Biomedical subjects

D M Koceja

Publications and source records attributed to D M Koceja.

At least 19 recordsLinked to original sources

PubMed2007

Effect of inversion and ankle bracing on peroneus longus Hoffmann reflex.

This study examined peroneus longus (PL) Hoffmann reflex (H-reflex) during sudden inversion perturbation of the ankle/foot complex under an ankle brace and non-brace condition. Ten healthy subjects volunteered. H-reflexes were tested on the up-sloping portion of the recruitment curve, utilizing a control trial M-wave above motor threshold to maintain consistency between subjects and conditions. The PL H/maximum M-wave (M(max)) ratio was established using the PL H-reflex and PL M(max) peak-to-peak measures. The mean ratio across five trials for each subject under each ankle brace (brace, no brace) and surface (flat, inversion) conditions was utilized for analysis. The 1 x 4 repeated measures ANOVA revealed a significant main effect for treatment condition (P<0.0001). The PL H/M(max) ratio significantly increased during sudden inversion-no ankle brace condition compared with the flat surface no-ankle brace condition (P=0.04). Application of an ankle brace had no effect on PL H/M(max) ratio during inversion (P=0.78). During this study PL H/M(max) ratios increased during an inversion perturbation in healthy ankles. This is believed to occur due to heightened sensorimotor demand placed on the nervous system during this motion. Moreover, application of an ankle brace during inversion does not appear to affect PL H/M(max) ratio.

Adult↗

PubMed2006

Implications for using H-max/M-max ratio in H-reflex parameters for elderly subjects compared with young subjects.

The H-max/M-max ratio has long been used to understand motoneuron excitability induced by the Ia fibers. However, we contend that when comparing young and elderly subjects, this measurement can be controversial. We compared the modulation of the soleus H-max and M-max at five different muscle lengths between elderly and young subjects. The young subjects demonstrated a significant modulation of both H-max and M-max between dorsiflexion (DF) and plantarflexion (PF) positions. In contrast, the elderly subjects demonstrated no difference in H-max and M-max between DF and PF positions. However, it was more interesting to note that those elderly subjects who had similar H-max/M-max ratios to the young subjects at 0 deg showed identical modulation of H-max and M-max to that of the young In this paper, we discuss that H-reflex comparisons between young and elderly subjects may be confounded by the initial H-max/M-max ratio. This finding has implications for both the statistical analysis of this data as well as the theoretical interpretation of H-reflex measurements.

Adult↗

PubMed2004

The effect of the ankle joint angle in the level of soleus Ia afferent presynaptic inhibition.

The factors that are responsible for the relationship between motoneuron excitability and muscle length may have both mechanical and/or neurophysiologic origins. The aim of the study was to investigate the changes in the level of presynaptic inhibition, as measured with a soleus H-reflex conditioning protocol, and muscle length. Ten healthy volunteers were measured at three different ankle angles: 30 degrees plantar flexion, neutral position (0 degrees) and 15 degrees dorsiflexion. At each position the soleus H-reflex and the maximum M-wave were measured while the limb was relaxed. The H-reflex was conditioned by a stimulation of the common peroneal nerve, 100 ms prior to the tibial nerve stimulation. The results revealed that the level of presynaptic inhibition was higher at the neutral position in comparison to the dorsiflexed or plantarflexed positions. Additionally, the HMAX/MMAX ratio was significantly decreased when the joint position was set at dorsiflexion. Further, there was a significant correlation, independent of ankle joint angle, between presynaptic inhibition levels and the HMAX/MMAX ratio. The above findings support the concept that peripheral feedback from passive, static modifications in the joint angle and consequently in muscle length, can modify the input/output threshold of the motoneurons on a presynaptic level.

Adult↗

PubMed2003

Effect of mental imagery of a motor task on the Hoffmann reflex.

Research has found that mental imagery of a motor task may influence the Hoffmann reflex (H-reflex). However, this work has not examined the potential influence of background EMG (BEMG) on the H-reflex. In this study 23 adult participants (M=23.3 years, S.D.=3.2) were instructed to mentally image plantar flexion of the right foot at four intensities: 40, 60, 80 and 100% of maximum voluntary contraction (MVC) after completing practice trials of actual contractions at these intensities. Dependent measures were the BEMG activity and the peak-to-peak amplitude of the H-reflex. On each trial the peak-to-peak amplitude of the soleus H-reflex was measured in the right leg and averaged, BEMG (40 ms bin) was measured in the soleus and tibialis anterior of both legs. Following trials of plantar flexion at the target intensities participants completed 5 imagery trials at each intensity and 15 trials while performing this motor task. Five resting control trials were administered prior to and following the completion of all test trials. Administration of test trials was randomized within conditions. A main effect (P<0.05) for trial blocks was observed for H-reflex amplitude but not BEMG. The H-reflex increased linearly throughout testing, suggesting that the H-reflex was modified by the practice of imagery rather than the intensity of the imagined task.

