Correlation Between Ankle-Dorsiflexion and Hip-Flexion Range of Motion and the Functional Movement Screen Hurdle-Step Score.

CONTEXT: Functional movement screening (FMS) has been gaining popularity in the fields of sports medicine and performance. Currently, limited research has examined whether FMS screening that identifies low FMS scores is attributed primarily to limits in range of motion (ROM). OBJECTIVE: To compare scores from the FMS hurdle-step movement with ROM measurements for ankle dorsiflexion and hip flexion (HF). DESIGN: Correlational research design. SETTING: Sports medicine research laboratory. PARTICIPANTS: 20 healthy active male (age 21.2 ± 2.4 y, weight 77.8 ± 10.2 kg, height 180.8 ± 6.8 cm) and 20 healthy active female (21.3 ± 2.0 y, 67.3 ± 8.9 kg, 167.4 ± 6.6 cm) volunteers. INTERVENTION: All 40 participants completed 3 trials of the hurdle-step exercise bilaterally and goniometric ROM measurements for active ankle dorsiflexion and HF. MAIN OUTCOME MEASURES: Correlations were determined between ROM and FMS scores for right and left legs. In addition, mean data were compared between FMS scores, gender, and dominant and nondominant limbs. RESULTS: There were no significant correlations present when all participants were grouped. However, when separated by gender significant correlations were identified. There was a weak correlation with HF and both hurdle-step (HS) and average hurdle-step (AHS) scores on both left (r = .536, P = .015 and r = .512, P = .012) and right (r = .445, P = .049 and r = .565, P = .009) legs for women. For men, there was a poor negative correlation of HF and both HS and AHS on the left leg (r = -.452, P = .045 and r = .451, P = .046). CONCLUSION: Our findings suggest that although hip and ankle ROMs do not have a strong relationship with FMS hurdle-step scores, they are a contributing factor. More research should be conducted to identify other biomechanical factors that contribute to individual FMS test scores.

Effects of Core-Musculature Fatigue on Maximal Shoulder Strength.

CONTEXT: Core stability has been shown to affect lower-extremity motion, but activation of the core has also been observed just before movements of the upper extremity. However, there is limited evidence regarding the effects that core musculature has on upper-extremity strength. OBJECTIVE: To determine the effects of core fatigue on maximal shoulder strength. DESIGN: Crossover study. SETTING: Sports-medicine research laboratory. PARTICIPANTS: 23 participants (15 male and 8 female, age 21.3 ± 2.5 y, height 174.5 ± 10.3 cm, weight 71.3 ± 12.0 kg). INTERVENTION: All participants performed maximal voluntary isometric contractions in 3 different planes (sagittal, frontal, transverse) of shoulder-joint motion. A core-fatiguing protocol was conducted, and the same 3 shoulder-strength tests were repeated and compared with the initial measurements. MAIN OUTCOME MEASURES: Strength measures were recorded in kilograms with a dynamometer. RESULTS: Results showed a significant decrease in strength in the frontal (-0.56 ± 1.06 kg, P = .020) and transverse (-0.89 ± 1.49 kg, P = .012) planes but not in the sagittal plane (-0.20 ± 0.98 kg, P > .05). Furthermore, regardless of the specific strength test measured, results revealed that the 1st (-7.05% ± 11.65%, P = .012) and 2nd (-5.71% ± 12.03%, P = .042) strength-test measurements after the fatiguing protocol were significantly decreased, while the 3rd strength-test measurement (-4.19% ± 12.48%, P = .140) did not show statistical significance. CONCLUSION: These results indicate that decrease in core stability may have an influence on shoulder strength. The literature suggests that the core is designed for endurance, and this study helps validate its recovery properties. Further research is needed to determine the significance of this effect and how injury rates coincide.

Lack of neuromuscular origins of adaptation after a long-term stretching program.

CONTEXT: Static stretching is commonly used during the treatment and rehabilitation of orthopedic injuries to increase joint range of motion (ROM) and muscle flexibility. Understanding the physiological adaptations that occur in the neuromuscular system as a result of long-term stretching may provide insight into the mechanisms responsible for changes in flexibility. OBJECTIVE: To examine possible neurological origins and adaptations in the Ia-reflex pathway that allow for increases in flexibility in ankle ROM, by evaluating the reduction in the synaptic transmission of Ia afferents to the motoneuron pool. DESIGN: Repeated-measures, case-controlled study. SETTING: Sports medicine research laboratory. PARTICIPANTS: 40 healthy volunteers with no history of cognitive impairment, neurological impairment, or lower extremity surgery or injury within the previous 12 mo. INTERVENTION: Presynaptic and postsynaptic mechanisms were evaluated with a chronic stretching pro- tocol. Twenty subjects stretched 5 times a wk for 6 wk. All subjects were measured at baseline, 3 wk, and 6 wk. MAIN OUTCOME MEASURES: Ankle-dorsiflexion ROM, Hmax:Mmax, presynaptic inhibition, and disynaptic reciprocal inhibition. RESULTS: Only ROM had a significant interaction between group and time, whereas the other dependent variables did not show significant differences. The experimental group had significantly improved ROM from baseline to 3 wk (mean 6.2 ± 0.9, P < .001), 3 wk to 6 wk (mean 5.0 ± 0.8, P < .001), and baseline to 6 wk (mean 11.2 ±0.9, P < .001). CONCLUSIONS: Ankle dorsiflexion increased by 42.25% after 6 wk of static stretching, but no significant neurological changes resulted at any point of the study, contrasting current literature. Significant neuromuscular origins of adaptation do not exist in the Ia-reflex-pathway components after a long-term stretching program as currently understood. Thus, any increases in flexibility are the result of other factors, potentially mechanical changes or stretch tolerance.

