Biomedical subjects

D M Koceja

Publications and source records attributed to D M Koceja.

44 records · Page 3Linked to original sources

PubMed1989

Long-latency enhancement of quadriceps excitability from stimulation of skin afferents in young and old adults.

This study examined the role of cutaneous input on spinal excitability in young and old adults. Patellar tendon reflexes were elicited in 15 old adults (M = 75 yrs) and 25 young adults (M = 26 yrs) at intervals ranging from 15 to 175 ms following cutaneous stimulation to one of four skin sites: (a) ipsilateral calf, (b) contralateral calf (old adults only), (c) ipsilateral anterior thigh, and (d) contralateral anterior thigh. The younger adults had a more vigorous reflex response than the older adults, as indicated by peak force. Force latencies were also faster for the younger adults than the older adults. However, both age groups showed a long-latency facilitation of quadriceps excitability regardless of cutaneous stimulation site. Thus, it seems that low threshold cutaneous afferents contribute an excitatory input to the extensor motoneuron pool that is maintained with age.

Adult↗

PubMed1988

Conditioned patellar tendon reflexes in sprint- and endurance-trained athletes.

Tendon reflex characteristics were examined in endurance-trained, sprint-trained, and control subjects (10 SS/group) using a conditioned patellar tendon reflex (PTR) paradigm. Paired PTRs were administered using inter-tap intervals of 0, 25, 50, 75, 150, and 300 ms, with the left leg reflex elicited first, followed by a right leg PTR. A force transducer secured at the ankle was used to measure peak force, time to peak force, and reflex latency. In the unilateral condition, significant differences (P less than 0.05) existed between athletic groups, with the sprint-trained athletes exhibiting greater peak force, faster time to peak force, and faster reflex latency than the endurance athletes. Significant differences (P less than 0.05) also existed for the conditioned reflex. There was a slight depression in reflex parameters in the untrained and sprint-trained groups up to an interval of 50 ms. At later intervals (greater than 50 ms), a marked enhancement occurred in all groups for all dependent measures studied. This longer latency excitatory effect persisted until the 150 ms interval. These differences in both simple and conditioned reflexes in individuals trained for endurance and sprint activities may reflect inherent differences in muscle-tendon stiffness or neural organization.

Adult↗

PubMedDate not supplied

Contralateral influences on patellar tendon reflexes in young and old adults.

In an effort to more fully investigate age-related changes in spinal reflex parameters, we measured force-time characteristics of the patellar tendon reflex in aged subjects and contrasted these with data obtained from college-age individuals. We also conditioned the tendon jerk with a tap to the contralateral tendon. The results showed a marked tendon reflex enhancement in the old group, consisting of greater overall reflex force produced by the quadriceps. In both groups, the contralateral conditioning stimulus produced a short-latency inhibition (at 25 msec) followed by a longer-latency facilitation (beginning at 75 msec). Both the early inhibition and the later reflex enhancement were greater in the aged subjects. We suggest that some age-related change may occur at the spinal level to compensate for decrements in more complex motor functioning.

Achilles Tendon↗

PubMedDate not supplied

Comparison of heteronymous monosynaptic Ia facilitation in young and elderly subjects in supine and standing positions.

BACKGROUND: The control of posture and balance is a primary concern among the elderly. Postural instability has been identified as a contributor to the greater incidence of falling among this segment of the population. One important neuromuscular mechanism identified as important in the control of posture and balance is the segmental reflex system. The purpose of this study was to examine the role of presynaptic inhibition in modulating the reflex system in young and elderly subjects. METHODS: To estimate the influence of body position on presynaptic inhibition to the soleus motor pool between young and elderly subjects, 11 young (mean age=23.9 yrs.) and 9 elderly (mean age=72.1 yrs.) subjects were examined in two different body positions: supine and standing. This study utilized the heteronymous facilitation protocol, as described by Hultborn et al. (1987), to estimate presynaptic inhibition of the Ia afferent pathway onto the soleus alpha-motoneuron pool. Maximal soleus H-reflex (H-max) and motor response (M-max) amplitudes were determined prior to testing at each condition, and the H-max/M-max ratio at each body position was determined. To estimate presynaptic inhibition at each body position, subjects received 24 test soleus H-reflex stimuli ( approximately 15% M-max), and 24 soleus H-reflexes conditioned by stimulation of the ipsilateral femoral nerve. RESULTS: Results demonstrated a significant decrease in H-max/M-max ratio from supine (66.1%) to standing (56.8%) for the young subjects, whereas the elderly subjects demonstrated no changes in the H-max/M-max ratio between body positions (39.8% supine; 39.8% standing). The conditioning stimulus produced a significant change in the test reflex for the young subjects during supine testing (51.1% increase) but not standing (3.4% increase). The elderly subjects demonstrated no significant changes in the test reflex produced by the heteronymous conditioning at either condition (17.6% increase supine; 4.9% increase standing). CONCLUSIONS: These results demonstrate differential effects of both H-reflex modulation and heteronymous conditioning for elderly subjects when compared with young adults. These differences may be an adaptive phenomenon of the aging neuromuscular system, exemplified by a decreased ability to modulate the reflex system in the elderly group.

Adult↗

PubMedDate not supplied

Hoffmann reflex profiles and strength ratios in postoperative anterior cruciate ligament reconstruction patients.

