Achilles tendon adaptation in cross-country runners across a competitive season.

Ultrasound tissue characterization (UTC) is an imaging tool used to quantify tendon structural integrity. UTC has quantified Achilles tendon (AT) acute response to load in athletes; however, AT response to cumulative load over a season is unknown. The purpose of this study was to evaluate AT response across a four-month competitive season in collegiate cross-country (XC) runners. Participants (n=21; male=9, female=12; age=19.8±1.2 years; height=171.9±8.9 cm; weight=60.2±8.5 kg) were imaged using the UTC device with a 10-MHz linear-array transducer mounted in a tracking device. The device captures images at 0.2 mm intervals along the AT. UTC algorithms quantified the stability of pixel brightness over every 17 contiguous transverse images into four echo types (I-IV). A total of 168 scans (n=21, bilateral limbs) were performed monthly across the four-month season (Aug=M1, Sep=M2, Oct=M3, Nov=M4). Echo-type percentages (%) were calculated from each scan. Generalized estimating equations (GEE) linear regression models evaluated echo-type % change (ß) over the season (M1=reference). Type I increased from M1 to M4 (ß=9.10, P<.01; 95%CI: 7.01, 11.21) and Type II decreased from M1 to M3 (ß=-2.71, P=.018; 95%CI: -4.96, -0.47) and M1 to M4 (ß=-10.19, P<.01; 95%CI: -12.22, -8.17). Type III increased from M1 to M3 (ß=0.42, P=.003; 95%CI: 0.19, 0.65) and M1 to M4 (ß=0.49, P=.002; 95%CI: 0.18, 0.81), Type IV increased from M1 to M4 (ß=0.57, P<.01; 95%CI: 0.29, 0.84). A positive adaptation in AT structural integrity was observed over the XC season, with a ~10% shift from Type II to Type I UTC echo types, suggesting AT resilience to a competitive season of repetitive loading in highly trained runners.

The influences of sex and posture on joint energetics during drop landings.

Previous observations suggest that females utilize a more erect initial landing posture than males with sex differences in landing posture possibly related to sex-specific energy absorption (EA) strategies. However, sex-specific EA strategies have only been observed when accompanied by sex differences in initial landing posture. This study (a) investigated the potential existence of sex-specific EA strategies; and (b) determined the influences of sex and initial landing posture on the biomechanical determinants of EA. The landing biomechanics of 80 subjects were recorded during drop landings in Preferred, Flexed, and Erect conditions. No sex differences in joint EA were identified after controlling for initial landing posture. Males and females exhibited greater ankle EA during Erect vs Flexed landings with this increase driven by 12% greater ankle velocity, but no change in ankle extensor moment. No differences in hip and knee EA were observed between conditions. However, to achieve similar knee EA, subjects used 7% greater mean knee extensor moment but 9% less knee angular velocity during Flexed landings. The results suggest that sex-specific EA strategies do not exist, and that the magnitude of knee joint EA can be maintained by modulating the relative contributions of joint moment and angular velocity to EA.

Effect of fatigue on landing performance assessed with the landing error scoring system (less) in patients after ACL reconstruction. A pilot study.

BACKGROUND: Fatigue has been shown to affect performance of hop tests in patients after anterior cruciate ligament reconstruction (ACLR) compared to uninjured controls (CTRL). This may render the hop test less sensitive in detecting landing errors. The primary purpose of this study was to investigate the effect of lower extremity fatigue on landing performance assessed with the Landing Error Scoring System (LESS) in patients after ACLR compared to a CTRL group. It is plausible that fatigue would have an effect on confidence and risk appraisal in the ACLR group. The secondary purpose was to determine the relationship between psychological responses and LESS scores after fatigue. METHODS: Twelve patients following ACLR (6 males, 6 females) who were tested at 10 ± 2.4 months after surgery participated in the current study and were compared to 10 subjects in the control group (5 males, 5 females). Subjects performed a jump-landing task and the landing was assessed using the Landing Error Scoring System (LESS) both before and after fatigue. Digital video camcorders recorded frontal and sagittal plane views of the subject performing the task. The LESS was scored using video replay. Psychological responses in the ACLR group were assessed with the ACL-RSI questionnaire. RESULTS: Patients after ACLR had a median LESS of 6.5 which reflects a poor result (LESS >6) in the pre-fatigue condition compared to controls who had a LESS of 2.5 which is considered excellent (≤4). In the post-fatigue condition, median LESS in patients after ACLR increased to 7.0 whereas in the control group the LESS increased to 6.0 both of which reflect a poor result. The median increase in LESS was larger in the control (2.0) group compared to patients after ACLR (1.0) but the difference was not significant (p=0.165). CONCLUSIONS: Patients after ACLR have higher LESS scores at baseline compared to a control group. Fatigue resulted in an increase in scores on the LESS in both groups. LEVEL OF EVIDENCE: 3b.

