Browsing by Author "Aboodarda, Saied Jalal"
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Item Open Access Characterizing the effect of precise exercise intensity prescription on physiological adaptations to endurance training - an intensity domain-specific approach(2023-06) Inglis, Erin Calaine; Murias, Juan M; Reimer De Bruyn, Raylene A; Keir, Daniel A; Aboodarda, Saied Jalal; Boone, Jan; Townsend, Nathan EExercise intensity determines the magnitude of the metabolic disturbance which is directly related to the upregulation of signalling pathways responsible for the adaptative responses to exercise training. The exercise intensity domain schema describes four distinct domains (i.e., moderate-, heavy-, severe- and extreme-intensity) each characterized by distinct metabolic responses. These domains are separated by exercise thresholds – of which the position varies widely between individuals. The most commonly used endurance exercise intensity prescription approach utilizes a percentage of maximal values (i.e., maximal oxygen uptake (V̇O2max) or maximal heart rate (HRmax)) to assign intensity. However, a major limitation to this approach is that it ignores the existence of individual exercise thresholds and the exercise intensity domains they create. This is problematic as research has shown that a given percentage of maximal values does not ensure a homogenous metabolic disturbance across individuals which complicates the interpretation of previous research studies that utilized this approach. Therefore, the true contribution of exercise intensity in modulating changes in response to endurance exercise training is unknown. The aim of this thesis was to apply a domain-based approach that precisely accounts for the metabolic disturbance of the intervention, to allow for the determination of the true effect of intensity on V̇O2max, submaximal thresholds, oxygen uptake (V̇O2) kinetics, and central and peripheral adaptations. The main findings were that i) changes in V̇O2max were intensity-domain dependent such that, with the exception of sprint interval training (SIT), greater magnitudes of change were found with progressively greater intensities with severe-intensity exercise (i.e., high-intensity interval training) producing the greatest magnitude of change, ii) this intensity-domain dependency was less pronounced when evaluating changes in the estimated lactate threshold and the maximal metabolic steady state and did not apply to the extreme-intensity domain (i.e. was not evident with SIT), iii) greater intensities of exercise resulted in central adaptations (i.e., maximal cardiac output and maximal stroke volume), with evidence for some peripheral adaptations to be present as well, iv) when compared to control, there was an equal speeding of V̇O2 kinetics across intervention with no significant correlations between changes in the speed of V̇O2 kinetics and performance variables.Item Open Access Critical power estimation provides a good approximation of the power output associated with the maximal metabolic steady state in both trained and untrained participants(2024-08-29) Lindstrom, Brynn Eric Alexander; Murias, Juan Manuel; Aboodarda, Saied Jalal; Holash, John; Zagatto, Alessandro MouraCritical power (CP) estimation is a well-established method to identify the power output (PO) associated with the maximal metabolic steady state (MMSS) of exercise. CP estimation requires multiple time to task failure (TTF) trials and the precision of this evaluation in untrained individuals could be questionable due to their inexperience with performing highly demanding efforts to volitional exhaustion. Thus, the goal of this study was to compare whether the accuracy of CP to approximate the MMSS was affected by the training status of the individuals. Participants underwent: i) a ramp incremental test to task failure to determine maximal oxygen consumption (V̇ O2max) and peak PO (POpeak); ii) a series of 4-5 TTF trials at average POs ranging from 70 to 90% of POpeak performed on separate days, to obtain TTF durations of ~3-15 min for CP estimations; iii) 2-3 30-min constant PO rides to establish MMSS. The PO associated to CP was significantly greater than that associated to MMSS in both untrained (155±39 W vs. 147±34 W, respectively) and trained (233±37 W vs. 225±39 W, respectively) individuals (F = 13.2, p = 0.001, η2 = 0.375, effect size d = 0.14). Despite this, no significant differences in the PO at CP and the PO at MMSS were observed between the untrained and trained groups (bias = 7.5 W for both groups; F = 0.01, p = 0.99, η2 = 0.001; statistical power = 99%) and for both