effects of exercise on somatosensory-evoked potentials
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Intern. J. Neuroscience, 113:315–322, 2003Copyright 2003 Taylor & Francis0020-7454/03 $12.00 + .00DOI: 10.1080/00207450390162119
EFFECTS OF EXERCISE ONSOMATOSENSORY-EVOKED POTENTIALS
SERPIL BULUT
Firat UniversityFaculty of MedicineDepartment of NeurologyElazig, Turkey
RECEP ÖZMERDIVENLIHALE BAYER
Firat UniversityDepartment of Physical EducationElazig, Turkey
The aim of this study was to investigate the effect of acute and regularexercise on somatosensory-evoked potentials (SEP). The study group wasdesigned as 9 female and 7 male volleyball players, and the control groupas 9 female and 7 male sedentary students. The P1 and P2 latency andamplitude values were measured by tibial nerve stimulation on both lowerextremities in the study groups before and after exercise on a treadmill.Intra-group comparison was made to evaluate the acute effects of exer-cise, and inter-group comparison for the chronic effects of it.
Statistically significant difference was determined in pre-exercise rightP2 amplitudes and post-exercise left P2 latencies of female volleyballplayers and sedentary girls. There was significant difference betweenonly the pre-exercise left P2 latency when comparison was made be-tween the sportsmen and sedentary male subject groups. There weresignificant differences between the pre-exercise left P1 and P2 latencyvalues of sportswomen and right P2 amplitudes of sedentary femalesubjects. There was no significant difference between left P2 latencyvalues of sportsmen and sedentary male subjects.
Received 13 August 2002.Address correspondence to Dr. Serpil Bulut, Firat University, Faculty of Medicine, Depart-
ment of Neurology, TR23119 Elazig, Turkey. E-mail: [email protected]
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In conclusion, it was determined that acute and regular exercise shortenedthe latency of sensory-evoked potentials while decreasing their ampli-tudes. When evaluating the sensory-evoked potentials in electrophysiol-ogy laboratories, the exercise capacity and physical activity levels ofthe subjects should be considered.
Keywords exercise, somatosensory-evoked potentials
Somatosensory-evoked potentials (SEP) are an electrophysiologicaltechnique in which peripheral and central nervous systems can beevaluated simultaneously. SEP response parameters reflect patholo-gies that affect the somatosensory pathways from peripheral nerve,spinal cord, and up to the sensory cerebral cortex. Pathologies in-volving the peripheral nervous system, medulla spinalis, and soma-tosensory tracts reaching to sensory-cerebral cortex cause changesin SEP. Physiological factors such as age, height, and length ofextremity are known to affect SEP latencies and amplitudes (Harper& Michael, 1999).
The object of this study was to evaluate and discuss the effects ofregular and acute exercise on somatosensory pathways by comparingthe SEP responses of both volleyball players and sedentary subjects.
MATERIALS AND METHODS
Volunteers among the students in Firat University, Physical Educa-tion and Sports Academy, and Faculty of Science-Literature wereelected as subjects in this study. The protocol of this study wasapproved by the local Ethics Committee for Human Use in Re-search. All subjects were informed thoroughly about the details ofthe study, and questioned about their own length of sports life, dailyschedule of the exercise, and systemic diseases. Among the volun-teers, 9 volleyball girls devoid of systemic diseases and who hadsimilar duration of sports life, daily length of exercise, age, height,and head circumference were included in the first study group, and7 volleyball boys with similar features were included in the secondstudy group. The control subjects were characterized by the lack ofregular physical training. Then, 9 sedentary girls were included inthe study group 3, and 7 sedentary boys in group 4.
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Effects of Exercise on Somatosensory-Evoked Potentials 317
Before the study, all subjects underwent a thorough neurologi-cal examination and nerve conduction studies for one upper andone lower extremity. Body temperature was measured by usingmouth thermometer before and right after exercise, and every 10min thereafter until it dropped to the pre-exercise level (Magnie etal., 1998).
Subjects were placed on their backs on the examination table in aquiet room to record the SEP potentials. First right then left lowerextremity tibial nerves were stimulated by superficial stimulator be-hind the medial malleolus by the help of Dantec Keypoint Electro-myography device (DANTEC, DK-2740 Skovlunde, Denmark). Thestimulus duration was set as 0.2 ms, the interval as 2 s, and theintensity as the 50% excess of the minimal stimulus enough to getminimal remote muscle response. A needle electrode was used forrecordings. An active electrode was placed on scalp 2 cm behindvertex, and the reference on frontal region in the midline. A groundelectrode was placed on forehead. The recording electrodes wereestablished on the same position during exercise. Filters were ad-justed to 0.5–2000 Hz, analysis interval as 200 ms, and the averageresponse of the 250–500 stimuli was taken. Latencies and ampli-tudes of P1 and P2 waves were measured as milliseconds (ms)and milliVolt (mV), respectively. SEP responses were repeatedafter the normalization of the body temperature in the post-exerciseperiod.
Subjects performed aerobic exercise on a treadmill (Star Trae Tr900) set at the speed of 3.2 km, and an incline of 2% for 12 min. Inall groups, the heart rate was kept below 170/min during the exer-cise by the help of a heart rate monitoring device placed on the leftauricular pulp.
