Alexis Ortiz

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.

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.

Landing Mechanics During Side Hopping and Crossover Hopping Maneuvers in Noninjured Women and Women With Anterior Cruciate Ligament Reconstruction

To compare, landing mechanics and electromyographic activity of the lower extremities during side hopping and crossover hopping maneuvers, in noninjured women and women with anterior cruciate ligament (ACL) reconstruction.

Reliability of selected physical performance tests in young adult women.

The purposes of this investigation were to establish the reliability of selected physical performance tests in women athletes and nonathletes and to determine performance differences between groups. Fifty women (25 athletes, 25 nonathletes) performed 5 tests in 2 sessions. The performance tests included the figure-eight hop test, up-and-down hop test, side-to-side hop test, hexagon hop test, and zigzag run test. Intraclass correlation coefficients (ICC [2, 1]) were calculated for trial-to-trial, intertester, and day-to-day reliability. Independent t-tests with Bonferroni adjustment (a = 0.01) were used for each individual test to compare differences between groups. All tests showed good reliability values (ICC >= 0.76) in the nonathlete group for all conditions and varied reliability values (0.48�0.99) among conditions in the athlete group. The independent t-tests showed a statistically significant group effect (t >= 3.041; p <= 0.004) for all tests. The results showed that these physical performance tests are reliable measurement tools in the female population.

Biomechanical Evaluation of the Athlete's Knee: From Basic Science to Clinical Application

Clinical screening to assess knee biomechanical dysfunctions and its comorbidities has been of interest for researchers and clinicians in recent years. Although research in the area of knee injury mechanics has elucidated some of the biomechanical predisposing factors that lead to knee injury, clinicians are still puzzled on how to translate these findings to their clinical practice. Highly instrumented, costly equipment and time‐consuming data analyses are some of the difficulties of using 3‐dimensional biomechanical analysis in the clinic. However, several biomechanical lower‐extremity assessment tools are available and feasible to use in the clinic to guide proper clinical decision making that may impact prevention of knee injuries in the physically active population. The purpose of this article was to review screening techniques for assessment of lower extremity biomechanics and to translate these findings to clinical practice and to bridge the gap between basic science and clinical application. After reading this article, clinicians should be able to (1) identify lower‐extremity factors related to knee injury, (2) appropriately select functional tasks to evaluate patients, and (3) make intervention recommendations or appropriate referral to address altered lower‐extremity biomechanics related to knee injury.

Longitudinal social cognitive influences on physical activity and sedentary time in Hispanic breast cancer survivors.

This study evaluated the effect of two home‐based exercise interventions (one culturally adapted and one standard) on changes in social cognitive theory (SCT) variables, physical activity (PA), and sedentary time (ST), and determined the association between changes in SCT variables and changes in PA and ST in Hispanic breast cancer survivors.

Biomechanical deficiencies in women with semitendinosus-gracilis anterior cruciate ligament reconstruction during drop jumps.

OBJECTIVE To compare landing mechanics and neuromuscular recruitment strategies between women with semitendinosus-gracilis anterior cruciate ligament reconstruction (SG-ACLr) and noninjured women during double- and single-legged drop jumps. DESIGN Cross-sectional biomechanical study. SETTING Single university-based biomechanics laboratory. PARTICIPANTS Fourteen women 1-5 years post-SG-ACLr and 16 noninjured women participated in this study. METHODS After anthropometric measurements, warm-up, and familiarization procedures, participants performed 5 trials of a double- and single-legged drop jumps. MAIN OUTCOME MEASUREMENTS Dynamic knee valgus was measured as the distance between knee joints during the landing phase of the double-leg drop jumps. Medial knee displacement was the outcome considered during the landing phase of the single-leg drop jumps. For both drop jump tasks, neuromuscular recruitment was evaluated through rectified normalized electromyographic activity of the quadriceps and hamstrings (amplitude and latency), and quadriceps/hamstrings electromyographic co-contraction ratio. RESULTS Although the SG-ACLr group demonstrated a tendency toward a greater dynamic knee valgus during both drop jumps, these differences did not reach statistical significance. EMG data revealed different neuromuscular strategies for each group, depending on the specific jump. CONCLUSIONS These findings suggest that women with SG-ACLr have a tendency toward greater dynamic knee valgus that could predispose to additional knee injuries. Rehabilitation specialists need to be aware of existing kinematic and neuromuscular deficiencies years after SG-ACLr. Taking this into consideration will aid in prescribing appropriate interventions designed to prevent re-injury.

