Knee joint function and the energy cost of level walking in soccer players.

OBJECTIVES: To study self reported knee joint problems and the energy costs of level walking in soccer players. METHODS: Seventeen soccer players and twelve control subjects between 18 and 27 years old participated in the study. A questionnaire was used to establish the amount of participation in soccer and the frequency and extent of knee injuries. The physiological cost index (PCI) was used as an index of the energy costs of level walking. RESULTS: Soccer players had a significantly higher PCI than control subjects (p = 0.0001). Control subjects had a mean (SD) PCI of 0.23 (0.06) beats/m and soccer players had a mean PCI of 0.42 (0.12) beats/m. Some 82% of the soccer players experienced knee joint problems, whereas only 25% of the control group had problems. CONCLUSIONS: This study shows that college soccer players have a higher rate of self reported knee problems and higher energy costs of level walking than people who do not play soccer.

The zeta pulse: a new stimulus waveform for use in electrical stimulation of the nervous system.

A new waveform which can be used instead of pulses for general electrical stimulation of the nervous system is described. This new waveform has been called the 'Zeta' pulse. The potential advantages of the use of this waveform are discussed together with a brief review and discussion of the mechanisms of extracellular stimulation in nervous tissue. A circuit diagram for the generation of the Zeta waveform is given.

Prolonged ambulatory canine colonic motility.

Canine gastrointestinal motility is studied at present in animals confined to a small cage or sling. The aims of this study were to record colonic activity over a 24-h period in eight dogs by an ambulatory method. Motility signals from implanted strain gauges were processed and stored via a portable battery-operated amplifier and digital recorder housed in a jacket. Ambulant interdigestive activity was the same as observed in laboratory experiments, with migrating colonic motor complexes (CMCs) and infrequent giant contractions (GCs). Feeding caused a multiphasic alteration in motility for 582.1 +/- 18.1 min (mean +/- SE). There were four distinct phases. During the "early" (0-2 h) postprandial period, phase 1 (mean duration: 55.1 +/- 4.0 min), which was distinguished by CMCs of high frequency and elevated amplitude in the proximal colon, and phase 2 (78.2 +/- 6.2 min), which had CMC characteristics similar to those in the interdigestive period, occurred. Phase 3 (218.8 +/- 13.6 min), a further period of increased motility, and phase 4 (339.1 +/- 14.0 min), characterized by low-amplitude long-duration CMCs, occurred during the "late" (2 h onward) postprandial response. With the exception of phase 3, postprandial phases were not always present following food intake, and their expression was markedly influenced by variations in meal time and by defecation immediately following feeding. Spontaneous defecation was characterized by a variety of motor profiles, with a GC accompanying two-thirds of episodes. We conclude that a more complete picture of canine colonic motility has been documented because of the development of the ambulatory system.

The neurodyne: a simple mains-powered constant-current stimulus isolator.

Electrical stimulation of neuronal tissue is a fundamental part of many experiments in neuroscience. It is now widely accepted that to minimise stimulus artefacts stimulators need to be both constant-current devices and also electrically isolated from ground. This difficult combination of parameters is usually only obtained with battery-powered devices. Here we describe a fully isolated and constant-current mains-powered stimulus interface ('Neurodyne') which is based around a toroidal transformer. It is simple to construct and has the ability to deliver analogue signals as stimuli as well as pulses. The signal amplitude can be up to 20 mA and has a voltage compliance of over 100 V. The device has been shown to perform satisfactorily when applied to a brain slice preparation in vitro.

A low-noise optically isolated preamplifier for use with extracellular microelectrodes.

This paper describes in detail the construction of a low-noise optically isolated preamplifier for recording extracellular action potentials from nerve cell bodies and axons. This preamplifier is less prone to pick up noise from extraneous sources of electromagnetic radiation than non-isolated designs.

Versatile digital data logger: storage of gastrointestinal motility data.

An inexpensive four-channel data logger for recording gastrointestinal potentials is described. A 512 K bytes memory and a sampling speed of 1.25 Hz per channel is adequate for these potentials and permits recordings for up to 27 hours. The small size and light weight allow the device to be carried in a pocket so that recordings can be made while the subject is freely ambulatory. A separate replay unit allows the data stored in the data logger to be presented to a chart recorder or to an interface card in a PC AT. This interface, a Microsoft C vers 5.0 program and the computer display the data as single frames or scrolled, expanded or condensed on either the time or amplitude axis. From the computer the data can be written to a printer and displayed as a chart or to an ASCII format file which can be used for analysis with statistical packages. Examples of recordings from both man and dog are illustrated and the analogue recorded data are compared with data digitally recorded. It is suggested that the data logger has many applications where long-term slow potential changes must be recorded under specially difficult conditions.

Basic instrumentation for fast cyclic voltammetry.

Fast cyclic voltammetry is a new voltammetric technique which has been especially useful for measurements of dopamine release in vivo. This paper describes methods for the construction of a basic fast cyclic voltammetric amplifier, and the associated apparatus necessary to carry out fast cyclic voltammetric experiments.

Isolated constant-current stimulation circuits for neuroscience applications.

A group of mains-powered circuits is described for constant-current stimulation of neuronal tissue. The circuits are linear in form and can be used for sine wave, ramp, or pulse stimulation. Both quasi-isolated and fully-isolated circuits are described.

A simple noise clipping circuit for neurophysiological audio monitors.

A very simple circuit is described which removes the low amplitude components of audio frequency signals, leaving the positive and negative peaks superimposed on a flat baseline. The clipping is symmetrical and adjustable in gain. Thus the baseline noise in audio monitors used in extracellular single-unit recording can be attenuated. This enhances the aural discrimination of single units and reduces aural fatigue.

Solar-powered ventilator alarm.

A ventilator alarm device is described with some unique features. It has a very low current consumption. This allows prolonged operation from small batteries which may be recharged from the ambient light in the room. The device is automatically activated and de-activated by the pressure wave from the ventilator. No external switches or other controls are necessary. The very small size means that the device can be directly attached to a ventilator 'in line' with the ventilator circuit. There are no tubing connexions between the ventilator and the alarm device and no separate shelf-space is required.