The analysis and interpretation of method comparison studies in rehabilitation research.

Rehabilitation researchers are frequently interested in comparing the results of two tests that measure the same function. There are practical as well as financial advantages to having more than one method of assessing a particular component of function. Investigations examining the results of two tests are referred to as method comparison studies and commonly analyzed using the Pearson product-moment correlation coefficient (r). Several researchers have argued that the Pearson r is a measure of linear association (co-variation) between variables and does not provide accurate estimates of direct agreement. We compared several commonly used quantitative methods to establish agreement and have demonstrated that the Pearson r is not appropriate for use in studies where the purpose is to determine whether two instruments are interchangeable. An alternative to the Pearson r for analyzing data from method comparison studies is presented. The new procedure, referred to as the limits of agreement method, is easy to compute and emphasizes the clinical comparability of two instruments (or raters) instead of focusing solely on the statistical relationship.

Effects of velocity of isokinetic training on strength, power, and quadriceps muscle fibre characteristics.

Twenty young men trained the right knee extensors and flexors on an isokinetic dynamometer three times weekly over a 10-week period. During each session, 10 men in the slow training group completed three sets of 8 maximal contractions at a rate of 1.05 rad s-1, whereas the other 10, the fast group, completed three sets of 20 contractions at a rate of 4.19 rad s-1. Subjects wer pre- and post-tested for peak torque and power on an isokinetic dynamometer at 1.05, 3.14, and 4.19 rad s-1. Proportions of muscle fibre-types and fibre cross-sectional areas were determined from biopsy specimens taken before and after training from the right vastus lateralis. When testing was conducted at 1.05 rad s-1, the slow group improved (P less than 0.05) peak torque by 24.5 N m (8.5%), but no change was noted for the fast group. Power increased (P less than 0.05) by 32.7 W (13.6%) in the slow group and 5.5 W (2.5%) in the fast. At 3.14 rad s-1, both groups increased (P less than 0.05) peak torque and power. At 4.19 rad s-1, the fast group increased (P less than 0.05) peak torque by 30.0 N m (19.7%), whereas no training effect was observed in the slow group. There was no significant change in power in either group at 4.19 rad s-1. No significant changes were observed over the 10-week training period in percentages of type I, IIa and IIb fibres, but both groups showed significant increases (P less than 0.05) in type I and IIa fibre areas.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiorespiratory responses to aerobic training by patients with postpoliomyelitis sequelae.

We examined the cardiorespiratory responses of 16 patients with postpoliomyelitis sequelae to a 16-week aerobic exercise program. The patients exercised at 70% of maximal heart rate. Dependent variables were resting and maximal heart rates, systolic and diastolic blood pressures, maximum oxygen consumption, maximum carbon dioxide consumption, respiratory quotient, and maximum expired volume per unit time. The exercise group was superior to the control group in watts, exercise time, maximum expired volume per unit time, and maximum oxygen consumption. No untoward events or loss of leg strength occurred as a result of the exercise regimen. We conclude that the aerobic training program employed in this study is a safe, short-term procedure and that patients with postpolio sequelae respond to training in a manner similar to healthy adults.

Safety and characteristics of exercise testing early after acute myocardial infarction.

Five hundred and seventy physicians, researchers and clinicians (42% response) responded to a mailed questionnaire about the safety and nature of exercise testing conducted less than or equal to 4 weeks after acute myocardial infarction (AMI). Of 570 institutions, 193 reported that they routinely performed testing early after AMI and data were provided on 151,949 tests. A majority (111 or 58%) used a low-level testing protocol, 50 (26%) used symptom-limited testing and 32 (16%) used both types. Testing was routinely conducted less than or equal to 14 days after AMI by 147 (76%) respondents, whereas 46 (24%) tested 15 to 28 days after AMI. Thirty-three (17%) respondents used a standardized research protocol and 160 (83%) did not. There were 41 (0.03%) fatal, 141 (0.09%) major nonfatal and 2,124 (1.4%) other cardiac complications reported during testing. No difference in incidence of major complications was observed at centers using a clinical versus research protocol. Compared with clinic-based testing, hospital-based testing had an increased risk for all major (2.1) and nonfatal major complications (2.1). Although a symptom-limited protocol increased the overall risk for major cardiac complications by 1.9 times compared with a low-level protocol, the incidence of fatal complications during symptom-limited testing (0.03%) was quite low and this greater risk is of dubious clinical importance.

