Yitzhak Weinstein

Iron deficiency caused by 7 weeks of intensive physical exercise

SummaryThe present study was designed to evaluate the effect of an intensive physical training program involving both isometric and isotonic activities on the body iron status of 8 females and 11 males (age 20± 1 year). The training was carried out over a 7 week period and included 8 h of varying physical activities each day. Venous blood samples were obtained from the subjects prior to the beginning of the training, on day 2 and in weeks 2, 4, 6 and 7 of the program. Blood samples were analyzed for iron, ferritin and hemoglobin (Hb) concentrations, total iron binding capacity (TIBC) and red blood cell count (RBC). Iron levels of males and females decreased 65% after 2 weeks of training (p<0.001). At the end of the training program 5 males and 6 females had lower than normal iron values (<13.4 μmol·l−1). TIBC increased 25% in women and 18% in men following 2 and 4 weeks of training (p<0.001) and remained at this elevated level throughout the training period. Ferritin levels decreased 50% in both sexes after 4 weeks of exercise (p<0.05) and remained at this level until the end of the training. Hb and RBC decreased 8–10% in both sexes during the training period. In two of the women anemia occurred after 4 weeks of training. The development of latent iron deficiency in a substantial number of participants after a relatively short period of training is uncommon and may reflect the high intensity of exercise required in this program. The decline in body iron status may affect the performance of the subject during training. We suggest that the iron status of athletes engaged in intensive training be examined regularly and consideration be given to iron supplementation.

The effect of environmental temperature on testosterone and cortisol responses to high intensity, intermittent exercise in humans.

Abstract The purpose of this study was to examine the testosterone, cortisol, and the molar ratio of testosterone to cortisol (T:C) blood concentration responses to intermittent, high intensity exercise in the heat. Eight active men [mean age 25 (SD 3) years, mass 71.1 (SD 5.5) kg, height 175.9 (SD 4.4) cm] performed two series of five 15-s Wingate anaerobic power tests in both hot (H, 35°C) and thermoneutral (TN, 22°C) environments. Each period of exercise was separated by 30-s of active recovery. Each series was separated by 60 min of passive recovery. Blood samples were obtained before (PRE), immediately post (IP), and 5(5R), 10(10R), 15(15R), 30(30R), 45(45R), and 60(60R) min following exercise. Peak power was significantly higher, during the first series of exercise, in the H compared to TN. No significant differences were seen in any of the variables between the first and second series of exercise in either environmental condition. Furthermore, no significant differences between these conditions were observed in heart rate, blood lactic acid concentration, or rectal temperature. A significant decrease in cortisol concentration was observed between PRE and IP, during both conditions. However, no significant interactions between TN or H were seen. No change from PRE was observed in testosterone or T:C during either TN or H. It would appear that testosterone and cortisol respond similarly to repeated periods of short duration high intensity exercise, in either thermoneutral or moderately hot environments.

A treadmill test of sprint running

Anaerobic power is characterized by a high degree of specificity regarding both the recruited muscles as well as the recruitment pattern. The popular Wingate Anaerobic Test (WAnT) is a cycling test that does not satisfy the need for a running‐specific anaerobic test. We describe such a test, using a novel type of a commercially available treadmill (BRL 1800, Gymrol, France). The ergometer is equipped with a torque motor to neutralize the frictional resistance of the treadmill belt, and a hip‐belt harness connected to a horizontal rod. Force applied to the harness is monitored by a strain gauge mounted on the rod, while vertical movement is monitored by a potentiometer at the posterior fixed end of the rod. These, in conjunction with the treadmill belt speed, enable the computation of horizontal and vertical power as well as the combined total output. Power is calculated both as ‘peak’ power (highest 2.5 s segment) and ‘mean’ power (20 s duration). Preliminary results of young athletes were generally consistent with the expected age‐related changes in anaerobic power. Values obtained on the anaerobic treadmill were always higher than the corresponding WAnT values previously obtained in comparable age groups. The higher values were probably due to the larger muscle mass involved and the shorter peak and mean power durations (2.5 and 20 s versus 5 and 30 s in the WAnT, respectively). This test should enable not only running‐specific anaerobic power monitoring but also the characterization of the relationship between the horizontal and vertical components of that power.

Effect of creatine feeding on maximal exercise performance in vegetarians.

