Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
3,644
result(s) for
"Physical Exertion - physiology"
Sort by:
Fatiguing handgrip exercise alters maximal force-generating capacity of plantar-flexors
Exercise-induced fatigue causes changes within the central nervous system that decrease force production capacity in fatigued muscles. The impact on unrelated, non-exercised muscle performance is still unclear. The primary aim of this study was to examine the impact of a bilateral forearm muscle contraction on the motor function of the distal and unrelated ankle plantar-flexor muscles. The secondary aim was to compare the impact of maximal and submaximal forearm contractions on the non-fatigued ankle plantar-flexor muscles. Maximal voluntary contractions (MVC) of the forearm and ankle plantar-flexor muscles as well as voluntary activation (VA) and twitch torque of the ankle plantar-flexor muscles were assessed pre-fatigue and throughout a 10-min recovery period. Maximal (100 % MVC) and submaximal (30 % MVC) sustained isometric handgrip contractions caused a decreased handgrip MVC (to 49.3 ± 15.4 and 45.4 ± 11.4 % of the initial MVC for maximal and submaximal contraction, respectively) that remained throughout the 10-min recovery period. The fatigue protocols also caused a decreased ankle plantar-flexor MVC (to 77 ± 8.3 and 92.4 ± 6.2 % of pre-fatigue MVC for maximal and submaximal contraction, respectively) and VA (to 84.3 ± 15.7 and 97.7 ± 16.1 % of pre-fatigue VA for maximal and submaximal contraction, respectively). These results suggest central fatigue created by the fatiguing handgrip contraction translated to the performance of the non-exercised ankle muscles. Our results also show that the maximal fatigue protocol affected ankle plantar-flexor MVC and VA more severely than the submaximal protocol, highlighting the task-specificity of neuromuscular fatigue.
Journal Article
High-Intensity Interval Training Elicits Higher Enjoyment than Moderate Intensity Continuous Exercise
Exercise adherence is affected by factors including perceptions of enjoyment, time availability, and intrinsic motivation. Approximately 50% of individuals withdraw from an exercise program within the first 6 mo of initiation, citing lack of time as a main influence. Time efficient exercise such as high intensity interval training (HIIT) may provide an alternative to moderate intensity continuous exercise (MICT) to elicit substantial health benefits. This study examined differences in enjoyment, affect, and perceived exertion between MICT and HIIT. Twelve recreationally active men and women (age = 29.5 ± 10.7 yr, VO2max = 41.4 ± 4.1 mL/kg/min, BMI = 23.1 ± 2.1 kg/m2) initially performed a VO2max test on a cycle ergometer to determine appropriate workloads for subsequent exercise bouts. Each subject returned for two additional exercise trials, performing either HIIT (eight 1 min bouts of cycling at 85% maximal workload (Wmax) with 1 min of active recovery between bouts) or MICT (20 min of cycling at 45% Wmax) in randomized order. During exercise, rating of perceived exertion (RPE), affect, and blood lactate concentration (BLa) were measured. Additionally, the Physical Activity Enjoyment Scale (PACES) was completed after exercise. Results showed higher enjoyment (p = 0.013) in response to HIIT (103.8 ± 9.4) versus MICT (84.2 ± 19.1). Eleven of 12 participants (92%) preferred HIIT to MICT. However, affect was lower (p<0.05) and HR, RPE, and BLa were higher (p<0.05) in HIIT versus MICT. Although HIIT is more physically demanding than MICT, individuals report greater enjoyment due to its time efficiency and constantly changing stimulus.
NCT:02981667.
Journal Article
Examining the alignment between subjective effort and objective force production
Ratings of Perceived Exertion (RPE) are frequently used to prescribe exercise intensity. A central assumption of using RPE scales is that the subjective perception of effort maps onto objective performance in a consistent way. However, the degree and shape of how RPE aligns with objective performance is not fully understood. Here, we investigate the degree and shape of alignment, as well as how time (i.e., how frequently an effort needs to be performed) and mental effort (i.e., if one has to invest mental effort and physical effort) correspond with the alignment. In a randomized within-subjects experiment, we used a grip-to-scale method that asked participants (N = 43) to repeatedly squeeze a handgrip dynamometer with four to-be-produced RPE target levels relative to their subjective maximum strength (representing 20%, 40%, 60%, or 80%). We found that the RPE-force alignment was not the same across RPE-levels: Whereas subjective differences from 20–40% and 40–60% were met by comparable differences in produced force, a substantially larger difference was observed for the 60–80% interval. Interestingly, exploratory post-hoc analyses revealed that this was mirrored by an increase in variance at the higher effort levels. In addition, at constant RPE-levels, participants produced less force over time, and this effect was more pronounced at lower RPE target levels. Lastly, anticipating mental effort after the physical effort slightly altered the alignment as a function of the to-be-produced RPE-level and experimental duration. Taken together, our results indicate that the mapping of perceived effort on objective performance is intricate, and several factors affect the degree and shape of how RPE and performance align. Understanding the dynamic adjustment of RPE-performance alignment across different RPE levels is particularly relevant for contexts that use RPE as a tool for training load prescription.
