Evidence for complex integration and dynamic neural regulation of skeletal muscle recruitment during exercise in humans

A model is proposed in which the development of physical exhaustion is a relative rather than an absolute event and the sensation of fatigue is the sensory representation of the underlying neural integrative processes. Furthermore, activity is controlled as part of a pacing strategy involving active neural calculations in a “governor” region of the brain, which integrates internal sensory signals and information from the environment to produce a homoeostatically acceptable exercise intensity. The end point of the exercise bout is the controlling variable. This is an example of a complex, non-linear, dynamic system in which physiological systems interact to regulate activity before, during, and after the exercise bout

Influence of Different Performance Levels on Pacing Strategy During the Women's World Championship Marathon Race.

Purpose To analyse pacing strategies displayed by athletes achieving differing levels of performance during an elite level marathon race. Methods Competitors in the 2009 IAAF Women’s Marathon Championship were split into Groups 1, 2, 3, and 4 comprising the first, second, third, and fourth 25% of finishers respectively. Final, intermediate, and personal best (PB) times of finishers were converted to mean speeds, and relative speed (% of PB speed) was calculated for intermediate segments. Results Mean PB speed decreased from Group 1 to 4 and speed maintained in the race was 98.5 + 1.8%, 97.4 + 3.2%, 95.0 + 3.1% and 92.4 + 4.4% of PB speed for Groups 1-4 respectively. Group 1 was fastest in all segments and differences in speed between groups increased throughout the race. Group 1 ran at lower relative speeds than other groups for the first two 5 km segments, but higher relative speeds after 35km. Significant differences (P<0.01) in the percentage of PB speed maintained were observed between Groups 1 and 4, and 2 and 4 in all segments after 20 km, and Groups 3 and 4 from 20-25 km and 30-35 km. Conclusions Group 1 athletes achieved superior finishing times relative to their PB than athletes in other Groups who selected unsustainable initial speeds resulting in subsequent significant losses of speed. It is suggested that psychological factors specific to a major competitive event influenced decision making by athletes and poor decisions resulted in final performances inferior to those expected based on PB times

Fatigue, aging and the neuromuscular system

Bibliography: p. 400-445.The aim of this thesis was to investigate the relationship between chronic exercise activity, aging, the neuromuscular system and the symptom of fatigue in a series of studies. The hypothesis of the thesis was that in contrast to the accepted dogma that exercise is beneficial to an individual, increasing longevity and improving quality of life, excessive or chronic exercise activity may accelerate the aging process, lead to neuromuscular damage, and cause the development of pathological symptoms or levels of fatigue

From catastrophe to complexity: a novel model of integrative central neural regulation of effort and fatigue during exercise in humans

It is a popular belief that exercise performance is limited by metabolic changes in the exercising muscles, so called peripheral fatigue. Exercise terminates when there is a catastrophic failure of homoeostasis in the exercising muscles. A revolutionary theory is presented that proposes that exercise performance is regulated by the central nervous system specifically to ensure that catastrophic physiological failure does not occur during normal exercise in humans

The Effect of Power Alternation Frequency During Cycling on Metabolic Load and Subsequent Running Performance

The purpose of this study was to determine whether the frequency of power output alternation during cycling affects subsequent running performance. Eleven male triathletes completed a graded cycle test to determine peak oxygen uptake and the corresponding power at 35% delta. Two performance tests were then conducted, each comprising of a thirty minute cycling protocol followed by a 5 km free pace run. Mean cycling power was equal for both trials (35% delta), however the frequency of power alternations differed. In one trial cycling power output alternated every five minutes, whereas in the other trial cycling power output alternated every one minute. Power was set to alternate 15% above and below the 35% delta value. No significant difference was found between trials for the subsequent 5 km running performance time (P = .63). A significant difference was observed for overall mean heart rate between cycle trials (P = .045), however no significant difference was observed for overall mean oxygen uptake, minute ventilation, respiratory exchange ratio, blood lactate, rating of perceived exertion or pedal cadence (P > 0.05). When data was divided into 5 minute epoch stages rating of perceived exertion was significantly different between cycle trials at epochs three (minutes 10-15; P = .046) and five (minutes 20-25; P < 0.001). We conclude that when power is alternated equally during cycling, the frequency of power change (maximum of five minutes, minimum of one minute) does not affect subsequent running performance

Sit-to stand ground reaction force changes after hip resurfacing or total hip replacement: a pilot study

Two groups of osteoarthritis patients had their ground reaction forces measured during a sit-to-stand task at three months post-operation. One group had a 32mm femoral head fitted during a total hip replacement procedure and the other group had a hip resurfacing procedure. Three validated orthopaedic score questionnaires and an activity questionnaire were completed prior to surgery and at three months post-operation. This pilot study showed that there were no significant differences in the ground reaction forces in the operated and non-operated limb between the groups although both groups exhibited significantly higher ground reaction forces on the non-operated limb compared to the operated one. None of the orthopaedic scores showed any significant differences between the groups, despite the resurfacing group reporting higher levels of sporting activity at three months postoperation

