Microrollers flow uphill as granular media.

Pour sand into a container and only the grains near the top surface move. The collective motion associated with the translational and rotational energy of the grains in a thin flowing layer is quickly dissipated as friction through multibody interactions. Alternatively, consider what will happen to a bed of particles if one applies a torque to each individual particle. In this paper, we demonstrate an experimental system where torque is applied at the constituent level through a rotating magnetic field in a dense bed of microrollers. The net result is the grains roll uphill, forming a heap with a negative angle of repose. Two different regimes have been identified related to the degree of mobility or fluidisation of the particles in the bulk. Velocimetry of the near surface flowing layer reveals the collective motion of these responsive particles scales in a similar way to flowing bulk granular flows. A simple granular model that includes cohesion accurately predicts the apparent negative coefficient of friction. In contrast to the response of active or responsive particles that mimic thermodynamic principles, this system results in macroscopic collective behavior that has the kinematics of a purely dissipative granular system.

Dynamic Leap and Balance Test: Ability to Discriminate Balance Deficits in Individuals With Chronic Ankle Instability.

CONTEXT: The Dynamic Leap Balance Test (DLBT) is a new dynamic balance task that requires serial changes in base of support with alternating limb support and recovery of dynamic stability, as compared with the Y modification of the Star Excursion Balance Test (Y-SEBT), which assesses dynamic stability over an unchanging base of support. OBJECTIVES: To assess the dynamic balance performance in 2 different types of dynamic balance tasks, the DLBT and the SEBT, in subjects with unilateral chronic ankle instability (CAI) when compared with matched controls. The authors hypothesized that the DLBT score would significantly differ between the CAI involved and uninvolved limbs (contralateral and healthy matched) and demonstrate a modest (r = .50) association with the SEBT scores. DESIGN: Case-control. SETTING: Controlled laboratory. PARTICIPANTS: A total of 36 physically active adults, 18 with history of unilateral CAI and 18 without history of ankle injury, were enrolled in the study. CAI subjects were identified using the Identification of Functional Ankle Instability questionnaire. INTERVENTIONS: The DLBT and the SEBT were performed in a randomized order on a randomly selected limb in CAI and healthy subjects. MAIN OUTCOME MEASURES: Time taken to complete the DLBT and the reach distances performed on the SEBT were compared between the CAI and the healthy subjects. RESULTS: There were no statistically significant differences (P < .05) in SEBT reach distances between groups. The DLBT time was greater (P < .01) for unstable ankles compared with the stable ankle. The authors found no correlation (P > .05) between DLBT time and any of the SEBT reach distances suggesting that the DLBT provides unique information in the assessment of patients with CAI. CONCLUSION: The DLBT challenges the ability to maintain postural control in CAI subjects differently than the SEBT. There is a need of more dynamic balance assessment tools that are functional and clinically relevant.

The Comparative Effects of Ankle Bracing on Functional Performance.

Ankle sprains represent a common musculoskeletal injury that clinicians are tasked with preventing and treating. Because of the prevalence of this injury, ankle braces have been designed to prophylactically protect the joint and reduce the incidence of repetitive sprains. Although an abundance of literature exists focusing on the efficacy of braces in preventing ankle sprains in young, healthy, and physically active populations, there is a scarcity of evidence specific to the impact of these apparatuses on functional performance; therefore, the purpose of this critically appraised topic (CAT) is to investigate the effects of ankle braces on functional performance measures in such individuals. The outcomes of this CAT will assist sport rehabilitation specialists with informed clinical decision making in managing young, healthy, and physically active populations using ankle braces. Do ankle braces hinder functional performance measures when compared with an unbraced condition in a young, healthy, and physically active population? A minimum of level II evidence research studies were surveyed for this CAT. For this CAT, 1 randomized controlled trial and 3 prospective cohort studies were selected. One study found a statistically significant main effect of increased agility run times while participants wore ankle braces. Another study demonstrated a statistically significant decrease in vertical jump height and ankle range of motion while wearing braces. No other statistically significant findings were reported among studies comparing unbraced with braced conditions. Current data indicate that young, healthy, and physically active individuals may experience varied performance effects when executing specific functional performance tasks while wearing ankle braces. In general, bracing does not appear to significantly impair performance on most functional tasks; however, decrements were noted to increases in agility run time and decreases in vertical jump height. Subsequent analysis indicated that a brace may result in decreased ankle plantarflexion, dorsiflexion, eversion, and inversion range of motion, which may underpin noted performance deficits.