groups, the biases were significantly greater than 0 (untrained z = 2.57; trained z = 2.95). The 95% CI for the LOA were -13 to 28 W, and -11 to 26 W for untrained and trained, respectively. These findings indicate that, despite a significant (albeit small) difference between CP and MMSS, the CP model provided a close approximation of the PO associated with the MMSS in both untrained and trained participants. This indicates that the quality of the CP model was not affected by training status, which suggests that previous experience with highly demanding exercise is not a key component of the quality of the prediction.Item Open Access Decrements in Cycling Performance are Dependent on the Intensity and Duration of Prior Exercise(2020-08-31) Fullerton, Madison; Murias, Juan M.; Passfield, Louis; MacInnis, Martin J.; Aboodarda, Saied JalalThe maximal lactate steady state (MLSS) is a physiological model that can be used to delineate the heavy- from the severe-intensity domain of exercise. The importance of this threshold has been repeatedly demonstrated, as it differentiates intensities that result in stable physiological responses from those that progress towards maximal values. To understand the implications that exercise performed at this intensity has on subsequent performance, a recent study demonstrated that time-to-exhaustion (TTE) performance is reduced following prior exercise performed at the power output (PO) corresponding to MLSS (MLSSp) and reduced even further following a small (i.e., 10 watt (W)) increase above MLSSp. Therefore, the purpose of this thesis was to determine whether submaximal intensities (i.e., sub-MLSSp) as well as different durations at MLSSp would have any impact on subsequent TTE performance, within the severe-intensity domain. The results from this thesis demonstrated curvilinear and linear reductions in TTE performance following increase in the intensity and duration of the preceding bout of exercise, respectively. These results highlight that the capacity within the severe-intensity domain is dependent on both the intensity and duration of a prior bout of exercise. Moreover, these findings also illustrate the importance of properly determining thresholds and the exercise intensity domains on an individual basis, as small changes in the PO surrounding MLSS have detrimental effects on performance. Lastly, this thesis also highlighted the importance of perceptual responses during exercise. Rating of perceived exertion (RPE) was associated with the reduction in TTE performance for both the intensity and duration conditions, indicating that the capacity within the severe-intensity domain can be estimated by RPE assessed immediately prior to each TTE trial.Item Open Access The development of neuromuscular fatigue throughout constant power output cycling below, at, and above the maximal lactate steady state in young and healthy females and males(2022-04-20) De Almeida Azevedo, Rafael; Murias, Juan; MIllet, Guillaume; Aboodarda, Saied Jalal; Hureau, Thomas; Dekerle, Jeanne; Hureau, Thomas; Keir, DanielExercise-induced neuromuscular fatigue development (NMF) is a transient phenomenon in which its etiology, amplitude (i.e., pre- to post-exercise changes) and time course (i.e., changes during the exercise bout) are directly affected by exercise intensity and sex of the population. It has been suggested that NMF development is related to the metabolic disturbance during the exercise, which might also underpin the increase in O2 cost of work as shown by the development of oxygen uptake slow component (V̇O2SC). However, it is currently unknown if NMF development is affected by slight manipulations in exercise intensity around the heavy and severe boundary, herein defined as the maximal lactate steady state (MLSS), thus demarcating metabolic responses that are stable (i.e., below and/or at) or unstable (i.e., above). Moreover, it is unknown if NMF development around the MLSS, and thus different metabolic responses, would be the same between females and males, and until the time to task failure (TTF). The specific objectives were to compare the effects of exercising at MLSS, as well as slightly below and above MLSS in NMF development, in females and males, regarding: (i) the total NMF amplitude after 30 min bouts of exercise and subsequent performance until TTF; (ii) the time course of NMF throughout a 30 min bout of exercise and at task failurewithin a broader range of exercise intensities around the MLSS (i.e., (i) at the MLSS, (ii) +10W and (iii) -10W, and (iv) +15% and (vi) -15%); (iii) if the relationship between the development of NMF and V̇O2SC