Mechanical power during maximal treadmill walking and running in young and elderly men

Joint power, joint work and lower limb muscle activity for transitions between level walking and stair ambulation at three inclinations

To enhance human mobility, training interventions and assistive lower limb wearable robotic designs must draw insights from movement tasks from daily life. This study aimed to analyze joint peak power, limb and joint work, and muscle activity of the lower limb during a series of stair ambulation conditions. We recruited 12 subjects (25.4±4.5 yrs, 180.1±4.6 cm, 74.6±7.9 kg) and studied steady gait and gait transitions between level walking, stair ascent and stair descent for three staircase inclinations (low 19°, normal 30.4°, high 39.6°). Our analysis revealed that joint peak power, limb and joint work, and muscle activity increased significantly compared to level walking and with increasing stair inclination for most of the conditions analyzed. Transition strides had no increased requirements compared to the maxima found for steady level walking and steady stair ambulation. Stair ascent required increased lower limb joint positive peak power and work, while stair descent required increased lower limb joint negative peak power and work compared to level walking. The most challenging condition was high stair inclination, which required approximately thirteen times the total lower limb joint positive and negative net work during ascent and descent, respectively. These findings suggest that training interventions and lower limb wearable robotic designs must consider the major increases in lower limb joint and muscle effort during stair ambulation, with specific attention to the demands of ascent and descent, to effectively improve human mobility.

ECT generalized seizure drives heart rate above treadmill stress test maximum

OBJECTIVES

Heart rate (HR) accelerates with the electroconvulsive therapy (ECT) seizure and decelerates when it ends. The peak HR during ECT seizure has been reported to reflect clinical impact. We aimed to identify the expected range for ECT peak HR and how it varies with age and sex, as a reference in clinical use.

METHODS

We examined medical records for the maximum peak seizure HR over the ECT course for all ECT patients over defined periods at 2 clinical sites. Methohexital-succinylcholine anesthesia was usually used. Subject totals were 87 men and 90 women.

RESULTS

Electroconvulsive therapy peak HR was 140 to 180 bpm and did not fall with age through 80 years, separately for men and women. A few patients lay outside this cluster and showed age-related decrease. Overall and including the extreme elderly, peak HR fell by 0.29 bpm/yr.

CONCLUSIONS

Electroconvulsive therapy seizure peak HR less than 140 bpm points to weakness of the ECT seizure (and need to increase stimulus dose), cardiac disease, or medication effect limiting HR. Electroconvulsive therapy peak HR exceeds treadmill exercise maximum HR after 60 years and falls significantly less with age than the 0.7 to 1 bpm/yr reported for maximum HR with treadmill exercise stress. These comparisons suggest that ECT peak HR and treadmill maximum HR are limited by different aspects of physiology, and that exercise HR is limited by metabolic demand and humoral activity rather than the heart itself.