The purpose of this study was to correlate the extent of myofibrillar disruption with muscle protein synthetic rate (MPS) following an isolated bout of concentric or eccentric elbow flexor resistance exercise. Six strength-trained males performed 8 unilateral sets of 8 repetitions at 80% concentric 1RM. The absolute amount of work performed by each arm was controlled by having both the concentrically-exercised (CON) and eccentrically-exercised (ECC) arms lift or lower the same weight through the same range and magnitude. Biopsies from biceps brachii of each arm, extracted ~21 h post -exercise, were analyzed electron microscopically to quantify myofibrillar disruption. The severity of disruption was classified as focal (FOC), moderate (MOD), or extreme (EXT). MPS of both arms was calculated from the increment in L- [1,2-¹³C₂] leucine abundance in biopsy samples relative to the mean plasma [1, 2-¹³C₂] -α-KIC enrichment at isotopic plateau using the primed-constant infusion technique over ~10 h so that the midpoint of the assessment period was ~24 h post-exercise. The severity of disruption was significantly (P < 0.001) greater in both the FOC (11.2%) and MOD (12.2%) compared to the EXT (1.6%) rating. Absolute disruption of fibers was significantly greater (P = 0.007) in the ECC (44.7%) as compared to baseline (BASE) samples (3.9%), obtained following 5 d where no arm training had occurred. In addition, ECC samples showed ~40% greater total disruption than CON samples (44.7% vs. 26.7%). Despite this, a positive correlation (r = 0.89) was found between individual values for MPS and the percentage of disrupted fibers in tissue from the ECC but not CON arm. These findings indicate that, in strength-trained males, residual myofibrillar disruption from a previous training session is essentially repaired within 5 d, but that resistance exercise induced muscle damage did not appear to provide the activating signal for elevating MPS between -21-29 h post-exercise. / Thesis / Master of Science (MSc)

Background & Rationale: During high intensity muscle contractions phosphocreatine is enzymatically degraded by creatine kinase (CK) to form creatine and the free energy which is released used to phosphorylate ADP to ATP. Creatine is then rephosphorylated during periods of relative ATP abundance (ie. rest) by CK back to phosphocreatine. Recognition of the importance of the phosphocreatine system to energy transduction has led many to believe that creatine monohydrate supplementation, which may lead to increases in phosptocreatine (PCr), may be beneficial during high intensity exercise. Several studies have demonstrated that creatine monohydrate supplementation for as few as three days can result in significant performance gains during exercise such as sprinting, or a weight lifting program. A common observation during these studies is a 1-2 kg increase in lean body mass (LBM). Although most researchers have speculated that this increase in LBM is due to water retention, some 𝘪𝘯 𝘷𝘪𝘵𝘳𝘰 work has demonstrated that creatine may stimulate protein synthesis. The purpose of this investigation was to examine whether a loading dose of creatine (20g/d x 7d) would have any affect on mixed muscle protein synthesis (MPS) in resting human skeletal muscle. Methods: A total of 22 young healthy subjects (n = 11 male, n = 11 female) were included in the study. On the day of measurement, subjects were provided with a meat free pre-packaged diet that was based upon individual diet records. Measurements of mixed muscle protein fractional synthetic rate (FSR) were completed over a 14 h resting period using a primed constant infusion of L[1-¹³C]leucine and muscle biopsies of 𝘲𝘶𝘢𝘥𝘳𝘪𝘤𝘦𝘱𝘴 𝘧𝘦𝘮𝘰𝘳𝘪𝘴 at isotopic plateau. Subjects were then randomly assigned to either a creatine (20g/d x 7d) or a placebo (isoenergetic glucose polymer) group. Following 7 days of supplementation, subjects reported to the lab under the same conditions as in the pre-trial, and resting mixed muscle protein FSR was again determined. Results: There were no significant between group differences in the baseline subject characteristics. No significant difference in FSR was observed with regards to condition (Pl: pre-0.63 ± 0.02 %/h; pst-0.71 ± 0.016 %/h; Cr: pre-0.56 ± 0.02 %/h; pst-0.58 ± 0.023 %/h) (creatine supplementation), time, or gender (Males: pre-0.06 ± 0.02 %/h; pst-0.068 ± 0.023 %/h; Females: pre-0.057 ± 0.02 %/h; pst-0.058 ± 0.015 %/h) Creatine supplementation resulted in a 13.1% increase in total creatine, however, no significant increases; in PCr or free Cr were observed. Similarly, no significant increases for fat free mass (FFM), or total mass were observed. Conclusion: It is concluded that creatine monohydrate supplementation for 7 d at 20g/d significantly increases muscle total creatine concentration, however, does not significantly affect muscle protein FSR in males or females. / Thesis / Master of Science (MSc)