is maintained regardless the exercise duration and intensity around the MLSS. The results are organized in three different studies, divided into chapters III, IV and V of the present thesis. The first study (chapter III), showed that the total amplitude of NMF development was exacerbated once exercising above the MLSS compared to below the MLSS, regardless the sex. The second study (chapter IV) showed that the time course of NMF was the same regardless of the exercise intensity and sex, wherein ~75% of the overall development of NMF occurred within the first 5 min of exercise. Finally, the third study (chapter V) showed that the development of both NMF and V̇O2SC were similar and correlated regardless of the exercise intensity and duration. Collectively, these findings provide a detailed characterization of the amplitude and time course of NMF development in exercise intensities around the MLSS in both females and males. As a possible explanation to these results, and highlighted in each study, was that slight change in exercise intensity around the MLSS, possibly, elicited distinct metabolic disturbance within the muscles, specially once exercising above compared to below the MLSS. Therefore, it was suggested that the development of both NMF and V̇O2SC might be related to metabolic disturbance occurring within the muscles.Item Open Access Effects of Fatigue on Neuromuscular Function and Mechanical Properties in Young and Elderly Populations(2019-08-20) Lopes Krüger, Renata; Millet, Guillaume Y.; Samozino, Pierre; Edwards, William Brent; Murias, Juan M.; Bilodeau, Martin; Kent-Braun, Jane A.; Aboodarda, Saied JalalNeuromuscular (NM) fatigue is defined as an exercise-related decrease in maximal power or isometric force. However, in the past 20 years, most studies have assessed isometric force only. The evaluation of dynamic measures provides important additional information to the fatigue-induced changes in NM function, especially when exploring age-related changes in fatigability. The few studies that explored dynamic measures of NM fatigue have assessed power output during single-joint movements. Therefore, measures of force production capacity (maximal power, velocity and torque) during multi-joint lower limb movements are unknown. The purpose of this thesis was to examine the effects of different intensities/durations of cycling exercises on torque-velocity properties and NM function in aging and young populations. The specific objectives were: (i) to assess kinetics of central and peripheral fatigue and recovery immediately after different cycling exercises in young individuals; (ii) to compare dynamic vs. isometric measures of NM fatigue following cycling and during recovery in young individuals; and (iii) to explore age-related differences in dynamic and isometric measures (including central and peripheral components of fatigue) of NM fatigue induced by cycling. Thanks to an innovative ergometer, NM fatigue was assessed with a minimal delay (10 s) through dynamic measures of force production capacity during 7-s cycling sprints and maximal isometric force. Our findings showed that: (i) NM fatigue is indeed determined by the exercise intensity/duration and previous studies that investigated NM fatigue with a delay (~ 3 min) might have misinterpreted fatigue amplitude and etiology as well as the course of recovery; (ii) isometric and dynamic measures behave differently after fatigue and so they are not interchangeable as they do not share the same physiological mechanisms; and (iii) younger individuals are as fatigable (for the Wingate and moderate-intensity exercise) or more fatigable (for severe-intensity exercise) than older subjects when considering isometric and dynamic measurements of NM fatigue and peripheral fatigue is greater in younger individuals after the severe- and moderate-intensity exercises, but not following the Wingate. This thesis provides the first comprehensive evaluation of age-related NM fatigue due to dynamic exercises with large muscle mass, i.e. exercises often performed in daily-life and rehabilitation activities.Item Open Access Effects of midsole cushioning stiffness on Achilles tendon stretch during running(2020-12-09) Esposito, Michael Jonathan Stuart; Stefanyshyn, Darren John; Edwards, William Brent; Aboodarda, Saied JalalFootwear midsole material can have a direct influence on running performance. However, the exact mechanism of improved performance remains unknown. It is speculated that changes to midsole stiffness may influence the energy return from the Achilles tendon, reducing the metabolic cost. The purpose of this study was to