Exercise for Adults Living with Human Immunodeficiency Virus Infection in the Era of Highly Active Antiretroviral Therapy

Human Immunodeficiency Virus (HIV) infection is now considered a chronic, long-term disease, potentially affecting all body systems and causing disturbances in functional status. Beside the immune system, the cardiovascular, neuromuscular, and musculoskeletal systems are three of the body systems most affected by HIV and/or its treatment. With these systems affected, mobility and functional activities can be limited in people with this chronic infection. Aerobic and resistive exercise programs have improved bodily function, Health Related Quality of Life (HRQoL), and increased participation in daily life activities of individuals living with HIV. Rehabilitation professionals involved in the treatment of people living with HIV infection must consider exercise prescription or promotion of an active lifestyle as part of their routine clinical evaluation and management. The purpose of this review is twofold: 1) provide rehabilitation clinicians a summary of the effects of exercise on the cardiovascular, neuromuscular, and musculoskeletal systems of adults infected with HIV and 2) discuss the short and long-term benefits of regular aerobic and/or resistive exercise in this population.

Reliability and concurrent validity between two-dimensional and three-dimensional evaluations of knee valgus during drop jumps.

Purpose The aim of this study was to establish the concurrent validity and reliability of four different two-dimensional (2D) video-based techniques for quantifying frontal plane knee kinematics during a 40 cm double-legged drop jump. Participants and methods A convenience sample of 16 healthy participants (nine males and seven females; age: [mean ± standard deviation] 25.5±2 years; body mass index: 24.33±2.98 kg/m2) participated in this investigation. A total of five trials during a 40 cm drop jump maneuver with a countermovement jump were used as the functional task. Four knee valgus measures, such as two different frontal plane projection angle measures, knee-to-ankle separation ratio (KASR), and knee separation distance (KSD), were measured using 2D and three-dimensional (3D) systems. To generalize to the greater population of possible evaluators, the testers performing the biomechanical analyses were three novice physical therapists. Intra- and intertester intraclass correlation coefficients (ICCs) were estimated for 2D analysis variables. ICCs were estimated for all measures between systems to determine concurrent validity of the 2D system. Results All four 2D measures showed good to excellent reliability (ICC: 0.89–0.99). KASR and KSD showed excellent correlation (ICC: 0.96; 95% CI: 0.82–0.98 and ICC: 0.94; 95% CI: 0.90–0.96, respectively) with the 3D system, while both methods of frontal plane projection angle showed poor to moderate correlation (ICC: 0–0.57) with the 3D system. Conclusion 2D KASR and KSD measures are cost effective, reliable, and highly correlated with the same measures using 3D techniques for the evaluation of knee valgus.

Core Stability for the Female Athlete: A Review

&NA; The anatomical core that is addressed in stability training refers to the combination of all muscles that surround the lumbo‐pelvic‐hip complex. Weakness of these muscles has been proposed to be related to greater incidence of lower extremity injuries in female athletes in sports that require jumping and high‐speed running combined with cutting/pivoting maneuvers. Core stabilization and strengthening programs are thought to promote increased lumbo‐pelvic‐hip stability and increased neuromuscular recruitment toward the intended goal of decreasing low back and lower extremity injuries. Despite anecdotal reports of these positive training effects, a direct relationship between core strength and greater athletic performance has not been strongly supported in the literature. An understanding of the available evidence will assist those involved with the training and rehabilitation of female athletes in using an evidence‐based approach when developing training programs in order to reduce the increased incidence of lower extremity injuries in female athletes. Literature for this review was identified through the electronic databases MEDLINE, PUBMED, CINAHL, and SPORTDISCUS. The keywords core stability, female athlete, injury, lower extremity, low back, and pelvis were used alone and in various combinations.