Forces associated with head lifting efforts as well as mouth pressure were measured on four supine normal men, at five different lung volumes from FRC to TLC, and with the head positioned at two different heights above the bed. Positioning the head at one of the two heights (3cm and 10cm) provided for a change in length of the sternocleidomastoid (SCM) muscle. Graded efforts of head lift, and graded inspiratory pressure manoeuvres were executed and corresponding electromyograms of the SCM were measured. The mass lifted during efforts of head lift under static conditions (HSL) was measured with a self-contained transducer system located under the head of the subject. The muscle pressures at different lung volumes were obtained from pressure transducer records by adding the pressure-volume relaxation curve to the inspiratory mouth pressure-volume curve. The electromyogram of the SCM was obtained from surface electrodes, amplified and processed with a smoothing integrator to obtain the mean rectified electromyogram (MRE). For every subject, the relationships between MRE and MASS LIFTED, and between MRE and MUSCLE PRESSURE were linear for every lung volume at every head height above the bed ( r² >0.95 ). Data from all subjects were put together to form a single linear relationship (MRE vs MASS LIFTED and MRE vs MUSCLE PRESSURE) for every head height above the bed. The variability was greater at 3cm than at 10cm of head height. For both the head lift manoeuvre and the respiratory manoeuvre, there was a greater variability due to lung volume, on the slope and intercept of the curves at 3cm, than at 10cm of head height. Furthermore, more EMG was generated at 10 cm than at 3cm for a constant mechanical output, i.e., head lift or muscle pressure. Statistical tests were performed on the curves. Slope and intercept of the curves at different lung volumes, for a specific manoeuvre and head height above the bed were not significantly different ( p<0.05 ). The curves at different lung volumes were then put together to form a single linear relationship for both manoeuvres at both heights. Slope and intercept of the "pooled" curves, at both 3cm and at 10cm, were tested for both head lift and respiratory manoeuvres. It was found that the slopes were significantly different ( p<0.05 ) while the intercepts were net. Using the input variable, MRE, as the common factor, a linear relationship between the two output variables, MASS LIFTED and MUSCLE PRESSURE, was determined at each head height. Interpretation of the resulting relationships shows that: (a) About 50% of the maximum inspiratory muscle pressure can be generated without using the SCM muscle. (b) For the head located at 3cm above the bed, the production of muscle pressure from 50% to 100% Pmusc(max) corresponds to lifting, with the head, a mass equivalent to 4.5 times the head mass, while at 10cm above the bed, the same respiratory manoeuvre corresponds to lifting a mass equal to 1.3 times the head mass. (c) Changes in lung volume do not bring about as great changes in length of the SCM muscle as do changes in head height. / Thesis / Master of Engineering (ME)

