Graduation date: 1992

Few studies have examined the acute effects of resistive-type exercise on lipid-lipoprotein profiles. This study examined the acute effects of a single session of circuit weight training (CWT) on plasma lipid-lipoprotein profiles: triglycerides (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), and the ratio of TC to HDL-C. The subjects in the study were 17 healthy, nonsmoking male university students, ages of 18-25 years, enrolled in weight lifting classes. Subjects were required to fast overnight (at least 12 hours) before CWT. Subjects repeated a four-station weight training circuit three times, with a resistance determined by their individual 3 repetition maximum (3-RM). The stations were bench press, parallel squat, leg extension, and seated row. Blood samples were drawn from the antecubital vein at pre-CWT, completion of the 1st and 3rd circuits, and 15 min post-CWT. All concentrations of plasma lipid and lipoprotein cholesterol were corrected for plasma volume changes. A repeated measures ANOVA was used to determine if significant differences existed among mean values for the dependent variables (i.e., levels of TG, TC, HDL-C, LDL-C, and TC/HDL-C ratio at specified time points). Results of the study indicated that plasma TC and HDL-C levels were changed significantly during and following CWT. However, the change was not in the anticipated direction: Plasma TC and HDL-C levels were lower at completion of the 1st circuit of CWT (p<0.05). The ratios of TC to HDL-C were changed significantly, reflecting a decrease in HDL-C during CWT and a slight increase in HDL-C at 15 min post-CWT. Plasma TG and LDL-C levels were not changed significantly during CWT or 15 min post-CWT. It was concluded that apparent changes in lipoprotein patterns occur during short-term moderate intensity CWT and return to pre-CWT levels in a relatively short time. / Graduation date: 1991

published_or_final_version / Sports Science / Master / Master of Science in Sports Science

FGF21 is a stress-inducible hormone predominantly secreted from the liver. FGF21 acts as a downstream target gene of hepatic transcription factor PPARα that plays an obligatory role in mediating metabolic adaptation responses to prolonged fasting. However, the physiological roles of FGF21 in regulating glucose homeostasis during adaptive starvation responses and its underlying mechanisms remain unknown. Furthermore, FGF21 is induced by both acute and chronic exercise training in both rodents and human. The physiological significances and the underlying mechanisms for exercise-induced FGF21 production have not been explored so far. Therefore, this study aims to investigate: 1) the mechanisms whereby FGF21 mediates the role of PPARα activation in modulating hepatic gluconeogenesis in response to prolonged fasting; 2) the physiological roles and mechanisms whereby FGF21 regulates exercise capacity and insulin sensitivity via its actions in the muscle during exercise; 3) the roles of FGF receptor-1 (FGFR1) and co-receptor βKlotho in mediating the metabolic effects of FGF21 during fasting and exercise. Our results show thatFGF21 is induced by fasting in the liver and enters into the brain. Both FGF21knockout (KO) mice and PPARα KO mice exhibit severe hypoglycemia and defective hepatic gluconeogenesis during prolonged fasting, and these changes are accompanied by impaired activation of the hypothalamic-pituitary-adrenal (HPA)axis and blunted release of corticosterone from adrenalgland. Moreover, intracerebroventricular injection of recombinant FGF21 reverses fasting hypoglycemia and impairment in hepatic gluconeogenesis by restoring corticosterone production in both FGF21 KO and PPARα KO mice. These effects are abrogated by blockage of hypothalamic FGFR1or by pharmacological inhibition of ERK1/2in the hypothalamus. In addition,FGF21 acts directly on the hypothalamic neurons to activate FGFR1/βKlotho-ERK1/2-CREBsignaling pathway, thereby leading to the transcriptional activation of corticotropin-releasing hormone (CRH) and subsequent activation of the HPA axis. FGF21 is also induced in the liver by exercise and FGF21 KO mice have decreased exercise capacity associated with lower mitochondrial content and thus lower insulin sensitivity compared to wildtype (WT)mice after exercise training.AMPK-PGC-1α signaling pathway is impaired in the muscle of FGF21 KO mice during exercise.FGF21treatmentincreasesmitochondrial content in myotubes, while inhibition of AMPK and knockdown of FGFR1, βKlotho and PGC-1αblocksthis effect. Moreover, FGF21 regulates genes and proteins involved in different steps of the autophagy process and these alterations are mediated by FGFR1/βKlotho-PGC-1α signaling cascade. Furthermore, replenishment of FGF21 reverses the reduced mitochondrial content and insulin sensitivity by restoring PGC-1α expression and subsequent increase in mitochondrial biogenesis and suppression of autophagy in the muscle of FGF21 KO mice. In conclusion, our results identify FGF21 as a critical hormonal regulator of glucose homeostasis during prolonged fasting, by coupling hepatic PPARα activation to corticosterone release via stimulation of the HPA axis in the brain. Moreover, FGF21 acts in the muscle through two distinctive mechanism to maintain mitochondrial homeostasis during exercise training, involving both biogenesis of new mitochondria and decreased clearance of stressed mitochondria and thus to mediate the beneficial effects of exercise on lipid and glucose metabolism. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

No description available.

No description available.

This study compared the plantar force distribution between forward ice hockey skating and treadmill skating. Four varsity hockey players from McGill University (age = 22.1 +/- 1.2 years, height = 1.8 +/- 0.1 m, mass = 82.2 +/- 8.6 kg) skated on ice surface and on a specialized treadmill at three velocities (22, 24 and 26 +/- 0.5 km/hr). Results showed higher plantar forces were seen during treadmill skating prior to push off and this discrepancy was due to consistently larger forces in the fore region of the foot. This phenomenon was speculated to be the result of differences in skate stability during ice and treadmill skating. With respect to the loading dynamics, the heel region was the same during ice and treadmill skating.

The purpose was to compare the blood lactate response and performance of varsity hockey players to recreational players, and to provide a shift by shift analysis of blood lactate accumulation in a simulated ice hockey task. Ten university, varsity players and ten recreational players performed a continuous aerobic treadmill test (VO2max), a 45 s Wingate test, and four trials of the Repeat Sprint Skate (RSS) test. Each RSS test consisted of four repetitions of a 91.4 m skate with repetitions initiated on 30 s intervals. To simulate game, competition, 5 min of recovery separated each RSS test. Results indicated: (1) performance of the varsity players was superior (p < 0.01) to that of the recreational players in the RSS test; (2) four shifts of the RSS test elicited similar peak blood lactate concentrations for the varsity and recreational groups; (3) change in blood lactate following 15 min of passive recovery was similar in the two groups, and (4) there was a significant relationship (&prop; = 0.05) between performance indices in the RSS test and corresponding variables measured in the 45 s Wingate test.

No description available.

It was the purpose of the present study to determine the shape of the TEPR function during a dichotic shadowing task when the imposed work load is beyond the capability of the subject.It was hypothesized that as the task became increasingly difficult, the plotted functions of the maximum TEPR and words/s produced would start out small, increase rapidly, then level off or decrease reflecting the amount of information processing actually done. Ratings of subjectively perceived effort would also follow this pattern, whereas ratings of perceived task difficulty would continue to increase. Analyses were performed on mixed between-subjects and within-subjects designs using Two-way Analyses of Variance for repeated measures. The Newman-Keuls Procedure was used for all post-hoc comparisons.The results clearly demonstrated that the maximum TEPR reflects information actually being processed rather than the imposed difficulty of the task. Subjective ratings of perceived effort appear to reflect the same. The TEPR is not a good indicator of perceived task difficulty since ratings of task difficulty continued to increase after the TEPR leveled off.