Individuals with diabetic autonomic neuropathy (DAN) exhibit an increased resting heart rate but depressed maximal heart rate. Thus, the purpose of this study was to examine the validity of using either percent of heart rate reserve (HRR) or a rating of perceived exertion (RPE) scale to prescribe exercise intensity in diabetic individuals both with and without DAN.
The subjects consisted of 23 individuals with type 2 diabetes, ages 45-75 years, with (DAN; n = 13) or without (No DAN; n = 10) clinical signs of DAN, as assessed by heart rate variability using the expiration-to-inspiration ratio of the R-R interval. Peak aerobic capacity was determined using a graded protocol on a cycle ergometer, with RPE, heart rate, and VO(2) values recorded at each stage.
The subjects were similar with the exception of depressed autonomic function in DAN subjects. Peak respiratory exchange ratio values were significantly higher (P < 0.05) in the DAN group (1.08 +/- 0.02 vs. 1.02 +/- 0.01 in No DAN subjects), although DAN subjects exhibited a significantly lower (P < 0.05) peak exercise heart rate. A similarly highly linear relationship between %HRR and percent VO(2) reserve (VO(2)R) existed for both groups (r = 0.98). A similar slightly weaker relationship (r = 0.94) was found between RPE and %VO(2)R.
In conclusion, in diabetic individuals, %HRR provides an accurate prediction of %VO(2)R and can be used to prescribe and monitor exercise intensity, regardless of the presence of DAN. The RPE scale is also a valid, albeit slightly less accurate, method to monitor exercise intensity in diabetic individuals.
"Again, the time course of the _ VO 2 response was not reported, but the mean ± SD resting _ VO 2 of 3.0 ± 0.40 mL kg -1 min -1 was very similar to the present study. Other studies have assessed resting _ VO 2 using only 3 min for acclimation and 10 min for assessment, making the achievement of a _ VO 2 steady state unlikely and the accuracy of the resting _ VO 2 values questionable (Colberg et al. 2003; Davenport et al. 2008; Mezzani et al. 2007; Rotstein and Meckel 2000; Swain and Leutholtz 1997; Swain et al. 1998 "
[Show abstract][Hide abstract] ABSTRACT: The time necessary to obtain a steady state for an accurate and reliable assessment of resting VO2 remains unclear and was the purpose of this study. Thirty healthy men, aged 17-28 years, visited the laboratory twice for the assessment of resting VO2, which was assessed as follows: (a) 24 h abstention from physical exercise, alcohol, soft drinks and caffeine, (b) fasting for at least 8 h, (c) an acclimation period of 10 min, and (d) 60 min assessment in a supine position. Resting VO2 significantly changed during the 60 min (F = 37.4, P < 0.001), exhibiting a monoexponential decrease before reaching an asymptote. Post hoc pairwise comparisons showed that significant differences existed between consecutive means until the 30 min time point, after which there were no significant differences. The VO2 response across trials exhibited high test-retest reliability, with within-subject coefficients of variations at each time point ranging from 2.8 to 7.0 % and intraclass correlation coefficients ranging from 0.90 to 0.99. The reliability was higher from the 25 min time point onwards. Based on these findings, the following recommendations are made to promote accurate assessment of resting VO2: (a) initiate the resting VO2 measurement with 10 min of acclimation to the assessment apparatus, (b) determine resting VO2 for a minimum of 30 min, until an apparent VO2 steady state has been achieved; and (c) determine resting VO2 for a further 5 min, with the average of this last 5 min of data being regarding as the resting VO2.
"However, one cannot use the normal calculations for heart rate of 220 minus age to calculate the maximum intensity and to derive a target for intensity of exercise, because of the resting tachycardia in patients with autonomic dysfunction. Therefore, individuals must rely on use of perceived exertion to prescribe exercise intensity in diabetic autonomic neuropathy . Chronic exercise is associated with enhanced cutaneous blood flow in Type 2 diabetes , restoration of baroreceptor sensitivity , as well as improved vagal activity and exercise capacity after 12 weeks of endurance training in early cardiac autonomic neuropathy, but not severe cardiac autonomic neuropathy . "
[Show abstract][Hide abstract] ABSTRACT: Diabet. Med. 28, 643–651 (2011)
It has long been recognized that cardiac autonomic neuropathy increases morbidity and mortality in diabetes and may have greater predictive power than traditional risk factors for cardiovascular events. Significant morbidity and mortality can now be attributable to autonomic imbalance between the sympathetic and parasympathetic nervous system regulation of cardiovascular function. New and emerging syndromes include orthostatic tachycardia, orthostatic bradycardia and an inability to use heart rate as a guide to exercise intensity because of the resting tachycardia. Recent studies have shown that autonomic imbalance may be a predictor of risk of sudden death with intensification of glycaemic control. This review examines an association of autonomic dysregulation and the role of inflammatory cytokines and adipocytokines that promote cardiovascular risk. In addition, conditions of autonomic imbalance associated with cardiovascular risk are discussed. Potential treatment for restoration of autonomic balance is outlined.
Diabetic Medicine 06/2011; 28(6):643-51. DOI:10.1111/j.1464-5491.2010.03184.x · 3.12 Impact Factor
"Rather, Swain and colleagues (Swain and Leutholtz, 1997; Swain et al., 1998) showed that %HRR values are more closely related to the values of %V ˙ O 2 reserve (%V ˙ O 2R ), i.e., to a percentage of the difference between resting and peak oxygen uptake. Similar conclusions have been reached in recent studies with obese subjects (Byrne and Hills, 2002), heart disease patients (Brawner et al., 2002), diabetic individuals (Colberg et al., 2003), and elite road cyclists (Lounana et al., 2007). While research has demonstrated that HR is a valid tool to prescribe exercise intensity for lower-body exercise, very few studies have investigated the HR-V ˙ O 2 relationship for upperbody exercise. "
[Show abstract][Hide abstract] ABSTRACT: Previous studies have demonstrated that during lower-body exercise the percentage of heart rate reserve (%HRR) is equivalent to the percentage of the oxygen consumption reserve (%V˙O(2R)) but not to a percentage of the peak oxygen consumption (%V˙O(2peak)). The current study examined these relationships in trained surfboard riders (surfers) during upper-body exercise. Thirteen well-trained competitive surfers performed a stepwise, incremental, prone arm-paddling exercise test to exhaustion. For each subject, data obtained at the end of each stage (i.e., HR and V˙O(2) values) were expressed as a percentage of HRR, V˙O(2peak), and V˙O(2R) respectively and used to determine the individual %HRR-%V˙O(2peak) and %HRR-%V˙O(2R) relationships. Mean slope and intercept were calculated and compared with the line of identity (slope=1, intercept=0). The %HRR versus %V˙O(2R) regression mean slope (0.88±0.06) and intercept (20.82±4.57) were significantly different (p<0.05) from 1 and 0, respectively. Similarly, the regression of %HRR versus %V˙O(2peak) resulted in a line that differed in the slope (p<0.05) but not in the intercept (p=0.94) from the line of identity. Predicted values of %HRR were significantly higher (p<0.05) from indicated values of %V˙O(2R) for all the intensities ranging from 35% to 95% V˙O(2R). Unlike results found for lower-body exercise, a given %HRR during prone upper-body exercise was not equivalent to its corresponding %V˙O(2R). Thus, to ensure more targeted exercise intensity during arm-paddling exercise, individual HR-V˙O(2) equations should be used.
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