Intersession reliability of Hoffmann reflex gain and presynaptic inhibition in the human soleus muscle.

UNLABELLED: Hayes BT, Hicks-Little CA, Harter RA, Widrick JJ, Hoffman MA. Intersession reliability of Hoffmann reflex gain and presynaptic inhibition in the human soleus muscle. OBJECTIVE: To determine the day-to-day reliability of Hoffmann reflex (H-reflex) gain and presynaptic inhibition of spinal reflexes in the human soleus muscle. DESIGN: Controlled trial. SETTING: Research laboratory. PARTICIPANTS: Volunteers (N=30; mean +/- SD age, 23.4+/-3.9y; height, 175.64+/-10.87cm; mass, 84.50+/-24.18kg) with no history of lower extremity pathology and/or injury participated. INTERVENTIONS: Subjects lay prone with the head, shoulders, arms, and hips supported in a static position by a massage body pillow and the ankle positioned at 90 degrees . Recording electrodes were placed over the soleus and tibialis anterior muscle bellies, and the stimulating electrodes were positioned over the tibial nerve in the popliteal space and the common peroneal nerve near the fibular head. MAIN OUTCOME MEASURES: The H-reflex and motor wave recruitment curves were then measured and recorded. Presynaptic inhibition was also assessed in the soleus muscle, and a conditioning stimulation of the common peroneal nerve (1 x motor threshold = motor threshold) was used prior to soleus H-reflex measurement. Two testing sessions took place between 2 and 7 days, and each session occurred at the same time of day. RESULTS: Assessments of H-reflex gain and presynaptic inhibition yielded test-retest reliability of R equal to . 95 and .91, respectively. CONCLUSIONS: Measures of presynaptic inhibition and H-reflex gain (H slope/M slope) in the human soleus muscle are consistent and reliable day to day.

The interrelationships among sex hormone concentrations, motoneuron excitability, and anterior tibial displacement in women and men.

CONTEXT: Sex hormone fluctuations have been implicated as a contributing factor to the high rates of noncontact injury to the anterior cruciate ligament in females. OBJECTIVE: To determine the strength of the relationships among variables of sex hormone concentrations, motoneuron excitability, and anterior tibial displacement (ATD) in women and men and to determine if these relationships differ between the sexes. DESIGN: Cohort study. SETTING: Sports medicine laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-eight regularly menstruating women (age = 22.4 +/- 3.4 years) and 15 men (age = 22.3 +/- 3.7 years) participated in the study. INTERVENTION(S): Fluctuations in sex hormones were determined for the participants. Female participants were tested every other day of their menstrual cycles, whereas male participants were tested every fourth day during the 28-day period. MAIN OUTCOME MEASURE(S): We measured Hoffmann reflexes (maximum Hoffmann reflex [H(max)] to maximum M-wave [M(max)] ratio in the soleus), ATD under a 134-N load, and saliva concentrations of estrogen and progesterone. The independent variable was sex. Pearson product moment correlation coefficients were calculated for each participant by pairing measurements made on the same day. Two-tailed independent-samples t tests were used to determine the difference between the male and female correlations for each variable. RESULTS: Over the course of the study, the relationships between H(max)ratioM(max) and estrogen, H(max)ratioM(max) and progesterone, ATD and estrogen, and ATD and progesterone were not different between the sexes. However, the relationship between ATD and progesterone was different between the sexes (P = .036). CONCLUSIONS: The observed correlations did not support our hypothesis that the relationships between sex hormone levels and reflex activity or between sex hormone levels and ATD would be different for women compared with men. If sex hormone concentrations significantly contribute to anterior cruciate ligament ruptures because of changes in laxity or in motoneuron excitability, their mechanism of action is likely multifactorial and complex.

Three-MHz Ultrasound Heats Deeper Into the Tissues Than Originally Theorized.

OBJECTIVE: To measure muscle temperature of ultrasound at 1-MHz and 3-MHz frequencies at a depth of 2.5 cm and to compare treatment durations for vigorous heating (increase of 4 degrees C) and for heating to 40 degrees C. DESIGN AND SETTING: A counterbalanced, repeated-measures design with 1 fixed, independent variable, 1.5-W/cm(2) ultrasound treatment (1 MHz, 3 MHz, or control [sham]) using a Theratouch 7.7 ultrasound device. Dependent variables were end-treatment temperature at 2.5 cm, time to vigorous heating, and time to reach 40 degrees C. SUBJECTS: Eighteen healthy volunteers (age = 24.6 +/- 2.3 years, height = 173.0 +/- 9.7 cm, mass = 72.0 +/- 16.3 kg) without a history of lower leg injury. MEASUREMENTS: The medial triceps surae intramuscular temperature at 2.5 cm was measured every 10 seconds using an implantable thermocouple. Each of the 3 ultrasound frequencies was applied in counterbalanced order at 24-hour intervals. RESULTS: Ultrasound of 3 MHz produced both vigorous heating (at 3.4 minutes) and an absolute temperature of 40 degrees C (at 4 minutes). CONCLUSIONS: Our results suggest that 3-MHz ultrasound heats 0.5 cm deeper than suggested by others. With our machine, 3-MHz ultrasound was more effective in heating muscle at this depth than 1-MHz ultrasound.