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Biomedical subjects

K F Metz

Publications and source records attributed to K F Metz.

33 records · Page 2Linked to original sources
PubMed1986

Chronic low level physical activity as a determinant of high density lipoprotein cholesterol and subfractions.

Physical activity has been associated with reduced risk of coronary heart disease. A mechanism for the reduced risk may be through increased high density lipoprotein cholesterol (HDL-C) and subfractions, in particular HDL2-C. Research associated with increased physical activity investigating HLD-C have assessed the effects of intense aerobic activity. The current research evaluated the relationship between low intensity, long duration activity to HDL-C and subfractions in 35 active postal carriers. Measurements of physical activity via the Large Scale Integrated monitor and reported miles walked, and lipoproteins were assessed at 3-month intervals over a 1-year period. Reported miles walked/day (5.3) was significantly correlated with HLD2-C (r = 0.50, P = 0.003) and approached significance for HDL-C (r = 0.29, P = 0.06). The Large Scale Integrated measures were correlated with HDL-C (r = 0.44, P = 0.008) and HDL2-C (r = 0.44, P = 0.007). Controlling for either age, alcohol consumption, body mass index, or leisure time activity did not reduce the relationship between reported miles walked or Large Scale Integrated readings and HDL2-C, suggesting that the increased HDL-C was the result of long duration, low intensity physical activity.

Age Factors↗
PubMed1986

Effect of blood pH on peripheral and central signals of perceived exertion.

Ten male subjects underwent exercise testing in three modes, arms (A), legs (L), and arms + legs (A + L), after ingesting 0.3 g X kg-1 body weight of either NaHCO3 to induce alkalosis or CaCO3 as a placebo (i.e., six exercise trials). Ratings of perceived exertion (RPE: Borg, 15-pt scale) for the arms (RPE-A), legs (RPE-L), chest (REP-C), and overall body (RPE-O) did not differ between acid-base conditions at 20, 40, or 60% VO2max for all three exercise modes. At 80% VO2max, 1) RPE-A was lower (P less than 0.01) during A; 2) RPE-L was lower (P less than 0.01) during L; and 3) RPE-A and RPE-L were lower (P less than 0.01) during A + L under the NaHCO3 as compared to the CaCO3 condition. Differences were not found for RPE-L during A or for RPE-A during L. RPE-C and RPE-O were lower (P less than 0.01) under NaHCO3 during A, L, and A + L. Blood acid-base, VO2, and cardiorespiratory responses were not differentially influenced by exercise mode. Blood pH was significantly higher under NaHCO3 than CaCO3 at pre-exercise and 80% VO2max. VO2, heart rate, and tidal volume did not differ between acid-base conditions at any exercise intensity. VE and respiratory rate did not differ between acid-base conditions at 20, 40, or 60% VO2max but were significantly lower under NaHCO3 at 80% VO2max. RPE-A and L were positively related to blood [H+], and RPE-C was positively related to VE for all exercise modes.

Acid-Base Equilibrium↗
PubMed1984

Hemoglobin concentration and aerobic work capacity in women following induced erythrocythemia.

The effect of induced erythrocythemia on hemoglobin concentration ([Hb]) and aerobic work capacity was determined for nine women. Cycle tests were performed at prereinfusion (T1), 2 days after a placebo infusion (T2), 2 days postreinfusion of 334 ml of red blood cells (T3), 8 days postreinfusion (T4), and 14 days postreinfusion (T5). T1 and T2 responses did not differ, negating a placebo effect. [Hb] increased from 12.7 g X dl at T1 to 14.7 g X dl at T3 and then remained constant at T4 and T5. Hematocrit increased from 38.1% at T1 to 44.9% at T3 and then remained constant at T4 and T5. Submaximal O2 uptake (VO2) and stroke volume (SV) did not change from T1 through T5. Submaximal cardiac output (Q) and heart rate (HR) decreased from T1 to T3 and then remained constant at T4 and T5. Arteriovenous O2 difference increased from T1 to T3 and then remained constant at T4 and T5. Maximal VO2 was greater at T3 (2.65 l X min-1), T4 (2.66 l X min-1), and T5 (2.60 l X min-1) than at T1 (2.41 l X min-1). Physical work capacity was greater at T3 (10,740 kg X m), T4 (10,980 kg X m), and T5 (10,380 kg X m) than at T1 (8,747 kg X m). Maximal values for Q, HR, and SV were unchanged from T1 through T5. At maximum, arteriovenous O2 difference and Hb flow rate increased from T1 to T3 and then remained constant at T4 and T5. The greater postreinfusion [Hb] improved O2 transport capacity and appeared to regulate circulatory responses.

