Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control
Fatigue effects on body balance
Introduction
The mechanical characteristics of the muscles are not sufficient to compensate for the torques produced by external perturbations leading to stance destabilization. Therefore, balance is actively controlled by the central nervous system (CNS), which calls into action the various relevant postural muscles as and when needed (Nardone et al., 1990). During quiet stance, little activity on the part of the postural muscles is normally required (Schieppati et al., 1994), thanks to the ability of the CNS to anticipate minimal body destabilization. In turn, the CNS relies on proprioceptive, visual and vestibular input. Accordingly, when any of these inputs is defective, body sway increases and muscle activity increases concurrently, in order to maintain balance (see Dietz, 1992).
Apart from the role of the possible alterations in the sensory input, little information exists as to other causes that may affect the control of body balance under specific physiological conditions. In particular, it is not known how fatigue, which is typically an internal perturbation, may alter this function. It was therefore deemed worthwhile to address this issue, all the more so since fatigue is a phenomenon caused by a combination of processes which occur at different sites (Balestra et al., 1992; Sharpe and Miles, 1995; see Enoka and Stuart, 1992, and Gandevia et al., 1995), and is therefore likely to affect a complex task such as body balance in several ways.
With this aim, we compared common indicators of body sway (sway area (SA) and sway path (SP)) prior to and after two types of exercises (treadmill walking and cycle ergometer pedalling), each performed both below and above the threshold of fatigue. It was found that strenuous exercise does indeed affect body balance during maintenance of quiet upright stance, but the consequent increase in sway is short-lasting and of moderate extent. Preliminary results have been presented in abstract form (Schieppati et al., 1996).
Section snippets
Subjects
A total of 13 young healthy subjects were selected for testing (six males and seven females, aged 18–39 years). All gave their informed consent, although the specific aims of the experiments were not conveyed. The local ethics committee approved the use of the experimental procedure. Each subject attended two experimental sessions on different days (three of the subjects attended four sessions on separate days).
Balance assessment
The three components of the force acting on each of the four transducers of a
Fatiguing exercise
All subjects crossed the 60% value of the maximal heart rate in the first part of the exercise (6 min±1.0 SEM). Then the exercise lasted for 19.0±1.0 min (Fig. 1A). The final power output produced by the subjects at the end of fatiguing exercise was, on average, 122.8±13.8 W (Fig. 1B). The final heart rate attained was 93.0±3.1% of the maximum heart rate, i.e. well above the estimated AT (see Section 2) (Fig. 2A). All subjects perceived the exercise either as hard or very hard. On average, the
Discussion
Physical exercise produced various effects on body sway variables in young normal subjects during quiet upright stance. The effects depended on the type of exercise (treadmill walking as opposed to cycling), on the intensity of the work (above or below the estimated anaerobic threshold), and on the visual conditions. All effects appeared immediately after the exercise and had a short duration, vanishing by about 15 min after the end of the exercise.
Treadmill walking produced transient
Acknowledgements
The technical support of Dr Giuseppe Valmadre in preliminary experiments is gratefully acknowledged. Rosemary Alpress scrutinized the English. This study was supported in part by the grants Ricerca Corrente 1996/1997 and Ricerca Finalizzata 1993 from the Ministero della Sanità, Rome, Italy.
References (28)
- et al.
Effects of fatigue on the stretch reflex in a human muscle
Electroenceph. clin. Neurophysiol.
(1992) - et al.
Quantification of postural sway in normals and patients with cerebellar diseases
Electroenceph. clin. Neurophysiol.
(1984) - et al.
The limits of equilibrium in young and elderly normal subjects and in Parkinsonians
Electroenceph. clin. Neurophysiol.
(1994) - et al.
Behind the scenes of cardiopulmonary exercise testing
Clin. Chest Med.
(1994) - American College of Sports Medicine. Guidelines for Exercise Testing and Prescription. Williams and Wilkins, Baltimore,...
- et al.
Slow force recovery after long-duration exercise: metabolic and activation factors in muscle fatigue
J. Appl. Physiol.
(1993) Psychophysical bases of perceived exertion
Med. Sci. Sports Exer.
(1982)- et al.
Perceived exertion related to heart rate and blood lactate during arm and leg exercise
Eur. J. Appl. Physiol.
(1987) - Cresswell, A.G., Heuer, J., Johansson, R., Ovendal, A. and Thorstensson, A. The effect of selective lower leg muscle...
- et al.
Effect of vision and stance width on human body motion when standing: implications for afferent control of lateral sway
J. Physiol. (Lond.)
(1993)
Postural sway in normals and atactic patients. Analysis of the stabilizing and destabilizing effects of vision
Agressol.,
Human neuronal control of automatic functional movements: interaction between central programs and afferent input
Physiol. Rev.
Neurobiology of muscle fatigue
J. Appl. Physiol.
Muscular activity during ergometer cycling
Scand. J. Rehabil. Med.
Cited by (242)
Human-exoskeleton cooperation for reducing the musculoskeletal load of manual handling tasks in orchid farms
2024, Computers and Electronics in AgricultureThe Effectiveness of Active Insoles In Reducing The Impacts of Fatigue on Standing Stability and Balance Among Military Forces: A Biomechanical Evaluation
2023, Journal of Health and Safety at WorkDynamic postural control and physical stress: an approach to determining injury risk in real sporting conditions
2023, German Journal of Exercise and Sport Research