Journal Article
Fatigue in sport and exercise
This book surveys the research evidence into exercise-induced fatigue and discusses how knowledge of fatigue can be applied in sport and exercise contexts. The book examines the different \"types\" of fatigue and the difficulties of identifying which types are prevalent during different types of exercise. It introduces the fundamental science of fatigue, focusing predominantly on physiological and neuromuscular aspects, and explores key topics in detail, such as energy depletion, lactic acid, dehydration, electrolytes and minerals, and the perception of fatigue.-- From publisher's description.
Book
Transcranial direct current stimulation to enhance athletic performance outcome in experienced bodybuilders
Transcranial direct current stimulation (tDCS) is currently under investigation as a promising technique for enhancement of athletic performance through modulating cortical excitability. Through consecutive randomization, 12 experienced bodybuilders were randomly assigned to two arms receiving either sham or real tDCS over the primary motor cortex (leg area) and left temporal cortex (T3) for 13 minutes in the first session. After 72 hours, both groups received the inverse stimulation. After the brain stimulation, cerebral hemodynamic response (using frontopolar hemoencephalography) was examined upon taking three computer-based cognitive tasks i.e. reasoning, memory and verbal ability using the Cambridge Brain Science-Cognitive Platform. Subsequently, the bodybuilders performed knee extension exercise while performance indicators including one-repetition maximum (1RM), muscular endurance (SEI), heart rate (ECG), motivation (VAS), surface electromyography over quadriceps femoris muscle (sEMG) and perceived exertion (RPE) were evaluated. The real tDCS vs. sham group showed decreased RPE and HR mean scores by 14.2% and 4.9%, respectively. Regarding muscular strength, endurance, and electrical activity, the 1RM, SEI, and sEMG factors improved by 4.4%, 16.9%, and % 5.8, respectively. Meanwhile, compared to sham, real tDCS did not affect the athletes' motivation. Incidentally, it turned out that subjects who underwent T3 anodal stimulation outperformed in memory (p = 0.02) and verbal functions (0.02) as well as their corresponding frontopolar hemodynamic response [(memory HEG (p = 0.001) and verbal HEG (p = 0.003)]. Our findings suggest that simultaneous tDCS-induced excitation over the M1 leg area and left temporal area may potentially improve the overall athletic performance in experienced bodybuilders (Trial registration: IRCT20181104041543N1, Registered on 4 Nov. 2018, retrospectively registered).
Journal Article
Human health and physical activity during heat exposure
This book provides fundamental concepts in human thermal physiology and their applications in general public, occupational, military, and athletics settings from the biometeorological perspective. The book includes a section on human physiology, epidemiology and special considerations in aforementioned populations, and behavioral and technological adjustments people may take to combat thermal environmental stress and safeguard their health. The book is the first of its kind to compile multiple disciplines--human physiology, climatology, and medicine--in one to provide fundamental concepts in human thermal physiology and their applications in general public, occupational, military, and athletics settings from the biometeorological perspective; Developed by experts, scientists, and physicians from exercise physiology, climatology, public health, sports medicine, and military medicine; Highlights special considerations and applications of thermal physiology to general public, occupational, military, and athletics settings.
Book
The impact of a commercial lower extremity exoskeleton on metabolic load, perceived exertion, and physiological response to a challenging military relevant task: A randomized cross-over design pilot study
To assess physiological metrics during the use of a commercially available bilateral active ankle exoskeleton during a challenging military-relevant task and if use of the exoskeleton during this task influences: metabolic load, physiological measures or rate of perceived exertion.
Nine healthy volunteers (5M, 4F) completed this randomized cross-over design trial, with a baseline visit and two randomized test sessions (with/without the exoskeleton). Variables included impact on time to exhaustion during walking on a treadmill at varying speeds and gradients (0-15%) at 26.7°C, 50% humidity with a loaded rucksack (30% body weight). The primary outcome measure was change in metabolic cost with/without the exoskeleton (O2 consumption, metabolic equivalents); secondary outcomes were change in heart rate and perceived exertion between conditions.
Participants averaged 22.4 ± 4.5 years old, 173.7 ± 7.4 cm tall, weighed 80.9 ± 13.9 kg, and VO2max of 43.8 ± 10.6 mL/kg/min. Total kcals did not differ between conditions (with/without exoskeleton; t = 0.98; p = 0.357). Kcals/min were significantly lower (1.06 kcals/min) with the exoskeleton (t = 3.94; p = 0.004). Average oxygen consumption (VO2) was significantly lower (2.36 mL/kg/min) with the exoskeleton (t = 2.81; p = 0.023), and peak VO2 was 3.33 mL/kg/min lower with the exoskeleton (t = 2.37; p = 0.045). Peak and Average METS were also lower with the exoskeleton by 0.98 (t = 2.61; p = 0.031) and 1.23 (t = 2.39; p = 0.044) respectively.
Results suggest a powered ankle exoskeleton may decrease energy consumption during military relevant tasks when conducted in a laboratory environment. There may also be physiological benefits such as reduced core temperate and heart rate. Replication of this work in the field environment is warranted.
Journal Article