Abstract The effect of creatine supplementation on exercise performance in vegetarians was examined. Creatine was ingested for 1u2009week by a group of vegetarians (VC) and meat-eaters (MC); a control group of meat-eaters was fed only glucose (MG). Exercise performance during three, 20-s maximal cycling tests (modified Wingate anaerobic test, WAnT) was determined before and after creatine supplementation. Blood samples were also drawn before and after exercise prior to and after supplementation. Basal plasma creatine (after an overnight fast) averaged (SE) 11 (2)u2009μM in VC, and 24 (2) and 23 (7)u2009μM in MG and MC, respectively (Pu2009<u20090.05 for VC vs meat-eaters). These findings were expected, since most of the bodys exogenous creatine source is meat. There was no significant difference in any other parameter between groups prior to supplementation. Creatine feedings significantly increased body mass (≅1u2009kg) and mean power output during the WAnTs (≅5%) to a similar extent in the VC and MC groups (Pu2009<u20090.05–0.001). These parameters were not affected by supplementation in the MG group. Peak power output was also significantly increased by supplementation in MC (≅5%, Pu2009<u20090.05), but not in VC. It is concluded that vegetarians and meat-eaters respond to creatine feedings with similar increases in mean power output during short-term, maximal exercise.

The Effect of Mental Training with Biofeedback on the Performance of Young Swimmers

Cette recherche porte sur la relation que l’entrainement mental entretient avec le biofeedback et la performance. C’est une version adaptee de l’approche en cinq etapes de Wingate qui a ete utilisee comme technique de preparation mentale en vue de l’amelioration des performances en natation chez des nageurs de 11 a 14 ans. Les participants (N= 38) ont ete distribues au hasard a l’une des deux conditions suivantes: (a) Un entrainement experimental regulier assorti de trois etapes du programme Wingate; (b) Un entrainement de controle regulier avec de la relaxation. Apres une mesure de depart, les participants ont ete testes sur des scores d’evaluation et sur leur performance reelle deux fois sur une periode de quatorze semaines. Le groupe experimental progressa davantage, mais le groupe controle s’ameliora aussi. Ces resultats sont examines a partir des travaux anterieurs sur l’approche de Wingate. En outre, on aborde certains problemes methodologiques et theoriques qui concernent specialement l’appel a de telles procedures dans d’autres specialites sportives chez les enfants, les adolescents, et les adultes. n nThe purpose of the present study was to investigate the relationship between mental training with biofeedback and performance. An adapted version of the Wingate five-step approach was used as a mental preparation technique for enhancing the swimming performance among 11–14-year-old children swimmers. Participants (n= 38) were randomly assigned to one of two conditions: (a) experimental—regular training plus three stages of the Wingate mental training program, and (b) control—regular training and relaxing activities. After a baseline measurement, participants were tested on evaluation scores and actual performance twice during a 14-week period. Results indicated that the experimental group exhibited a greater increase in performance, although the control group also displayed some improvements. Results are discussed in reference to previous work on the Wingate approach to mental training. In addition, several methodological and theoretical aspects are discussed that are particularly relevant to the use of such interventions with other athletic tasks among children, adolescents, and adults.

Effect of an iron supplement on body iron status and aerobic capacity of young training women

SummarySerum iron deficiency has a high incidence in female athletes. We investigated the effects of a daily oral iron supplement, (160 mg) administered during an intensive 7-week physical training programme, on body iron status, and the maximal aerobic capacity (VO2max) of 13 women (group A) compared to 15 who took a placebo (group B). The subjects were 19 years old. Blood samples were obtained before training began and on days 1, 7, 21 and 42 of training. They were analysed for packed cell volume (PVC) and for haemoglobin (Hb), 2,3-diphosphoglycerate (2,3-DPG), haptoglobin, iron and ferritin concentrations. TheVO2max was measured on days 0, 21 and 42 of training. Following 21 days of training Hb, PCV and ferritin were significantly higher (P⩽0.01) in group A compared to group B. Over the training period Hb rose by 9.3% and 2.4% in groups A and B, respectively. At the end of training 66% of group B exhibited ferritin concentrations below 10 ng·ml−1, while none of group A had such low values. MeanVO2max of group A had increased by 7.5% following 21 days of training (P⩽0.01) and by 15.3% after 42 days. No appreciable increase inVO2max had occurred in group B by day 21 (significantly lower thanVO2max of group A;P⩽0.05), however by day 42 it had increased by 14.3% (P⩽0.05). In both groups 2,3-DPG·g Hb−1 had increased significantly (P⩽0.005) by day 7 (22%) and remained at that level for an additional 35 days. We concluded that a daily oral iron supplement given to young women during intensive training improved several haematological variables and their body iron status. This improvement was associated with an increasedVO2max only during the early stages of their training (day 21) compared with the placebo group.

