Biomedical subjects

J Ty Hopkins

Publications and source records attributed to J Ty Hopkins.

8 recordsLinked to original sources

PubMed2006

Muscle activation following sudden ankle inversion during standing and walking.

Dynamic response characteristics of ankle musculature following sudden ankle inversion have traditionally been tested in a static, standing position. However, this model does not take into consideration muscle activity and loading characteristics associated with active gait. This study compared muscle reaction times and amplitudes from sudden ankle inversion during standing (standing group) and walking (walking group) using one of two similar devices for each of these conditions. Surface EMG was collected from the peroneus longus (PL), brevis (PB), and tibialis anterior (TA) of the dominant leg from 25 subjects (age 20 +/- 1 years, height 174.0 +/- 10.2 cm, mass 74.3 +/- 12.9 kg) for each condition (walking and standing). Time to total inversion ROM (28 degrees ) was greater in the walking group (114.9 +/- 15.0 ms) than the standing group (65.6 +/- 17.8 ms, P < 0.05), whereas reaction time was less in the peroneals in the walking group (PL 56.9 +/- 8.4 ms, PB 60.1 +/- 10.6 ms, TA 65.0 +/- 14.9 ms) compared to the standing group (PL 74.3 +/- 8.5 ms, PB 73.5 +/- 8.2 ms, TA 73.3 +/- 8.3, P < 0.05). Additionally, Peak normalized EMG (% MVIC) for the walking condition (PL 367 +/- 254, PB 405 +/- 359, TA 84 +/- 39) exceeded that of the standing condition (PL 310 +/- 239, PB 328 +/- 215, TA 76 +/- 39, P < 0.05), and average normalized EMG (% MVIC) was greater in the peroneals for the walking condition (PL 233 +/- 171, PB 280 +/- 255) than the standing condition (PL 164 +/- 131, PB 193 +/- 137, P < 0.05). The differences noted between the conditions provide evidence that a dynamic response to ankle injury mechanisms is much different in a walking model compared to a traditional standing model. A walking model may be a more functional approach for evaluating dynamic response characteristics of ankle musculature due to sudden ankle inversion.

Adult↗

PubMed2006

Effects of neuromuscular training on the reaction time and electromechanical delay of the peroneus longus muscle.

OBJECTIVE: To examine the influence of a 6-week neuromuscular training program on the electromechanical delay and reaction time of the peroneus longus muscle. DESIGN: A 2 x 2 pre-post factorial design. SETTING: Human performance research center biomechanics laboratory. PARTICIPANTS: Thirty-six healthy, physically active, college-age subjects were recruited for this study and 26 completed it. There were 5 men and 8 women in the treatment group (mean age +/- standard deviation, 21.9+/-2.1 y; height, 173.7+/-11.1cm; weight, 67.4+/-17.8 kg) and 6 men and 7 women in the control group (age, 21.8+/-2.3 y; height, 173.7+/-11.9 cm; weight, 70.8+/-19.4 kg). Subjects were not currently experiencing any lower-extremity pathology and had no history of injuries requiring treatment to either lower extremity. INTERVENTIONS: Subjects in the treatment group completed a 6-week neuromuscular training program involving various therapeutic exercises. Subjects in the control group were asked to continue their normal physical activity during the 6-week period. MAIN OUTCOME MEASURES: The electromechanical delay of the peroneus longus was determined by the onset of force contribution after artificial activation, as measured by electromyographic and forceplate data. Reaction time was measured after a perturbation during walking. Data were analyzed using two 2 x 2 analyses of covariance (covariate pretest score). Group (treatment, control) and sex (male, female) were between-subject factors. RESULTS: Neuromuscular training caused a decrease in reaction time to perturbation during walking compared with controls (F=4.030, P=.029), while there was a trend toward an increase in electromechanical delay (F=4.227, P=.052). There was no significant difference between sexes or the interaction of sex and treatment in either reaction time or electromechanical delay. CONCLUSIONS: The 6-week training program significantly reduced reaction time of the peroneus longus muscle in healthy subjects. Neuromuscular training may have a beneficial effect on improving dynamic restraint during activity.

Adult↗

PubMed2004

Effects of ankle joint effusion on lower leg function.

