Przebieg procesów sensomotorycznych i funkcji bioelektrycznej układu wzrokowego pod wpływem zwiększania intensywności wysiłku fizycznego u młodych aktywnych ruchowo mężczyzn
Authors: Zwierko Teresa 
Published: August 2024

THE EFFECT OF INCREASED PHYSICAL EFFORT ON VISUOMOTOR PROCESSING AND THE BIOELECTRICAL FUNCTION OF THE VISUAL SYSTEM IN PHYSICALLY ACTIVE YOUNG MEN
Sensorimotor processing depends on the functional status of the human body. Empirical and theoretical evidence indicate that information processing might be affected by the intensity of physical activity, complexity of task, selection of a research subjects and experimental procedures. Although there are a number of hypotheses concerning the effect of these factors on sensorimotor processing during exercise, the effect of progressively increased physical effort on visuomotor processing needs to be examined in more detail. On one hand, exercise has a beneficial effect on the excitation and activity of the central nervous system, but on the other, intense physical activity may interfere with neural signal transmission. Therefore, it is important to investigate visuomotor processing during activities with varying physical load and to determine the effect of exercise on consecutive stages of visual information processing. In particular, it is important to determine the neurophysiological correlates of early stages of visual information processing during exercise.
The main objective of this study was to investigate the impact of progressively increased physical effort on visuomotor processing in physically active young men by measuring the latency and accuracy of (motor) reactions to visual stimuli appearing in the central and peripheral vision, and recording the bioelectric response of cells in visual system during the transmission of neural signals. The intensity of physical effort was manipulated using individual load (W) at (1) 40% VO2max (below lactate threshold), (2) 60% VO2max (range of the lactate threshold) and (3) 80% VO2max (above lactate threshold).
Study Objectives:
1. To determine the effect of increased physical effort on latency and accuracy of motor reaction to visual stimuli appearing in the central and peripheral vision in tasks with varying complexity.
2. To determine the effect of increased physical effort on the bioelectric function of the retinal and postretinal visual pathway.
3. To determine the relationship between parameters describing the bioelectric function of visual system and parameters describing changes in the components of motor reaction to visual stimuli appearing in the central and peripheral visual field after progressively increased physical effort.
Study Hypotheses:
H-1. Progressively increased physical effort will affect the accuracy and latency of visuomotor processing. The direction and size of these changes will depend on the intensity of the physical effort. Specifically, as the intensity of physical effort increases the latency of motor response to visual stimuli will be reduced until a critical value of exercise intensity is reached, which will be followed by a significant prolongation of the motor response.
H-2. The accuracy and latency of visuomotor processing after exercise with increasing intensity will depend on the level of complexity of the task. Motor performance will be less accurate and slower when the complexity of the task is higher after exercise with increased intensity of physical effort
H-3. Physical effort will affect the early sensory stage of visual information processing, as measured by changes in the bioelectric function of the retina and postretinal visual pathway.
H-4. There will be a positive relationship between (i) changes in bioelectric response of the retina and postretinal visual pathway and (ii) changes in the course of visuomotor processing after exercise. These relationships will shed light on the nature of the interactions between the functional alterations of neuronal functions in the visual system and the effectiveness of the visuomotor processing after exercise with increasing intensity
Methodology
Subjects. Thirty eight physical education students (experimental group) who were not professional sportsmen (men aged 21.39 &plusmn; 1.2 years) were recruited from the Institute of Physical Culture at the University of Szczecin. All subjects participating in the experiment had intact basic functions of the eye, confirmed by routine eye examinations. In addition, three experiments of the study involved a control group of 15 people, selected according to the same criteria as for the experimental group.
Procedure. Subjects completed one effort test with incremental intensity using a cycloergometer (Monark E834, Varberg, Sweden), The experiment began with a 10 min rest in a reclining position, after which time blood was collected from a finger for biochemical determinations. Subjects completed a 5-min warm up at 25 watt (W). The effort- test commenced at 70 W, with 70 revolutions per min (rpm). The exercise continued with an increasing workload (20 W increments every 3 min) until refusal. During the last 15 sec of each 3-min effort at a given workload, capillary blood samples were drawn from a fingertip for the enzymatic determination of blood lactate concentration (Dr Lange Cuvette Test LKM 140, Germany) using miniphotometer LP 20 Plus (Dr Lange, Germany). Resting heart rate and its change during exercise was measured using a Polar S610 heartrate monitor (Polar, Finland. Oxygen consumption during exercise was estimated using an Oxycon gas analyzer (Jaeger, Germany). Individual lactate threshold was calculated using a linear regression graph log LA and the log of effort intensity. Based on the results of the exercise test, each subject was assigned an individual workload value (W) at (1) 40% VO2max &ndash; load value below the lactate threshold, (2) lactate threshold, which in the case of the experimental group was on average approximately 60% of VO2max ( x % VO2max = 60.79) and (3) 80% VO2max (above lactate threshold).
