The adaptive response of humans to exercise: Impact of exercise intensity, fibre-type specific responses and molecular patterns of response

In an attempt to improve the current understanding of the adaptive response to exercise in humans, this dissertation performed a series of studies designed to examine the impact of training intensity and mode on aerobic capacity and performance, fibre-type specific adaptations to training, and individual patterns of response across molecular, morphological and genetic factors. Project #1 determined that training intensity, session dose, baseline VO2max and total training volume do not influence the magnitude of change in VO2max by performing a meta-regression, and meta-analysis of 28 different studies. The intensity of training had no effect on the magnitude of increase in maximal oxygen uptake in young healthy participants, but similar adaptations were achieved with lower training doses following high intensity training. Project # 2 determined the acute molecular response, and training-induced adaptations in aerobic performance, aerobic capacity and muscle phenotype following high-intensity interval training (HIT) or endurance exercise (END). The acute molecular response (fibre recruitment and signal activation) and training-induced adaptations in aerobic capacity, aerobic performance, and muscle phenotype were similar following HIT and END. Project # 3 examined the impact of baseline muscle morphology and molecular characteristics on the training response, and if muscle adaptations are coordinated. The muscle phenotype of individuals who experience the largest improvements (high responders) were lower before training for some muscle characteristics and molecular adaptations were coordinated within individual participants. Project # 4 examined the impact of 2 different intensities of HIT on the expression of nuclear and mitochondrial encoded genes targeted by PGC-1α. A systematic upregulation of nuclear and mitochondrial encoded genes was not present in the early recovery period following acute HIT, but the expression of mitochondrial genes were coordinated at an individual level. Collectively, results from the current dissertation contribute to our understanding of the molecular mechanisms influencing skeletal muscle and whole-body adaptive responses to acute exercise and training in humans.

Straight but not Narrow; Within-Gender Variation in the Gender-Specificity of Women's Sexual Response

Gender differences in the specificity of sexual response have been a primary focus in sexual psychophysiology research, however, within-gender variability suggests sexual orientation moderates category-specific responding among women; only heterosexual women show gender-nonspecific genital responses to sexual stimuli depicting men and women. But heterosexually-identified or “straight” women are heterogeneous in their sexual attractions and include women who are exclusively androphilic (sexually attracted to men) and women who are predominantly androphilic with concurrent gynephilia (sexually attracted to women). It is therefore unclear if gender-nonspecific responding is found in both exclusively and predominantly androphilic women. The current studies investigated within-gender variability in the gender-specificity of women’s sexual response. Two samples of women reporting concurrent andro/gynephilia viewed (Study 1, n = 29) or listened (Study 2, n = 30) to erotic stimuli varying by gender of sexual partner depicted while their genital and subjective sexual responses were assessed. Data were combined with larger datasets of predominantly gyne- and androphilic women (total N = 78 for both studies). In both studies, women reporting any degree of gynephilia, including those who self-identified as heterosexual, showed significantly greater genital response to female stimuli, similar to predominantly gynephilic women; gender-nonspecific genital response was observed for exclusively androphilic women only. Subjective sexual arousal patterns were more variable with respect to sexual attractions, likely reflecting stimulus intensity effects. Heterosexually-identified women are therefore not a homogenous group with respect to sexual responses to gender cues. Implications for within-gender variation in women’s sexual orientation and sexual responses are discussed.