Rudi Klein

Enhancement of 2000-m rowing performance after caffeine ingestion.

PURPOSE To investigate the effect of caffeine ingestion on short-term endurance performance in competitive rowers. METHODS In this randomized double-blind crossover study, eight competitive oarsmen (peak oxygen uptake [VO2peak] 4.7+/-0.4 L x min(-1), mean +/- SD) performed three familiarization trials of a 2000-m rowing test on an air-braked ergometer, followed by three experimental trials at 3- to 7-d intervals, each 1 h after ingesting caffeine (6 or 9 mg x kg(-1) body mass) or placebo. Trials were preceded by a standardized warm-up (6 min at 225+/-39 W; 75+/-7.7% VO2peak). RESULTS Urinary caffeine concentration was similar before ingestion (approximately 1 mg x L(-1)) but rose to 6.2+/-3.6 and 14.5+/-7.0 mg x L(-1) for the low and high caffeine doses, respectively. Plasma free fatty acid concentration before exercise was higher after caffeine ingestion (0.29+/-0.17 and 0.39+/-0.20 mM for 6 and 9 mg x kg(-1), respectively) than after placebo (0.13+/-0.05 mM). Respiratory exchange ratio during the warm-up was also substantially lower with caffeine (0.94+/-0.09 and 0.93+/-0.06 for the low and high dose) than with placebo (0.98+/-0.12). Subjects could not distinguish between treatments before or after the exercise test. Both doses of caffeine had a similar ergogenic effect relative to placebo: performance time decreased by a mean of 1.2% (95% likely range 0.4-1.9%); the corresponding increase in mean power was 2.7% (0.4-5.0%). Performance time showed some evidence of individual differences in the effect of caffeine (SD 0.9%; 95% likely range 1.5 to -0.9%). CONCLUSIONS Ingestion of 6 or 9 mg x kg(-1) of caffeine produces a worthwhile enhancement of short-term endurance performance in a controlled laboratory setting.

Effects of High-Impact Exercise on Ultrasonic and Biochemical Indices of Skeletal Status: A Prospective Study in Young Male Gymnasts

Physical activity has been proposed as one strategy to enhance bone mineral acquisition during growth. The aim of this study was to determine whether frequent impact loading associated with gymnastics training confers a skeletal benefit on pre‐ and peripubertal male gymnasts. We measured broadband ultrasonic attenuation (BUA, dB/MHz) at the calcaneus (CBUA); ultrasound velocity (m/s) at the calcaneus (CVOS), distal radius (RVOS) and phalanx (PVOS); serum osteocalcin (OC); total alkaline phosphatase (ALP) and insulin‐like growth factor‐I (IGF‐I) every 3–4 months over an 18‐month period in elite male gymnasts and matched normoactive controls (pubertal stage ≤2). Ground reaction forces of common gymnastics maneuvers were determined using a force platform and loading histories of the upper and lower extremities approximated from video recordings. Ultrasound results were expressed as a standardized score (Z score) adjusted for age, height, and weight. At baseline, no differences were detected between the gymnasts (n = 31) and controls (n = 50) for CBUA, although ultrasound velocity at each site was higher in the gymnasts (0.6–1.5 SD) than the predicted mean in controls (p ≤ 0.001). Over 18 months, CBUA Z scores increased significantly in the gymnasts from baseline (0.3 vs. 1.0, p < 0.05, n = 18). In contrast, ultrasound velocity did not increase in either group, although CVOS and RVOS remained significantly higher in gymnasts compared with controls (range p < 0.01 and < 0.001). No differences between groups were found for OC, ALP, or IGF‐I at any time. Gymnastics training was associated with on average 102 and 217 impacts per session on the upper and lower extremities, respectively, with peak magnitudes of 3.6 and 10.4 times body weight. These results suggest that frequent high‐impact, weight‐bearing exercise during the pre and peripubertal period may enhance the mechanical competence of the skeleton, perhaps offering an important strategy for osteoporosis prevention if the benefits are maintained.

