<p> It is known that high-resistance training induces morphological changes in skeletal muscle. Following a resistance training program, increases in maximum torque generating capacity are observed due to both neural adaptations and hypertrophic gains within the trained muscle. Although it has been established that a muscle hypertrophies due to the addition of myofibrillar proteins through increased protein synthesis, the exact mechanism which stimulates the hypertrophic response is unknown.</p> <p> Previous reports have shown that training in the absence of eccentric contractions generally produces less muscle growth and strength gains, as well as inflicting less damage to the muscle ultrastructure. Likewise, fast eccentric contractions have been shown to increase muscular strength to a greater extent than slow contractions. It has been hypothesized that fast eccentric contractions may maximize muscular damage, thus invoking a greater response of repair mechanisms, including satellite cell recruitment, which would allow an increased addition of contractile proteins to be added to the injured muscle, increasing muscle size and strength to a greater degree.</p> <p> The effect of fast and slow eccentric training was investigated using a bilateral, within subject model. Twelve men trained one arm fast (3.66 rad/s) and one arm slow (0.52 rad/s) for 8 weeks on an isokinetic training apparatus. Type I muscle fibre size increased with training by an average of 9.3±12.0% (P<0.05, main effect for time). Type II muscle fibres increased more in the subjects' fast trained arm when compared to the slow trained arm according to ATPase histochemical analysis (P<0.05, time x condition interaction). Likewise, whole arm cross-sectional area showed that the fast trained arms had an average increase of 6.8±5.5 % whereas the slow arms only had an average increase CSA of 5.1±5.7% (P=0.065, time x condition interaction). Maximum torque generating capacity was also increased to a greater degree (P<0.05, time x condition interaction) in the fast trained arm with an average of 10.3±16.4 Nm, whereas the slow trained arm increased only 7.3±15.0 Nm, across testing speeds. A decrease in the percentage of type IIx fibres was seen in both arms after training according to both ATPase histochemical staining and MHC gel electrophoresis; however, the percentage of type IIa fibre area increased in the fast trained arms (8.4±8.6%) more significantly (P<0.05, time x condition interaction) than the slow trained arms (1.7±10.9%).</p> <p> Seven males were trained in a similar manner to determine the extent of muscle damage which was evaluated by both Z-band streaming and force production decrements. After a single exercise bout of fast eccentric training in one arm and slow eccentric training in the other, it was determined that a 1.97±0.74 areas of moderate Z-band streaming per mm^2 of muscle in the fast exercised arm compared to 0.89±0.79 areas of moderate Z-band streaming per mm^2 of muscle in the slow trained arm (P<0.05). In conclusion, training using fast (3.66 rad/s) eccentric contractions causes a greater degree of muscle damage, hypertrophy, and strength gains than does training with slow (0.52 rad/s) eccentric contractions.</p> / Thesis / Master of Science (MSc)

Evolutionary models of adolescent and young adult risk-taking posit that risk-taking increases during this period of the life span as a strategic way for males, in particular, to show dominance, increase perceptions of attractiveness by the opposite-sex, and maximize their chances of acquiring a romantic partner (and ultimately produce offspring). Consistent with this perspective, existing research demonstrates that attractive females increase risk-taking in single males, in part by enhancing males’ sensitivity to rewards and diminishing their ability to inhibit impulsive behavior. By contrast, romantically committed males engage in less risk taking than their single counterparts, although the mechanisms underlying the effect of romantic partners/partnerships on male risk-taking are less clear. In the present study, I employed a behavioral paradigm that has been used in prior studies of peer influence to examine how romantic partners affect decision-making processes and risk-taking behavior in young heterosexual males (18 to 24 years old). I also explored whether there are particular individual and relationship characteristics that moderate the effect of romantic partners on males’ decision-making. This study was conducted using a sample of 134 romantically involved males (mean age=20.2, SD=1.65; 64% White) who were randomly assigned to participate in one of three experimental conditions: alone, in the presence of an attractive female confederate, or in the presence of their romantic partner. Across conditions, I compared males’ behavioral performance on five outcome measures: risk taking (using the Stoplight Task), preference for immediate rewards (using a Delay Discounting Task), reward learning and cost avoidance (using a modified version of the Iowa Gambling Task), and inhibitory control over both neutral and emotionally charged stimuli (using cognitive and emotional versions of the Stroop Task). I found that the presence of romantic partners diminishes risk taking in males, but that romantic partners do not have a significant impact on males’ sensitivity to rewards (neither immediate nor long-term), sensitivity to loss (i.e., cost avoidance), or their ability to inhibit attention to interfering—neutral or emotional—stimuli. However, improvements in cognitive control in the presence of romantic partners were observed among males who report low levels of passionate love. That is, mildly infatuated males exhibited better cognitive control in the presence of their romantic partners relative to mildly infatuated males who were alone. Partner presence had no such effects among males who reported being highly infatuated with their girlfriends. The presence of an attractive female stranger triggered a protective response among romantically involved males—prompting them to take fewer risks (when they are highly committed to their partners), to more quickly avoid decisions that lead to long-term loss (among older males only), and to exhibit better cognitive control (only among males in relatively longer relationships). The presence of an attractive female stranger did not affect males’ sensitivity to rewards. Evidently, the relative impact of an attractive female stranger on males’ risk taking and decision-making is highly dependent on individual and relationship factors, a finding that emphasizes the importance of context when it comes to understanding males’ relative susceptibility to temptation (e.g., other females) and opportunities for potential risk (e.g., infidelity). By contrast, the dampening effect of romantic partners on male risk taking is neither dependent on individual or relationship characteristics nor the result of romantic partners’ influence on reward sensitivity or inhibitory control. However, given the finding that romantic partners enhance cognitive control when feelings of passionate love are relatively low, future research should examine how passionate love and cognitive control interact to predict risk taking. Although I could not identify potential mechanisms to explain why the presence of romantic partners diminishes males’ risk-taking, the current study demonstrates that under specific circumstances—such as when there is high relationship commitment or when the relationship is relatively long—the presence of an attractive female stranger can stimulate romantically involved males to engage regulatory processes that may contribute to their reduced inclination toward risky behavior in that context. This finding is consistent with prior studies and suggests that the presence of tempting stimuli and potential threats to relationship fidelity can trigger males’ deliberate engagement of regulatory processes in effort to maintain their current romantic relationship. In contrast, males’ reduced inclination to engage in risky behavior in the presence of their romantic partners may be automatically activated (without inducing a particular psychological state) regardless of individual and relationship characteristics. / Psychology