Adult↗

PubMed2003

Post-activation depression of the soleus H-reflex in the elderly.

OBJECTIVES: This study examined the effect of age on the spinal mechanism post-activation depression (PD) and its relationship with postural sway. METHODS: Two groups, young (n = 10, 25.2 +/- 5.2 yr) and elderly (n = 10, 74.6 +/- 6.3 yr) participated in this study. Soleus H-reflex amplitude (peak-to-peak EMG) was measured prior to and after a passive dorsiflexion about the ankle (from 120 degrees plantarflexion to 110 degrees plantarflexion at 15 degrees/s). All H-reflex measurements were recorded at an ankle joint angle of 110 degrees. For each group, stimulus intensity was set at 25% of maximal motor response (M-max) and PD measurement intervals were randomly assigned at 0, 1, 2, 3, 4, 5, 10, 15, and 18 seconds post-movement. To ascertain whether PD was related to postural sway, standing sway area (mm2) was also measured. Subjects stood motionless (20 second duration) on a Kistler force platform during two conditions: with and without vision. RESULTS: A split-plot ANOVA (Group x Interval) indicated significant differences (F(1.18) = 14.80, p < 0.05) in PD between young and elderly, as well as a Group x Interval interaction (F(10, 180) = 16.02, p < 0.05). Simple main effects identified significant (p < 0.05) intervals at 0, 1, 2, and 3 seconds. The elderly had on average 16.1% less H-reflex depression during the first three seconds after muscle activation. Additionally, a split-plot ANOVA (Group x Condition) indicated significant differences (F(1, 18) = 10.72, p < 0.05) in sway area between young and elderly, but regression analysis indicated post-activation depression and postural sway were not significantly correlated. CONCLUSIONS: It is concluded that the integrity of the Ia-motoneuron synapse as measured with a PD protocol, is different between young and elderly subjects, but that this difference is not related to postural sway.

Adult↗

PubMed2002

Electromyographic changes of agonist and antagonist calf muscles during maximum isometric induced fatigue.

The purpose of this study was to examine electromyographic changes of the agonist and antagonist muscles during fatigue. Nine healthy, untrained subjects exerted a maximum voluntary heel lifting contraction with their dominant limb. The EMG activity over the soleus and the tibialis anterior muscles was recorded during the contraction. The results showed that the torque output during heel lifting and the soleus EMG activity decreased, whereas the tibialis anterior EMG revealed a small but non-significant decrease. However, the ratio of the tibialis anterior to the soleus EMG increased significantly at the end of the fatigue protocol, a fact that reveals that the decrease rate of the antagonist's activity was significantly lower than the decrease rate of the agonist activity. It is concluded that during a maximal fatigue protocol, both the agonist and antagonist muscle activity may decline, however, the slower rate of antagonist's activity decrease relative to the agonist's activity is a finding that requires further investigation. This finding may reflect a higher level of agonist and antagonist muscle co-activation and probably a relatively higher opposing torque from the antagonist muscles at the end of the fatigue session.

Adult↗

PubMed2001

Effect of magnetic insoles on postural sway measures in men and women during a static balance test.

Numerous anecdotal reports have suggested a growing public enthusiasm for magnetic devices for treatment of pain and various motor and sensory dysfunctions. Although the principles behind magnetic therapy are well documented, a complete technical explanation of whether static magnet application is effective is lacking due to a paucity of scientific research. In this study the effectiveness of magnetic insoles on postural sway measures during a single application were investigated. Twenty-eight adults (14 old, 14 young) were assessed on postural sway measures while performing a static two-legged stance test on a Kistler force platform under two treatment conditions (magnetic insoles, nonmagnetic insoles). Significant reductions in total sway area and lateral sway scores were obtained by the older adults while standing on the magnetic insoles. These preliminary results indicate that treatment of postural instability using magnetic insoles may be a viable alternative for older adults.

