3-minute Rest Period Research Articles

Different Effects of Concentric and Eccentric Muscle Actions on Plasma Volume

The effects of concentric (CON) and eccentric (ECC) contractions on A plasma volume (PV), heart rate (HR), and lactate in responses to protocols in different body positions were investigated. CON or ECC contractions were performed in either a single-exercise (6 sets of 12 repetitions of leg extensions completed at 80% of 12 repetition maximum [12RM] with 3-minute rest periods) or multiexercise (4 sets of 10 repetitions for both CON and ECC trials of bench press, leg extension, military press, and leg curl at 80% of 10RM with 90-second rest periods) protocols. HR and lactate increased significantly for both protocols from pre- to postexercise for CON but not ECC trials. APV was greater following both CON single-exercise (−11.48 ± 1.38%) and multiexercise (−4.64 ± 0.33%) trials vs. ECC single-exercise (−1.62 ± 1.69%) and multiexercise (−1.26 ± 1.20) trials. Data demonstrate ECC exercise in response to single and multiexercise protocols at the same absolute workload as CON exercise produces less cardiovascular stress.

Different effects of concentric and eccentric muscle actions on plasma volume.

The effects of concentric (CON) and eccentric (ECC) contractions on Delta plasma volume (PV), heart rate (HR), and lactate in responses to protocols in different body positions were investigated. CON or ECC contractions were performed in either a single-exercise (6 sets of 12 repetitions of leg extensions completed at 80% of 12 repetition maximum [12RM] with 3-minute rest periods) or multiexercise (4 sets of 10 repetitions for both CON and ECC trials of bench press, leg extension, military press, and leg curl at 80% of 10RM with 90-second rest periods) protocols. HR and lactate increased significantly for both protocols from pre- to postexercise for CON but not ECC trials. DeltaPV was greater following both CON single-exercise (-11.48 +/- 1.38%) and multiexercise (-4.64 +/- 0.33%) trials vs. ECC single-exercise (-1.62 +/- 1.69%) and multiexercise (-1.26 +/- 1.20) trials. Data demonstrate ECC exercise in response to single and multiexercise protocols at the same absolute workload as CON exercise produces less cardiovascular stress.

Plasma von Willebrand factor in Thoroughbreds in response to high-intensity treadmill exercise

Abstract Objective To determine whether plasma von Willebrand factor (vWf) concentration changes in horses during and after treadmill exercise. Animals 5 mature, fit Thoroughbreds. Procedure A blood sampling catheter was placed in the right jugular vein. A warm-up period was followed by a 3-minute rest period. Horses were galloped at racing pace until fatigued (about 2 minutes). Blood samples were collected prior to warm-up, during the postwarm-up rest period, 1 minute into the run, at cessation of the run, and 5 to 120 minutes after cessation of the run. vWF activity was measured by ELISA and corrected for plasma volume changes (measured by changes in plasma albumin concentration). Platelet-poor plasma from 10 clinically normal, resting horses was pooled, assigned a value of 100 U/dl, and served as a control for all assays. Results vWf activity began increasing 1 minute after horses reached full speed. At 5 minutes after cessation of exercise, vWf values had increased by mean of 92% (P < 0.05) from baseline. vWf activity returned to baseline by 15 minutes after exercise, and remained there until 90 minutes after exercise, when it began to increase. Conclusion and Clinical Relevance The spontaneous decrease in vWf values after completion of exercise was unexpected because vWf has a long half-life in circulation. This unexpected finding is compatible with increased vWf consumption and suggests that microvascular trauma may occur in horses during strenuous exercise. (Am J Vet Res 1997;58:71–76)

Reliability of Isokinetic Measurements of Trunk Muscle Performance

The purpose of this investigation was to assess the reliability of isokinetic trunk muscle performance. Sixty-one volunteers participated (29 men, 32 women; age range, 20-60 years). All subjects were without low-back symptoms at the time of testing. All testing was performed with the subject initially standing, using speeds of 60, 120, and 180 degrees per second. Ten repetitions of flexion and extension were performed reciprocally at each speed, with a 3-minute rest period between speeds. Test-retest intervals were 1 and 3 weeks from the initial test. Peak torque-to-body-weight ratios, extension-to-flexion ratios, and average work per repetition were calculated for each speed for flexion and extension. Data were analyzed with analysis of variance, intraclass correlation coefficients, and Pearson correlation coefficients. Intraclass correlation coefficient values ranged from .74 to .88 for measurements derived from peak torque, and from .88-.93 for measurements derived from work (with the exception of .69 for men at 180 degrees/sec). Standard error of measurements ranged from 8 to 32 ft-lb, with a tendency to increase with increasing speeds. It was concluded that, when using this protocol, isokinetic measurements of muscle function offer the clinician sensitive and reliable measurements of trunk muscle performance and that incorporating increased practice with women and longer rest periods with men may further decrease error associated with these isokinetic trunk strength measurements.

The measurement of fatigue in hot working conditions.

Abstract The N.S.W. Division of Occupational Health was requested to provide information to assist a Mines Rescue Station to choose a type of self-contained breathing apparatus which would be likely to permit the greatest duration of exposure of Mines Rescue personnel to hot and humid environment whilst performing heavy work, without collapse. A number of subjects were tested in a heat chamber, performing a work cycle of 2 minutes duration, followed by a 3-minute rest period, at temperatures of 30°c, 35°c, 38°C and 4l°c Dry Bulb with a Wet Bulb temperature about 1° lower in each case, until the subject was either unable to continue or until the rectal temperature reached 38·8°c to 38·9°c. Pulse rates, skin temperature, and sweat losses were also recorded. The experiments confirmed that a rectal temperature of 38·8°c to 38·9° will, in most cases, coincide closely with the onset of exhaustion. Sweat loss and pulse rate were found to be unreliable methods of measuring fatigue and that skin temperature was completely unreliable as an index of fatigue except when the temperature and humidity were high.