Bruce Etnyre

Effects of visual and auditory cues on gait in individuals with Parkinson's disease

The purpose of this study was to determine if combining visual and auditory cues has a greater effect on the gait pattern of patients with Parkinsons disease (PD) than the cues applied individually. Twenty-four individuals with idiopathic PD were recruited. Patients, while off antiparkinsonian medications, were measured on a 7.62-m walkway during two trials for each of four conditions performed in random order: without cues, with a visual cue, with an auditory cue and with both cues simultaneously. The auditory cue consisted of a metronome beat 25% faster than the subjects fastest gait speed. Brightly colored parallel lines placed along the walkway at intervals equal to 40% of a subjects height served as the visual cue. Average gait speed, cadence and stride length were calculated for each condition. Gait velocity, cadence and stride length significantly improved (p<005) when cues were used. Visual and auditory cues improved gait performance in patients with PD, but they did so in different ways. Auditory cueing significantly improved cadence, but visual cueing improved stride length. The simultaneous use of auditory and visual cues did not improve gait significantly more than each cue alone.

H-reflex changes during static stretching and two variations of proprioceptive neuromuscular facilitation techniques

The effects of 3 stretching methods on the motor pool excitability of the soleus muscle as measured by the Hoffmann reflex have been compared with the objective of revealing central nervous system influences promoting muscle compliance to lengthening. The H-wave was reduced slightly throughout the static stretch method. The contract-relax (CR) method produced profound inhibition during the first several hundred milliseconds following contraction, but gradually increased to values similar to static stretch (SS) values 2 sec following contraction. Hoffmann reflex values for the contract-relax-antagonist-contract (CRAC) method were greatly depressed throughout the stretching phase with a slight increase after 2 sec. It was concluded that several inhibitory neural influences can have an additive effect in profoundly reducing motor pool excitability. Under the assumption that greater motor pool inhibition reduces muscle contractibility and therefore allows more muscle compliance, it is suggested that the proprioceptive neuromuscular facilitation (PNF) methods, particularly those involving reciprocal activation, provide the greatest potential for muscle lengthening. This is supported by previous studies which compared gains in range of motion using these 3 stretching methods (Holt et al. 1970; Moore and Hutton 1980; Etnyre and Abraham 1985).

Event Standardization of Sit-to-Stand Movements

Background and Purpose: Unlike gait analysis, no commonly accepted method for studying sit-to-stand (STS) movements exists. Most previous studies describing STS events used various methods to identify movement events while restricting sitting positions and movements. The present study observed natural rising from a sitting position using a simple method for measuring this common task. The purposes of this study were to compare commonly performed STS movements and to propose a standard system for defining identifiable sequential events. Subjects and Methods: Ground reaction forces of 100 adults who were healthy (50 male, 50 female) were recorded using a force platform as each participant performed 4 methods of rising from sitting on a standard chair. The 4 STS conditions were: with arms free, with hands on knees, using armrests, and with arms crossed. Results: For each subject, 11 recorded events from the vertical, fore-aft, and lateral dimensions were identified for all arm-use conditions. The only significant and clinically relevant force difference among arm-use conditions was that the armrests condition produced less average force than the other 3 conditions during the seat-off and vertical peak force events. Among average event times, the armrests condition showed significantly longer time to the vertical peak force event than the other conditions. Discussion and Conclusion: Because these events occurred invariably in sequential order for every individual for all arm-use conditions in a relatively large sample of observations during natural STS movements, this method may be useful for establishing a standard method to assess and compare patient functionality and allow comparisons among STS research studies.

Landing Mechanics between Noninjured Women and Women with Anterior Cruciate Ligament Reconstruction during 2 Jump Tasks

Background Women with anterior cruciate ligament reconstruction have different neuromuscular strategies than noninjured women during functional tasks after ligament reconstruction and rehabilitation. Hypothesis Landing from a jump creates high loads on the knee creating dynamic instability in women with anterior cruciate ligament reconstruction, whereas noninjured women have stable knee landing mechanics. Study Design Controlled laboratory study. Methods Fifteen noninjured women and 13 women with anterior cruciate ligament reconstruction performed 5 trials of a single-legged 40-cm drop jump and 2 trials of a 20-cm up-down hop task. Multivariate analyses of variance were used to compare hip and knee joint kinematics, knee joint moments, ground-reaction forces, and electromyographic findings between the dominant leg in noninjured women and reconstructed leg in women with anterior cruciate ligament reconstruction. Results No statistically significant differences between groups were found for peak hip and knee joint angles for the drop jump task. Statistically significant differences in neuromuscular activity (P = .001) and anterior-posterior knee shear forces (P < .001) were seen in women with anterior cruciate ligament reconstruction compared with noninjured women in the drop jump task. However, no statistically significant differences (P > .05) between groups were found for either peak hip and knee joint angles, peak joint kinetics, or electromyographic findings during the up-down hop task. Conclusion Women with anterior cruciate ligament reconstruction have neuromuscular strategies that allow them to land from a jump similar to healthy women, but they exhibit joint moments that could predispose them to future injury if they participate in sports that require jumping and landing.

