Acute endocrine responses to plyometrics versus resistance exercise in children

The purpose of this study was to examine the acute hormonal responses to a bout of resistance versus plyometric exercise in young male athletes. Specifically, changes in salivary cortisol, testosterone and testosterone-to-cortisol ratio from pre- to post-exercise between the two different exercise protocols were examined. Twenty-six peri-pubertal active boys participated in this cross-over study, completing two exercise sessions. During each session, participants first completed a 30 min control period, which did not include any exercise, and then was randomly assigned to perform a 45 min of either a resistance exercise or a plyometric exercise protocol. All participants crossed over to perform the other exercise protocol during their second exercise session, a week later. Four saliva samples during each protocol were taken at: baseline, pre-exercise, 5 min post-exercise and 30 min post-exercise. Significant increases in testosterone values were reported 5 min post-exercise following the resistance protocol, but not the plyometric protocol. Both exercise protocols resulted in significant cortisol decreases overtime, as well as significant testosterone-to-cortisol ratio increases. The post-exercise increases in salivary testosterone and testosterone-to-cortisol ratio followed the typical exercise induced anabolic response seen in adults. However, the post-exercise decrease in salivary cortisol was different than the typical adult response indicating an insufficient stimulus for this age group maybe due to their stage of the biological development. Thus, in the adolescent boys, exercise appears to change the anabolic to catabolic balance in favor of anabolism.

Salivary testosterone and cortisol : role of athletic setting, game outcome, and game location /

Many studies investigating the relationship between hormones and competition have focused on athletic competition. The athletic setting enables r researchers to investigate the hormone-behaviour relationship in a relatively controlled environment. However, research to date has been based on observations made from single status contests and/or weekend tournaments and as such, does not provide a clear picture of an individual's average hormonal responses to both victory and defeat. In appreciation of this limitation, the current study tracked elite hockey players throughout a hockey season, measuring pre- and post-game salivary testosterone and Cortisol as well as psychological measures. I was interested in determining whether status outcome (win vs. loss) would influence an individual's testosterone and Cortisol responses to competition. Furthermore, I was also interested in assessing whether testosterone and Cortisol responses were specific to the competitive environment or whether similar hormonal responses would occur during non-competitive practice sessions. Last, I was interested in whether there were any differences in pre-game hormonal and psychological states depending on where the status contest was held: home versus away. The results indicated that game outcome moderated the testosterone responses to competition. That is, testosterone increased significantly more after a victory compared to a defeat. Furthermore, a loss of status produced significantly hreports, the players did not show an anticipatory rise in either Cortisol or testosterone prior to competition. In addition to the effects of status outcome on hormonal levels, it was also found that these hormonal responses were specific to competition. The athletes in the current study did not demonstrate any hormonal responses to the practice sessions. Last, there were significant differences in pre-game testosterone as well as in selfconfidence, cognitive, and somatic anxiety levels depending on the location at which the status contest took place. Pre-game testosterone and self-confidence levels were significantly higher prior to games played in the home venue. In contrast, pre-game somatic and cognitive anxiety levels were significantly higher prior to games played in the away venue. The current findings add to the developing literature on the relationship between hormones and competition. This was the first study to detect a moderating effect of status outcome on testosterone responses in a team sport. Furthermore, this was also the first study in humans to demonstrate that post-contest Cortisol levels were significantly higher after a loss of status. Last, the current study also adds to the sport psychology literature by demonstrating that pre-game psychological variables differ depending on where the status contest is being held: higher self-confidence at home and higher somatic and cognitive anxiety away. Taken together, the results from the current thesis may have important practical relevance to coaches, trainers and sport psychologists who are always trying to find ways to maximize performance. post-game Cortisol levels than did an increase in status. In contrast to previous

