Kinesiology Commons^™

The Effect Of Central Chemoreceptors On The Peripheral Respiratory Chemoreflex Response To Hypoxia In Humans, Nasimi A. Guluzade

Electronic Thesis and Dissertation Repository

We measured the peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic carbon dioxide tensions (PCO₂) to determine the form of the relationship between PChS and central PCO₂. Twenty participants completed three repetitions of modified rebreathing tests with end-tidal PO₂ (P_ETO₂) clamped at 150, 70, 60, and 45 mmHg. PChS was computed at 1-mmHg intervals of P_ETCO₂ as follows: the differences in V̇_E between the three hypoxic profiles and the hyperoxic profile (∆V̇_E) were calculated; three ∆V̇_E values were plotted against corresponding calculated oxyhemoglobin …

Plantar Flexor Dynamic Contractile Rates Are Not Dependent On Calcaneal Tendon Stiffness, Sohum Kulkarni

Electronic Thesis and Dissertation Repository

The ability to rapidly generate muscular torque and velocity is important in specialized activities and daily tasks of living. Tendon stiffness is one factor in the neuromuscular system that influences musculoskeletal torque transmission. Previous studies have reported weak-to-moderate correlations between tendon stiffness and rate of torque development (RTD). However, these correlations have been reported only for isometric contractions which may not be relevant to contractions involving joint rotation (i.e., dynamic). The purpose was to investigate the effect of calcaneal tendon stiffness on the dynamic rates of torque (RTD) and velocity (RVD) development in plantar flexor muscles. Young adult males (n=13) …

The Effect Of Breathing Patterns Common To Competitive Swimming On Gas Exchange And Muscle Deoxygenation During Heavy-Intensity Fartlek Exercise, Kevin J. Grossman

Electronic Thesis and Dissertation Repository

The purpose of this study was to compare the respiratory and muscle deoxygenation (HHb) responses of regulated breathing versus free-breathing, during continuous exercise (CONLD) and intermittent 5s breath holds (BH) (CONLD-BH), intermittent 5s sprint (FLK) and combined 5s BH and sprint (FLK-BH) followed by 25s of free-breathing. Oxygen uptake(V̇O₂)was unchanged between CONLD (2.12±0.35L/min) and CONLD-BH (2.15±0.42L/min; p=0.116), and FLK (2.24±0.40L/min) and FLK-BH (2.20±0.45L/min; p=0.861). Δ[Hb_tot]: CONLD (3.3±1.6µM) > CONLD-BH (-2.5±1.2µM; ∆177%; p<0.001), but unchanged between FLK (2.0±1.6µM) and FLK-BH (0.82±1.4µM; p=0.979). Δ[HHb]: CONLD (7.3±1.8µM) > CONLD-BH (7.0±2.0µM; ∆4%; p=0.011), and FLK (6.7±1.8µM) < FLK-BH (8.7±2.4µM; p<0.001). It is suggested that the unchanged V̇O₂ between CONLD and CONLD-BH was supported by increased deoxygenation, reflected by decreased ∆[Hb_tot] and blunted …

Direct Electrical Stimulation Of Prefrontal Cortex Modulates The Transient Heart Rate Response To Exercise In Conscious Humans, Bartek Kulas

Electronic Thesis and Dissertation Repository

Prefrontal cortical regions play an essential role in generating appropriate cardiovascular adjustments, particularly in cardio-vagally mediated heart rate (HR) responses to active tasks. Functional imaging studies provide correlational evidence that this region coordinates HR responses to exercise, however, direct experimental evidence of prefrontal cortical HR regulation in humans is not available. Seven persons with epilepsy implanted with intracranial electroencephalography (iEEG) completed 2-second isometric handgrip (IHG) contractions at no-stimulation (NO-STIM) or sham-stimulation (SHAM) conditions, and during direct electrical stimulation (STIM) of the orbitofrontal and medial prefrontal cortex. HR responses to IHG during NO-STIM and SHAM increased HR by Δ4.9±2.7 bpm, compared …

Spinal Excitability Changes Following Sensory Electrical Stimulation Of The Forearm, Devin K. Box

Electronic Thesis and Dissertation Repository

Sensory electrical stimulation can be used to suppress tremor in Parkinson’s disease. This study investigated the central mechanism underlying this suppression in healthy participants. Reciprocal inhibition (RI) of the wrist flexors before and after a session of sensory electrical stimulation (SES) applied to the antagonistic extensor muscles was assessed using electromyography. It was hypothesized that a 15-minute session of SES, rated by participants as a 3 on a 0-10 pain scale, would produce an increase in RI. Seven of the 18 participants experienced an increase in RI at 0-5 minutes post stimulation, which returned to baseline at 10-15 minutes. The …