determine if changes in footwear midsole stiffness elicit changes in Achilles tendon stretch, and it was hypothesized that the footwear condition with better running economy for an individual will have greater Achilles tendon stretch. Fourteen runners with personal best 10km times less than 40 minutes completed two testing sessions. Two footwear conditions were evaluated and consisted of a stiff and compliant midsole. Session one determined the moment arm of the Achilles tendon using dynamometer testing. Session two was a treadmill running session where kinetics, kinematics, metabolic and ultrasound data were collected while participants ran at a submaximal speed in each shoe condition. Main outcome variables were differences in Achilles tendon pseudo-stretch and differences in running economy, quantified as the energy cost of running. Correlation analysis was performed to assess the existence of a linear relationship between the variables. There was a moderate positive correlation between the difference in pseudo-stretch and the difference in running economy, which was statistically significant (r = 0.563, p = 0.036, d = 0.58). Twelve participants had greater pseudo-stretch and better running economy in the same footwear condition and two participants did not have greater pseudo-stretch and better performance in the same footwear condition. Based on estimates, the difference in energy returned from the Achilles tendon was 3.8 % on average of the mechanical energy required per step. Energy returns of this magnitude would be relevant and could cause the improved running economy observed. These results suggest that the energy returned from the Achilles could be a valid mechanism for improving running economy due to changes in footwear. These findings lead the way for future research to further understand the mechanism behind improved running economy. Understanding how footwear modifications affect internal mechanisms could have large ramifications on potential strategies for assisting and supporting locomotion.Item Open Access Neuromuscular fatigue, cardiorespiratory, and perceptual responses are dependent on the amount of active muscle mass during exhaustive ramp incremental cycling(2021-09) Zhang, Mu Ye; Aboodarda, Saied Jalal; MacInnis, Martin; Iannetta, Danilo; Pageaux, BenjaminExercise tolerance is determined by an integration of neuromuscular (NM), cardiorespiratory, and perceptual responses, the contributions and components of which differ according to the amount of muscle mass engaged in the exercise task. The present thesis aimed to utilize an exhaustive single- (SL) and double-leg (DL) ramp incremental cycling model to assess the effect of active muscle mass on NM fatigue and recovery kinetics alongside cardiorespiratory and perceptual responses. Twelve recreationally active males (age: 30 ± 5 years) performed counterweighted SL and DL ramp incremental cycling exercises to task failure. Central and peripheral fatigue were assessed at baseline, task failure, and 1, 4, and 8 min of recovery. Cardiorespiratory and perceptual responses were measured throughout the cycling tasks. The results from this study demonstrated that with similar exercise durations, maximal voluntary force and peripheral fatigue of the knee extensors declined more following SL cycling, along with increased perceived effort and leg pain. On the other hand, higher cardiorespiratory responses and dyspnea were evoked during DL cycling. Central fatigue and NM fatigue recovery did not largely differ between tasks. These findings suggest that the interplay between NM, cardiorespiratory, and perceptual determinants of exercise tolerance during incremental cycling to task failure is muscle mass-dependent. More specifically, while metabolic perturbations within working locomotor muscles (i.e., reflected in peripheral fatigue and muscle pain) are not the primary limiting factors during larger muscle mass exercise, they may instead play a primary role in modulating smaller muscle mass exercise tolerance. The present thesis may have implications on utilizing smaller muscle mass exercise in clinical and performance settings to enhance peripheral adaptations.Item Open Access The Effects of Simulated Altitude on Maximal and Submaximal Exercise(2021-04-26) Beever, Austin T; MacInnis, Martin J; Murias, Juan M; Aboodarda, Saied Jalal; Subudhi, Andrew WThe maximal lactate steady state (MLSS) identifies the upper limit of sustainable exercise; however, the extent to which an individual’s MLSS is affected by changes in altitude is unknown. The primary objective of this thesis was to determine the extent to which