Accreditation in the allied health professions.

Specialized accreditation in the allied health professions can and will fulfill its basic purpose if its efforts are guided by the principle that evaluation must place its emphasis on the outcome of the educational process, no matter how difficult it may be to assess. This requires the commitment and cooperation of both the accrediting body and the institution and program under review. Accreditation is a vitally important and valuable system in higher education in general, and the allied health professions are no exception. If the system is to be effective, however, every temptation must be resisted by all involved parties to debase it by using it for self-serving purposes. A recognized accrediting agency not only has the right, but indeed the responsibility, to ensure that the graduates of a program under review possess the prerequisite knowledge and skills essential for entrance into a given allied health profession. In cases where that minimal standard is not attained, the program should be required to remove those deficiencies in a timely manner or, if sufficiently serious, have its accreditation withheld or withdrawn. There should be no exceptions to this course of action. Every standard or essential adopted should be defensible on sound educational grounds, and every program should be evaluated according to whether it is in compliance. Accrediting bodies must direct their efforts toward evaluating educational quality. They must respect institutional rights and responsibilities and not even attempt to prescribe what will be taught or by whom, or who will administer a given program. The entire accreditation process must account for institutional diversity and should not discourage experimentation, innovation, or modernization. However, the standards and essentials that are ultimately adopted must be applied uniformly and fairly and not in an arbitrary or capricious manner. Hence, it is imperative that the standards and essentials be stated in such a way that they are clear and understandable. For those programs in which an enhancement or upgrading is deemed necessary for one or more aspects of the educational experience, it would be a genuine service to the institution and its consistuency if the accrediting agency could offer sound advice and suggestions for remedying those factors that may be causing or contributing to the observed deficiencies in the educational outcome. Any responsible institution would welcome such an approach, and the outcome should be an upgrading of the program under review with a concomitant enhancement of the profession involved.(ABSTRACT TRUNCATED AT 400 WORDS)

Prognostic endpoint yield of high-level versus low-level graded exercise testing.

The prognostic endpoint yield (PEY) of a low-level (less than or equal to 4.6 METS) vs a high-level graded exercise test administered soon after myocardial infarction was evaluated with 184 patients. Test endpoints considered prognostically significant for future cardiac events were (1) ST segment depression greater than or equal to 1mm, (2) angina pectoris, and (3) complex ventricular beats. Test endpoints were assigned to both low-level and high-level tests if they occurred less than or equal to 4.6 METS; test endpoints greater than 4.6 METS were assigned to the high-level test only. Allowing the 145 patients who were asymptomatic during the low-level test to continue into the high-level protocol revealed a 2.5 times greater occurrence of angina pectoris (38 vs 15), a 3.4 times greater occurrence of ST segment depression (27 vs 8), and twice the occurrences of ventricular beats (4 vs 2). This substantial increase in prognostic endpoint yield was demonstrated in the presence of a significantly longer exercise time with the high-level test (9.0 vs 5.1 min), with no significant difference between protocols for peak heart rate or systolic blood pressure. Therefore, a high-level graded exercise test appears to increase the yield of test endpoints with known prognostic importance.

Kinetic characterization of human heart and skeletal muscle CK isoenzymes.

The purpose of this study was to investigate the kinetic properties of human creatine kinase (CK) isoenzymes partially purified from heart and skeletal muscle. Utilizing the backward CK-catalyzed reaction of creatine phosphate + ADP in equilibrium creatine + ATP, Km values for heart and skeletal muscle CK MM (3.7 mmol/l) were significantly (p less than 0.05) greater than CK MB (2.1 mmol/l) which were significantly (p less than 0.05) greater than mitochondrial CK (1.8 mmol/l) at variable creatine phosphate and fixed ADP concentrations. However, Km values for similar isoenzymes from the two different tissues, i.e., CK MB from heart vs. skeletal muscle, were not different. These results show that kinetic analysis of CK isoenzymes cannot differentiate the tissue source of elevated blood CK isoenzymes after the acute stress of long distance running or after acute myocardial infarction.

Graded exercise testing early after myocardial revascularization surgery.

