Placebo in sports nutrition: a proof-of-principle study involving caffeine supplementation.

We investigated the effects of supplement identification on exercise performance with caffeine supplementation. Forty-two trained cyclists (age 37 ± 8 years, body mass [BM] 74.3 ± 8.4 kg, height 1.76 ± 0.06 m, maximum oxygen uptake 50.0 ± 6.8 mL/kg/min) performed a ~30 min cycling time-trial 1 h following either 6 mg/kgBM caffeine (CAF) or placebo (PLA) supplementation and one control (CON) session without supplementation. Participants identified which supplement they believed they had ingested ("caffeine", "placebo", "don't know") pre- and post-exercise. Subsequently, participants were allocated to subgroups for analysis according to their identifications. Overall and subgroup analyses were performed using mixed-model and magnitude-based inference analyses. Caffeine improved performance vs PLA and CON (P ≤ 0.001). Correct pre- and post-exercise identification of caffeine in CAF improved exercise performance (+4.8 and +6.5%) vs CON, with slightly greater relative increases than the overall effect of caffeine (+4.1%). Performance was not different between PLA and CON within subgroups (all P > 0.05), although there was a tendency toward improved performance when participants believed they had ingested caffeine post-exercise (P = 0.06; 87% likely beneficial). Participants who correctly identified placebo in PLA showed possible harmful effects on performance compared to CON. Supplement identification appeared to influence exercise outcome and may be a source of bias in sports nutrition.

Chronic lactate supplementation does not improve blood buffering capacity and repeated high-intensity exercise.

Since there is conflicting data on the buffering and ergogenic properties of calcium lactate (CL), we investigated the effect of chronic CL supplementation on blood pH, bicarbonate, and high-intensity intermittent exercise performance. Sodium bicarbonate (SB) was used as a positive control. Eighteen athletes participated in this double-blind, placebo-controlled, crossover, fully counterbalanced study. All participants underwent three different treatments: placebo (PL), CL, and SB. The dose was identical in all conditions: 500 mg/kg BM divided into four daily individual doses of 125 mg/kg BM, for five consecutive days, followed by a 2-7-day washout period. On the fifth day of supplementation, individuals undertook four 30-s Wingate bouts for upper body with 3-min recovery between bouts. Total mechanical work (TMW) for the overall protocol and for the initial (1st+2nd) and final (3rd+4th) bouts was determined at each session. Blood pH, bicarbonate, and lactate levels were determined at rest, immediately and 5 min after exercise. CL supplementation did not affect performance (P > 0.05 for the overall TMW as well for initial and final bouts), nor did it affect blood bicarbonate and pH prior to exercise. SB supplementation improved performance by 2.9% for overall TMW (P = 0.02) and 5.9% in the 3rd+4th bouts (P = 0001). Compared to the control session, SB also promoted higher increases in blood bicarbonate than CL and PL (+0.03 ± 0.04 vs +0.009 ± 0.02 and +0.01 ± 0.03, respectively). CL supplementation was not capable of enhancing high-intensity intermittent performance or changing extracellular buffering capacity challenging the notion that this dietary supplement is an effective buffering agent.

A new technique for determining 3-D joint angles: the tilt/twist method.

OBJECTIVE: To develop a new method of representing 3-D joint angles that is both physically meaningful and mathematically stable. DESIGN: The two halves of a joint are modeled as overlapping cylinders. This simple physical model is easily understood and yields mathematically stable angle equations. BACKGROUND: Two currently-used methods are the Euler/Cardan (joint coordinate system) method and the projection angle method. Both of these methods approach a singularity at 90 degrees that limits their use. The helical angle (attitude vector) method is mathematically stable but has limited physical meaning and is difficult to communicate. METHODS: Calculation of the tilt/twist angles is described. Tilt/twist angles are compared to Euler/Cardan, projection, and helical angles in terms of behavior and stability. RESULTS: Through a small range of angulation, tilt/twist angles match the specific projection and Euler/Cardan angles previously found to be appropriate for describing spinal motion. Through larger ranges, tilt/twist angles do not match the other angles studied. Although not as stable as helical angles, tilt/twist angles are twice as stable as Euler/Cardan and projection angles, reaching a singularity only at 180 degrees. CONCLUSIONS: Because of their mathematical stability and simple physical interpretation, tilt/twist angles are recommended as a standard in describing angular joint motion.