Dependent Variables. The latency and accuracy of visuomotor processing were measured using the Vienna Test System 29.1 (Schuhfried, Austria). The following parameters were measured: simple motor reaction to stimuli appearing in the central visual field (S1 version), differential motor reaction to stimuli that appear in central visual field (S4 version) and differential motor reaction to stimuli that appear in peripheral visual field (peripheral perception test).
Bioelectrical function of the visual system was evaluated using clinical examinations established in accordance with the current procedures of ISCEV international standards, i.e. protocol established by the International Society for Clinical Electrophysiology of Vision. An electoretinogram was used to evaluate retinal function (system UTAS-E 2000 LKC Technology, Gaithersburg, MD, USA). Retinal bioelectric function was estimated using a full-field flash electroretinogram ERG (LKC UTAS-E-2000 LKC Technology, Gaithersburg, MD, USA.). Visual evoked potentials (VEPs) recordings were recorded to measure the neural conductivity of the visual pathway. VEPs were recorded with a Reti Scan (Roland, Germany).
Three experiments were performed in order to evaluate the effect of exercise on the visuomotor processing. During the experiments tests were carried out to measure reaction times to stimuli appearing in the central and peripheral visual field. The order of the tasks was randomized. The first reaction test (T) recording was performed at rest (T0). A 5-min warm-up on the cycloergometer (max 25 W) with the individually established frequency of revolutions, preceded the first 10-min effort (W1) at an intensity below lactate threshold (40% VO2max, 68-72 rpm). Directly after the effort, reaction test recording was performed (T1). The participant then performed a 10-min effort (W2) at the lactate threshold intensity (60% VO2max, 68-72 rpm), followed by the next reaction test recording (T2). Subsequently, a 10 min exercise was performed (W3), at an intensity above the lactate threshold (80% VO2max, 68-72 rpm) after which the reaction test recording was made (T3). During the experiment, heart rate was monitored. In the control group, the examinations involved 4 reaction test recordings made in 10 min intervals without physical effort.
Two experiments were performed in order to estimate the retinal bioelectric function, (1) under scotopic conditions and (2) under fotopic conditions. In both experiments, monocular stimulation was performed using the right eye. The contact lens electrode was applied to the subject&rsquo;s topically anaesthetised cornea and the first electoretinogram was recorded in resting conditions (ERG0). The subsequent three ERG recordings (ERG1, ERG2, ERG3) were made immediately after efforts with incremental intensities performed on a cycloergometer (W1, W2, W3). Similarly to the previous procedure, W1 was preceded by a 5 min warm-up (R) and the exercise on the cycloergometer during the consecutive 10 min efforts was performed at the established frequency of pedal revolutions (68&ndash;72 rpm). In the clinical experiment, also a fifth ERG examination was made (ERGk) in control conditions &ndash; 1 hour after the completion of the last exercise.
The purpose of the third clinical experiment was to analyze the effects of physical effort with increasing intensity on the visual evoked potentials (VEPs). By using pattern- reversal VEPs elicited by checkerboard stimuli with large and small checks, visual stimulation for right eye was applied. The procedure was conducted as in the ERG experiments.
Results and Conclusions 1. In a group of young and physically active men, progressively increased physical effort caused varied changes (in the direction and range) in the latency of visuomotor processing. Reaction time to visual stimuli decreased during exercise until a critical value of exercise intensity was reached. When the critical value of intensity was reached reaction time stabilized or increased. The critical value of exercise intensity depended on the complexity of the sensorimotor task: the higher the level of complexity, the higher exercise intensity at which the critical point occurred. 2. Changes in the accuracy of responses after progressively increased physical effort were related to the degree of complexity of the task. For tasks of lesser complexity, the accuracy of motor response was not affected by the intensity of exercise. In contrast, when performing tasks of greater complexity, the accuracy of visuomotor processing was enhanced by low-and-moderate intensity effort (40% and 60%VO2max) and accuracy was reduced by high intensity effort (80% VO2max). 3. Bioelectrical retinal cell response depended on the intensity of exercise. The increase in the intensity of exercise distorted the internal functions of retinal cell layers to a greater extent than retinal receptor functions. Consequently, retinal sensitivity to changes in bioelectric function was greater under scotopic conditions than under photopic conditions after increased physical effort. 4. Exercise with increasing intensity affected the course of bioelectrical neuronal activity in the postretinal visual pathway. Changes in the parameters of visual evoked potentials depended on exercise intensity and the type of pattern used in stimulation. Increased exercise intensity was accompanied by the impairment of bioelectrical function in the postretinal visual pathway, indicating the possibility of signal transmission delays caused by visual fatigue induced by exercise. 5. Concurrent and delayed relationship between the bioelectric function of the visual system and the effectiveness of visuomotor processing was observed under the conditions of progressively increased physical effort.