Muscle Metabolism during Exercise in Hemiparetic Patients

Abstract

1. A group of eight male patients with moderate hemiparesis was studied at rest and during 40 min of exercise on four occasions. Both two-leg and one-leg exercise were performed and each leg was studied separately. Arterial concentrations and leg exchange of carbohydrate substrates and free fatty acids were examined. In addition, the concentrations of intramuscular metabolites for each leg were measured at rest and immediately after exercise. 2. In two-leg exercise, oxygen uptake for the paretic leg was significantly lower than for the non-paretic leg at rest (55%) as well as during exercise (40%). Glucose uptake by the paretic leg was smaller (25–50%) and there was no measurable net leg exchange for lactate. Recordings of pedal pressure indicated that the paretic leg did considerably less work than the non-paretic leg throughout the exercise period. The rate of uptake of oleic acid was lower for the paretic leg (50%) in the resting state but similar for the two legs during exercise. The recovery of 14CO2 from [14C]oleic acid during exercise was significantly reduced for the paretic leg. 3. During one-leg exercise, oxygen and glucose uptakes by the working leg were similar for the paretic and non-paretic leg but lactate release was significantly greater for the paretic leg during exercise (30–45%). 4. The concentrations of ATP and creatine phosphate in the basal state were similar for the two legs. ATP and creatine phosphate fell significantly in the two legs during both the two-leg and the one-leg exercise period. The most marked decrease in ATP was noted for the paretic leg during one-leg exercise. The pattern of glycogen depletion during one-leg exercise for the paretic leg indicated primarily activation of the type II fibres. In contrast, the depletion pattern for the non-paretic leg suggested mainly recruitment of type I fibres. 5. The results indicate that, during exercise, paretic muscle shows a reduced blood flow, an augmented lactate production and a diminished capacity to oxidize free fatty acids. These metabolic derangements may be referrable to an augmented number and increased activation of type II muscle fibres as well as to alterations in the structure of muscle mitochondria. In addition, the present study indicates that one-leg exercise should be preferred to two-leg exercise when studying leg muscle circulation and metabolism in hemiparetic patients.

Human genome comparison of paretic and nonparetic vastus lateralis muscle in patients with hemiparetic stroke

“…In addition, transcript levels for glycerol-3-phosphate dehydrogenase 2 (GPD2), which is integral to muscle glycolysis, are significantly elevated in the paretic compared with the nonparetic leg. These findings are consistent with evidence based on muscle MHC isoform profiles that show that paretic leg skeletal muscle shifts to fast-twitch muscle fibers with increased reliance on anaerobic metabolism during single-leg exercise after stroke [3,12]. Prior muscle biology studies have demonstrated plasticity of muscle fiber composition and enzymatic activity that depend on the specific task requirements of individual muscles [21]; physical activity level [22]; and stimulus applied to the muscle, such as electrical stimulation [20].…”

“…Alterations in skeletal muscle are pronounced on the hemiparetic side after stroke and include gross muscular atrophy, increased intramuscular fat, and a shift to a fast myosin heavy chain (MHC) phenotype with reduced muscle oxidative capacity [8][9][10][11]. These muscle abnormalities after stroke have clear implications, since fast-twitch muscle fibers are more fatigable and have anaerobic metabolism [12]. The loss of slow-twitch fibers that take up glucose in response to insulin is relevant to the high prevalence of insulin resistance in stroke survivors [13].…”

Effects of Use and Disuse on Non-paralyzed and Paralyzed Skeletal Muscles

“…This transformation process was demonstrated early on by Grimby et al as they found that several individuals from seven months to ten years post traumatic SCI were estimated to have approximately 90% fast twitch muscle fibers in vastus lateralis, gastrocnemius and soleus muscles [30]. Likewise, over 3 decades ago Landin and colleagues found that after CVA, there was a shift from slow twitch oxidative muscle fibers to fast twitch anaerobic based muscle fibers of the paretic vastus lateralis muscle [34]. Since then other researchers have Aging and Disease • Volume 7, Number 3, June 2016 4 discovered similar results in various paretic muscle groups [32,35,36].…”

Role of walking-exercise therapy after stroke

“…These fibers fatigue easily and are less sensitive to insulin [55]. After stroke, there is a major shift to fast MHC fiber type [20, 54,56]. Therefore, stroke survivors are supposed to fatigue more rapidly and to be more resistant to insulin response [57,58].…”

“…Paretic muscle also shows an abnormal composition: there is a loss of type I muscle fibers as well as fiber atrophy, and reduced oxidative capacity [52][53][54]. Skeletal muscle contains fibers expressing different myosin heavy chain (MHC) isoforms.…”