Contributory Factors to Unsteadiness During Walking Up and Down Stairs in Patients With Diabetic Peripheral Neuropathy

Abstract

OBJECTIVEAlthough patients with diabetic peripheral neuropathy (DPN) are more likely to fall than age-matched controls, the underlying causative factors are not yet fully understood. This study examines the effects of diabetes and neuropathy on strength generation and muscle activation patterns during walking up and down stairs, with implications for fall risk. RESEARCH DESIGN AND METHODSSixty-three participants (21 patients with DPN, 21 diabetic controls, and 21 healthy controls) were examined while walking up and down a custom-built staircase. The speed of strength generation at the ankle and knee and muscle activation patterns of the ankle and knee extensor muscles were analyzed. RESULTSPatients with neuropathy displayed significantly slower ankle and knee strength generation than healthy controls during stair ascent and descent (P < 0.05). During ascent, the ankle and knee extensor muscles were activated significantly later by patients with neuropathy and took longer to reach peak activation (P < 0.05). During descent, neuropathic patients activated the ankle extensors significantly earlier, and the ankle and knee extensors took significantly longer to reach peak activation (P < 0.05). CONCLUSIONSPatients with DPN are slower at generating strength at the ankle and knee than control participants during walking up and down stairs. These changes, which are likely caused by altered activations of the extensor muscles, increase the likelihood of instability and may be important contributory factors for the increased risk of falling. Resistance exercise training may be a potential clinical intervention for improving these aspects and thereby potentially reducing fall risk.Diabetic peripheral neuropathy (DPN) is a chronic complication of diabetes, affecting up to 50% of older patients (1,2). It is characterized by sensory loss in the lower limbs, altered sense of joint position, and impaired muscular function, which can result in alterations to gait (1-5). Patients with neuropathy are five times more likely to fall than age-matched controls, with over half of patients reporting at least one fall per year (6,7). Falls while walking down stairs account for 60% of all fall-related deaths, making this activity 10 times more hazardous than level-ground walking (8).

Resistance exercise training increases lower limb speed of strength generation during stair ascent and descent in people with diabetic peripheral neuropathy

“…Despite the speed at which strength was generated being increased significantly at both joints during stair ascent and descent, the time‐to‐peak, previously suggested to be closely related to the speed of strength generation, varied between groups (longer time‐to‐peak of the knee extensors in the diabetes intervention groups (with and without neuropathy) during stair descent, and a shorter time‐to‐peak of the knee extensors during ascent) and showed no changes in line with the increases in the speed of strength generation after the intervention that were observed previously to differentiate between participant groups (Fig a,b) . An increase in muscle strength as a result of the exercise intervention may therefore be the main causative factor for the faster strength generation observed at the ankle and knee, rather than increased speed of muscular activations.…”

“…The present intervention study follows on from a previously published study by this research group, in which we observed decreased knee and ankle speed of strength generation in patients with diabetes and DPN compared with control subjects during stair ascent and descent, in a larger cohort of patients . The participants from the previous study were given the option to participate in the present interventional study, but because of the time commitment associated with the intervention (1 h per week for 16 weeks, during standard working hours) fewer patients were able to commit to the 16‐week intervention programme than were originally expected.…”

“…The present study shows for the first time that a resistance exercise training intervention can improve the speed of ankle and knee strength generation during stair ascent and descent in patients with diabetes, and particularly in patients with DPN. Previous studies have shown that people with a high risk of falling have a decreased speed of strength generation [6][7][8][9]; therefore, the increased speed of strength generation of the ankle and knee are expected to improve stability during the initial weight acceptance phase of the stair-walking tasks, and ultimately contribute towards reducing the risk of falling on stairs. During the weight acceptance phase of stair ascent and stair descent, strength is rapidly generated to perform an absorptive action, controlling the flexion of the ankle and knee as gravity acts to 'pull' the body down onto the step.…”

“…We have previously shown that during stair ascent and descent, patients with DPN are slower to develop strength at the ankle and knee on initial step contact (measured using the rate of joint torque development), compared with controls [6]. This is important, as previous studies have shown that people who are slower to develop strength at the ankle and knee joints have an increased risk and rate of falling [6][7][8][9]. We have also shown that altered knee and ankle extensor muscle activation patterns in people with neuropathy may be related to the slower strength generation observed [6].…”

“…This is important, as previous studies have shown that people who are slower to develop strength at the ankle and knee joints have an increased risk and rate of falling [6][7][8][9]. We have also shown that altered knee and ankle extensor muscle activation patterns in people with neuropathy may be related to the slower strength generation observed [6]. If the timing and speed of muscle activations can be positively modified, therefore, in people with neuropathy, the speed of strength generation may consequentially be increased during stair ascent and descent, which could in turn reduce the risk of falling.…”