Twenty-five patients with a mean age of 59.7 ± 11.8 (SD) years who were hemiparetic due to a cerebrovascular lesion of the cortex were assessed to determine the degree of neuromuscular dysfunction produced in the affected lower limb. Dysfunction was postulated to be the result of a secondary lower motoneuron lesion precipitated by the primary upper motoneuron lesion. The effects of cerebrovascular disease on skeletal muscle were assessed through an evaluation of the motor unit which involved assessment of excitable muscle mass (M-wave amplitudes), motor unit counts, peripheral nerve conduction velocities, evoked contractile properties of the dorsiflexor muscles (tibialis anterior) of the lower limb and degree of motor dysfunction expressed as a function of motor unit activation and maximum voluntary contraction (twitch interpolation method). Results showed preservation of the skeletal muscle with normal contraction times (108 ± 33 ms and 106 ± 35 ms, affected limb versus unaffected limb) and half relaxation times (119.3 ± 41 ms and 114 ± 32 ms respectively). Twitch torque was maintained and did not show significant differences between limbs (2.3 ± 1.6 N.m and 2.4 + 1.5 N.m., paretic vs. non-paretic limb). Voluntary force production of the affected limb, (10 ± 12.1 N.m) however, was 38% of that produced by the unaffected limb (26 + 1.4 N.m.) and measures of mean percent motor unit activation of the paretic limb were 58% of that produced by the unaffected limb. Interpolated twitch results showed that mean percent motor unit activation was significantly different in the affected limb (46 ± 36%) than the unaffected limb (79 + 19.6%). These results indicate that some motoneurone in hemiplegic patients were healthy but not readily activated. No effect was seen for age, sex of the subject and time post stroke. No significant difference in the pattern of results was observed between initial and final test results for subjects examined more than once. Conclusions were that skeletal muscle integrity was preserved probably due to spinal reflex activity and force production was depressed due, in part, to an inability to fully activate motor units. The inability to activate motoneurone may occur because some motoneurone are in a dysfunctional state. The following data from the present experimental work revealed several trends suggesting the possibility of a sick motoneuron hypothesis due to transynaptic motoneuron degeneration and the existence of a secondary lower motoneuron lesion in stroke syndrome. These trends are: 1) decreased motor unit counts of a sub-group of the total sample consisting of subjects under 60 years of age approached conventional levels of significance. Mean values for the affected limb were 73.8 ± 52 and 130.0 ± 61 for the unaffected limb (P < 0.05, F =5.05, critical F =5.59) In addition, M-wave amplitudes showed significant differences between limbs in the sub-group (4.0 + 2.3 mV and 5.7 ± 2.2 mV affected vs unaffected limb p<0.05), indicating that transynaptic motoneuron loss may have occurred; 2) decreased nerve conduction velocities and prolonged terminal latencies in the motor nerves of the paretic limbs also suggest sick motoneurone and the possibility of a dying back phenomenon of the terminal nerve endings; 4) normal M-wave amplitudes and twitch torque values of the tibialis anterior muscle coupled with the prolonged terminal latencies may be indicative of collateral sprouting of terminal axons which have taken over previously denervated muscle fibres. Future studies are needed to confirm or refute these observations. / Thesis / Master of Science (MS)

No description available.

No description available.

Creatine kinase (CK) primarily serves as an energy buffer assisting in regulating ATP homeostasis through synthesis of ATP from ADP and phosphocreatine (PCr). This enzyme is bound in the sarcomere near sites of ATP consumption via acto-myosin ATPase (A‧M‧ATPase) and research in cardiac muscle has found that PCr can alter contractile performance (maximal isometric force and Ca²⁺ sensitivity). Based on this evidence, CK and A‧M‧ATPase may be coupled in skeletal muscle. Therefore the purpose of this investigation was to determine the influence of the CK system on contractile performance and energy utilization in skeletal muscle. When skinned fibers (membrane removed) were provided a limited supply of [ATP] (0.1 mM), this resulted in increased Ca²⁺ sensitivity. The addition of PCr to low ATP solutions restored Ca²⁺ sensitivity and allowed normal isometric force generation across a range of [Ca²⁺] via ATP synthesis by CK. This was also possible with only CK reaction substrates (ADP, PCr) in the absence of ATP. Based on these findings, endogenous CK activity in glycerol skinned skeletal muscle fibers is sufficient to permit normal function of the contractile apparatus. Energy utilization was studied by indirect assessment of ADP production. Decreased net ADP production as measured by NADH fluorescence revealed endogenous CK was able to convert ADP produced by A‧M‧ATPase to ATP in skeletal muscle across a range of both [Ca²⁺] and [ATP]. This was confirmed directly via high-performance liquid chromatography measurements of ATP and ADP by showing that skinned skeletal muscle bundles have sufficient endogenous CK activity to produce ATP from substrates (ADP, PCr) and the ability to maintain low [ADP] in the presence of PCr. This study adds to the evidence for specific compartmentation of CK near sites of ATP utilization and contributes to the body of knowledge on contractile performance in skinned skeletal muscle fibers. By showing how changing demands on skeletal muscle (through increased Ca²⁺) alters force production and Ca²⁺ sensitivity, these findings lend support for the importance of endogenous CK as a pathway of ATP regeneration in skeletal muscle. / Ph. D.

The existence of a glycogen-sarcoplasmic reticulum has been demonstrated by a number of researchers. This complex is suspected to participate in the calcium uptake activities of the sarcoplasmic reticulum (SR). Removal of glycogen particles associated with this complex may alter the calcium handling abilities of the SR. This experiment sought to determine what effect exercise and treatment with a-amylase had on the abilities of the SR to regulate intracellular calcium ([Ca2+]i). Rats were either run on a treadmill for 60 min at a speed of 21 m/min and a 10% grade or were not exercised. Animals were then killed by decapitation after inhalation of CO2. Left and right gastrocnemius muscles were excised from both groups and underwent SR vesicle preparation to separate the heavy and light SR fractions (HSR and LSR respectively). Left hindlimb muscle homogenate also underwent 60 min incubation with a-amylase to digest glycogen before differential centrifugation. Treatment with a-amylase significantly depressed rate of calcium uptake by LSR and HSR fractions by 22.89% and 25.22% respectively (p<0.05). alpha-Amylase had no effect on SR's rate of calcium release. There was no effect of exercise on calcium uptake or release rates. Glycogen concentration associated with the SR was unaffected by either alpha-amylase treatment or exercise. These results indicate that treatment with alpha-amylase decreases the ability of the SR to sequester calcium ions. / Master of Science

No description available.