Standing flexion deficits predict self-reported outcomes in women after ipsilateral hamstring anterior cruciate ligament reconstruction.

PURPOSE: To profile the standing flexion angle and its association with subjective outcomes in ipsilateral hamstring tendon autograft anterior cruciate ligament-reconstructed patients. A secondary aim was to describe prone position-measured hamstring strength as a predictor of flexion angle. METHODS: Fifteen women (mean age, 20.47 ± 1.96 years; mean height, 1.69 ± 0.08 m; mean weight, 68.51 ± 12.64 kg; mean Tegner score, 6.80 ± 1.52), at a mean of 25.93 ± 11.25 months after surgery, were matched to 15 healthy participants by sex and approximate age, height, mass, and activity level (mean age, 20.93 ± 1.22 years; mean height, 1.65 ± 0.06 m; mean weight, 66.52 ± 10.69 kg; mean Tegner score, 6.13 ± 1.06). The independent variable was leg condition (involved, uninvolved, or matched). Dependent variables included goniometric flexion angle, Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale scores, and absolute isokinetic hamstring strength. We used 1-tailed paired and 2-sample t tests to analyze side and group differences, respectively. Corresponding effect sizes (d) were also quantified. Linear regression assessed relations between flexion angle and the KOOS, as well as strength and flexion angle. P < .05 denoted statistical significance. RESULTS: The involved leg showed a significantly lesser flexion angle (112.9° ± 8.1°) compared with the uninvolved leg (116.1° ± 8.4°, P = .024) and matched leg (117.1° ± 4.5°, P = .044), with corresponding weak side (d = 0.380) and strong group (d = 0.958) effect sizes. Significant associations existed between flexion angle and subjective outcomes (r(2) = 60.3% and P = .001 for KOOS pain subscale, r(2) = 37.8% and P = .015 for KOOS subscale for function in activities of daily living, and r(2) = 39.2% and P = .012 for KOOS subscale for function in sports and recreation) for the involved leg. Hamstring strength was not a significant predictor of flexion angle for all legs (P > .05). CONCLUSIONS: Our results support the hypotheses that standing flexion angle insufficiencies exist for the involved leg, superior subjective outcomes are associated with greater flexion capacity, and hamstring strength at deep knee angles does not predict the standing flexion angle. LEVEL OF EVIDENCE: Level IV, therapeutic study, case series.

Injury/illness physician referral profile from a youth university-sponsored summer sport camp program.

Participation at university-sponsored summer sport camps is popular among youth athletes; however, there is a dearth of information to describe the injuries/illnesses experienced by camp participants. Data from a university-sponsored sport camp program from 2008 to 2011 were accessed retrospectively. The sport camp program had approximately 80 camps for 28 sports over 12 weeks annually. Male and female participants were 10 to 17 years old. Athletic trainers maintained medical documentation and provided medical referrals. Referrals were made for 9.9% (n=478) of all injuries/illnesses. Emergency department referrals were made for 2.9% of injuries/illnesses. University health services received 42.5% of referrals. There were 1.1 referrals per 100 participants. Boys comprised 60.7% of referrals. Rugby had the highest referral rate--5.0 per 100 participants. These data help increase physician preparedness and guide the delivery of sports medicine services for related sport camp programs as a means to improve quality of care delivered to participants.

Premature knee osteoarthritis after anterior cruciate ligament reconstruction dependent on autograft.