Locomotor sensitization and conditioned place preference for amphetamine in late adolescent and adult male and female rats /

reports, the players did not show an anticipatory rise in either Cortisol or testosterone prior to competition. In addition to the effects of status outcome on hormonal levels, it was also found that these hormonal responses were specific to competition. The athletes in the current study did not demonstrate any hormonal responses to the practice sessions. Last, there were significant differences in pre-game testosterone as well as in selfconfidence, cognitive, and somatic anxiety levels depending on the location at which the status contest took place. Pre-game testosterone and self-confidence levels were significantly higher prior to games played in the home venue. In contrast, pre-game somatic and cognitive anxiety levels were significantly higher prior to games played in the away venue. The current findings add to the developing literature on the relationship between hormones and competition. This was the first study to detect a moderating effect of status outcome on testosterone responses in a team sport. Furthermore, this was also the first study in humans to demonstrate that post-contest Cortisol levels were significantly higher after a loss of status. Last, the current study also adds to the sport psychology literature by demonstrating that pre-game psychological variables differ depending on where the status contest is being held: higher self-confidence at home and higher somatic and cognitive anxiety away. Taken together, the results from the current thesis may have important practical relevance to coaches, trainers and sport psychologists who are always trying to find ways to maximize performance. the cycle. The sex-specific age differences in locomotor responses to amphetamine are not due to gonadal immaturity, as females are cycling at this stage of adolescence. However, age differences may reflect the ongoing maturation of the neural substrates that that are involved in locomotor sensitizing, but not rewarding effects of amphetamine.

Menstrual status and thermoregulatory responses of active adolescents during exercise in a cold environment

This study examined the interactions between the reproductive status and the thermoregulatory responses during exercise in the cold in girls involved in competitive sports. Four girls with established menstrual cycles comprised the eumenorrheic menarcheal group (EM) and 5 non-menstruating girls comprised the pre-menarcheal group (PM). During the first visit maximal oxygen consumption, height, weight and percent body fat (%BF) were measured. The second visit involved: a determination of metabolic rate in thermoneutrality (21°C) involving 10-min rest and 20-min cycling (30% of VCL max), and a cold stress test (5°C, 40% humidity, <0.3 m/s air velocity) involving 20-min rest and 40-min cycling (30% of VCL max.). Subjects in the EM group were tested twice in the chamber during the follicular and luteal phases. Pre-menarcheal subjects were found to have significantly (p<0.05) lower core temperatures during the final stages of cold exposure. Overall, body fat was not significantly correlated with core temperature in the cold, however there was a significant surface-to-mass ratio difference between the groups. While in the follicular phase, EM girls had a higher core temperature during cold exposure. Therefore, reproductive hormonal status seems to be an important factor in terms of cold tolerance in females during adolescence.

Young children's behavioral responses to the distress of others /

The relationship between child temperament and parenting factors in the development of prosocial behavior during the toddler years was investigated by examining children's helping behaviors and responses to the distress of others as observed and as reported by mothers and teachers. These behaviors were linked to the sociability, emotionality, and attention shifting of toddlers. Children who are relatively high in characteristics such as language skills and sociability appear more likely to exhibit competent prosocial behaviors than children who are relatively low in these skills. Prosocial competence was also linked to maternal comfort, maternal control over children's emotions, and family expressiveness, although the latter two variables related to children's behaviors differently, depending on whether children were low or high in emotional intensity.

Emptying the bell jar: an exploration of adolescent responses to a women's literature unit /

This study examines adolescent student responses to a women's literature unit taught within a grade 12 Writer's Craft course. Current research (Gilligan, 1989, Pipher, 1994 & Slack, 1999) suggests that there is a great under-representation of female authors in the high school literature curriculum. The use of women's literature may draw attention to important literary figures who are historically overlooked within the curriculum. It gives voice to a marginalized group and presents students with alternative subjects and heroes. It encourages students to develop a critical perspective and reevaluate assumptions about institutions, ideologies, language and culture. It also allows me, as a teacher, to reflect on my own teaching practices and explore alternate feminist pedagogical principles and teaching styles encouraging multiplicity of voices, deconstruction of power relations, and alternative assessment tools within the classroom. As an educator, it is important for me to teach curriculum that is relevant and meaningful to students and help them become critical, self-reflective thinkers. It is also important for me to assist students in their exploration of self and encourage them to expand their awareness of historical, social and global issues. Sylvia Plath's (1963) The belljar is used as the primary text taught within this unit. In this novel, the bell jar is a central image that signifies entrapment and isolation. "To the person in the bell jar, blank and stopped as a dead body, the world itself is the bad dream"(p.l 54). As a metaphor, the bell jar resonates with young readers in a variety of ways.

