Eccentric and blood flow restriction exercises in women induce hypertrophy.

BACKGROUND: The purpose of the study was to assess the mechanical and metabolic effects of eccentric (ECC) resistance training and blood flow restriction (BFR) exercise on the elbow flexors in recreationally trained females. METHODS: Seventeen females (ECC: 30.0±7.6 years, 165.6±5.4 cm, 67.1±8.5 kg; ECC+BFR: 24.4±2.2 years, 163.7±9.3 cm, 67.6±12.2 kg) were randomized to two groups and trained twice weekly for four weeks. The ECC+BFR group trained at 30% 1-rep max (1-RM), 3x20 repetitions, and the ECC group trained at 60% 1-RM, 3×10 repetitions. The BFR cuff was pressurized to 60% of maximal occlusion. Both groups performed the ECC portion of a bicep curl with assistance to return the arm back to starting position. Rate of perceived exertion (RPE) and blood lactate were measured each week. Testing was conducted at baseline and post-training and included: body composition, thickness and cross-sectional area (CSA) of the elbow flexors, arm circumference, bicep curl 1-RM, and inverted rows to exhaustion. RESULTS: There was no significant group difference for any of the variables (P>0.05). A training effect was shown with both groups increasing right arm circumference (P=0.004), muscle thickness (P<0.001), CSA (P=0.001), 1-RM for the right (P=0.001) and left arms (P=0.014), and inverted rows (P=0.001). Both groups showed significant decreases in lactate (P=0.047) and RPE (P<0.001). CONCLUSIONS: Females can produce muscular gains with ECC and BFR training similar to previous results seen in males.

The Effect of Current Low Back Pain on Volitional Preemptive Abdominal Activation During a Loaded Forward Reach Activity.

BACKGROUND: A volitional preemptive abdominal contraction (VPAC) supports trunk stability during functional activity. Pain-free individuals can sustain VPAC during function, but such has not been reported for individuals with current low back pain (cLBP). OBJECTIVE: To examine whether cLBP affects VPAC performance during a loaded forward reach (LFR) task. DESIGN: Observational crossover study. SETTING: Laboratory. PARTICIPANTS: A total of 18 controls and 17 subjects with cLBP with pain ratings of 1/10 to 4/10 on a visual analog scale. INTERVENTIONS: Transverse abdominis (TrA) thickness measurements were recorded by blinded researchers from M-mode ultrasound imaging during 4 conditions: (1) quiet standing without abdominal drawing-in maneuver (ADIM); (2) quiet standing with ADIM; (3) LFR without ADIM; and (4) LFR with ADIM. A physical therapist with 29 years of experience collected historical and examination data. MAIN OUTCOME MEASURES: TrA muscle thickness (mm). RESULTS: A 2 (group) × 2 (contraction) × 2 (reach) analysis of variance demonstrated a significant group × contraction interaction (F [1, 31] = 4.499, P = .04) where ADIM produced greater TrA thickness increases in PLBP subjects (2.18 mm) versus controls (1.36 mm). We observed a significant main effect for reach (F [1, 31] = 14.989, P < .001), where LFR activity produced a greater TrA thickness (6.15 ± 2.48 mm) versus quiet standing (5.30 ± 2.12 mm). CONCLUSIONS: Subjects with cLBP demonstrated a greater increase in TrA activation during ADIM versus controls.

Spinal height change in response to sustained and repetitive prone lumbar extension after a period of spinal unloading.

OBJECTIVE: The purpose of this study was to investigate if differences in spinal height changes in healthy individuals were observed after a period of spinal unloading using repetitive as compared with sustained lumbar extension exercises. METHODS: This study used a pretest, posttest, crossover design. Asymptomatic participants were recruited using convenience sampling. Thirty-two participants (15 male; 17 female) without back pain were included in the data analysis (mean, 24.4 years; range, 20-41 years). Participants performed sustained or repetitive prone lumbar extension exercises after 1 hour of sustained spinal unloading. Spinal height was measured using a stadiometer before and after the repetitive and sustained prone lumbar extension exercises. RESULTS: Paired t tests revealed no significant difference in spine height after repetitive (P = .774) or sustained (P = .545) prone lumbar extension after a period of spinal unloading. No significant difference between spinal height changes occurred between sustained (mean [SD], -0.28 [2.59] mm) and repetitive (mean [SD], -0.12 [2.42] mm) lumbar extension (P = .756). CONCLUSION: In this group of asymptomatic individuals, sustained and repetitive lumbar extension exercises did not appear to affect spinal height after a period of spinal unloading.