Gender differences in the incidence and prevalence of patellofemoral pain syndrome.

The purpose of this investigation was to determine the association between gender and the prevalence and incidence of patellofemoral pain syndrome (PFPS). One thousand five hundred and twenty-five participants from the United States Naval Academy (USNA) were followed for up to 2.5 years for the development of PFPS. Physicians and certified athletic trainers documented the cases of PFPS. PFPS was defined as retropatellar pain during at least two of the following activities: ascending/descending stairs, hopping/jogging, prolonged sitting, kneeling, and squatting, negative findings on examination of knee ligament, menisci, bursa, and synovial plica, and pain on palpation of either the patellar facets or femoral condyles. Poisson and logistic regressions were performed to determine the association between gender and the incidence and prevalence of PFPS, respectively. The incidence rate for PFPS was 22/1000 person-years. Females were 2.23 times (95% CI: 1.19, 4.20) more likely to develop PFPS compared with males. While not statistically significant, the prevalence of PFPS at study enrollment tended to be higher in females (15%) than in males (12%) (P=0.09). Females at the USNA are significantly more likely to develop PFPS than males. Additionally, at the time of admission to the academy, the prevalence of PFPS was not significantly different between genders.

Gender differences in active musculoskeletal stiffness. Part II. Quantification of leg stiffness during functional hopping tasks.

Leg stiffness was compared between age-matched males and females during hopping at preferred and controlled frequencies. Stiffness was defined as the linear regression slope between the vertical center of mass (COM) displacement and ground-reaction forces recorded from a force plate during the stance phase of the hopping task. Results demonstrate that subjects modulated the vertical displacement of the COM during ground contact in relation to the square of hopping frequency. This supports the accuracy of the spring-mass oscillator as a representative model of hopping. It also maintained peak vertical ground-reaction load at approximately three times body weight. Leg stiffness values in males (33.9+/-8.7 kN/m) were significantly (p<0.01) greater than in females (26.3+/-6.5 kN/m) at each of three hopping frequencies, 3.0, 2.5 Hz, and a preferred hopping rate. In the spring-mass oscillator model leg stiffness and body mass are related to the frequency of motion. Thus male subjects necessarily recruited greater leg stiffness to drive their heavier body mass at the same frequency as the lighter female subjects during the controlled frequency trials. However, in the preferred hopping condition the stiffness was not constrained by the task because frequency was self-selected. Nonetheless, both male and female subjects hopped at statistically similar preferred frequencies (2.34+/-0.22 Hz), therefore, the females continued to demonstrate less leg stiffness. Recognizing the active muscle stiffness contributes to biomechanical stability as well as leg stiffness, these results may provide insight into the gender bias in risk of musculoskeletal knee injury.

Epidemiology of concussion in collegiate and high school football players.

Despite evolutionary changes in protective equipment, head injury remains common in football. We investigated concussion in football and associated epidemiologic issues such as 1) incidence of injury, 2) common signs and symptoms, and 3) patterns in making return-to-play decisions. We received 242 of 392 surveys (62%) that were sent to high school and collegiate certified athletic trainers at the beginning of three football seasons. Of the 17,549 football players represented, 888 (5.1%) sustained at least one concussion, and 131 (14.7% of the 888) sustained a second injury during the same season. The greatest incidence of concussion was found at the high school (5.6%) and collegiate division III (5.5%) levels, suggesting that there is an association between level of play and the proportion of players injured. Players who sustained one concussion in a season were three times more likely to sustain a second concussion in the same season compared with uninjured players. Contact with artificial turf appears to be associated with a more serious concussion than contact with natural grass. Only 8.9% of all injuries involved loss of consciousness, while 86% involved a headache. Overall, 30.8% of all players sustaining a concussion returned to participation on the same day of injury.