Responses of crayfish to a reflective environment /

This thesis examines how dominance status of crayfish alters responses to their own reflection. Crayfish are social animals that fight to develop a dominance hierarchy consisting of dominant and subordinate members. After socialization, crayfish were videotaped in an aquarium with mirrors on one half of the tank and a non-reflective plastic on the other half. Dominants paired for 14 days perform more cornering, turning, crossing and spent more time in a reflective environment versus a non-reflective environment. Subordinate crayfish exhibit more reverse walking in a mirrored environment while isolated crayfish show no preference for reflection. This change in behaviour occurs immediately for dominants paired for 30 min while subordinates require 3 days of pairing to exhibit the same behaviour as subordinate crayfish paired for 14 days. Thus, 30 min of pairing is required to enhance responses to a reflection observed in dominant crayfish while 3 days is required to decrease subordinate responses to a reflection. These findings propose that male socialized crayfish respond to their mirror image as they do a male conspecific. Their responses depend on both their dominance status and the length of socialization which suggests that crayfish are learning to behave in a characteristic manner as a result of their social experience.

The cardiovascular hemodynamic responses to various levels of orthostatic stress in children

The ability of the cardiovascular system to quickly and efficiently adapt to an orthostatic stress is vital for the human body to function on earth. The way in which the various aspects of the cardiovascular system work together to counteract an orthostatic stress has been previously quantified in the adult population. However, there are still many unknowns surrounding the topic of how the cardiovascular system functions to cope with this same stress in children. The purpose of this study was to describe the cardiovascular hemodynamic adaptations to various levels of orthostatic stress induced using a lower body negative pressure (LBNP) chamber in pre-pubertal boys. A secondary purpose was to determine indices of baroreceptor sensitivity (BRS) at both rest and during low levels of LBNP in this same pediatric sample. Finally, this study aimed to compare the relative responses to LBNP between the children and adults. To complete the study 20 healthy pre-pubertal boys and adult males (9.3 ± 1.1 and 23 ± 1.8 years of age respectively) were recruited and randomly exposed to three levels of LBNP (15, 20 and 25 mmHg). At rest and during the application of the LBNP heart rate (HR), manual and bcat-by-beat systolic (SBP), diastolic (DBP) and mean arterial blood pressure (MAP) were monitored continuously. Aortic diameter was measured at rest and peak aortic blood velocity (PV) was recorded continuously for at least I minute during each baseline and LBNP condition. From the raw data HR, stroke volume (SV), cardiac output (Q), total peripheral resistance (TPR), low frequency baroreceptor sensitivity (LF BRS), high frequency baroreceptor sensitivity (HF BRS) and LFIIIF ratio were calculated. At rest, llR wa'i higher and SBP, SV, Q and LF/HF ratio were lower in the children compared to the adult males (pgJ.05). In response to the increasing LEN!> IIR and TPR increased, and LF BRS. SV and Q decreased in the adult group (pSf).05). while the same levels of LBNP caused an increase in TPR and a decrease in SBP, SV and Q in the children (pSf).05). Although not significant, the LF/HF ratio in the adult group showed an increasing trend in response to increased negative pressure (p=O.088). As for resting BRS, there were no significant differences in LF or HF BRS between the children and the adults despite a tendency for both measures to be 18% lower in the children. Also the LF/HF ratio was almost significantly greater in the adults compared to the children (p=O.057). In addition, a comparison between the relative adult and child responses to LBNP yielded no significant group by level interactions. This result should be taken with caution though, as the low sample size and high measurement variability generated very low statistical power for this analysis. In conclusion, the results of this study suggest that the hemodynamic adaptations to an orthostatic stress were less pronounced in the prepubertal males, most likely due to an underdeveloped autonomic system. These results need to be strengthened by further research before any implications can be derived for health care purposes.