BACKGROUND: Inversion ankle sprains are among the most frequently encountered injuries in and outside of sport. Altered feedback from joint damage and/or edema may negatively affect dynamic stabilization, thereby increasing the patients' susceptibility to further injury. In order to understand better how the sensorimotor system responds to the presence of ankle edema during a functional task, further examination is warranted. OBJECTIVE: To quantify muscle activation in the peroneal, tibialis anterior, and soleus musculature as well as to determine ankle joint peak torque, peak power, and root mean square (RMS) power during a closed kinetic chain activity following artificial ankle effusion. DESIGN: Dependent variables were compared within subjects across time intervals and between groups. SETTING: All data were collected in the biomechanics laboratory. PARTICIPANTS: Subjects were 20 healthy, neurologically sound volunteers (age 21.9 +/- 2.1 y, height 174.5 +/- 9.3 cm, mass 79.3 +/- 15.9 kg) with no lower extremity injuries. INTERVENTIONS: Subjects were prepared for surface electrodes on the peroneus longus (PL), tibialis anterior (TA), soleus (Sol), and medial malleolus (ground). Anthropometric measures for the lower extremity were recorded for use by the Omnikinetic closed chain dynamometer. Measurements were taken prior to ankle effusion (baseline), immediately following effusion (post), and again at 30 minutes. MAIN OUTCOME MEASUREMENTS: Testing consisted of 6 repetitions at 35% of 1-repetition max and a constant speed of 1.5 Hz. Separate two-way MANOVAs with repeated measures on time intervals were used to detect differences between groups (effusion and control) over time for torque, power, and RMS power and for peak and average EMG. RESULTS: An overall time x group interaction was detected for EMG (F4,72=3.878; P=0.007) and kinetic variables (F6,70=5.55; P=0.0001). Average and peak PL EMG decreased immediately following effusion (Sidak's; P=0.048), and average EMG remained depressed 30 minutes following effusion (Sidak's; P=0.02). Immediately posteffusion, a decrease in ankle torque was detected (Sidak's; P=0.007). No differences in TA or Sol EMG, power, or RMS power were detected (P>0.05). CONCLUSIONS: Decreases in ankle plantarflexion torque and PL EMG indicate that a neuromuscular deficit exists in the presence of edema that could increase the susceptibility for further ankle injury.

Adult↗

PubMed2004

Low-Level Laser Therapy Facilitates Superficial Wound Healing in Humans: A Triple-Blind, Sham-Controlled Study.

OBJECTIVE: Low-level laser therapy (LLLT) has been promoted for its beneficial effects on tissue healing and pain relief. However, according to the results of in vivo studies, the effectiveness of this modality varies. Our purpose was to assess the putative effects of LLLT on healing using an experimental wound model. DESIGN AND SETTING: We used a randomized, triple-blind, placebo-controlled design with 2 within-subjects factors (wound and time) and 1 between-subjects factor (group). Data were collected in the laboratory setting. SUBJECTS: Twenty-two healthy subjects (age = 21 +/- 1 years, height = 175.6 +/- 9.8 cm, mass = 76.2 +/- 14.2 kg). MEASUREMENTS: Two standardized 1.27-cm(2) abrasions were induced on the anterior forearm. After wound cleaning, standardized digital photos were recorded. Each subject then received LLLT (8 J/cm(2); treatment time = 2 minutes, 5 seconds; pulse rate = 700 Hz) to 1 of the 2 randomly chosen wounds from either a laser or a sham 46-diode cluster head. Subjects reported back to the laboratory on days 2 to 10 to be photographed and receive LLLT and on day 20 to be photographed. Data were analyzed for wound contraction (area), color changes (chromatic red), and luminance. RESULTS: A group x wound x time interaction was detected for area measurements. At days 6, 8, and 10, follow-up testing revealed that the laser group had smaller wounds than the sham group for both the treated and the untreated wounds (P < .05). No group x wound x time differences were detected for chromatic red or luminance. CONCLUSIONS: The LLLT resulted in enhanced healing as measured by wound contraction. The untreated wounds in subjects treated with LLLT contracted more than the wounds in the sham group, so LLLT may produce an indirect healing effect on surrounding tissues. These data indicate that LLLT is an effective modality to facilitate wound contraction of partial-thickness wounds.

Journal Article↗

PubMed2003

Intrasession and intersession reliability of the quadriceps Hoffmann reflex.

The Hoffmann reflex (H-reflex) is a resting electromyographic (EMG) measurement of motoneuron pool recruitment. While the soleus H-reflex has been studied extensively, the study of the quadriceps H-reflex has been limited for various reasons. To date no data exist regarding the reliability of this measurement within and between sessions over an extended period of time. The purpose of this study was to establish quadriceps H-reflex reliability over a four-week period consisting of 6 testing sessions. Eleven neurologically sound volunteers (age: 20 +/- 2 yr, height: 181.9 +/- 9.9 cm; mass: 84.2 +/- 17.8 Kg) participated in this study. Subjects were prepared for EMG surface electrodes over the vastus medialis and medial malleolus (ground). A stimulating bar electrode was placed over the femoral nerve, and a stimulus was delivered at 20 sec intervals with increasing amplitude to obtain a peak quadriceps H-reflex. Ten peak H-reflex measurements were recorded for each session. The stimulator amplitude was increased further to obtain the peak efferent motor response (M-response) for normalization of peak H-reflex measurements. The procedure was repeated at 1 hr, 24 hr, 1, 2, and 3 weeks following the initial session. Intraclass correlation coefficients (ICC (2.1) and ICC (3.1)) were calculated using normalized peak H-reflex measurements. Strong reliability was detected within a session (10 trials ICC (2.1) = 0.957, ICC (3.1) = 0.970; 5 trials ICC (2.1) = 0.961, (ICC (3.1) = 0.970). ICC (2.1) calculations yielded strong reliability between the first and second (1 hr) session (0.956) but moderate reliability between days 1 and 2 (0.787) and between all session over 4 weeks (0.756). ICC (3.1) calculations were also computed to determine the reliability for the fixed selection of sessions. This calculation yielded strong reliabilities between days 1 and 2 (0.969) and between all sessions over 4 weeks (0.911). Within a measurement session quadriceps H-reflex measurements are very reliable, and we recommend 5 trials to establish a measurement. Between measurement sessions these data provide evidence of strong reliability for these fixed sessions (ICC (3.1)), and generalized evidence for moderate reliability over a 4-week period has also been provided (ICC (2.1)). These data provide valuable information for the researcher and practitioner as to the reliability of this measurement in detecting changes in the neuromuscular system.

