DEVELOPMENT OF A TRIAXIAL FORCE PLATFORM FOR THE MEASUREMENT OF FORCE AT A BICYCLE PEDAL

The main purpose of this work is to present the methodology used to develop a triaxial force platform for the use at a pedal bicycle; this platform is based on the flexion of beams where strain gages are bonded for the measurements of force components FX, FY and FZ, as well as the force moments MX and MY. The theoretical analysis of this force platform was realized by the Finite Element method, with the simulation of 384 combinations of static loads (force and moments) at different directions. Deformation data numerically obtained is related to the position were sensors will be placed. Output signals obtained were numerically organized and graphically analyzed, in order to show the mathematical relation between force and strain, which is used to generate a "calibration matrix", free of mechanical coupling which usually appears in multiaxis systems. At last, a test was made, simulating an input load, and the output signal obtained was practically equal

Whole Body Vibration at Different Exposure Frequencies: Infrared Thermography and Physiological Effects

The aim of this study was to investigate the effects of whole body vibration (WBV) on physiological parameters, cutaneous temperature, tactile sensitivity, and balance. Twenty-four healthy adults (25.3±2.6 years) participated in four WBV sessions. They spent 15 minutes on a vibration platform in the vertical mode at four different frequencies (31, 35, 40, and 44 Hz) with 1 mm of amplitude. All variables were measured before and after WBV exposure. Pressure sensation in five anatomical regions and both feet was determined using Von Frey monofilaments. Postural sway was measured using a force plate. Cutaneous temperature was obtained with an infrared camera. WBV influences the discharge of the skin touch-pressure receptors, decreasing sensitivity at all measured frequencies and foot regions (P≤0.05). Regarding balance, no differences were found after 20 minutes of WBV at frequencies of 31 and 35 Hz. At 40 and 44 Hz, participants showed higher anterior-posterior center of pressure (COP) velocity and length. The cutaneous temperature of the lower limbs decreased during and 10 minutes after WBV. WBV decreases touch-pressure sensitivity at all measured frequencies 10 min after exposure. This may be related to the impaired balance at higher frequencies since these variables have a role in maintaining postural stability. Vasoconstriction might explain the decreased lower limb temperature

Thermographic evaluation of hind paw skin temperature and functional recovery of locomotion after sciatic nerve crush in rats

INTRODUCTION: Peripheral nerves are often damaged by direct mechanical injury, diseases, and tumors. The peripheral nerve injuries that result from these conditions can lead to a partial or complete loss of motor, sensory, and autonomic functions, which in turn are related to changes in skin temperature, in the involved segments of the body. The aim of this study was to evaluate the changes in hind paw skin temperature after sciatic nerve crush in rats in an attempt to determine whether changes in skin temperature correlate with the functional recovery of locomotion. METHODS: Wistar rats were divided into three groups: control (n = 7), sham (n = 25), and crush (n = 25). All groups were subjected to thermographic, functional, and histological assessments. RESULTS: DT in the crush group was different from the control and sham groups at the 1st, 3rd and 7rd postoperative days (p,0.05). The functional recovery from the crush group returned to normal values between the 3rd and 4th week post-injury, and morphological analysis of the nerve revealed incomplete regeneration at the 4th week after injury. DISCUSSION: This study is the first demonstration that sciatic nerve crush in rats induces an increase in hind paw skin temperature and that skin temperature changes do not correlate closely with functional recovery