Seasonal changes in behavioural and thermoregulatory responses to hypoxia in the Eastern Chipmunk (Tamias striatus) /

Mammalian heterotherms, such as hibemators, are known to be more tolerant of low oxygen tensions than their homeothermic counterparts. It has been suggested that this relative hypoxia tolerance is related to their ability to deal with dramatic changes in body temperature during entry to and arousal from torpor. However, hibemators demonstrate dramatic seasonality in both daily heterothermy and overall torpor expression. It was of interest to test if seasonal comparisons of normothermic individuals within a single species with the capacity to hibernate produce changes in the response to hypoxia that would reflect a seasonal change in tolerance to low oxygen. In particular, the species studied, the Eastern chipmunk {Tamias striatus), is known to enter into torpor exclusively in the winter. To test for seasonal differences in the metabolic and thermoregulatory responses to hypoxia, flow-through respirometry was used to compare metabolic rate, minimum thermal conductance, body temperature, and a thermal gradient used to assess selected ambient temperature in response to hypoxia in both summer and winter acclimated animals. Although the animals periodically expressed torpor throughout the winter, no differences between season in resting metabolic rate, body temperature or minimum thermal conductance were observed in normoxia. The metabolic trials indicated that chipmunks are less responsive to hypoxia in the winter than they are in the summer. Although body temperature dropped in response to hypoxia in both seasons, the decrease was less in the winter, and there was no corresponding decrease in metabolic rate. Providing the animals with a choice of ambient temperatures in hypoxia resulted in a blunting of the drop in body temperature in both seasons, suggesting that the reported fall in body temperature set point in hypoxia is not fully manifested in the behavioural pathways responsible for thermoregulation in chipmunks. Instead, body temperature in hypoxia appears to be highly dependent on ambient temperature and oxygen concentration. The results of this study suggest that the season in which the responses to hypoxia are measured is important, especially in a heterotherm where seasonality can affect the degree to 1 which the animal is tolerant of hypoxia. Winter-acclimated chipmunks appear more capable of defending metabolic heat production in hypoxia, a response consistent with the increased thermogenic capacity observed in animals that must periodically enter and arouse from torpor during hibernation.

Meloidogne incognita (nematode) parasitism of Lycopersicon esculentum (tomato) plants : Ethylene action in susceptible and resistant host responses

Involvement of ethylene in the etiology of tomato plants (Lycopersicon esculentum) infected with the root-knot nematode (Meloidogyne incognita) was investigated. Endogenous root concentrations of ethylene were not significantly different in uninfected resistant var. Anahu and susceptible var. Vendor plants. Exposure of resistant plants to high doses of infectious nematode larvae did not affect root ethylene concentrations during the subsequent 30 day period. The possibility that ethylene may be involved in the mechanism of resistance is therefore not supported by these experiments. In no experiments did ethylene concentrations in roots of susceptible plants increase significantly subsequent to ~ incognita infestation. This result is not consistent with the hypothesis in the literature which suggests that increased ethylene production accompanies gall formation. Growth of susceptible tomato plants was affected by ~ incognita infestation such that root weights increased (due to galling), stem heights decreased and top weights increased. The possibility that alterations in stem growth resulted from increased production of 'stress' ethylene is discussed. Growth of resistant plants was unaffected by exposure to high doses of ~ incognita and galls were never detected on the roots of these plants. Root ethane concentrations generally varied in parallel with root ethylene concentrations although ethane concentrations were without exception greater. In 4 of 6 experiments conducted ethane/ethylene ratios increased significantly with time. These results are discussed in the light of published data on the relationship between ethane and ethylene synthesis. The term infested is used throughout this thesis in reference to plants whose root systems had been exposed to nematodes and does not distinguish between the susceptible and resistant response.

The effects of the menstrual cycle and hormonal contraceptives on the central thermoeffector threshold temperatures and width of the interthreshold zone

