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Biomedical subjects

E Cafarelli

Publications and source records attributed to E Cafarelli.

52 records · Page 3Linked to original sources
PubMed1982

Effect of pH on sensation and vastus lateralis electromyogram during cycling exercise.

Six male subjects performed 30 min of cycling exercise: 15 min at 50% of maximum oxygen consumption (VO2 max) and 15 min at 80% VO2 max. On random days subjects ingested 300 mg/kg body wt of NH4Cl to induce acidosis, NaHCO3 to induce alkalosis, or CaCO3 as a placebo during a 3-h preexercise period. Blood pH at the onset of exercise was 7.238 in acidosis, 7.435 in alkalosis, and 7.394 in the placebo control. A direct ratio scaling technique was employed to measure the sensation of how hard exercise felt. Sensory intensity increased twofold after 15 min at 50% VO2max (P less than 0.01). There was no effect of pH on how hard exercise felt during 50% VO2max bouts. Sensory intensity at the end of heavy exercise increased 20% more in acidosis but was not different in alkalosis compared with placebo (P less than 0.05). There was no difference in integrated electromyogram (EMG) between conditions, but there was an average 13% integrated EMG increase by the end of exercise (P less than 0.05). Plasma lactate was lower in acidosis and higher in alkalosis than placebo at 80% VO2max. These data indicate that during heavy exercise acidotic pH accelerates the change in sensory intensity, but this phenomenon is not necessarily associated with changes in the integrated surface EMG.

Acidosis↗
PubMed1982

Peripheral contributions to the perception of effort.

The effort of any brief static or dynamic muscular contraction is probably sensed as force. Force sensation may operate according to one of the following three mechanisms: 1) feedforward, where a copy of central motor outflow is fed directly to the sensory cortex; 2) feedback, afferent input to the cortex from peripheral receptors activated by contracting muscle; and 3) feedforward + feedback, expected and actual results of contraction are compared and continuously adjusted. Using both static and dynamic contractions as models, data have been obtained that support either feedforward or feedback mechanisms. It is suggested that experimental circumstances have much to do with isolating one part of a system that probably contains feedforward and feedback elements.

Animals↗
PubMed1979

Circulatory regulation during exercise in different ambient temperatures.

Three relatively fit subjects performed duplicate 20- to 25-min cycle ergometer exercise bouts at moderate and heavy intensities (40% and 70% Vo2 max) in ambient temperatures of 20, 26, and 36 degrees C. They approached a steady state in internal body temperature (Tes) in all but the heavy exercise in the heat, where Tes rose consistently, averaging 38.84 degrees C at the termination of exercise. Cardiac output (Q), estimated by a rebreathing technique, was proportional to Vo2 and independent of the body temperatures, except during the lower exercise intensity in the heart, where Q averaged 1.31 . min -1 higher throughout. In any environment, forearm blood flow was linearly related to Tes above the Tes threshold for vasodilation, but during heavy exercise in the heat this relationship was severely attenuated above a Tes around 38.0 degrees C, when forearm blood flow exceeded 15 ml.min -1 .100 ml -1. Plasma volume decreases during exercise were primarily a function of the intensity of exercise. During heavy exercise in the heat the relative vasconstriction contributes to the maintenance of an adequate stroke volume preventing a fall in Q. In this case, circulatory regulation has precedence over temperature regulation.

Adult↗
PubMed1978

Effect of contraction frequency on effort sensations during cycling at a constant resistance.

Five subjects performed 6 min of cycling exercise at a constant resistance (2 kg) and three pedalling frequencies (30, 50 and 75 rev.min-1). The resulting exercise intensities required 32, 45, 68% of their average Vo2max. Electromyographic tracings (EMG) from the left quadriceps and magnitude estimates of overall effort sensations were made continuously. There was no difference in the area of the smooth rectified EMG resulting from frequency or number of contractions. Slopes of the effort-time functions were not significantly different between 30 and 50 rev.min-1 and thus raised the issue of discriminability between cycling exercise intensities. The difference in slope between 50 and 75 rev.min-1 was significant (p less than 0.01). Oxygen uptake averaged for all subjects reached steady state between about 2-3 min of exercise but magnitude estimates of effort increased continuously during exercise. Thus, no correspondence was found between effort and Vo2 when the peripheral signal to the effort sense was held constant. It is concluded that the second input to the effort sense does not arise from cardiovascular and respiratory responses to oxygen demand from the periphery.

Electromyography↗
PubMed1977

Peripheral and central inputs to the effort sense during cycling exercise.

The relationships between some physical and physiological events, and perceived effort were studied at several equivalent work outputs (W) at two pedalling rates (30 and 60 rev-min-1). Subjects judged effort throughout a 4 min exercise bout. After 4 min at any W it was always more effortful to pedal at 30 rev-min-1 even though there were no differences in VE, VO2, or integrated electromyography per minute (IEMG-min-1) between pedalling rates. Effort was related to VO2 and IEMG-min-1 but it was more effortful to pedal at 30 rev-min-1. Effort was also related to pedal resistance and IEMG of single contractions but was influenced by pedalling rate after 4 min of exercise. At any resistance it was more effortful to pedal at 60 rev-min-1, however, when effort was plotted as a function of resistance after 15 s, there was virtually no effect of pedalling rate. The rate effect grows with time from the onset of exercise and appears to be related to the central signal to the effort sense. The interaction of peripheral and central signals suggests a model of the effort sense during 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↗