Anterior cruciate ligament (ACL) reconstructions are common postoperative orthopedic conditions encountered by sports rehabilitation specialists. The rationale for reconstructing the ACL is to restore mechanical stability of the knee joint and prevent associated musculoskeletal sequelae. The selection of available autogenous graft options for surgical interventions continues to be a controversial topic in orthopedic sports medicine. Two established methods for reconstructing the ACL include using the ipsilateral patellar tendon or the semitendinosus and gracilis tendons. Both procedures yield advantages and disadvantages. However, a current outcome trend suggests that the bone-patellar tendon-bone (BPTB) procedure may serve as a catalyst for accelerating the progression of knee osteoarthritis. Such a consequence poses unique athletic health care concerns, especially with the increased incidence of ACL injuries and reconstructions among younger individuals. Therefore, implementing a semitendinosus and gracilis (STG) technique for ACL reconstruction may provide a means of decreasing the incidence of premature tibiofemoral or patellofemoral osteoarthritis in the physically active population. Sports rehabilitation specialists must be aware of this phenomenon to help sports medicine personnel and physically active patients identify expected trend outcomes with diverse ACL-reconstruction methods.

Systematic review of efficacy for manual lymphatic drainage techniques in sports medicine and rehabilitation: an evidence-based practice approach.

Manual therapists question integrating manual lymphatic drainage techniques (MLDTs) into conventional treatments for athletic injuries due to the scarcity of literature concerning musculoskeletal applications and established orthopaedic clinical practice guidelines. The purpose of this systematic review is to provide manual therapy clinicians with pertinent information regarding progression of MLDTs as well as to critique the evidence for efficacy of this method in sports medicine. We surveyed English-language publications from 1998 to 2008 by searching PubMed, PEDro, CINAHL, the Cochrane Library, and SPORTDiscus databases using the terms lymphatic system, lymph drainage, lymphatic therapy, manual lymph drainage, and lymphatic pump techniques. We selected articles investigating the effects of MLDTs on orthopaedic and athletic injury outcomes. Nine articles met inclusion criteria, of which 3 were randomized controlled trials (RCTs). We evaluated the 3 RCTs using a validity score (PEDro scale). Due to differences in experimental design, data could not be collapsed for meta-analysis. Animal model experiments reinforce theoretical principles for application of MLDTs. When combined with concomitant musculoskeletal therapy, pilot and case studies demonstrate MLDT effectiveness. The best evidence suggests that efficacy of MLDT in sports medicine and rehabilitation is specific to resolution of enzyme serum levels associated with acute skeletal muscle cell damage as well as reduction of edema following acute ankle joint sprain and radial wrist fracture. Currently, there is limited high-ranking evidence available. Well-designed RCTs assessing outcome variables following implementation of MLDTs in treating athletic injuries may provide conclusive evidence for establishing applicable clinical practice guidelines in sports medicine and rehabilitation.

The relationship between grading and instrumented measurements of anterior knee joint laxity.

CONTEXT: The relationship between clinical judgments of anterior knee laxity and instrumented measurement of anterior tibial translation is unclear. OBJECTIVE: To examine the relationship between certified athletic trainers'grading of anterior knee laxity and instrumented measurements of anterior tibial translation. DESIGN: Randomized, blinded, clinical assessment. SETTING: Laboratory. PARTICIPANTS: Model patients receiving evaluation of anterior knee laxity. INTERVENTION: Twelve model patients were evaluated using a MEDmetric KT1000 knee ligament Arthrometer to establish instrumented measurements of anterior translation values at the tibio-femoral joint. Twenty-two certified athletic trainers were provided with operational definitions of potential laxity grades and examined the model patients to make judgments of anterior knee laxity. MAIN OUTCOME MEASURES: Correlation between clinical judgments and instrumented measurements of anterior tibial translation. RESULTS: Clinical judgments and instrumented measurements were mutually independent. CONCLUSIONS: Anterior tibial translation grading by certified athletic trainers should be interpreted with caution during clinical decision-making.

The Effects of Fatigue and Chronic Ankle Instability on Dynamic Postural Control.