Three-dimensional head kinematics and cervical range of motion in the diagnosis of patients with neck trauma.

OBJECTIVE: To create a statistical model using three-dimensional (3D) head kinematics and range of motion (ROM) to distinguish between people with whiplash syndrome and asymptomatic controls. STUDY DESIGN: Cross-sectional study to estimate validity of diagnostic measures. METHODS: Fifty-one asymptomatic controls (most of whom were women), 18-35 yr old and 30 matched whiplash trauma patients seeking care from suburban outpatient clinics were sought. 3D kinematic parameters of head motion were obtained during tracking tasks (e.g., flexion, extension, etc.) and cervical ROM was measured via a head mounted inclinometer. Their level of pain and disability was assessed via a self-administered neck disability index questionnaire and visual analog pain scale (VAS). RESULTS: A scoring system of biomechanical abnormalities derived from the vertical piercing point, its second derivative and symmetry during oblique tasks. The scores ranged from a minimum of 0 to a maximum of 3. A cutoff of > or = 0.5 correctly identified the greatest number of subjects and minimized false positives (sensitivity 77%, specificity 82%, likelihood ratio 4.5). ROM performed similarly well at a cutoff of 1 SD below the normative mean (sensitivity 77%, specificity 84%, likelihood ratio 3.9). CONCLUSIONS: There is potential for biomechanical analysis to objectively detect abnormalities. The statistical model yielded moderate to high sensitivity and specificity using 3D helical-axis parameters of the head and standard ROM. The model development will continue via this process in future studies. These data could be a first step toward the creation of useful, noninvasive protocols for the diagnosis and management of soft tissue trauma of the neck.

A computationally efficient method for solving the redundant problem in biomechanics.

Determining the optimal set of musculotendon forces with which to produce a forward dynamic simulation of movement typically involves a huge investment of time and computational resources. A new, computationally efficient method is proposed that simultaneously achieves the desired trajectory and the dynamically optimized set of muscle stresses, and hence forces, according to the maximal endurance criterion function of Crowninshield and Brand (1981). Muscle-induced accelerations of the system resulting from unit stress contractions of individual muscles are superposed via the new pseudoinverse method to yield the desired motion trajectory. The method is tested on a control problem involving a five degree-of-freedom (DOF), 30 muscle, upper extremity model, which incorporates a dual rigid-body forearm to represent pronation and supination more adequately. The pseudoinverse method delivered the desired motion to within 0.25 degrees for each DOF during a three-second simulation. It is anticipated that the methodology can be easily and accurately applied to other highly redundant optimal control problems in biomechanics.

A hospital-based case-control study on hepatocellular carcinoma in Fukuoka and Saga Prefectures, northern Kyushu, Japan.

Three hundred and sixty-eight case-control sets (male 287 pairs; female 81 sets) were collected for a hospital-based case-control study of primary hepatocellular carcinoma (HCC) conducted in Northern Kyushu, Japan. All incident cases of HCC were collected weekly from the inpatients (aged 40-69) of the Second Department of Internal Medicine, Kurume University Hospital between April, 1986 and May, 1992. One control for a male case and 4 controls for a female case were sampled, being matched to a case on age (same 5-year age class), sex, residence (prefecture) and time of hospitalization (within 2 months after a case interview) from the inpatients of two general hospitals in Kurume. Information was collected by interview in person by a well-trained interviewer and from a review of hospital records by the authors. Multivariate analyses based on a conditional logistic regression model without an interaction term revealed that hepatitis B surface antigen (HBsAg) positive status (odds ratio (OR) = 8.67; 95% confidence interval (95%CI) = 2.54-29.57), history of blood transfusion over 10 years previously (2.40; 1.26-4.56), parental history of hepatic diseases (2.31; 1.11-4.80) and heavy alcohol drinking (60 < or = drink-years) by age 40 (3.23; 1.61-6.51) were statistically significant risk factors of male HCC. Univariate analysis for females also showed an elevated OR of HBsAg (7.58; 1.96-29.35). Although the sample size was limited, univariate analysis indicated that anti-hepatitis C virus antibody by c100-3 antigen positive status had a statistically significant OR for HCC in both sexes.

Hepatocellular carcinoma and its risk factors--their annual changes and effects on the age at onset.