Chronic and Acute Flexibility of Men and Women Using Three Different Stretching Techniques

Abstract This investigation compared chronic and acute range of motion (ROM) changes of hip flexion and shoulder extension between men and women using three stretching techniques and a control group during a 12-week program. The treatment groups performed either static stretching (SS), contract-relax (CR), or contract-relax with agonist-contraction (CRAC) stretching techniques. The ROM measurements were obtained before beginning any treatment, then once every 3 weeks thereafter. All treatment groups significantly increased ROM compared with the control group. Although women possessed greater ROM than men throughout the program, their comparative increases were not significantly different from the mens increases. It was concluded that the proprioceptive neuromuscular facilitation (PNF) techniques (i.e., CR and CRAC) were more effective than the SS method for increasing ROM for both hip flexion and shoulder extension for both sexes. Men derived better overall effects using the CRAC method while women showe...

Influence of pain distribution on gait characteristics in patients with low back pain: Part 1: Vertical ground reaction force

Study Design. In a cross-sectional study, vertical ground reaction force (GRF) during 2 speeds of walking were compared between 3 age- and sex-matched groups: back pain only (BPO) group, back pain with referred leg pain (LGP) group, and a control group. Objective. The purpose was to evaluate the influence of pain distribution on vertical GRF of patients with low back problems during 2 walking speed conditions: preferred and fastest speeds. Summary of Background Data. People with low back pain often have difficulty walking. A better understanding of how pain distribution differentially affects walking will facilitate clinicians’ assessment and enhance treatment in patients with low back pain problems. Methods. All participants walked on a 7.62-m walkway. Vertical GRF parameters were recorded during stance phase using a force platform for each walking speed condition. Multivariate analysis of covariance was used for statistical analysis, with gait velocity as the covariate. Results. The BPO and control groups did not differ significantly in vertical GRF during both walking speed conditions (P ≥ 0.11). All vertical GRF parameters of the LGP group, except the peak loading force (P = 0.374), were significantly less than those of the control group during preferred walking speed condition (P ≤ 0.008). However, there was no significant difference in the vertical GRF components between LGP and control groups during the fastest walking speed condition (P ≥ 0.07). Conclusions. Pain distribution of people with low back problems differentially influences the vertical GRF they experience during walking. When walking at preferred speed, those with referred leg pain seem to use additional strategies besides walking slowly to attenuate the amount of force imposed on their painful leg. When challenged to walk at their fastest speed, people with back pain only walk as fast and withstand comparable amount of force as their pain-free counterparts.

Antagonist muscle activity during stretching: a paradox re-assessed

The purpose of this investigation was to examine and compare the simultaneous electromyographic activity from surface and implanted wire electrodes of an antagonist pair of muscles during a reversal stretching technique. Previous studies reported increased electromyographic activity of a muscle being stretched during antagonist muscle activation. Five male subjects performed a stretching method which consisted of active plantarflexion, followed by active dorsiflexion. Adjacent surface and implanted wire electrodes were applied to the soleus and tibialis anterior muscles. Comparison of the surface electrode recordings showed apparent cocontraction during dorsiflexion. However, no activity was observed on the soleus wire electrode trace during the dorsiflexion phase of the stretching method. Power spectral analysis showed a significant (P less than 0.001) frequency shift between plantarflexion (91.9 V2.Hz-1) and dorsiflexion (66.1 V2.Hz-1) from the surface electrode recordings. Cross-correlation between tibialis anterior and surface soleus activity during dorsiflexion provided strong evidence that the apparent electromyographic soleus signal originated in the tibialis anterior muscle with an average of 8.7 ms delay of the surface soleus signal. Although not generalizable to other studies, it was concluded that in this study the tracings from the surface electrodes, which gave the appearance of co-contraction between antagonist muscles, were actually cross-talk between the electrodes. The rationale for antagonist contraction during stretching in order to inhibit contraction of the muscle being stretched is supported with this evidence and is consistent with those studies which show greater range of motion gains using the reversal technique.

Fatigue effects on knee joint stability during two jump tasks in women.