Aged↗

PubMed2001

Effect of a reduced base of support in standing and balance training on the soleus H-reflex.

The present study provides evidence that a reflex at the segmental level can adapt over a two hour experiment in a functionally appropriate manner in response to a balance training task. Subjects (N=9) received soleus (S) H-reflexes in blocks of seven trials while free standing on a normal base-of-support (NBOS) and while standing on a plafform with a reduced base-of-support (RBOS) in the sagittal plane. During the RBOS condition, the H-reflex served as a postural perturbation. Subjects were instructed to suppress the H-reflex when it was evoked, as an attempt to maintain a balanced state. Background EMG from the S and tibialis anterior muscles, the S M-wave, and stimulus current were maintained at a constant level during the experiment. Subjects initially received a block of NBOS trials, followed by 4 RBOS blocks (training), a second NBOS block, four additional RBOS blocks, and a third NBOS block with the protocol repeated on three different days (D1, D2 and D3) within the same week. The S H/M ratio was depressed 9% upon standing on the RBOS. With training the S H/M ratio decreased by 22% on Dl, 18% on D2 and 6% on D3. The ratio between the H-reflex and background S EMG (H-reflex gain) decreased 10% on D1, 40% on D2 and 23% on D3 when the first NBOS and first RBOS blocks were compared. Due to a slight increase in the S EMG across blocks, the H-reflex gain decreased considerably more across blocks than the H/M ratio. Although the S H/M ratio underwent an 7% decrease from D1 to D3, the differences were not significant. Individually, however, six of the nine subjects decreased their H/M ratios from 12-42% across days. The results may reflect the inception of longer-term adaptations of the segmental stretch reflex system.

Adaptation, Physiological↗

PubMed2000

Postural sway characteristics in women with lower extremity arthritis before and after an aquatic exercise intervention.

OBJECTIVE: To examine the reliability of postural sway assessment in women with lower extremity arthritis and to ascertain the effects of an aquatic exercise intervention program on these measures. DESIGN: The reliability of postural sway measures was analyzed by within-subjects (Subject times Trial) analysis of variance (ANOVA). The effects of aquatic exercise were analyzed by repeated measures ANOVA using a planned comparison approach with an independent 2 x 2 (Group times Test) design. SETTING: Testing in a motor control research laboratory; aquatic exercise in a warm water pool at an area YMCA. PARTICIPANTS: Volunteer sample, 24 women with lower extremity arthritis (rheumatoid [RA] n = 11, osteo [OA] n = 13) randomly assigned into an aquatic exercise group (n = 14) or control group (n = 10). INTERVENTION: Postural sway measures under a two-legged stance test on two separate test days: day 1, pretest; day 2, posttest, administered after a 6-week aquatic exercise program. RESULTS: Reliability correlation coefficients for postural sway measures ranged from .64 to .94 for both subject groups. Aquatic exercise subjects significantly reduced lateral sway and total sway area scores (by 18% to 30%) under both visual conditions after the 6-week intervention. Postural sway scores were significantly higher under the no-vision condition than under the vision condition in each group for both test sessions. Both OA and RA groups had normal sagittal/lateral ratio scores. CONCLUSION: Women with lower extremity arthritis can be reliably assessed on postural sway measures on a stable two-legged stance test. Although they had normal sagittal/lateral sway ratio scores (ie, scores typical for nonarthritic peers), vision played an important role in their postural stability for this balance task. Aquatic exercise reduced postural sway in women with lower extremity arthritis, as demonstrated by a two-legged stance test, and this exercise program appears to be a viable treatment for increasing postural stability in this population.

Analysis of Variance↗

PubMed2000

Environmental changes in soleus H-reflex excitability in young and elderly subjects.

The purpose of this study was to examine the role of task complexity on soleus H-reflex modulation in young and elderly subjects. Twelve young (mean age = 29.2yrs) and 10 elderly (mean age = 75.1 yrs) apparently healthy individuals were examined under four experimental conditions: (1) eyes open on normal floor surface; (2) eyes open on foam floor surface; (3) eyes closed on normal floor surface; and (4) eyes closed on foam surface. Under each condition, soleus H-reflexes, and background electromyography (EMG) (40 ms window prior to stimulation in both the soleus and the tibialis anterior) were recorded. Postural sway in each condition was also assessed using a Kistler force platform. Results indicated differential reflex modulation between young and elderly subjects. Specifically, young subjects depressed the amplitude of the reflex as task complexity was increased. Elderly subjects, on the other hand, increased the amplitude of the H-reflex when utilizing visual cues, but decreased H-reflex amplitude when vision was occluded. Postural sway in both groups increased as task complexity was increased. There existed a significant difference in the relationship between tibialis anterior activation and soleus H-reflex between the two groups. These results demonstrate differential reflex adjustments between young and elderly subjects as task complexity is increased, and may provide useful information pertaining to postural control in the elderly.