Rupture of the anterior cruciate ligament (ACL) typically leads to surgical reconstruction followed by an extensive rehabilitation program. One of the most commonly experienced complications associated with ACL rupture and reconstruction is quadriceps muscle atrophy. A clear understanding of the exact mechanisms associated with ACL related atrophy remains undocumented. The purpose of the present study was to investigate maximum H-reflex to maximum M-wave ratio as well as quadriceps deficit for both isometric and isokinetic peak torques in a post ACL reconstruction population. Forty subjects volunteered for participation in this study. The experimental group comprised 20 subjects who had undergone patellar tendon graft reconstruction of a torn ACL. A matched control group of 20 subjects were also measured for comparative purposes. The results indicated the control group had significantly higher quadriceps to quadriceps ratio than did the ACL group [t(38) = 9.05 p < .001]. In contrast, there was no difference in the H-max/M-max ratio for either group or leg. The strength findings of this study support previous findings. The spinal reflex results support the need for additional research in this area, specifically with more acutely injured subjects.

Adult↗

PubMedDate not supplied

Assessment of motoneuron excitability using recurrent inhibition and paired reflex depression protocols: a test of reliability.

Motor output may be regulated by both pre- and post-synaptic mechanisms. The purpose of this study was to investigate the reliability of two measurement protocols, which purport to examine spinal mechanisms responsible for gating motoneuron excitability. Nine subjects (aged 29 +/- 5 years) were tested using two soleus H-reflex protocols; 1) recurrent inhibition (RI) and 2) paired reflex depression (PRD). The dependent variable for each protocol was the peak-to-peak amplitude of the conditioned Hoffmann reflex (H-reflex). Seven trials were obtained for each subject under each condition as well as control values to assess test-retest reliability. After all trials were collected the subjects rested for at least five minutes after which the process was repeated. Each subject returned to the lab after a period of no less than 24 hours at which time the process was repeated. Protocol #1: Control reflexes (20% of maximal motor response) were obtained during quiet stance. After obtaining control trials two reflex responses were elicited which were separated by 10 ms on each trial to assess recurrent inhibition (Pierrot-Deseilligny et al., 1976; Bussel and Pierrot-Deseilligny, 1977). Protocol #2: Again a double-pulse technique was used to assess reflex activation history on motoneuron pool output (Trimble et al., 2000). This protocol utilized two reflex stimuli of the same intensity separated by 80 ms. The peak-to-peak amplitude of the control, RI conditioned and PRD conditioned H-reflexes exhibited intraclass reliability estimates of .97, .97 and .93 respectively. To achieve a reliability of rI > or = .80, it is recommended that a minimum of 2 trials be used for the RI protocol and that 4 trials be used for the PRD protocol. The results indicate that both techniques provide a means to objectively and reliably measure spinal mechanisms for gating motoneuron pool output.

Adult↗

PubMedDate not supplied

Comparison of electrically and mechanically induced soleus H-reflex depression.

OBJECTIVES: The aim of the present investigation was to compare the responses of mechanically-evoked and electrically-evoked conditioning among three different stimulus intensities and provide possible insight in determining whether these two types of inhibitory conditioning demonstrate the same response across the motor pool. METHODS: The soleus H-reflex was tested under three different stimulus intensities (25% Hmax, 50% Hmax, and Hmax), and peak to peak amplitudes were recorded after either mechanical or electrical conditioning. For electrical conditioning, the ankle was held at 90 degrees, whereas mechanical conditioning utilized a 10 degree passive dorsiflexion at 15 degrees/sec back to the 90 degree position. All H-reflex measurements were recorded with the ankle at 90 degrees. RESULTS: A 3 x 2 (stimulus intensity x treatment condition) repeated measures ANOVA indicated significant main effects for stimulus intensity (FGG = 16.23; p = .003) and condition (FGG = 28.48; p < .001), as well as an interaction (F(2,18) = 6.59; p = .008). Simple main effects identified significantly more H-reflex depression for mechanical conditioning (94%, 91%, and 44%) compared to electrical conditioning (65%, 55%, and 19%) at 25% Hmax, 50% Hmax, and Hmax, respectively. CONCLUSIONS: There appears to be more mechanically than electrically stimulated H-reflex depression when testing at 25% Hmax, 50% Hmax, and Hmax. These results demonstrate the influence of Ia discharge properties on H-reflex depression and may suggest differences in the affinity of Ia terminals to intrinsic presynaptic inhibition at different stimulus intensities.

Adult↗

PubMedDate not supplied

Quadriceps mediated changes in soleus motoneuron excitability.

In an effort to investigate the interactions of the quadriceps and soleus muscles, the isometric force-time curve of the Achilles tendon-tap reflex (ATR) was measured in 10 college age subjects. The tendon-jerk was conditioned with a tap to the ipsilateral or contralateral patellar tendon, or by an electrocutaneous (3x perception) stimulus applied to the belly of the quadriceps. The conditioning stimulus preceded the test ATR by 25, 40, 55, 70, 85, 100, 115, 130 or 145 ms. The results indicated that the ipsilateral conditioning tendon-tap produced a wave of short-latency facilitation (40 ms) and long-latency inhibition (85-130 ms) to the triceps surae muscles. The ipsilateral cutaneous conditioning, however, did not alter reflex excitability. A contralateral conditioning to the patellar tendon again produced short-latency (50-70 ms) facilitation, whereas the electrocutaneous stimulus did not alter motoneuron excitability. Moreover, a barrage of electrocutaneous impulses to either the ipsilateral or contralateral quadriceps (1 minute/60 pps) did not significantly alter motoneuron excitability of the soleus muscle. These results indicate that motoneuron excitability changes are observed in the soleus muscle with mechanical conditioning but not with electrocutaneous conditioning. Several neurophysiological mechanisms are proposed to mediate these changes.

Achilles Tendon↗