Windows SPSS program was used for statistical analysis. Age,height, weight, length of sports life, head circumference, body tem-perature before and after exercise, and resting heart rate values ofthe groups were compared by Kruskal-Wallis One-Way ANOVATest. SEP latencies and amplitudes before and after exercise foreach group were evaluated by Wilcoxon-Rank test. Mann WhitneyU test was used in comparing the pre-and post-exercise values ofthe sportsmen and sedentary girls (Group 1 and 3) and boys (Group2 and 4), respectively.
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RESULTS
After comparing the subjects by demographic features, no differ-ence was noted among all groups in terms of age, head circumfer-ence, and body temperature taken before and after exercise. Motorand sensory nerve velocity, amplitude, and latency values of thecompound muscle, and nerve action potential were within the nor-mal range limits of our laboratory. Resting heart rates were found tobe significantly higher in the sedentary groups (Group 3 and 4) inrespect to the sportsmen groups (p < .001) (Table 1). Also, a sig-nificant difference was noted regarding the length of sports life inthe sportsmen groups (p < .05) (Table 1). In order to eliminate theeffects of physiological factors on evoked potentials, inter-groupcomparison was made only between the groups with similar demo-graphic features (Group 1–3 and Group 2–4).
Comparing the SEP latencies and amplitudes of sedentary andsportsmen girls (Group 1–3), pre-exercise right P2 amplitudes andpost-exercise left P2 latencies were found to be significantly differ-ent (p < .001, p < .05, respectively) (Table 2).
SEP latencies and amplitudes of all groups recorded before andafter exercise when body temperature normalized were comparedwith each other. There was a decrease in sportswomen post exerciseamplitude and latency values of SEP but this decrease was statisti-cally significant only for left P1 and P2 (p < .01, p < .05, respec-tively) (Table 2). In sedentary female subjects (Group 3), there weresignificant differences in right P2 latency (p < .05), right P2 ampli-
TABLE 1. Demographic characteristics of the groups (mean ± standard deviation)
Group 1 Group 2 Group 3 Group 4(n = 9) (n = 7) (n = 9) (n = 7)
Age (years) 21.1 ± 1.9 20.2 ± 1.3 21.4 ± 0.9 19.5 ± 0.9Height (cm) 162.3 ± 5.6 162.6 ± 5.1 180.4 ± 4.1 172.7 ± 3.0Weight (kg) 57.6 ± 4.3 63.4 ± 7.1 58.2 ± 3.5 66.2 ± 3.1HC (cm) 57.2 ± 1.2 58.8 ± 1.0 57.4 ± 1.3 59.1 ± 0.8LSL (years) 4.5 ± 2.4 6.1 ± 2.1 – –RHR 55.3 ± 3.2 50.5 ± 4.7 75.4 ± 5.7 72.7 ± 4.3BT (pre-ex) 36.5 ± 0.4 36.3 ± 0.7 36.6 ± 0.5 36.5 ± 0.6BT (post-ex) 36.6 ± 0.3 36.4 ± 0.6 36.6 ± 0.8 36.7 ± 0.3
HC = head circumference; LSL = length of sports life; RHR = resting heart rate; BT = body temperature.
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Effects of Exercise on Somatosensory-Evoked Potentials 319
TABLE 2. Comparison of pre- and post-exercise SEP responses in Group 1 and 3 (mean ±standard deviation)
Group 1 (n = 9) Group 3 (n = 9)
Pre-exercise Post-exercise Pre-exercise Post-exercise
Right P1 latency 35.55 ± 2.19 35.87 ± 1.62 38.04 ± 3.49 35.28 ± 1.32(ms)
Right P2 latency 55.01 ± 2.99 54.53 ± 2.91 55.27 ± 1.41a* 50.32 ± 1.67a*
(ms)Right P1 amplitude 1.98 ± 0.09 1.65 ± 0.17 3.06 ± 0.81 2.08 ± 0.30
(mV)Right P2 amplitude 1.71 ± 0.06b‡ 1.45 ± 0.24 4.71 ± 0.19b‡,a‡ 1.59 ± 0.74a‡
(mV)Left P1 latency 35.84 ± 2.00a† 28.07 ± 2.21a† 35.10 ± 1.59a† 29.08 ± 1.37a†
(ms)Left P2 latency 55.01 ± 2.78a* 48.04 ± 2.76a*, b* 59.04 ± 2.76 54.81 ± 2.26b*
(ms)Left P1 amplitude 3.02 ± 0.68 2.14 ± 0.61 3.17 ± 0.70 2.95 ± 0.58
(mV)Left P2 amplitude 1.74 ± 0.18 1.89 ± 0.09 2.54 ± 0.36 2.01 ± 0.11
(mV)
aIntra-group, binter-group.*p < .05; †p < .01; ‡p < .001.
tude (p < .001), and left P1 latency (p < .01) (Table 2). There weresignificant differences between left P2 latency value of sportsmenand sedentary male subjects in both intra-group and inter-group com-parisons (p < .01, p < .05, respectively) (Table 3).