Resistance to common viruses during intralymphatic injections of tumor cell vaccines. Correlation with circulating cytokines.

Patients with advanced malignancies who received intralymphatic injections of irradiated tumor cell suspensions ("vaccines") were unexpectedly found to be resistant to common viral diseases; 17 patients with a documented past history of viral infections who have been observed for 48 to 148 months (median 108 months), were analyzed. The resistance to viruses was found to correlate closely with the presence, in the serum, of certain cytokines. Specifically, the interleukins, -2, -6, -8 and interferon-gamma, at low but sustained levels appeared to be possibly responsible for the nonspecific protection against viral infections obtained by intralymphatic injections of cellular material. These findings suggest that viral infections in normal or immunosuppressed individuals at particular risk might be prevented by treatments aimed at attaining very modest levels of certain cytokines.

Effects of 13 cis-retinoic acid on growth and differentiation of human follicular carcinoma cells (UCLA R0 82 W-1) in vitro.

Dedifferentiation of human thyroid tumors is frequently found in humans. The effect of retinoids (13 cis-RA) was studied on the proliferation and differentiation of a human follicular cell line in vitro (UCLA R0 82 W-1). A significant and dose-dependent reduction (P less than 0.001) in cell number and [3H] thymidine uptake was found in cells exposed to 13 cis-RA up to 10 microM. Higher concentrations of 13 cis-RA, however, led to a dose-dependent restoration of cell proliferation. Various parameters of differentiation increased under the influence of 13 cis-RA (10 microM) over nonexposed cells. The 125I uptake increased 4-fold over that in control nonexposed cells (P less than 0.05). [125I] Epidermal growth factor binding increased 5-fold, and [125I] human TSH binding increased significantly after exposure to 13 cis-RA (P less than 0.02). Deiodinase activity, however, was significantly lower in 13 cis-RA exposed cells than in control cells. The present study shows that 13 cis-RA (10 microM) drives the tumor cells toward a more normal state of proliferation and differentiation.

[Experimental study of conjugates of a catabolite common to halothane, enflurane and fluroxene in guinea pigs]. / Etude expérimentale des conjugués d'un catabolite commun à l'halothane, enflurane et fluroxène chez le cobaye

The authors sensitized guinea pigs to a halothane catabolite, trifluoroacetic acid, combined with guinea pig albumin. They then exposed the animals to halothane. There was no correlation between the presence of humoral and cell-mediated immune reactions obtained with the catabolite and the incidence of liver necrosis.

[Diagnostic tests for hypersensitivity to halogen compounds]. / Tests diagnostiques d'hypersensibilité aux agents halogenes

The authors present a critical analysis of immunological tests used by some authors to establish the diagnosis of halothane-induced hepatitis. These tests include the lymphocyte transformation test (LTT), the leukocyte migration inhibition test (LMIT) and detection of auto-antibodies. It has not been possible for all investigators to reproduce the results of these tests. The inhibition of these tests is not specific for halothane since it is also observed after infectious and serum viral hepatitis.

[Effect of general anesthesia on complement. Effect of the atmosphere in the operating room on the immune response of anesthesiologists]. / Action de l'anesthésie générale sur le complément. Effets de l'atomosphére de la salle d'opération sur la réponse immunitaire des anesthésiologistes

Variations in the C3 and C4 fractions of complement were studied in 15 patients who underwent surgery with either spinal anesthesia (5 cases) or general anesthesia using nitruos oxyde and a halogen compound (10 cases). Little peroperative variation was observed. An increase in C4 was observed in all cases postoperatively. Only a slight increase in C3 was observed after spinal anesthesia. The immune response of anesthetists exposed to halothane was investigated using PHA-induced lymphocyte stimulation (normal in males, elevated in females) and lymphocyte transformation to halothane and its metabolites (no evidence of allergy was observed).

Humoral immunity to a metabolite of halothane, fluroxene, and enflurane.

Trifluoroacetate, a common metabolite of halothane, fluroxene, and enflurane, conjugated to guinea-pig albumin elicits specific serum antibody in guinea pigs. Two classes of antibodies were found: hemolytic, gamma-2, and anaphylactic, gamma-1. Repeated injections of the antigen, trifluoroacetyl-guinea pig albumin, often led to disappearance of circulating antibodies.