Validity of musculoskeletal ultrasound for identification of humeroradial joint chondral lesions: a preliminary investigation.

CONTEXT: Epicondylalgia is a common condition involving pain-generating structures such as tendon, neural, and chondral tissue. The current noninvasive reference standard for identifying chondral lesions is magnetic resonance imaging. Musculoskeletal ultrasound (MUS) may be an inexpensive and effective alternative. OBJECTIVE: To determine the intrarater reliability and validity of MUS for identifying humeroradial joint (HRJ) chondral lesions. DESIGN: Cross-sectional study. SETTING: Clinical anatomy research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-eight embalmed cadavers (14 women, 14 men; mean age = 79.5 ± 8.5 years). MAIN OUTCOME MEASURE(S): An athletic trainer performed MUS evaluation of each anterior and distal-posterior capitellum and radial head to identify chondral lesions. The reference standard was identification of chondral lesions by gross macroscopic examination. Intrarater reliability for reproducing an image was calculated using the intraclass correlation coefficient (3,k) for measurements of the articular surface using 2 images. Intrarater reliability to evaluate a single image was calculated using the Cohen κ for agreement as to the presence of chondral lesions. Validity was calculated using the agreement of MUS images and gross macroscopic examination. RESULTS: Intrarater reliability was 0.88 (95% confidence interval = 0.77, 0.94) for reproducing an image and 0.93 (95% confidence interval = 0.80, 1.06) for evaluating a single image. Identifying chondral lesions on all HRJ surfaces with MUS demonstrated sensitivity = 0.93, specificity = 0.28, positive predictive value = 0.58, negative predictive value = 0.77, positive likelihood ratio = 1.28, and negative likelihood ratio = 0.27. CONCLUSIONS: Musculoskeletal ultrasound is a reliable and sensitive tool for a clinician with relatively little experience and training to rule out HRJ chondral lesions. These results may assist with clinical assessment and decision making in patients with lateral epicondylalgia to rule out HRJ chondral lesions.

Co-contractive activation of the superficial multifidus during volitional preemptive abdominal contraction.

OBJECTIVE: To investigate whether the superficial multifidus (MF) muscle at the lower lumbar spine displayed co-contraction during volitional preemptive abdominal contraction (VPAC) through the abdominal drawing-in maneuver (ADIM) or the abdominal bracing maneuver (ABM) in 3 different postural positions. DESIGN: A within-subject cohort design. SETTING: A clinical laboratory. PARTICIPANTS: A healthy convenience sample of 21 women and 13 men; mean age (SD), 25.5 ± 6.5 years. METHODS: We collected surface electromyographic measurements for the superficial MF at the L5 vertebral level and abdominal wall muscles. Ultrasound imaging was used during screening and testing sessions for confirming transverse abdominis muscle activation while subjects maintained a relaxed state without volitional abdominal contraction (no-VPAC) and performed ADIM and ABM in 3 postural positions: supine, 4-point kneeling, and upright standing. MAIN OUTCOME MEASUREMENT: The frequency of superficial MF co-contraction occurrences (percentage of the total number of conditions) was measured during ADIM and ABM in 3 different postural positions. DATA ANALYSES: A Cochran Q test for k-related samples (α = 0.05) was used for data analysis. RESULTS: Activation of the abdominal wall by using either VPAC strategy resulted in a significantly greater MF co-contraction occurrence when compared with no-VPAC in each position. The ABM produced a significantly higher MF co-contractive occurrence versus the ADIM in the supine position. CONCLUSION: Both VPAC strategies produced a co-contractive MF response, which appears to be important for lumbar segmental stabilization and control. Analysis of the results suggests that VPAC strategies are appropriate for coactivating the MF, which can enhance spinal protection and rehabilitation responses.

Effect of recurrent low back pain history on volitional pre-emptive abdominal activation during a loaded functional reach activity.