the MLSS-associated cycling power output (PO) (MLSSp), assessed in normoxia (NORM; FIO2=20.9 %) at 1111 m in Calgary, AB, is affected by acute exposure to simulated hypoxia (HYPO; FIO2=18.2 %) and hyperoxia (HYPER; FIO2=23.8 %). The secondary objective was to evaluate metabolic, cardiorespiratory, perceptual and neuromuscular responses to 30 min of cycling at similar relative intensities (i.e., MLSSp, and 10 W above the MLSSp (MLSSp+10)), and the same absolute intensity of exercise (i.e., the normoxic MLSSp; MLSSpNORM) in these same FIO2 conditions. Eleven (4 females, 7 males) participants completed this study. MLSSp decreased in HYPO (209±54 W) compared to NORM (225±58 W; p=0.001), but HYPER (230±56 W; p<0.001) was not different from NORM (p>0.05). Four participants reached task failure prior to 30 min in the HYPO condition at MLSSpNORM, in addition to two, three and three participants in NORM, HYPO and HYPER, respectively, at MLSSp+10. At MLSSp and MLSSp+10 blood lactate concentration ([BLa]), ventilation (V?E), heart rate (HR) and perceptual responses to exercise did not differ between FIO2 conditions (p>0.05), despite a difference in V?O2 (p<0.05). In contrast, at MLSSpNORM, V?O2 was similar across conditions (p>0.05), whereas [BLa], V?E, HR and perceptual response to exercise were exacerbated in HYPO compared to both NORM and HYPER (p<0.05). Exercising in each condition elicited neuromuscular fatigue—manifesting as a reduction in quadriceps isometric maximal voluntary contraction, high- and low-frequency doublet, and single twitch force amplitudes—but no differences were detectable between conditions at any exercise intensity (p>0.05). In summary, a small decrease in FIO2, relative to ambient conditions, reduced the cycling MLSSp and exacerbated metabolic, cardiorespiratory and perceptual responses to ~30 min of exercise at an absolute PO but not at similar relative intensities, whereas increasing the FIO2 by the same amount did not significantly affect MLSSp or physiological responses to exercise performed at the same absolute or relative intensities.Item Embargo The Role and Regulation of Hemoglobin Mass in Endurance Exercise(2024-06-05) Kontro, Hilkka; MacInnis, Martin; Sheel, William; Satish, Raj; Aboodarda, Saied Jalal; McGlory, ChrisEndurance performance relies on sustained oxygen delivery to skeletal muscles. Consequently, the maximum capacity to deliver oxygen is closely related to the total amount of hemoglobin (Hb) in the circulation, hemoglobin mass (Hbmass). Experimental reduction of Hbmass results in lowered oxygen delivery in maximal exercise and hence a lower maximal oxygen uptake (V̇O2max). At submaximal intensities, compensatory adjustments can be employed in response to Hbmass reduction to maintain oxygen delivery, potentially lessening the impact on intensities below V̇O2max; however, data relating to these effects are lacking. While females have a lower [Hb] and lower Hbmass than males, the influence of sex on hematological properties has not been thoroughly investigated. In addition, the regulation of Hb turnover in endurance training is poorly understood, owing to methodological limitations. The purpose of this thesis was to expand on the current understanding about the role and regulation of Hbmass in facilitating endurance exercise. In Study 1 (n=16), reducing effective [Hb] by ~5% using low-dose carbon monoxide inhalation destabilized the maximal lactate steady state. This effect was more prominent in trained individuals, suggesting higher sensitivity to impairments in oxygen delivery. In Study 2 (n=17), Hbmass was reduced by withdrawal of 7% of blood volume through phlebotomy. In a 60-min exercise bout, ventilation, lactate, and heart rate were increased in a time-dependent manner, and time-to-task failure in a subsequent maximal task was reduced. Study 3 explored sex-differences in a pooled analysis (n=79) of four datasets. This cross-sectional study revealed that, due to sex differences in hematological variables, females must achieve a similar fat-free mass-normalized V̇O2max with a lower Hbmass than males. Study 4 (n=5) piloted the use of deuterated water as a metabolic label to quantify the fractional synthetic rate (FSR) of Hb in vivo. The preliminary data showed that this 28-day protocol was feasible and yielded expected FSR values (<1%∙day-1). Future research should explore the mechanisms behind impaired submaximal exercise performance after reduced oxygen delivery; how males and females employ specific strategies to reach a given oxygen uptake; and how Hb synthesis is influenced by sex and regulated in response to exercise training.