A retrospective case-control study was carried out on patients with hepatocellular carcinoma (HCC) admitted between 1976 and 1985 to analyze the relationship between the cancer and risk factors. The following conclusions were reached: 1) the positive rate of Hepatitis B surface (HBs) antigen among the HCC patients decreased from 41% in the period 1976-1980 to 19% in the period 1981-1985. However, the risk of the patients positive for the antigen for HCC was higher in the second period (1:18.7) than in the first period (1:12.8), 2) drinking not only enhanced the risk for HCC 2.7 times, but also accelerated the onset of HCC by about 5 years, 3) blood transfusion enhanced the risk for HCC; HCC occurred in about 20 years on average after blood transfusion in the patients negative for the hepatitis B virus (HBV) and drinking history, and 4) smoking was suggested to be less related to the onset of HCC.

Reproducibility of reports of past history, smoking, drinking and dietary habits obtained by a personal interview for a case-control study on liver cirrhosis and hepatocellular carcinoma.

The reproducibility of responses on life style measurements observed during a personal interview was assessed by a test-retest method. Fifty-one apparently healthy male subjects were interviewed twice, mostly within a 10 week interval. Responses on past history, smoking and drinking habits yielded relatively high intraclass correlation coefficients between the two interviews, as compared to the responses on dietary habits for the previous 1 to 2 years, which varied depending on the food items.

Restoring unassisted natural gait to paraplegics via functional neuromuscular stimulation: a computer simulation study.

Functional neuromuscular stimulation (FNS) of paralyzed muscles has enabled spinal-cord-injured patients to regain a semblance of lower-extremity control, for example to ambulate while relying heavily on the use of walkers. Given the limitations of FNS, specifically low muscle strengths, high rates of fatigue, and a limited ability to modulate muscle excitations, it remains unclear, however, whether FNS can be developed as a practical means to control the lower extremity musculature to restore aesthetic, unsupported gait to paraplegics. A computer simulation of FNS-assisted bipedal gait shows that it is difficult, but possible to attain undisturbed, level gait at normal speeds provided the electrically-stimulated ankle plantarflexors exhibit either near-normal strengths or are augmented by an orthosis, and at least seven muscle-groups in each leg are stimulated. A combination of dynamic programming and an open-loop, trial-and-error adjustment process was used to find a suboptimal set of discretely-varying muscle stimulation patterns needed for a 3-D, 8 degree-of-freedom dynamic model to sustain a step. An ankle-foot orthosis was found to be especially useful, as it helped to stabilize the stance leg and simplified the task of controlling the foot during swing. It is believed that the process of simulating natural gait with this model will serve to highlight difficulties to be expected during laboratory and clinical trials.

Mammary carcinoma with pulmonary metastasis in a sow.

Mammary adenocarcinoma was diagnosed in a 3-year-old Landrace sow with prolonged infertility, anorexia and progressive emaciation after parturition. Gross examination confirmed a large tumour in the left anterior mammary gland with metastatic nodules on the pleura and in the parenchyma of lung. Microscopically, the tumour consisted mainly of solid adenomatous proliferations with numerous mitotic figures. Irregular glandular structures, solid nests of polygonal tumour cells without polarity and nests consisting of glandular, cribriform and solid portions were evident in dense fibrous stroma. Immunostaining revealed keratin in the tumour cells.

A planar model of the knee joint to characterize the knee extensor mechanism.

A simple planar static model of the knee joint was developed to calculate effective moment arms for the quadriceps muscle. A pathway for the instantaneous center of rotation was chosen that gives realistic orientations of the femur relative to the tibia. Using the model, nonlinear force and moment equilibrium equations were solved at one degree increments for knee flexion angles from 0 (full extension) to 90 degrees, yielding patellar orientation, patellofemoral contact force and patellar ligament force and direction with respect to both the tibial insertion point and the tibiofemoral contact point. The computer-derived results from this two-dimensional model agree with results from more complex models developed previously from experimentally obtained data. Due to our model's simplicity, however, the operation of the patellar mechanism as a lever as well as a spacer is clearly illustrated. Specifically, the thickness of the patella was found to increase the effective moment arm significantly only at flexions below 35 degrees even though the actual moment arm exhibited an increase throughout the flexion range. Lengthening either the patella or the patellar ligament altered the force transmitted from the quadriceps to the patellar ligament, significantly increasing the effective moment arm at flexions greater than 25 degrees. We conclude that the levering action of the patella is an essential mechanism of knee joint operation at moderate to high flexion angles.