Adult↗

PubMed1999

Age differences in postural sway during volitional head movement.

OBJECTIVE: To examine the role of a volitional self-paced head-turn movement on the postural sway characteristics of healthy young and elderly subjects. DESIGN: Cross-sectional design. SETTING: Motor control research laboratory. SUBJECTS: Ten young adults and 10 elderly subjects. MAIN OUTCOME MEASURES: Postural sway characteristics of each subject were examined using a Kistler force platform. Each subject was tested under four experimental conditions: (1) static postural sway with vision; (2) static postural sway without vision; (3) postural sway with vision and self-paced head-turn movement; and (4) postural sway with no vision and a self-paced head-turn movement. Subjects performed six 15-second trials in each experimental condition. Dependent variables analyzed on each trial were mean sway amplitude (in millimeters), sagittal sway standard deviation, lateral sway standard deviation, and frequency of sway (in hertz). RESULTS: During the static conditions (e.g., no voluntary movement), the young subjects produced significantly less postural sway than the elderly in both the vision condition (sway amplitude in the young, 3.80 mm; in the elderly, 4.89 mm) and the no-vision condition (young, 5.44 mm; elderly, 5.95 mm). This increased sway was the result of greater lateral sway in the elderly for the vision condition (3.73 vs. 2.68 mm), and greater sagittal sway for the elderly in the no-vision condition (5.55 vs. 4.70 mm). There were no significant differences between the groups in the frequency of sway. When asked to initiate and complete the head-turn, elderly subjects significantly increased their mean sway amplitude and decreased their frequency of sway, whereas the young subjects did not significantly alter their postural sway profiles. CONCLUSIONS: These results demonstrate different postural sway control strategies for young and elderly subjects when asked to perform volitional movements.

Accidental Falls↗

PubMed1999

Conditioned patellar tendon-tap reflexes in patients with ACL reconstruction.

The patellar tendon-tap stretch reflexes were examined in six neurologically healthy young subjects (mean age = 27.1 yrs) who had developed persistent quadriceps strength deficit due to ACL reconstruction. Each subject was tested on two separate days. A specially designed apparatus was used to examine the unilateral and conditioned patellar tendon-tap reflex response utilizing three different conditioning intervals: 25 ms, 75 ms, 150 ms, and a unilateral reflex (control). Peak isometric force and contraction time were measured by using a strain gauge. Also, peak-to-peak EMG was measured by using bipolar surface electrodes which were placed over the middle of the rectus femoris. All data were collected with a microcomputer (sample rate = 1 kHz). Due to the small sample, the Kruskal-Wallis nonparametric analysis of variance was performed. All subjects demonstrated quadriceps strength deficits in the ACL leg when compared with the contralateral leg. This analysis determined that for both the ACL leg and the Non ACL leg the size of stretch reflex was facilitated at the long-latency conditioning intervals (75 and 150 ms), whereas it was inhibited at the short-latency conditioning interval (25ms). However, the ANOVA model failed to reveal any differences in the conditioned stretch reflex between the ACL leg and the Non ACL leg. Also, no differences were observed at the unilateral condition. Taken together, these results indicate that ACL reconstruction results in significant strength deficits, but does not alter unilateral or conditioned reflex profiles.

Adult↗

PubMed1998

Soleus H-reflex gain in elderly and young adults: modulation due to body position.