STUDY DESIGN: A 2 (group) × 2 (abdominal contraction) × 2 (reach activity) crossover mixed design with repeated measures for contraction and activity examined the effects of a loaded (4.6 kg) forward-reach activity and abdominal drawing-in maneuver (ADIM) on transversus abdominis (TrA) contraction in subjects with nonspecific low back pain (NSLBP) history versus controls. OBJECTIVE: We measured TrA contraction during a loaded forward-reach activity while using the ADIM and examined if a NSLBP history affects TrA activity. SUMMARY OF BACKGROUND DATA: The ADIM supports trunk stability during function. Clinicians incorporate ADIM during patients' functional tasks. Pain-free individuals can sustain ADIM during function, such as forward-reach. However, this has not been tested in those with a NSLBP history. METHODS: Eighteen normal subjects and 18 subjects with a history of NSLBP participated. A blinded investigator recorded M-mode ultrasound imaging measurements of TrA thickness (mm) during 4 conditions as follows: (1) quiet standing without ADIM; (2) quiet standing with ADIM; (3) loaded forward-reach without ADIM; and (4) loaded forward-reach with ADIM. RESULTS: A mixed analysis of variance demonstrated a significant main effect for group (F [1, 34] = 5.404, P = 0.026; ), where TrA thickness was greater for NSLBP history (7.41 + 2.34 mm) versus controls (5.9 + 2.46 mm). A significant main effect was observed for abdominal contraction (F [1, 34] = 49.57, P < 0.0001; ), where TrA thickness was greater during ADIM (7.47 + 2.7 mm) versus without ADIM (5.84, 1.92 m). A significant main effect was observed for forward-reach activity (F [1, 34] = 12.79, P = 0.001; ), where TrA thickness was greater during a loaded forward-reach (7.04 + 2.6 mm) versus quiet standing (6.2 + 2.4 mm). There were no significant interactions. CONCLUSION: Individuals can use a volitional pre-emptive ADIM for trunk protection during loaded forward-reach, potentially reducing injury risk. A NSLBP history increases TrA activation during ADIM, suggesting an enhanced protective role. LEVEL OF EVIDENCE: 2.

The effect of isometric shoulder internal and external rotation on the acromiohumeral distance.

OBJECTIVE: This study aimed to determine the effect of isometric internal and external rotation at various degrees of shoulder abduction on the acromiohumeral distance (AHD). DESIGN: This was a prospective study that used a within-subject repeated-measures design and randomization of independent variables. Data from 29 of 58 (40 women, 18 men) prospectively enrolled healthy subjects were used for analysis. A still ultrasound image of the right subacromial space was taken to measure the AHD for each of three contraction conditions (rest, isometric internal, and external rotation) at three shoulder positions (neutral and 30 and 45 degrees of abduction). RESULTS: Intrarater reliability ranged from 0.86 to 0.99. At 45 degrees of shoulder abduction, the AHD was significantly smaller with isometric external rotation when compared with no contraction (P = 0.0015) and with isometric internal rotation (P = 0.0002). CONCLUSIONS: The AHD was not affected by resistive isometric internal rotation of the shoulder, although it decreased with resistive isometric external rotation at 45 degrees of shoulder abduction. Resistive isometric shoulder external rotation in a position of abduction should be used with caution when the goal is to maintain the AHD. Further research is required to determine the effects of isometric contraction in patients with subacromial impingement syndrome.

Reliability of a seated three-dimensional passive intervertebral motion test for mobility, end-feel, and pain provocation in patients with cervicalgia.

OBJECTIVES: Neck pain can be evaluated with passive intervertebral motion (PIVM). No study has evaluated the reliability of three-dimensional (3D) segmental PIVM testing of the cervical spine in symptomatic subjects in a functional, seated position. The purpose of this study was to evaluate inter-rater reliability of such 3D PIVM technique for pain provocation, hypomobility, and end-feel detection. METHODS: Subjects (n = 63), age 44±15·6 years, neck pain 3·4±1·6 cm with visual analog scale, were evaluated by two of three raters with varied manual therapy education and experience. To perform the test, the rater passively invoked side-bending motion at each cervical joint from C2-C3 to C6-C7, allowing segmental synkinetic rotation and extension to occur. Each joint was assessed for hypomobility, hard end-feel, and pain provocation. Kappa statistics were used to determine the inter-rater reliability for each variable for joints C2-C3 through C6-C7 for both the most painful and least painful sides. RESULTS: Percent agreements for pain provocation, hypomobility, and end-feel ranged 65-83%, 62-84%, and 68-87%, respectively. Kappa values for pain provocation, hypomobility, and end-feel on the most painful side were fair to moderate (0·29-0·53, 0·21-0·48, and 0·25-0·50, respectively), and on the least painful side were fair to substantial (0·43-0·65, 0·33-0·58, and 0·28-0·60, respectively). DISCUSSION: This is the first investigation to assess reliability of 3D cervical segmental testing in sitting and to assess reliability of end-feel. The seated 3D PIVM test has sufficient clinical reliability for use in patients with cervicalgia for the assessment of hypomobility, end-feel, and pain provocation.