Physiological correlates of performance in international-standard squash players

Tactical, technical and fitness factors are important for success in elite squash. While tactical and endurance fitness aspects have been explored, altered demands that have resulted from rule changes and absence of specific tests of high-intensity exercise capabilities have prevented identification of elements of fitness that correlate with performance in elite-standard players. Accordingly, the purpose of this study was to investigate relationships between test scores and player rank in such players. With institutional ethics approval, 31 players from the England Squash performance programme participated (11 women and 20 men, mean±SD body mass 62.4±5.5 kg and 73.1±7.5 kg respectively). After habituation, participants completed countermovement and drop-jump tests, squash-specific tests of change-of-direction speed and multiple-sprint ability and the multistage fitness test in one test session. Short recoveries were allowed between tests. World rank at the time of testing was obtained from the Professional Squash Association website. In men, change-of-direction speed (??=?0.59, p?=?0.02, n?=?14) multiple-sprint ability (??=?0.78, p<0.01, n?=?13) and fastest sprint from the multiple-sprint test (??=?0.86, p<0.01, n?=?13) correlated with world rank. In women, only fastest repetition from the multiple-sprint test correlated with world rank (??=?0.65, p?=?0.04, n?=?10). Measures of high-intensity exercise capability correlated with world rank in elite-standard men and women players. Endurance capability did not relate to rank in either the men or women. The results suggest that high-intensity, variable-direction exercise capabilities are important for success in elite squash

Clinically insignificant association between anterior knee pain and patellofemoral lesions which are found incidentally.

Patellofemoral chondral lesions are frequently identified incidentally during the arthroscopic treatment of other knee pathologies. A role has been described for arthroscopic debridement of such lesions when symptoms are known to originate from pathology of the patellofemoral joint. However, it remains unclear how to manage lesions which are found incidentally whilst tackling other pathologies. The purpose of this study was to establish the strength of association between anterior knee pain and patellofemoral lesions identified incidentally in a typical arthroscopic population. A consecutive series of patients undergoing arthroscopy for a range of standard indications formed the basis of this cross section study. We excluded those with patellofemoral conditions in order to identify patellofemoral lesions which were solely incidental. Pre-operative assessments were performed on 64 patients, where anterior knee pain was sought by three methods: an annotated photographic knee pain map (PKPM), patient indication with one finger and by palpated tenderness. A single surgeon, who was blinded to previous recordings, performed standard arthroscopies and recorded patellofemoral lesions. Statistical correlations were performed to identify the association magnitude. Associations were identified between incidental patellofemoral lesions and tenderness palpated on the medial patella (P=0.007, χ2=0.32) and the quadriceps tendon (P=0.029, χ2=0.26), but these associations were at best fair, which could be interpreted as clinically insignificant. In which case incidental patellofemoral lesions are not necessarily associated with anterior knee pain, we suggest that they could be left alone. This recommendation is only applicable to patellofemoral lesions which are found incidentally whilst addressing other pathology

Can patients really make an informed choice? An evaluation of the availability of online information about consultant surgeons in the United Kingdom.

Objectives - The National Health Service (NHS) 'Choose and Book' online scheme, which allows patients to select the location and time of hospital appointments, has now been extended to include the option for patients to select a specific consultant to carry out any necessary treatment. The aim of this study was to determine whether there is sufficient online information about consultants or consultant-led teams for patients to make an informed choice regarding a specific consultant. Design - A web-based analysis of the availability of information. Setting - North of England. Participants - Two hundred websites of orthopaedic surgeons. Main outcome measures - The websites were analysed using a bespoke template that took into account recommendations of the 2010 UK Government white paper. Each website was scored in relation to the availability of specific content relating to each surgeon. Results - The majority of websites detailed authorship information (73.2%), level of professional qualification (98.5%) and area of general (73.7%) and specialist (93.3%) interest. However, approximately 50% of websites provided no information in relation to update cycle, involvement in teaching or research and patient satisfaction. Only five (2.6%) of the websites presented death rates, and none indicated morbidity rates. Conclusions - For patients to be able to make informed choices about their healthcare, surgeons need to ensure that sufficient information is available online, according to the identified limitations of the websites investigated in this study

Multiple system modelling and analysis of physiological and brain activity and performance at rest and during exercise

One of the current interests of exercise physiologists is to understand the nature and control of fatigue related to physical activity to optimise athletic performance. Therefore, this research focuses on the mathematical modelling and analysis of the energy system pathways and the system control mechanisms to investigate the various human metabolic processes involved both at rest and during exercise. The first case study showed that the PCr utilisation was the highest energy contributor during sprint running, and the rate of ATP production for each anaerobic subsystem was similar for each athlete. The second study showed that the energy expenditure derived from the aerobic and anaerobic processes for different types of pacing were significantly different. The third study demonstrated the presence of the control mechanisms, and their characteristics as well as complexity differed significantly for any physiological organ system. The fourth study showed that the control mechanisms manifest themselves in specific ranges of frequency bands, and these influence athletic performance. The final study demonstrated a significant difference in both reaction time and accuracy of the responses to visual cues between the control and exercise-involved cognitive trials. Moreover, the difference in the EEG power ratio at specific regions of the brain; the difference in the ERP components’ amplitudes and latencies; and the difference in entropy of the EEG signals represented the physiological factors in explaining the poor cognitive performance of the participants following an exhaustive exercise bout. Therefore, by using mathematical modelling and analysis of the energy system pathways and the system control mechanisms responsible for homeostasis, this research has expanded the knowledge how performance is regulated during physical activity and together with the support of the existing biological control theories to explain the development of fatigue during physical activity.EThOS - Electronic Theses Online ServiceGBUnited Kingdo