The response to early graded exercise testing (GXT) was studied in 227 patients at a mean of 15.3 days after myocardial revascularization surgery (MRS). GXT followed a modified Bruce protocol without multiples of resting energy expenditure (MET) restrictions and a target heart rate (HR) of 90% of age-predicted maximal HR. The decision as to precisely when to administer the GXT after surgery was made on an individual case basis by the cardiovascular surgeon and the attending cardiologist. For the data analysis, patients were grouped according to the number of days the GXT was administered after surgery: group 1, 7 to 14 days (n = 164); group 2, 15 to 28 days (n = 46); and group 3, greater than 28 days (n = 17). The use of beta blockers was also determined on an individual case basis by the attending cardiologist rather than on a random basis. Ninety-seven of the 227 patients were on beta blockers. Ventricular ectopic activity (VEA), ST-segment changes (STTC), peak HR, peak systolic blood pressure (SBP), peak rate-pressure product (RPP), and peak METs were assessed during exercise. No major complications occurred during testing. Approximately two thirds (67.4%) of the tests were terminated voluntarily by the patient, and 22.5% were stopped by the attending physician. Only 10.1% of the subjects reached the target HR. Chi-square analysis failed to reveal any association between time of testing after surgery and either STTC or VEA. Analysis of variance failed to reveal any effects of group or beta blocker on peak METs attained during GXT; however, patients not using beta blocker medication attained higher peak HR, SBP, and RPP.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise testing early after myocardial infarction: historic perspective and current uses.

Exercise testing performed earlier than six weeks post-MI is accepted as "standard" medical practice. Although both heart rate-limited and symptom-limited exercise protocols are used with nearly equal frequency, the latter appears more valuable because the prognostic yield is greater without sacrificing patient safety. Treadmill or cycle ergometers are the preferred modes of testing because of higher exercise work loads imposed and increased sensitivity and specificity of results. The physiologic exercise responses to graded work loads among these acute MI survivors include a mean maximal heart rate range of 118 to 136 beats/min, a peak systolic blood pressure between 137 and 170 mmHg, a mean peak double product from 16,000 to 22,400, and a mean maximal work load between 4.8 and 7.0 METS. Exercise findings which are most clinically useful are greater than 1 mm ST segment depression from rest level, presence of angina pectoris during exercise, decrease in systolic blood pressure with increasing work, presence of complex or frequent VEBs, and exercise tolerance less than 4 METS. These exercise findings identify, in recent post-MI survivors, groups of patients that have significantly different estimated future cardiac morbidity and mortality rates. The most consistent indices of multi-vessel coronary heart disease are ST segment depression, angina pectoris, and poor exercise tolerance. The most important role of stress testing in this period post-MI is identification of individuals who urgently need evaluation for coronary bypass surgery. In addition to risk stratification, exercise testing provides valuable information regarding exercise prescription for cardiac rehabilitation, direct psychologic benefit for resuming an active lifestyle, and motivation for exercise participation. Although safety of the early post-MI stress test has not been systematically studied, reports from individual studies indicated low morbidity and mortality. Attesting to this is the frequency with which it is performed as a routine office procedure. Finally, there has been a growing use of this procedure not only among cardiologists but also among internists and family practice physicians.

Short- and long-term prognostic value of graded exercise testing soon after myocardial infarction.

We attempted to determine whether graded exercise testing (GXT) soon after a myocardial infarction (MI) using an unlimited metabolic equivalent (MET) level and target heart rate (HR) of 90% of the age-predicted maximal HR is a safe procedure and yields prognostic results different from tests that use lower level end points. We administered GXT to a random sample of 85 patients at a mean of 14.8 days post-MI. End points that included ST-segment depression (STD), angina pectoris (AP), ventricular ectopic activity, and achieved MET level during testing were evaluated as predictors of cardiac events that include death, recurrent nonfatal MI, and coronary artery bypass graft surgery. We conducted short-term follow-up monitoring for one year after the initial MI and long-term follow-up monitoring for a mean of 864.7 days. No serious complications occurred during testing. Angina pectoris, STD accompanied by AP, and achieved MET level were predictive (p less than .05) of future fatal and nonfatal cardiac events during the first year of follow-up monitoring. Fifty-nine percent of the patients with AP suffered a subsequent cardiac event within one year, whereas only 17% of those without AP experienced another cardiac event. Sixty-seven percent of the patients with both STD and AP had a subsequent cardiac event within one year, but only 22% of those without AP and STD had a subsequent cardiac event. For the long-term follow-up monitoring, the presence of AP and a low achieved MET level during testing were associated with subsequent cardiac events.(ABSTRACT TRUNCATED AT 250 WORDS)

Creatine kinase isoenzyme activities in men and women following a marathon race.

