38 h. T4 was definitely increased immediately after the race, but fell to below the initial level on the following day and was not restored to the pre-race level until 4 days after the race. T3 showed essentially the same pattern, though less pronounced, a major part of the changes being possibly due to plasma volume variations. TSH showed a tendency to rise immediately after the race, but rose further to 175% of the initial level on the following day and was not restored to the initial level 4 days after the race. The pattern of changes were independent of age. It is suggested that the prolonged rise in TSH is probably due to an exercise-induced increased peripheral need for thyroid hormone.

Renal osmol clearance during prolonged heavy exercise

Serum and urine osmolality and creatinine were measured in fifty-eight well-trained men, aged 21-57 years, in connection with three 70 km cross-country ski races taking place under essentially the same external circumstances, leading to slight dehydration. Although the race urine flow was low, 0.51 (0.05-1.10) ml/min, the urine osmolality and the urine to serum osmolality ratio were relatively low, averaging 860 (399-1220) mosm/kg H2O and 2.84 (1.32-4.10), respectively. Decreasing urine flow and endogenou- creatinine clearance were associated with decreasing urine to serum osmolality ratio, indicating declining urine concentrating ability. Thus, the data confirm the authors recent suggestion, based on the measurement of a limited number of urine solutes, that during prolonged heavy exercise a decrease in urine flow and glomerular filtration rate is accompanied by a decline in the urine concentrating ability.

Excretion of casts and uromucoid in urine after prolonged heavy exercise

Excretion of uromucoid, albumin and casts in urine were determined in twenty well-trained men, ten aged 20-30 years, and ten aged 50-60 years, before, during and after a 70 km cross country ski race. During the race there was only a slight increase in uromucoid excretion, but a marked increase in the excretion of casts and albumin. The older subjects had a tendency to lower urine output during the race compared to the younger group. Reduction of urine output below ca. 25 ml/h was accompanied by a conspicuous increase in urine cast and albumin concentrations, with only a slight increase in uromucoid concentration, and even a reduction in uromucoid excretion. No significant relationship was found between cast excretion and uromucoid concentration. Thus the gross cylindruria observed during longstanding exercise must be ascribed to other urinary factors facilitating the formation of casts.