Regulation of mental states and biofeedback techniques effects on breathing pattern

The purpose of the present study was to examine whether breathing pattern may be used as a reliable index for the effectiveness of techniques applied for the regulation of mental states. Heart rate (HR), breathing pattern, galvanic skin response (GSR), and electromyogram (EMG) of the frontalis muscle were measured in 39 male and female subjects aged 18–25 years during 10-minute treatment with relaxation technique (autogenic training and/or music) followed by 10 minutes of imagery training. In the first 7 sessions biofeedback (BFB) was not included, while during the last 6 sessions BFB was introduced and utilized by the subjects. Relaxation (music or autogenic training) led to a decrease in breathing frequency, attributed to lengthening of expiration time, as well as reduced HR, GSR, and frontalis EMG response. In most instances imagery training was related to an increase in these indices. Specifically, significant tachypnea was observed during imagery of sprint running. In most cases BFB substantially augmented the physiological responses. In conclusion, our data suggest that, compared with HR, GSR, and EMG responses, the breathing pattern is at least as sensitive to the mental techniques employed, and may be useful as a psychophysiological index for diagnosis and testing, especially in sport practice.

Effects of increased ventilation and improved pulmonary gas-exchange on maximal oxygen uptake and power output

Recent reports suggest that aerobic performance at very high levels may be limited by the pulmonary system. The purpose of the present study was to compare respiratory functions at rest and during graded maximal aerobic exercise (cycle ergometry) between well‐trained (TR, n= 11) and untrained (UT, n= 14) individuals while breathing atmospheric air, normoxic helium (He) and oxygen‐enriched mixture. When the subjects breathed air, TR exhibited lower exercise ventilatory reserve (MVV‐VEmax), ratio between minute ventilation (VE) and oxygen uptake (Vo2) and SaO2 than UT. Breathing HE resulted in an increase in VE and Vo2max in both groups but in an increased VE/Vo2 and SaO2 and maximal mechanical cycle ergometer load, only in TR. Compared with air, breathing an oxygen‐enriched mixture resulted in increased peak exercise SaO2 and maximal mechanical load in both groups. It is concluded that arterial O2 desaturation secondary to a relative hypoventilatory response may limit Vo2max and aerobic performance capacity at high work levels.

High-level Coaches’ Perceptions of their Professional Knowledge, Skills, and Characteristics

Abstract The purpose of this study was threefold: (a) to describe the different types of knowledge, skills, and individual characteristics of highlevel coaches from individual and team sports, as perceived by the coaches themselves; (b) to assess the similarities and differences between high-level individual and team coaches; and (c) to reflect on possible ways to improve the educational coaching programs for individual and team sports. Thirty-five high-level coaches from individual and team sports completed a questionnaire consisting of three parts: Knowledge, skills, and individual characteristics. Results revealed differences and similarities between team sport coaches (TSC) and individual sport coaches (ISC) in each of the three questionnaire components. It is recommended that coaches’ educational programs consider the research findings between ISCs and TSCs in their efforts to improve coaches’ knowledge and skills.

Physiological and cognitive responses to cold exposure in 11–12-year-old boys

This study investigated the effects of cold and exercise in the cold on the physiological and cognitive responses of 11–12‐year‐old boys. Children were dressed in sweat suits and exposed to cold (CD, 7°C), cool (CL, 13°C), and neutral (N, 22°C) environments for 110 minutes, with 10 minutes of light exercise (1 watt · kg body wt−1) midway through the exposure. A 30‐minute “recovery” in neutral conditions followed each session. Session order was randomized. Rectal temperature (Tre) decreased significantly more in CD compared to CL and N, and continued to decrease during the recovery period. Chest skin temperature (Tch) was significantly different between conditions and remained stable even in CD, despite the decrease in Tre. Tch returned to prechamber values during the recovery period. Hand temperature (Th) decreased during CL and CL, and remained significantly lower than prechamber values following the recovery. Exercise heart rate was lower in the CD and CL(115 ± 13 and 119 ± 20 beats · min−1) compared to N (130 ± 17 beats · min−1). No differences were observed in oxygen consumption between sessions. No differences were also observed between sessions in cognitive performance on language and math tests. It was concluded that while the study conditions did not appear to affect cognitive capacity in boys, they proved sufficient to disturb core temperature. This disturbance was not corrected 30 minutes following cold exposure. Am. J. Hum. Biol. 9:39–49