Serum samples from 14 men and 8 women were obtained pre-marathon (48 h) and at 24, 48, 72, and 96 h post-race to quantitate total serum creatine kinase activity (TCK), percentage of creatine kinase MB (CK-MB), and clearance rates (half-lives) of TCK and CK-MB. TCK was measured enzymatically, and the CK-MB isoenzyme was separated by agarose electrophoresis and quantitated by densitometry. The men's and women's post-race mean TCK levels were significantly elevated (P less than 0.05) above pre-race values at 24 h (3322 U . l-1, 946 U . l-1 and 48 h (1787 U . l-1, 508 U . l-1). In addition, CK-MB was significantly elevated both 24 h (5.1%, 3.3%) and 48 h (2.5%, 1.8%) post-race (P less than 0.05). The men's 24-h TCK was 22.3 times the pre-race value, while the women had an 8.6-fold increase in TCK. The mean 24-h post-race CK-MB activities were 166 U . l-1 for the men and 31 U . l-1 for the women. The mean increase in CK-MB activity was 41.5-fold for the men and 7.8-fold for the women. Furthermore, the men had a mean half-life (t1/2) of 30.4 h for TCK and 12.0 h for CK-MB; the women's t1/2's were 29.4 and 16.8 h, respectively. At all time points, the men evidenced significantly (P less than 0.05) higher TCK and CK-MB enzyme activities than did the women.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of fatigue level on rate of force development by the grip-flexor muscles.

Fifteen college-age males were tested for maximum voluntary contraction (MVC) of the grip flexors and were then subjected to five trials in which their strength levels were degraded to either 80%, 60%, or 40% MVC. Immediately following the fatigue bout, the subject released his grip and upon command attempted to squeeze as rapidly and forcefully as possible. Testing was also administered under a non-fatigued state (1.00 MVC); every subject was tested under each condition with the order of administration assigned at random. The data were analyzed based upon the amount of force generated at 4, 8, 16, 32, 64, 128, 256, and 512 ms following the initial deflection from the baseline. All values were normalized by dividing the force expressed by the maximum force developed under that condition at 512 ms. The data analysis revealed that for each fatigue level the pattern of force uptake was sigmoidal; however, differences in normalized force were observed among fatigue levels at 64 and 128 ms. In general, at those time intervals there was an inverse relationship between fatigue level and expressed force. Analysis of the force velocities revealed that during the period from 8 to 64 ms, the rate of tension uptake was adversely affected as the level of fatigue was increased.

Effects of variable fatigue levels on reaction-time components.

The effects of varying fatigue levels on reaction-time components were determined for 20 young, adult males. Each subject squeezed a hand-gripping device until strength decrements of 20, 40, or 60% were recorded; then the subject released his tension and then reacted to an auditory stimulus by gripping as quickly and forcefully as possible. Testing was also conducted under a nonfatigued state, and every subject was tested under all conditions. Total reaction time was divided into (a) a promoter component, the time from the stimulus to an alteration in the EMG of the finger flexors, and (b) a motor component, the time from the change in the EMG to the first sign of tension uptake. Analyses of variance failed to reveal any alterations in either reaction time or promoter time; however, there was a significant (p < .05) elongation of motor time when the muscle was fatigued, with motor time tending to increase linearly as fatigue increased. The results suggest that localized fatigue of this nature is primarily of peripheral (muscular) origin.

Recovery of muscular endurance following submaximal, isometric exercise.

Each of 22 subjects squeezed a hand-gripping device for as long as possible at a tension of 50% of his maximum voluntary contraction. When the prescribed tension could no longer be maintained, the subject was given a predetermined rest period and at its conclusion again squeezed the hand dynamometer in a second all-out bout. The length of the interbout rest period was either 5, 10, 20, 40, 80, 160, 320, 640, 1280, or 2560 sec. Each subject experienced every rest period with the order of administration assigned at random. At least three days intervened between successive testing sessions. The mean time the subjects persisted during the first bout was 120.25 sec. The percentage of recovery, calculated by dividing the holding time of the first bout into the time of the second, ranged from 20.3% after 5 sec of rest to 86.8% following the 2,560-sec rest interval. An analysis of the percentages of recovery at the various time periods revealed that the pattern of submaximal isometric endurance recovery folowed a three-component exponential curve.