Effects of exercise training on oxygen uptake kinetic responses in women with type 2 diabetes.

Abstract

U ntrained people with type 2 diabetes have been shown to have a re d u c e d VO 2 m a x c o m p a red with nondiabetic people, even in the absence of card i o v a scular disease (1). In addition, it has been re p o rted that VO 2 kinetics are impaired in women with type 2 diabetes (2). The causes of the exercise impairment are unknown, and thus the physiological and clinical significance of these findings warrants further study.VO 2 m a x is the classic measure of overall c a rd i o re s p i r a t o ry fitness and describes the highest oxygen uptake obtainable by an individual for a given form of exerc i s e despite increased eff o rt and increased work rate. In contrast, VO 2 kinetics measure the e fficiency of the card i o re s p i r a t o ry re s p o n s e to an imposed work demand. Specific a l l y, VO 2 kinetics describe the rate at which the c a rd i o re s p i r a t o ry system is able to deliver oxygen to skeletal muscle and the rate at which oxygen is consumed by skeletal muscle at the beginning of exercise. VO 2 k i n e t i c s a re measured during repeated submaximal constant-load exercise bouts. The rise to steady state is described by a time constant, .is determined by fitting an exponential c u rve to VO 2 kinetics data ( Fig. 1). A slowed is a marker of impaired oxygen delivery and/or extraction. It takes longer for an individual with a slowed to reach steady state.Although the exercise impairments in diabetes have been described, the eff e c t s of e x e rcise training on VO 2 kinetics in untrained women with diabetes and the baseline impairments discussed above are not well described. Although many studies have examined the metabolic effects of e x e rcise training in subjects with diabetes (3-5), fewer investigators have studied the e ffects of exercise training on card i o v a s c ular parameters such as VO 2 m a x in subjects with diabetes (3,4). In addition, the impact of exercise training on VO 2 kinetics in subjects with type 2 diabetes has not been well characterized. It appears that the exerc i s e e ff o rt expended by people with diabetes may be greater for a given workload (even at very low workloads) than for nondiabetic patients (2). Studying the card i o v a scular response to exercise training in diabetes may provide insight into tre a tment recommendations, such as optimal e x e rcise prescriptions, for this common disease with a significantly increased risk of c a rdiovascular morbidity and mort a l i t y.We hypothesized that VO 2 m a x and VO 2 kinetics would improve with exercise training in women with type 2 diabetes. To A b b re v i a t i o n s : A N O VA, analysis of variance; ECG, electro c a rdiogram; FFM, fat-free mass; FSH, folliclestimulating hormone; LOPAR, Low Level Physical Activity Recall Questionnaire; LV, left ventricular; MET, metabolic equivalent; RER, re s p i r a t o ry exchange ratio. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. O B J E C T I V E-Women with uncomplicated t...

Gymnasium-based unsupervised exercise maintains benefits in oxygen uptake kinetics obtained following supervised training in type 2 diabetes

“…The present findings reveal consistently faster _ VO 2 kinetics (i.e., lower MRT) across a wide range of submaximal intensities after training. These data confirm a previous report of a training-induced reduction in the time constant of pulmonary _ VO 2 during exercise, when the _ VO 2 response was assumed to be monoexponential (Brandenburg et al 1999). However, we used a biphasic or triphasic function to characterise this response (Whipp 2009) and showed that the improved mean response time of _ VO 2 , analogous to the finding by Brandenburg et al (1999), was associated with a significant reduction in the time constant of phase 2, as well as a significant reduction in the time constant and amplitude of phase 3 at the highest intensity.…”

“…The rate at which pulmonary oxygen uptake increases during the initial period of exercise ( _ VO 2 kinetics) is slower in young and middle-aged subjects with type 2 diabetes compared with nondiabetic controls (Regensteiner et al 1998;Brandenburg et al 1999;Bauer et al 2007;MacAnaney et al 2011a), although recent data suggests that _ VO 2 kinetics are not impaired in older men with type 2 diabetes compared with aged-matched healthy controls (Wilkerson et al 2011). There is some debate as to whether the source of the slower _ VO 2 kinetic responses observed in young and middle-aged diabetics is due to reduced O 2 delivery and (or) due to lower levels of O 2 extraction.…”

“…Short-term, supervised exercise training accelerates the kinetic response of _ V O 2 during submaximal exercise (Brandenburg et al 1999) and increases exercise tolerance in type 2 diabetes (reviewed by Zanuso et al (2010)). At present the physiological mechanisms underlying these exercise adaptations are not known, although they might include mechanisms that enhance O 2 delivery to (i.e., cardiac output, muscle blood flow) -and (or) O 2 -dependent metabolism within -contracting myocytes.…”

The Effect of Exercise Training on Physical Fitness in Type 2 Diabetes Mellitus

“…For example, it has been reported that increasing the exercise time by one minute on a Balke protocol stress test (which is equivalent to an increase in oxygen consumption of 1.44 ml/kg/min), reduces the risk of overall mortality in people with diabetes by 7.9% (Blair, Kohl III et al 1995;Brandenburg, Reusch et al 1999 Initial improvements of aerobic capacity appear to be more pronounced in individuals with low fitness regardless of obesity level. This was demonstrated in a study that compared women with T2DM to lean and overweight non-diabetic women in a three month exercise intervention (Brandenburg, Reusch et al 1999). The three groups took part in exercise sessions thrice weekly using a treadmill, a c5'cle ergometer or a rowing machine.…”

Meta-analysis of the effect of structured exercise training on cardiorespiratory fitness in Type 2 diabetes mellitus

“…Furthermore, many characteristics of skeletal muscle are associated with both low insulin sensitivity and low cardiorespiratory fitness (i.e. decreased capillary density, decreased proportion of Type 1 muscle fibres, higher glycolytic to oxidative enzyme ratio) [8,9,10,11,12,13,14,15].…”