BACKGROUND: The control of posture and balance in the elderly is a primary health concern. Postural instability directly leads to a greater incidence of falling in the elderly population. One important neuromuscular mechanism instrumental in the control of posture and balance is the reflex system. The purpose of this study was to examine the gain of the soleus H-reflex in young and elderly adults in two different body positions: standing and prone. METHODS: Eighteen neurologically healthy volunteers were categorized by age in two groups: young (n = 9, mean age = 23.3 yr) and elderly (n = 9, mean age = 71.7 yr). In each position, the resting H-max/M-max ratio was determined. The gain of the reflex was also assessed by instructing the subject to perform voluntary contractions of 10, 20 and 30% of their maximum voluntary contraction, using real-time EMG biofeedback. Data were sampled on-line using custom designed software (sample rate = 2 kHz). Dependent variables included the average background EMG of the soleus muscle (40 ms window prior to stimulation) and the peak-to-peak amplitude of the elicited soleus H-reflex. To examine the gain of the reflex, the peak-to-peak amplitude of the H-reflex was plotted against the background EMG activity for each contraction intensity. RESULTS: Results indicated the following: young subjects significantly depressed the H-max/M-max ratio when standing (69.3% prone, 55.1% standing), whereas elderly subjects increased the ratio (36.1% prone, 54.5% standing). Also, the young subjects modulated the gain of the reflex from prone to standing (3.30 prone, 3.68 standing), and the elderly subjects demonstrated no gain modulation in the different body positions (2.23 prone, 1.91 standing). In both body positions the young subjects demonstrated significantly higher gain that the elderly subjects. CONCLUSIONS: The results demonstrate different control strategies for young and elderly subjects between prone and standing body positions.

Adult↗

PubMed1997

Acetazolamide reduces peripheral afferent transmission in humans.

Carbonic anhydrase has been localized in skeletal muscle and nerve, thus, inhibition with acetazolamide (ACZ) may alter nerve and/or muscle function in healthy humans. ACZ (3 oral doses 14, 8, and 2 h prior to testing) reduced isometric force (37%) and peak to peak electromyographic (EMG) amplitude (1.38 mV to 0.83 mV), while increasing EMG latency associated with a unilateral Achilles tendon-tap. Reflex recovery profiles, following a contralateral conditioning tap, were similar in both placebo and ACZ experiments. ACZ led to significant changes in Hmax/Mmax ratio (52.19/14.42 to 45.73/15.65) and H-reflex latency (34.18 +/- 2.54 ms to 35.24 +/- 2.74 ms). Motor nerve conduction velocity and maximal voluntary isometric torque (knee extensors) were unaltered by ACZ. These data suggest that inhibition of the tendon-tap reflex and associated isometric force, following ACZ, is related to impairment of synaptic integrity between la fibers of the muscle spindle and the alpha motor neuron and not impairment of the muscle spindle or force-generating capacity.

Acetazolamide↗

PubMed1997

Dynamic balance testing with electrically evoked perturbation: a test of reliability.

OBJECTIVE: To investigate the reliability of a newly developed perturbation protocol for assessing dynamic balance. DESIGN: Each subject was tested in two experimental balance conditions, static and dynamic. The dependent variables for the static condition were sway area (SA), sway path length (SPL), sagittal sway standard deviation (SSD), and lateral sway standard deviation (LaSD). During the dynamic condition trials a stimulus was delivered to the tibial nerves of both legs to perturb the subjects. The subjects were instructed to return to the pre-perturbation level of steadiness as soon as possible after the stimulation. The dependent variables for the dynamic condition were dynamic phase duration (DPD), sway path mean (SPM), linear sway standard deviation (LiSD), and sagittal sway standard deviation (SSD). SETTING: The motor control laboratory of a university department of kinesiology. PATIENTS: Ten subjects from a population-based sample of healthy adults. MAIN OUTCOME MEASURE: An intraclass reliability estimate for all dependent measures in the static and dynamic conditions. RESULTS: In the static condition, the variables SA, SPL, SSD, and LaSD had reliabilities of .94, .98, .86, and .92, respectively, and in the dynamic condition the reliability estimates for DPD. SPM, LiSD, and SSD were .90, .71, .80, and .92, respectively. CONCLUSIONS: The results indicate the current technique provides a means of objectively measuring a subject's ability to regain static postural stability following electrically induced perturbation.

Adult↗

PubMed1997

Comparison of soleus H-reflex gain from prone to standing in dancers and controls.