Immediate changes in spinal height and pain after aquatic vertical traction in patients with persistent low back symptoms: a crossover clinical trial.

OBJECTIVE: To investigate the effect of aquatic vertical traction on spinal height, pain intensity, and centralization response compared with a land-based supine flexion position for patients with low back pain and signs of nerve root compression. DESIGN: Single-blind, repeated-measures crossover design. SETTING: Outpatient physical therapy clinic. SUBJECTS: Ninety-eight subjects were recruited using consecutive sampling, with 28 men and 32 women of a mean ± standard deviation (SD) age of 59.6 ± 11.6 years completing testing. INTERVENTION: Each subject participated in 2 sessions that consisted of loaded walking for 15 minutes, followed by either 15 minutes of land-based supine position or 15 minutes of aquatic vertical traction. MEASUREMENTS: Spinal height change, measured using a commercial stadiometer, was determined after completing loaded walking and after each intervention. RESULTS: The mean ± SD height change of 4.99 ± 2.88 mm after aquatic vertical traction was similar to that of 4.21 ± 2.53 mm after the land-based supine flexion (P = .0969). Paired t-test indicated that both interventions resulted in significant increased height (P < .0001). Decreases in pain after aquatic intervention (2.7 ± 2.1 cm) were significantly greater than decreases after land intervention (1.7 ± 1.7 cm; P = .0034), and centralization of symptoms was more pronounced after aquatic vertical suspension compared with the supine land-based flexion condition (P < .0001). A significant correlation between height change and both pain reduction (r = 0.39; P = .001) and centralization (r = 0.29; P = .013) was observed for the aquatic intervention only. CONCLUSION: Although both the aquatic and land interventions produced significant increases in overall spinal height, the aquatic intervention produced greater pain relief and centralization response in subjects with low back pain and signs of nerve root compression.

The deep neck flexor endurance test: normative data scores in healthy adults.

OBJECTIVE: To investigate (1) the average hold time for the deep neck flexors (DNF) endurance test in subjects without neck pain or pathology, and (2) whether different groups of subjects categorized by age, gender, and lifestyle display different hold times. DESIGN: Normative research. PATIENTS: A convenience sample of 126 adults participated. METHODS: Intertester reliability of 4 therapists was evaluated by using intraclass correlation coefficients. The DNF endurance test hold time was conducted on each subject twice. The 2 hold-time scores were averaged and recorded. RESULTS: Inter-rater reliability coefficient of reproducibility for DNF muscle endurance measured by 4 physical therapists was ICC (2,k) 0.66 (confidence interval, 0.34-0.86). The mean (SD) DNF endurance hold times for men was 38.9 ± 20.1 seconds, whereas women was 29.4 ± 13.7 seconds. Results of the 2 x 2 analysis of variance indicated that gender significantly influenced DNF endurance (F = 8.643; P = .004), whereas, the activity level did not (F = 3.143; P = .079). Correlations were not significant between age and DNF endurance (r = 0.11; P = .2) and between activity level and DNF endurance (r = -0.156; P = .08). CONCLUSIONS: Asymptomatic men displayed greater DNF endurance than women. The variability between subjects' DNF endurance capabilities was high. Age between 20 and 80 years and activity level did not affect DNF endurance. This is the first normative data set available for the DNF endurance test, which lays the foundation for further research in subjects with a history of cervicalgia and assists clinicians to objectify a milestone for DNF endurance deficits in patients.

Association of disturbances in the thoracic outlet in subjects with carpal tunnel syndrome: a case-control study.