Cardiodynamic Associations With Resilience In Undergraduate Students And The Effect Of A Mentorship Intervention, Rachel J. Knetsch

Electronic Thesis and Dissertation Repository

The National College Health Assessment (NCHA) indicates that a majority of Canadian university students report feeling overwhelmed, stressed, and anxious during their undergraduate studies. Resilience refers to positive adaptation, or the ability to maintain or regain mental health, despite experiencing adversity (Herrman et al., 2011). While autonomic indices have been used to describe chronic physiological stress, the role of heart rate variability (HRV) as an index of resilience remains unclear. This research tested the hypotheses that (1) there is a relationship between HRV and resilience scoresand (2) a mentorship intervention will improve HRV and resilience outcomes. Fifty-seven first year students …

Pilot Study: Heart Rate Variability Analysis And Mental Health Outcomes In University Female Hockey Players, Kaitlyn Jacobs

Electronic Thesis and Dissertation Repository

Exercise improves anxiety and depression, both of which are associated with impaired autonomic regulation of heart rate (HR). In turn, HR variability (HRV) is a reliable physiological indicator of external stressors. The following research tested the hypothesis that HRV is indicative of chronic resilience towards mental stress in female varsity hockey players. Seventeen varsity hockey players (HOCK, age 21 ± 1.5) and fifteen healthy controls (CTRL, age 21 ± 2.2) at Western University participated three times throughout a 7-month season. Participants completed questionnaires (brief resilience scale, BRS; generalized anxiety scale, GAD-7; mental health inventory, MHI; visual analog scale, VAS; short …

The Neuroprotective Effects Of Endurance Training On The Aging Brain, Katelyn Norton

Electronic Thesis and Dissertation Repository

Dysregulation of autonomic control often develops with advancing age, favoring a chronic state of heightened sympathetic outflow with parasympathetic withdrawal. However, the mechanisms of this age-related autonomic impairment are not known and may relate to alterations in brain structure (e.g. cortical atrophy) and/or altered neural function, particularly in regions related to the cortical autonomic network, namely, the medial prefrontal cortex (MPFC), insula cortex (IC), and hippocampus (HC). Exercise exerts beneficial effects on brain structure and, in the case of cognition, neurologic function; however, how exercise affects regions of the brain related to autonomic function are not known. This thesis tested …

Role Of Adenylyl Cyclase S674 In Central And Forearm Vasomotor Control, James Corkal

Electronic Thesis and Dissertation Repository

This study examined the cardiac and vasomotor responses to submaximal handgrip exercise and beta-adrenergic control in carriers (n = 6) and non-carriers (n = 4) of a genetic variant of adenylyl cyclase 6 (AC S674). Rhythmic handgrip contractions (1 minute bout; 2 second contraction-relaxation period) were performed at three different intensities (20, 40, and 60% of maximal voluntary contraction force) to test the vasodilatory response to exercise. Additionally, two 5 minute infusions of isoproterenol (0.01 and 0.02 µg·kg^-1·min^-1 diluted in 5% dextrose) and one 10 minute infusion of propranolol (0.1 mg·kg^-1 diluted in 0.9% saline) were …

Neuromuscular Function Following Lengthening Contractions, Geoffrey A. Power

Electronic Thesis and Dissertation Repository

Unaccustomed lengthening contractions have been shown to impair muscle function - however little is known regarding this impairment on muscle power - specifically, the velocity component of power during voluntary contractions in humans. The four studies presented in my thesis investigated power-loss following lengthening contractions in healthy young and old women and young men.

The purpose of Study 1 was to determine reliability of velocity-dependent power of the dorsiflexors using the isotonic mode of the Biodex Dynamometer. I determined the isotonic mode is reliable and can be used to track changes in velocity and power following fatigue and lengthening contractions. …

Neuroprotective Effects Of Long-Term Endurance Training On The Cortical Autonomic Network In The Aging Brain, Torri A. Luchyshyn

Electronic Thesis and Dissertation Repository

This study tested whether long-term endurance training in older adults (ET; n = 15, 55 ± 4 years, relative VO₂max = 50 ± 8 ml/kg/min) would alter cardiovagal control and preserve the cortical autonomic network compared to age-matched controls (CON; n = 15, 56 ± 4 years, relative VO₂max = 37 ± 9 ml/kg/min). The hypothesis predicts 1) altered deactivation patterns of the ventral medial prefrontal cortex (vMPFC) in response to isometric hand grip (IHG) and 2) greater indices of cardiovagal control; a) increased baroreflex sensitivity at rest, b) greater heart rate change (ΔHR) and c) …