The mechanisms leading to a hypertrophic versus an endurance phenotype, the hallmarks of resistance exercise (RE) or aerobic exercise (AE), respectively, are still largely unknown. In humans, exposure of exercise naïve persons to either AE or RE results in their skeletal muscle exhibiting generic ‘exercise stress-related’ signalling, transcription, and translation responses. However, with increasing engagement in AE or RE, the responses become refined, and the phenotype typically associated with each form of exercise emerges. Phosphorylation of specific residue sites has been a dominant focus, with canonical signalling pathways (i.e. AMPK and mTOR) studied extensively in the context of AE and RE, respectively. These alone, along with protein synthesis, have only begun to elucidate key differences in AE and RE signalling. Still, key yet uncharacterized differences exist in signalling and regulation of protein synthesis that drive unique adaptation to AE and RE. Omic studies are required help in understanding the mechanisms that lead to the divergent relationship between exercise and phenotypic outcomes of training. In study 1 of this thesis, 16 young, healthy subjects (n=4 pilot study and n=12 follow-up study; 6 males [M] and 6 females [F]) performed a unilateral session of AE or RE with biopsies taken before (Pre), immediately post (0h) and 3 hours (3h) following recovery. Muscle tissue (cohort 1: n=4) was subjected to deep phosphoproteomic analyses, identifying nearly 13000 individual phosphosites and unique clusters specifically associated with AE and RE. Follow-up studies (cohort 2: n=12) were performed, and the outcomes support a thesis that prolonged activation of the MKK3/6, p38, and MK2 signalling axis is a resistance exercise-specific phenomenon and is critical in the process of muscle hypertrophy. We also demonstrated that the activation of signalling through MKK3 is robustly correlated with the increase in myofibrillar protein synthesis that occurs after RE in humans (r2= 0.60, p<0.01). In study 2, we sought to determine the divergent changes in the skeletal muscle proteome induced earlier and later in a training program using both RE and AE, in parallel, in healthy young males and females. We investigated muscle adaptations to AE and RE training during the early untrained versus trained state using novel deuterium oxide labelling and proteomic techniques. A total of 14 (8F/6M) healthy individuals completed 10-wk of thrice weekly unilateral resistance and unilateral aerobic training. Our data illustrated the common and unique networks of protein regulation following AE and RE. Specifically we highlighted the influence that both AE and RE have on mitochondrial proteins, likely aimed at improving metabolic function and possibly underpinning an increase in oxidative capacity and in supporting tissue protein remodelling. In both AE and RE, we identified changes in protein abundance that did not align with individual protein synthetic rates, suggesting that targeted degradation of certain proteins may be an adaptive feature of the shared response to aerobic and resistance training. To date, this work represents the most in-depth analysis of protein-specific fractional synthesis rates in human muscle in vivo in response to differential forms of exercise training. Together, these studies generate novel insights into training mode-specific muscle adaptations by measuring widespread phosphorylation and protein-specific changes in combination with individual protein synthesis rates. / Thesis / Doctor of Philosophy (PhD) / While some exercises help muscles become stronger, others improve the ability to resist fatigue. However, the reasons behind these different changes are not fully understood. Learning more about these processes is important because it could help develop treatments or exercise plans to improve health, especially for people at risk of losing muscle mass. We conducted two studies to explore the reason behind these changes: In the first study, we used advanced techniques to see which proteins in muscles are activated by either aerobic (endurance) or resistance (strength) exercise. We found certain proteins that were specifically turned on by resistance exercise, which helps build muscle and strength. This discovery is important because it could help us find ways to prevent or treat muscle loss, especially as people get older. In the second study, we looked at which proteins in muscles increased or decreased with both types of exercise. We found that some proteins, especially those involved in energy production, are regulated similarly in both types of exercise. However, many other proteins respond differently to aerobic and resistance exercises. Together these studies add to our knowledge on how exercise helps muscle to become more fit and mighty.