INFLUENCE OF HIGH IMPACT LOADING ON ULTRASOUND BONE MEASUREMENTS IN CHILDREN : A CROSS-SECTIONAL REPORT

Abstract. Evidence suggests that weight-bearing exercise during the growing years may enhance peak bone mass. The purpose of this study was to compare ultrasound bone measurements, serum alkaline phosphatase (S-ALP), serum osteocalcin (S-OC), and dietary calcium in highly active and normal healthy male children. Subjects were 33 elite and subelite male gymnasts and 40 normoactive controls matched for age (9.4 ± 1.1 years), height (133.9 ± 5.9 cm), and weight (30.1 ± 3.8 kg). Measurements of broadband ultrasound attenuation (dB/MHz) through the calcaneus (CBUA) and ultrasound velocity (m/s) through the calcaneus (CVOS), distal radius (RVOS), and proximal phalanx of the index finger (PVOS) were performed using a Contact Ultrasonic Bone Analyzer (CUBA Research). Gymnasts had significantly greater CVOS (P < 0.001), RVOS (P < 0.0001), and PVOS (P < 0.05). There were no differences in CBUA, S-ALP, or S-OC between groups. RVOS correlated significantly with dietary calcium intake in all subjects (P < 0.05) and training time in the gymnasts (P < 0.05). Though gymnasts had significantly greater calcium intakes than controls (P < 0.05), whose mean value was below the RDA, after controlling for calcium intake in the gymnasts alone, RVOS was still significantly correlated with training time (P < 0.05). These preliminary results suggest that the heavy musculoskeletal loading inherent in gymnastics training produces positive adaptive responses in the growing skeleton. Furthermore, ultrasound appears to provide a safe, noninvasive means of comparing the skeletal status of exercising and normal healthy children, whereas single samples of biochemical markers did not discriminate between the groups.

PLASMA FOLLISTATIN CONCENTRATIONS INCREASE FOLLOWING LIPOPOLYSACCHARIDE ADMINISTRATION IN SHEEP

1. The effect of inflammation induced by lipopolysaccharide (LPS) injection on plasma follistatin (FS) concentrations was investigated.

Hormonal responses to physical training in high-level peripubertal male gymnasts

Abstract The effects of performing intensive training during growth remains controversial, with claims of negative effects upon growth and maturation purportedly due at least in part to a combination of hormonal disturbances and inappropriate nutrition. We examined the training-related responses of total testosterone (T), insulin-like growth factor-1 (IGF-1), cortisol (C) and diet in 16 peripubertal (pubertal stage ≤2) male gymnasts [mean (SD) age 10.5 (0.9) years, training 17.2 (5.6) h · week−1] and 17 controls [mean (SD) age 9.6 (1.2) years] over a 10-month period. Fasted, resting morning blood samples (0730–0900 hours) were taken from all children on Monday, Wednesday and Friday during a single week towards the end of each of three phases of gymnastics training: routine development (RD), pre-competition (PC) and strength conditioning (SC). Serum concentrations of T, C and IGF-1 did not differ between the groups at any time. The ratio between IGF-1 and cortisol was significantly reduced in gymnasts relative to controls during RD and SC training (P < 0.05), although no differences were detected for the T:C ratio. Diet did not correlate with any of the hormonal measurements, and no intergroup differences were found for the rate of growth in height. In summary, these results suggest that either the gymnastics training performed by these subjects was not intense enough to alter adrenal function, or that the gymnasts were well adapted to the training. In contrast, the reduction in the anabolic to catabolic balance represented by the IGF-1:C ratio is suggestive of a catabolic state, perhaps resulting from overstrain, insufficient recovery and/or inadequate caloric intake relative to energy output. While physical training during growth may induce a catabolic state, further research is needed to determine the biological significance of this finding, particularly with regard to growth and maturation.

Role of Peptide YY in blood vessel function and atherosclerosis in a rabbit model

Cardiovascular disease remains a burden for Westernized countries. Peptide YY (PYY) raises blood pressure, yet its role has not yet been determined in diseased arteries. This study aimed at identifying PYY and eNOS in diseased blood vessels and to determine which blood vessels respond to PYY. New Zealand White rabbits were fed an atherogenic diet (n = 6, 0.5% cholesterol + 1% methionine + 5% peanut oil) and control animals fed a normal diet (n = 6) for 4 weeks. Immunohistochemistry was used to determine the localization of PYY and eNOS in the aorta. The aorta, carotid, renal, iliac, inferior mesenteric, and renal interlobular arteries were removed, mounted in organ baths, and subjected to doses of PYY (10−9–10−7 mol/L) and then acetylcholine (10−6 mol/L). Immunohistochemistry of the aorta shows PYY staining in plaque macrophages, smooth muscle cells and endothelium, and these cells co‐expressed eNOS. PYY caused a minor vasoconstrictive response in all blood vessels studied but was blunted in arteries from control animals. Acetylcholine caused relaxation of PYY constricted blood vessels. This data clearly shows that PYY is present in atherosclerotic plaque and is a minor constrictor of the vasculature tree. Further studies aimed at understanding the role of PYY in cardiovascular disease are warranted.