INTRODUCTION: A limited amount of research has investigated the potential relationship between carpal tunnel syndrome (CTS) and thoracic outlet dysfunction. PURPOSE OF THE STUDY: To compare the prevalence of positive clinical tests suggestive of disputed neurogenic thoracic outlet syndrome (TOS) in subjects with CTS (CTS+) with that of subjects without CTS (control). STUDY DESIGN: Case-control study. METHODS: Subjects with electrodiagnostically confirmed CTS (CTS+) were recruited consecutively and matched by age (±2 years) and gender with asymptomatic (control) subjects. Subjects underwent clinical testing for neurogenic TOS using two provocative tests: modified Cyriax release test and elevated arm stress test (EAST). Subjects were tested for the presence of an elevated first rib using cervical rotation lateral flexion (CRLF) test. RESULTS: A total of 32 investigational subjects and 32 matched control subjects was included in each group (mean age: 43.5+5.9 years). A significantly greater number of CTS+ subjects presented with positive provocative testing for TOS (modified Cyriax release test p=0.005; EAST approached significance p=0.027) and for the presence of an elevated first rib (CRLF test p=0.003) as compared with controls. The likelihood of neck pain, shoulder pain, or an elevated first rib was 16 times greater in the CTS+ group as compared with that in the control group. CONCLUSIONS: A greater number of subjects with CTS presented with proximal dysfunctions suggestive of TOS and history of neck and shoulder pain. Evaluation of proximal structures involved with thoracic outlet dysfunction in persons with CTS has clinical merit. LEVEL OF EVIDENCE: Level III-b.

Change in spine height measurements following sustained mid-range and end-range flexion of the lumbar spine.

Workers lose height during the day. Flexion-based exercises and body positions are commonly prescribed to unload the spine and prevent back pain. Lumbar extension positions have been researched and result in an increase in spine height. End-range lumbar extension postures increase spine height to a greater extent than mid-range lumbar extension postures, but these positions are not always tolerated by patients with lumbar conditions. No study to date has investigated the effect of end-range versus mid-range lumbar flexion postures on spine height changes. The purpose of this study was to investigate the effects of two techniques commonly used in clinical settings to unload the lumbar intervertebral disc (IVD) segments through increasing spine height in: (1) a sidelying mid-range lumbar flexion position; and (2) a sidelying end-range lumbar flexion position. A total of 20 asymptomatic women and 21 asymptomatic men with a mean age of 23.8 years (±2.5) participated in the study. Subjects were randomized systematically into 2 groups to determine the order of testing position. Measurements were taken with a stadiometer in the sitting position to detect change in spine height after each position. Results of the paired t-tests indicated that compared to the spine height in sitting, the sidelying end-range lumbar flexion position resulted in a statistically significant (p < .001) mean spine height gain of 4.78 mm (±4.01) while the sidelying mid-range lumbar flexion position resulted in a statistically significant (p < .001) mean spine height gain of 5.84 mm (±4.4). No significant difference between the height changes observed following the two sidelying positions was found (p = .22). Sidelying lumbar flexion positions offer valuable alternatives to lumbar extension positions to increase spine height, possibly through increasing hydration levels of the lumbar IVD and could be proposed as techniques to offset spinal shrinkage and the biomechanical consequences of sustained loads.

Changes in transversus abdominis thickness with use of the abdominal drawing-in maneuver during a functional task.

OBJECTIVE: The purpose of this study was to examine an individual's ability to produce an increase in transversus abdominis (TrA) thickness during the performance of a functional task with the use of the abdominal drawing-in maneuver (ADIM). DESIGN: Within-subject repeated measures analysis of variance was used to examine the effects of the ADIM and a loaded forward-reaching activity on the dependent variable of TrA thickness. SETTING: Laboratory. PARTICIPANTS: Convenience sample of 8 women and 8 men, asymptomatic, with a mean age of 27.6 +/- 7.1 years. INTERVENTIONS: Ultrasound imaging measurements were recorded during 4 conditions: (1) while the patient was standing without the ADIM; (2) while the patient was standing with the ADIM; (3) during a loaded forward-reaching activity without the ADIM; and (4) during a loaded forward-reaching activity with the ADIM. MAIN OUTCOME MEASURES: Thickness of the TrA muscle. RESULTS: The measurement obtained by an investigator blinded to the condition revealed statistically significant differences in the thickness of the TrA between all uncontracted conditions as compared with all contracted conditions. No statistically significant difference in the thickness of the TrA in the contracted states during quiet standing versus loaded forward reach was observed. CONCLUSION: Subjects in this study demonstrated the ability to voluntarily activate the TrA during upright static and functional tasks. Additionally, the TrA thickness may change in a direction-specific manner. These findings support a protective role of the ADIM during functional activity and may add information to ways for promoting low back pain prevention. Future studies should include the effectiveness in the use of ADIM during functional tasks for the prevention of low back pain.

Changes in spinal height following sustained lumbar flexion and extension postures: a clinical measure of intervertebral disc hydration using stadiometry.