To examine the differences in soleus H-reflex gain between trained dancers and control subjects, the soleus H-reflex amplitude and background muscle activity of 9 trained dancers (means of 20.3 +/- 2.1 years of age, and 14.3 +/- 3.8 years of training) and 9 control subjects (mean 23.3 +/- 3.2 years of age) were compared at rest and at 10, 20, and 30% of a maximal voluntary soleus contraction during two conditions: prone and standing. The ratio of the maximal H-reflex (H-max) to the maximal motor response (M-max) was also measured during both conditions. Correlation was performed between background EMG and the resultant H-reflex to determine reflex gain. The results demonstrated that the control subjects and the dancers displayed a similar reflex gain during the prone condition (slope = 3.30 vs. 3.64, respectively). However, during the standing condition, dancers demonstrated a significantly lower reflex gain (slope = 1.78) than did control subjects (slop = 3.68). Furthermore, although both groups significantly decreased the H-max/M-max ratio from prone to standing, no differences were found between groups at either condition. This suggests that the differences in standing reflex gain between the dancers and control subjects were a product of differential control of reflex modulation involved in postural control. An initial hypothesis explaining the differences between the standing reflex gain of the groups relates to plasticity of central inhibitory control mechanisms, primarily presynaptic and/or reciprocal inhibition.

Adult↗

PubMed1997

A meta-analysis of the past 25 years of weight loss research using diet, exercise or diet plus exercise intervention.

OBJECTIVE: The therapeutic effectiveness of diet, exercise, and diet plus exercise for weight loss in obesity was determined. DATA SOURCES: All human research reported in English, published in peer-reviewed scientific journals within the past 25 y was reviewed. STUDY SELECTION: Acceptance criteria (n = 493 from > 700 studies) were that a therapeutic intervention of diet, exercise or diet plus exercise was employed, specifically for weight reduction in obese adult humans and that weight change was reported numerically. Only aerobic exercise studies were included, while drug, hormone and surgical treatments were excluded. DATA EXTRACTION: All data were extracted by the same investigator from the original research report. Except for gender and program type, all extracted data were numerical. DATA SYNTHESIS: ANOVA, with a Newman-Keuls post hoc test, was used to determine differences among programs (P < 0.05). One analysis was performed on the group mean data and one based on effect sizes. Analyses were repeated using initial body weight, initial percent body fat and program length, as covariates. RESULTS: Primarily, subjects aged 40 y have been studied (39.5 +/- 0.4 y, mean +/- s.e.m.) who are only moderately obese (92.7 +/- 0.9 kg, 33.2 +/- 0.5 body mass index (BMI), 33.4 +/- 0.7% body fat); for short durations (15.6 +/- 0.6 weeks). Exercise studies were of a shorter duration, used younger subjects who weighed less, had lower BMI and percentage body fat values, than diet or diet plus exercise studies. Despite these differences, weight lost through diet, exercise and diet plus exercise was 10.7 +/- 0.5, 2.9 +/- 0.4* and 11.0 +/- 0.6 kg, respectively. However, at one-year follow-up, diet plus exercise tended to be the superior program. Effect size and covariate analyses revealed similar program differences. CONCLUSION: Weight loss research over the past 25 y has been very narrowly focused on a middle age population that is only moderately obese, while the interventions lasted for only short periods of time. The data shows, however, that a 15-week diet or diet plus exercise program, produces a weight loss of about 11 kg, with a 6.6 +/- 0.5 and 8.6 +/- 0.8 kg maintained loss after one year, respectively.

Adult↗

PubMed1997

Heteronymous monosynaptic Ia facilitation from supine to standing and its relationship to the soleus H-reflex.

To measure changes in presynaptic inhibition, 10 subjects (5 male, 5 female) were tested under two conditions: supine and standing. This study utilized the heteronymous facilitation protocol, as described by Hulborn et al. (1987a), to measure presynaptic inhibition of the Ia afferent pathway onto the soleus alpha-motoneuron pool. The magnitude of the facilitation produced by the conditioning stimulus provides an indirect assessment of presynaptic inhibition from supine to standing. Maximal soleus H-reflex (H-max) and motor response (M-max) amplitudes were determined prior to testing at each condition. Subjects received 24 test H-reflex stimuli (approximately 15% M-max), and 24 conditioned stimuli at each body position. Results demonstrated a significant decrease in H-max/M-max ratio from supine (68.7%) to standing (54.8%). This was the result of changes in H-max between the two body positions with no significant changes in M-max. Significant inhibition of the conditioned H-reflex was also demonstrated from supine to standing (30.7% M-max vs 17.5% M-max). Furthermore, it was demonstrated that a strong correlation (r = .85) existed between individual changes in H-max/M-max ratio and the changes in facilitation of the conditioned H-reflex from supine to standing. This relationship helps explain the modulation of the H-reflex during static changes in body position, and it could also provide insight into the reflex modulation associated with more functional activities such as walking or running. These results are consistent with the hypothesis that presynaptic inhibition increases as body position is changed from supine to standing.

Adult↗