Adult↗

PubMed2002

Ankle cryotherapy facilitates soleus function.

STUDY DESIGN: A 2-factor (group and time) experimental design with repeated measures on time. OBJECTIVES: To determine the effects of ankle cryotherapy on voluntary and resting motor function of the soleus over a 60-minute period. To determine if a relationship exists between changes in torque production and Hoffmann reflex (H-reflex) following ankle joint cryotherapy treatment. BACKGROUND: Controversy surrounds the use of cryotherapy prior to activity and rehabilitation. While cooling muscle may have a deleterious effect on motor function, cooling the joint may enhance motor function around the joint. The H-reflex is a good resting measure of motoneuronal activity. However, its relationship to voluntary activity is unknown. METHODS AND MEASURES: Thirty subjects were pretested (baseline) for normalized H-reflex (defined as the ratio of maximum H-reflex [Hmax] to maximum direct motor response [Mmax]) and peak plantar flexion torque. A crushed ice bag was placed over the ankle of 15 subjects for 30 minutes. H-reflex and torque measurements were collected immediately following the cryotherapy treatment at 30, 60, and 90 minutes. Surface temperatures were recorded from the ankle and electrode site with each measurement interval. RESULTS: Both peak H-reflex and plantar flexion torque at 30, 60, and 90 minutes increased relative to baseline measurements. Each measurement was also greater than the corresponding control at 30, 60, and 90 minutes. A weak correlation (r = 0.38; P = 0.036) existed between changes in H-reflex and plantar flexion torque at 30 minutes. CONCLUSIONS: The soleus motoneuron pool is facilitated following a 30-minute crushed ice application to the ankle and over a 60-minute postcooling period. These data support the use of joint cooling prior to activity and rehabilitation.

Adolescent↗

PubMedDate not supplied

A joint dilemma.

Explore the source record for details and available documents.

Anterior Cruciate Ligament↗

PubMedDate not supplied

Knee joint effusion and cryotherapy alter lower chain kinetics and muscle activity.

CONTEXT: Cryotherapy has been shown to disinhibit the quadriceps muscle after joint effusion by a resting measure (Hoffmann reflex) of motor recruitment. I sought to determine whether cryotherapy-induced motor recruitment changes resulted in subsequent changes in functional movement. OBJECTIVE: To quantify muscle recruitment changes and knee joint function after joint effusion and subsequent joint cryotherapy. DESIGN: A 3 x 4 multivariate mixed-model design was used to compare groups (normative, effusion/control, effusion/cryotherapy) across time (preinjection, postinjection, 30 minutes postinjection, and 60 minutes postinjection). SETTING: Human performance laboratory. PATIENTS OR OTHER PARTICIPANTS: Forty-five volunteers (26 males, 19 females; age = 21 +/- 2 years, height = 174.8 +/- 10.2 cm, mass = 78.1 +/- 15.4 kg). INTERVENTION(S): Experimental joint effusion was used to elicit inhibition of the quadriceps muscle. Cryotherapy was a treatment intervention. MAIN OUTCOME MEASURE(S): Lower chain peak joint torque, peak and average power, knee anterior joint reaction force, and average and peak vastus medialis, vastus lateralis, medial hamstrings, and gastrocnemius muscle normalized electromyographic activity were collected during the extension phase of a seated, recumbent stepping motion with a resistance of 36% of 1-repetition maximum and a controlled cadence of 1.5 Hz. RESULTS: Decreases in peak torque and peak power were observed after effusion, whereas no decrease was observed over time in the cryotherapy or normative groups. A decrease in peak vastus lateralis activity was also noted after effusion relative to other groups. Also, the effusion/cryotherapy group had a greater knee anterior joint reaction force relative to the effusion/control and normative groups after effusion. CONCLUSIONS: Joint cryotherapy negated movement deficiencies represented by knee peak torque and power decreases. This could be due to facilitated vastus lateralis activation relative to other groups.

Journal Article↗