BACKGROUND: Decreased intervertebral disc height can result in diminished load carrying capacity of the spinal segment. Clinical means of assessing postures able to rehydrate the discs were investigated. OBJECTIVE: The purposes of this study were 3-fold: (1) to determine if our test protocol using a commercially available stadiometer demonstrated findings consistent with prior laboratory-based protocols; (2) to determine if hyperextension in the prone position and trunk flexion in the supine position caused increased spine height after sustained loading; and (3) to compare the effects of hyperextension in the prone position and trunk flexion in the supine position on spine height changes after a period of sustained loading. METHODS: This study used a pretest, posttest crossover design. Ten women and 11 men (mean age, 24 +/- 2.6 years) participated. Subjects held either 10 minutes of hyperextension in the prone position or 10 minutes of trunk flexion in the supine position in the recovery phase. Spine height was measured using a commercially available stadiometer. Spinal height change was determined from measurements taken after loaded sitting and measurements taken after hyperextension in the prone position and trunk flexion in the supine position. RESULTS: A 1-sample t test indicated no significant difference existed between our mean height change after 5 minutes of sitting and previously published validated findings. A paired t test indicated significant increase in height after both supine flexion and prone extension lying (P< .0001). The mean height gain was 3.11 mm using prone extension and 3.19 mm using the supine flexion protocol. A paired t test indicated no significant difference between these 2 recovery positions (P = .927). CONCLUSION: The stadiometer measurement protocol demonstrated that hyperextension in the prone position and trunk flexion in the supine position were easily effective positions for the temporary recovery of spine height after sustained loading. These findings lay the foundation for future research into the viscoelastic creep properties of the intervertebral disk under loading and therapeutic conditions.

Immunohistochemical and histological study of human uncovertebral joints: a preliminary investigation.

STUDY DESIGN: A descriptive cadaveric study. OBJECTIVE: To investigate the anatomy and innervation of the uncovertebral joint to determine if it is synovial in nature and capable of generating pain. SUMMARY OF BACKGROUND DATA: There is controversy with regard to the anatomic and histological makeup of the uncovertebral interface with some authors considering it a joint and others disc tissue. No research has investigated the presence of pain generating neurotransmitters within the uncovertebral cartilaginous and capsular tissue. METHODS: Tissue from uncovertebral capsule and cartilage was harvested for each uncovertebral surface starting at the C2-C3 to the C6-C7 cervical segment. The tissue was placed in 4% paraformaldehyde fixative, then dehydrated and embedded in paraffin. Ten micron sections were cut through the tissue blocks and mounted on slides. The tissue was rehydrated and either stained with hematoxylin and eosin (H and E) or immunostained with antisera against protein gene product 9.5 (PGP 9.5), substance P (SP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP). RESULTS: The sample consisted of 2 unembalmed fresh male human cadavers of a mean age of 83 years. Chondrocytes and synoviocytes were identified at the capsular tissue of each uncovertebral interface from C2-C3-C6-C7. Immunoreactivity for PGP 9.5, SP, CGRP, and NPY was observed at all uncovertebral interface levels in capsular tissue. CONCLUSION: The presence of both synoviocytes and chondrocytes has been recorded in the present study, suggesting that the uncovertebral interface is synovial in nature. Immunoreactivity to PGP 9.5, SP, CGRP, and NPY indicates the presence of nerve fibers from both the somatic and autonomic nervous systems. These findings suggest that the uncovertebral joints are potential pain generators in the cervical spine.

Effect of sex hormones on neuromuscular control patterns during landing.

The purpose of the study was to investigate the effects of sex hormones across menstrual cycle phases on lower extremity neuromuscular control patterns during the landing phase of a drop jump. A repeated-measures design was utilized to examine sex hormone effects in 26 recreationally active eumenorrheic women. Varus/valgus knee angle and EMG activity from six lower extremity muscles were recorded during three drop jumps from a 50 cm platform in each phase of the menstrual cycle. Blood assays verified sex hormone levels and cycle phase. The semitendinosus muscle exhibited onset delays (p0.006) relative to ground contact during the luteal phase, and demonstrated a significant (p0.05) difference between early and late follicular phases. Muscle timing differences between the gluteus maximus and semitendinosus were decreased (p0.05) in the luteal compared to early follicular phases. These results suggest a different co-contractive behavior between the gluteus maximus and semitendinosus, signifying a shift in neuromuscular control patterns. It appears that female recreational athletes utilize a different neuromuscular control pattern for performing a drop jump sequence when estrogen levels are high (luteal phase) compared to when they are low (early follicular phase).