Basal body temperature (BBT) and thermoeffector thresholds increase following ovulation in many women. This study investigated if solely central thermoregulatory alterations are responsible. Seven females in a non-contraceptive group (NCG) were compared with 5 monophasic contraceptive users (HCG) on separate accounts: pre-ovulation (Trial I; d 2-5) and post-ovulation (Trial 2; 4-8 d post-positive ovulation) for NCG, and active phase for HCG (d 2-5, d 18-21). During immersion in 28°C water to the axilla, participants exercised for 20-30 min on an underwater ergometer. After steadily sweating, immersion continued until metabolism increased two-fold due to shivering. Rectal (Tre) BBT was not different between trials for neither NCG (1: 37.34±0.16°C; 2: 37.35±0.27°C) nor HCG. At exercise termination, Tre forehead sweating cessation increased (P<0.05) in trial 2 irrespective of group (1: 37.55±0.39°C; 2: 37.90±0,46°C). Tre shivering onset did not increase (P>0.05) in trial 2 (1: 36.91±0.50°C; 2: 37.07±0,45°C). The widths of the interthreshold zone increased (P<0.05) in trial 2 (1: 0.64±0.22°C; 2: 0.82±0.37°C) due to the increased sweating threshold only. HCG cooled quicker (1: -l.15±0,43°C; 2: -1.00±0.50°C) than NCG participants (1: - 0.58±0.22°C; 2: -0.52±O.29°C), and tympanic (Tty) sweat thresholds were significantly (P<0.05) decreased (1: 34.76±0.54°C; 2: 35.39±0.61°C) versus NCG (l: 35.57±0.77°C; 2: 35.89±1.04°C). Lastly, Tre and Tty thresholds were significantly different (P

Electrocortical responses in reward paradigms and their variation related to personality

This thesis was conducted in order to investigate two issues: (1) how sensitive event related potentials (ERPs), and more specifically the medial frontal negativity and the P3 components, are to the valence and magnitude of reward-related stimuli, and (2) whether individual differences have an effect on the sensitivity of these ERP components to these characteristics. This was investigated using two reward-related paradigms. In the "pure gambling task" participants were asked to choose between two cards, each containing varying dollar amounts (large or small). The outcome of the choice (i.e., win or loss) was revealed after the choice was made. Additionally, participants were shown whether the non-chosen card would have been a win or a loss. In the "simple response task", participants were presented with five cues (large win, large loss, small win, small loss or zero) that labelled the trial as either a potential win, a potential loss or no change. Following the cue, a target appeared on the screen and the participant's task was to press the response key while the target was still visible. A success led to a win (gain in money) or no loss (no change) depending on the cue. Thirty participants completed both tasks; afterwards they filled out a set of questionnaires measuring personality and other individual differences relating to risk-taking behaviour. The results of both tasks showed that ERP components can differentiate between the valence and magnitude of reward-related stimuli, although no single component was uniquely related to either of the characteristics as previous suggested in the literature. Additionally, the context of the stimulus presentation (e.g., the task structure, condition within the task) affected the relationships between the ERP components and stimulus characteristics.

Effects of Proactive and Retroactive Augmented Information on Physiological Responses in Learning a Novel Motor Skill

Previous research has demonstrated superior learning by participants presented with augmented task information retroactively versus proactively (Patterson & Lee, 2008; 2010). Theoretical explanations of these findings are related to the cognitive effort invested by participants during motor skill acquisition. The present study extended previous research by utilizing the physiological index, power spectral analysis of heart rate variability, previously shown to be sensitive to the degree of cognitive effort invested during the performance of a motor task (e.g., increase cognitive effort results in increased LF/HF ratio). Participants were required to learn 18 different key-pressing sequences. As expected, the proactive condition demonstrated superior RS during acquisition, with the retroactive condition demonstrating superior RS during retention. Measures of LF/HF ratio indicated the retroactive participants were investing significantly less cognitive effort in the retention period compared to the proactive participants (p< .05) as a function of learning.

Icewine fermentation by Saccharomyces cervisiae : fundamental stress responses and comparative fermentation dynamics

Please consult the paper edition of this thesis to read. It is available on the 5th Floor of the Library at Call Number: Z 9999.5 B63 P54 2007

Postsecondary Artist Teachers' Responses to Computer Technology in Their Drawing Pedagogy

While the influence of computer technology has been widely studied in a variety of contexts, the drawing teaching studio is a particularly interesting context because of the juxtaposition of traditional medium and computer technology. For this study, 5 Canadian postsecondary teachers engaged in a 2-round Delphi interview process to discuss their responses to computer technology on their drawing pedagogy. Data sources included transcribed interviews. Findings indicated that artist teachers are both cautious to embrace and curious to explore appropriate use of computer technology on their drawing pedagogy. Artist teachers are both critical and optimistic about the influence of computer technology.