Ortiz, A, Olson, SL, Etnyre, B, Trudelle-Jackson, EE, Bartlett, W, and Venegas-Rios, HL. Fatigue effects on knee joint stability during two jump tasks in women. J Strength Cond Res 24(4): 1019-1027, 2010-Dynamic knee joint stability may be affected by the onset of metabolic fatigue during sports participation that could increase the risk for knee injury. The purpose of this investigation was to determine the effects of metabolic fatigue on knee muscle activation, peak knee joint angles, and peak knee internal moments in young women during 2 jumping tasks. Fifteen women (mean age: 24.6 ± 2.6 years) participated in one nonfatigued session and one fatigued session. During both sessions, peak knee landing flexion and valgus joint angles, peak knee extension and varus/valgus internal moments, electromyographic (EMG) muscle activity of the quadriceps and hamstrings, and quadriceps/hamstring EMG cocontraction ratio were measured. The tasks consisted of a single-legged drop jump from a 40-cm box and a 20-cm, up-down, repeated hop task. The fatigued session included a Wingate anaerobic protocol followed by performance of the 2 tasks. Although participants exhibited greater knee injury-predisposing factors during the fatigued session, such as lesser knee flexion joint angles, greater knee valgus joint angles, and greater varus/valgus internal joint moments for both tasks, only knee flexion during the up-down task was statistically significant (p = 0.028). Metabolic fatigue may perhaps predispose young women to knee injuries by impairing dynamic knee joint stability. Training strength-endurance components and the ability to maintain control of body movements in either rested or fatigued situations might help reduce injuries in young women athletes.

Soleus and vastus medialis H-reflexes: similarities and differences while standing or lying during varied knee flexion angles.

The H-reflex may be a useful measure to examine the lower extremity muscles activation and inhibition following an injury. Recording the vastus medialis H-reflex amplitudes in healthy subjects while standing or lying during varied knee flexion angles may establish a reference for comparison for patients with ACL injury. Vastus medialis and soleus H-reflexes were recorded from 14 healthy subjects while lying and standing during 0, 30, 45, and 60 degrees knee flexion. EMG unit was used to electrically stimulate the tibial and femoral nerves (using 0.5 ms pulses at 0.2 pps of H-maximum amplitude) and to record four traces of the soleus and vastus medialis H-wave and one trace of the M-wave peak-to-peak amplitudes. Repeated measures three-way ANOVAs were calculated with the global alpha=0.05. Results showed that (1) the average soleus H-reflex amplitude was significantly less during standing than lying across all knee flexion conditions, (2) the average vastus medialis H-reflex amplitudes showed no measurable significant differences between neutral standing compared with lying, (3) the average vastus medialis H-reflex amplitudes were significantly greater during standing knee flexion conditions (30, 45, and 60 degrees ) than lying or neutral standing, and (4) there were no differences between soleus and vastus medialis H-reflex amplitudes during lying across all knee flexion conditions. Data from H/M ratio follow the same pattern of H-amplitude. Recording the vastus medialis H-reflex amplitude during standing and knee flexion may be a reflective of the knee function. It is more specific than the soleus H-reflex because it reflects the changes in the excitability of the quadriceps motoneurons acting directly around the knee joint.

The Influence of Pain Distribution on Walking Velocity and Horizontal Ground Reaction Forces in Patients with Low Back Pain

Objective. The primary purpose of this paper was to evaluate the influence of pain distribution on gait characteristics in subjects with low back problems (LBP) during walking at preferred and fastest speeds. Design. Cross-sectional, observational study. Setting. Gait analysis laboratory in a health professions university. Participants. A convenience age- and gender-matched sample of 20 subjects with back pain only (BPO), 20 with referred leg pain due to back problems (LGP), and 20 pain-free individuals (CON). Methods and Measures. Subjects completed standardized self-reports on pain and disability and were videotaped as they walked at their preferred and fastest speeds along a walkway embedded with a force plate. Temporal and spatial gait characteristics were measured at the midsection of the walkway, and peak medial, lateral, anterior, and posterior components of horizontal ground reaction forces (hGRFs) were measured during the stance phase. Results. Patients with leg pain had higher levels of pain intensity and affect compared to those with back pain only (t = 4.91, P < .001 and t = 5.80, P < 0.001, resp.) and walking had an analgesic effect in the BPO group. Gait velocity was highest in the control group followed by the BPO and LGP group and differed between groups at both walking speeds (F 2.57 = 13.62, P < .001 and F 2.57 = 9.09, P < .001, for preferred and fastest speed condition, resp.). When normalized against gait velocity, the LGP group generated significantly less lateral force at the fastest walking speed (P = .005) and significantly less posterior force at both walking speeds (P ≤ .01) compared to the control group. Conclusions. Pain intensity and distribution differentially influence gait velocity and hGRFs during gait. Those with referred leg pain tend to utilize significantly altered gait strategies that are more apparent at faster walking speeds.