DISCUSSION
Despite the known effects of some physiological factors on soma-tosensory-evoked potential responses, few studies exist about theeffects of exercise on SEP responses (Allison et al., 1983; Delpontet al., 1991; Magnie et al., 1998; Psatta & Matei, 1988; Sokol et al.,1981). Shortening of “time to reaction,” improvement of musclestrength, and increment of physical capacity in sportsmen are clinicalevidence of the exercise effect on neurophysiological parameters.
Different results have been obtained in the studies investigatingthe effects of acute exercise and regular exercise on evoked potentials.Thomas et al. (1991) evaluated the pre- and post-exercise auditoryevoked responses (AER) in the bicycle riders and concluded that
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post-exercise III and V wave latencies were relatively shortened,which correlated with the post-exercise body temperature elevation.On the other hand, Magnie found no difference between pre-exer-cise VEP and AER recordings and post-exercise recordings takenafter the normalization of the body temperature, and found no spe-cific effect of exercise on the evoked potentials (Magnie et al., 1998).
In this study, volleyball players and sedentary subjects with simi-lar demographic features were investigated to determine whetherthere was a physiological effect of acute and regular exercise onevoked potentials unrelated to the body temperature elevation. Pre-exercise P1 and P2 waves in sedentary and sportsmen subjects werecompared to investigate the effects of regular exercise on SEP re-sponses. Despite the fact that all wave latency values of the sports-men group were smaller than those of sedentary group, this differ-ence was statistically significant only for P2 latency value.
In studies investigating the effects of isometric contraction onSEP at cortical levels, a decrease in SEP amplitude during contrac-tion has been reported, but the possible mechanism responsible forthis decrease in amplitude has not been completely revealed (Chuang
TABLE 3. Comparison of pre- and post-exercise SEP responses in Group 2 and 4 (mean ±standard deviation)
Group 2 (n = 7) Group 4 (n = 7)
Pre-exercise Post-exercise Pre-exercise Post-exercise
Right P1 latency 37.35 ± 1.92 38.07 ± 1.55 40.11 ± 3.11 39.80 ± 2.61(ms)
Right P2 latency 58.55 ± 2.32 56.60 ± 1.97 58.94 ± 4.95 58.45 ± 4.84(ms)
Right P1 amplitude 1.35 ± 0.22 0.74 ± 0.43 2.07 ± 0.28 1.46 ± 1.13(mV)
Right P2 amplitude 1.21 ± 0.15 1.05 ± 0.79 1.39 ± 0.10 1.26 ± 0.77(mV)
Left P1 latency 38.24 ± 1.85 38.58 ± 1.31 39.58 ± 2.54 39.94 ± 2.79(ms)
Left P2 latency 58.10 ± 1.25a†,b* 52.57 ± 2.11a† 62.98 ± 1.49a†,b* 56.22 ± 2.16a†
(ms)Left P1 amplitude 1.74 ± 0.10 1.66 ± 0.88 2.02 ± 0.20 1.76 ± 1.75
(mV)Left P2 amplitude 1.38 ± 0.07 1.32 ± 0.86 1.20 ± 0.08 0.96 ± 0.46
(mV)
aIntra-group, binter-group.*p < .05; †p < .01; ‡p < .001.
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Effects of Exercise on Somatosensory-Evoked Potentials 321
et al., 1999; Huttunen et al., 1991; Jones et al., 1989; Nishihira etal., 1996; Rossini et al., 1996).
The most remarkable parameter (latency and amplitude of rightP2, latency of left P1) change was observed in sedentary femalesubjects. The sedentary females experienced the most difficulty intolerating the applied exercise protocol, whereas in sedentary malesubjects, a post-exercise decrease in P2 latency was the only param-eter to be statistically significant. The difference between male andfemale sedentary groups may be explained by less physical activityof females than their male counterparts in Turkey. This may alsosuggest that acute exercise has more influence on somatosensorialtracts. The sportsmen were less affected by acute exercise comparedto sportswomen, since their age in sports was longer and their sportsperformance was better than the sportswomen. This may be ex-plained by adaptation of the peripheral and central nervous systemto the exercise.
Despite the reports of acute exercise on visual and auditory evokedpotentials in sedentary and sportspersons, to our knowledge there isno report on the effects of exercise on SEP (Magnie et al., 1998;Thomas & Mitchell, 1996). The most striking finding of this studyis that the amplitude of measured waves was smaller in all sportspersonsthan in sedentary subjects and this value was even reduced afterexercise. This finding indicates that regular exercise has decreasingeffects on amplitude of SEP as observed in reflex responses (Ozmer-divenli et al., 2002). The finding that the smaller wave amplitudesof the males with higher sports age than females supports this hy-pothesis. The finding of longer P1 and P2 latency values in themale study group than the female study group may be explained bythe fact that this group was taller than the female study group.
In conclusion, this study reveals that acute and regular exerciseleads to a decrease in amplitude and shortening in latency of the SEPvalues. In electrophysiological evaluation of SEP, the exercise capac-ity and physical activity levels of the subjects should be considered.
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