Adult↗
PubMed1982

Differentiated perceptions of exertion and energy cost of young women while carrying loads.

Differentiated local ratings of perceived exertion from the legs and central ratings from the chest, and oxygen consumption, were determined during load carriage in seven young women. Subjects walked for 6 min at 3.22, 4.83, 6.44, or 8.05 km X h-1 carrying (1) no load, (2) a load equal to 7.5% of body weight (mean: 4.66 kg) or (3) a load equal to 15% of body weight (mean: 9.32 kg). Thus, each subject underwent 12 separate tests. The external loads were in the form of lead pellets carried in a plastic scuba belt worn around the waist. A differentiation threshold was found at 6.44 km X h-1 for the 0% and 7.5% loads and at 4.83 km X h-1 for the 15% load. At speeds below the threshold, the perception of exertion was similar in the legs, chest and overall. At higher speeds, exertion was perceived to be more intense in the legs than overall and less intense in the chest than overall, suggesting that the local legs signal was the dominant factor in shaping the overall sensation of exertion. The oxygen uptake was greater for the 15% load than for either the 0% or 7.5% loads, but was similar for the 0% and 7.5% loads. Findings suggested a critical weight limit for external loads that could be transported without increasing the metabolic cost beyond that required to move the body weight alone. This limit fell between 7.5% and 15% of the body weight. When oxygen uptake was expressed per kg of total weight transported, there was no loss of metabolic efficiency while carrying loads up to 15% of the body weight.

Adult↗
PubMed1982

Effect of induced erythrocythemia on hypoxia tolerance during physical exercise.

The effect of induced erythrocythemia on hypoxia tolerance during physical exercise was determined for five male mountain climbers. Treadmill testing was performed under four conditions: 1) prereinfusion, normoxia (Pre-N); 2) prereinfusion, hypoxia (Pre-H); 3) postreinfusion, normoxia (Post-N); and 4) postreinfusion, hypoxia (Post-H). An altitude of 3,566.2 m was simulated by having subjects breath a gas mixture of 13.5% O2-86.5% N2 at normal barometric pressure. Tests were administered immediately before and 24 h after autologous transfusion of 750 ml of red blood cells. Hematocrit increased from 43.3% at prereinfusion to 54.8% at postreinfusion. Hemoglobin concentration increased from 13.80 g X 100 ml-1 at prereinfusion to 17.63 g X 100 ml-1 at postreinfusion. Maximal O2 uptake (VO2 max, 1 X min-1) increased (P less than 0.05) by 12.8% (3.28 to 3.70) from Pre-N to Post-N and 13.0% (2.62 to 2.96) from Pre-H to Post-H. Treadmill performance time (s) increased (P less than 0.05) by 15.8% (793 to 918) from Pre-N to Post-N and 8.9% (687 to 748) from Pre-H to Post-H. VO2 max decreased by 20.1% from Pre-N to Pre-H and by 9.8% from Pre-N to Post-H. Treadmill time decreased by 13.4% from Pre-N to Pre-H and 5.7% from Pre-N to Post-H. The calculated change in hypoxia tolerance following reinfusion indicated that physiological altitude was improved by 463.6 m. It was concluded that induced erythrocythemia increased hypoxia tolerance during physical exercise.

Adult↗
PubMed1975

Hyperthermia: effect on exercise prescription.

Ten healthy male university students pedaled a bicycle ergometer (Monark) for three sessions each lasting 30 minutes. Each subject worked at an individually predicted work load corresponding to approximately 40% of maximal aerobic capacity. The same predicted work load was conducted at 24 degrees C, 44 degrees C and 54 degrees C for each subject. For practical purposes, the results reveal approximately a one beat per minute increase in exercise heart rate for each 1 degree C increase in ambient temperature above neutral (24 degrees C). The practice of exercising cardiac patients in hot ambient temperatures which produce potentially hazardous heart rate levels was challenged. Seasonal reevaluation of exercise heart rate prescriptions is of importance. Hopefully, these findings will also be of some importance to various community gymnasiums and to self-motivated joggers.

Adolescent↗