OBJECTIVE: Deficits in static postural control related to chronic ankle instability (CAI) and fatigue have been investigated separately, but little evidence links these factors to performance of dynamic postural control. Our purpose was to investigate the effects of fatigue and CAI on performance measures of a dynamic postural-control task, the Star Excursion Balance Test. DESIGN AND SETTING: For each of the 3 designated reaching directions, 4 separate 5 (condition) x 2 (time) x 2 (side) analyses of variance with a between factor of group (CAI, healthy) were calculated for normalized reach distance and maximal ankle-dorsiflexion, knee-flexion, and hip-flexion angles. All data were collected in the Athletic Training Research Laboratory. SUBJECTS: Thirty subjects (16 healthy, 14 CAI) participated. MEASUREMENTS: All subjects completed 5 testing sessions, during which sagittal-plane kinematics and reaching distances were recorded while they performed 3 reaching directions (anterior, medial, and posterior) of the Star Excursion Balance Test, with the same stance leg before and after different fatiguing conditions. The procedure was repeated for both legs during each session. RESULTS: The involved side of the CAI subjects displayed significantly smaller reach distance values and knee-flexion angles for all 3 reaching directions compared with the uninjured side and the healthy group. The effects of fatigue amplified this trend. CONCLUSIONS: Chronic ankle instability and fatigue disrupted dynamic postural control, most notably by altering control of sagittal-plane joint angles proximal to the ankle.

Cryotherapy, Sensation, and Isometric-Force Variability.

OBJECTIVE: To determine the changes in sensation of pressure, 2-point discrimination, and submaximal isometric-force production variability due to cryotherapy. DESIGN AND SETTING: Sensation was assessed using a 2 x 2 x 2 x 3 repeated-measures factorial design, with treatment (ice immersion or control), limb (right or left), digit (finger or thumb), and sensation test time (baseline, posttreatment, or postisometric-force trials) as independent variables. Dependent variables were changes in sensation of pressure and 2-point discrimination. Isometric-force variability was tested with a 2 x 2 x 3 repeated-measures factorial design. Treatment condition (ice immersion or control), limb (right or left), and percentage (10, 25, or 40) of maximal voluntary isometric contraction (MVIC) were the independent variables. The dependent variables were the precision or variability (the standard deviation of mean isometric force) and the accuracy or targeting error (the root mean square error) of the isometric force for each percentage of MVIC. SUBJECTS: Fifteen volunteer college students (8 men, 7 women; age = 22 +/- 3 years; mass = 72 +/- 21.9 kg; height = 183.4 +/- 11.6 cm). MEASUREMENTS: We measured sensation in the distal palmar aspect of the index finger and thumb. Sensation of pressure and 2-point discrimination were measured before treatment (baseline), after treatment (15 minutes of ice immersion or control), and at the completion of isometric testing (final). Variability (standard deviation of mean isometric force) of the submaximal isometric finger forces was measured by having the subjects exert a pinching force with the thumb and index finger for 30 seconds. Subjects performed the pinching task at the 3 submaximal levels of MVIC (10%, 25%, and 40%), with the order of trials assigned randomly. The subjects were given a target representing the submaximal percentage of MVIC and visual feedback of the force produced as they pinched the testing device. The force exerted was measured using strain gauges mounted on an apparatus built to measure finger forces. RESULTS: Sensation of pressure was less (ie, it took greater pressure to elicit a response) after ice immersion, thumbs were more affected than index fingers, and the decrease was greater in the right limb than the left. Two-point discrimination was not affected by cryotherapy but was higher in the finger than in the thumb under all conditions. Isometric-force variability (standard deviation of mean isometric force) was greater as percentage of force increased from 10% to 40% of MVIC. Targeting accuracy (root mean square error) was decreased at 40% of MVIC. Accuracy and force variability were not affected by cryotherapy. CONCLUSIONS: The application of cryotherapy and reduced sensation of pressure appear to have little effect on motor control of the digits. These results support the hypothesis that the use of cold is not contraindicated for use as an analgesic before submaximal rehabilitative exercise focusing on restoring neuromuscular control to injured tissues.