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1.
Knee Surg Sports Traumatol Arthrosc ; 22(10): 2377-81, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24651980

RESUMO

PURPOSE: Tibial tuberosity-trochlear groove distance (TT-TG) has been regarded as a useful tool for establishing therapeutic choices for patellar instability. Recently, it has been shown that TT-TG negatively correlated with the quadriceps angle, suggesting that if used individually, neither provide a valid measure of instability. This study aimed to compare TT-TG distance between both knees in patients with unilateral instability to assess whether this measurement is a decisive element in the management decisions for patellar instability. METHODS: Sixty-two patients (18 male and 44 female), reporting to a specialist patella clinic for recurrent unilateral patellar instability, were included in the study. Patients underwent bilateral long leg computed tomography scan to determine TT-TG distance in both knees. Tibial TT-TG in symptomatic and asymptomatic knees in the same individual was compared statistically. RESULTS: Mean TT-TG distance in the symptomatic knee was 16.9 (±4.9) mm, compared to 15.6 (±5.6) mm in the asymptomatic knee. Tibial TT-TG was not significantly different between stable and unstable knees (n.s.). CONCLUSIONS: The lack of difference in TT-TG distance between stable and unstable knees suggests that TT-TG distance alone may not be a decisive element in establishing therapeutic choices for patellar instability. It should, therefore, be interpreted with caution during clinical evaluations. LEVEL OF EVIDENCE: II.


Assuntos
Instabilidade Articular/diagnóstico por imagem , Articulação do Joelho/diagnóstico por imagem , Tíbia/diagnóstico por imagem , Adolescente , Adulto , Feminino , Fêmur/diagnóstico por imagem , Humanos , Masculino , Patela/diagnóstico por imagem , Músculo Quadríceps/diagnóstico por imagem , Estudos Retrospectivos , Tomografia Computadorizada por Raios X , Adulto Jovem
2.
Knee Surg Sports Traumatol Arthrosc ; 20(12): 2399-404, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22278658

RESUMO

PURPOSE: The quadriceps angle (Q-angle) represents the angle between the vector of action of the quadriceps and the patellar tendon. An increased Q-angle has been associated with an increased risk of patellar instability, although there is disagreement on its reliability and validity as it is affected by the position of the limb and contraction of the quadriceps. Tibial tuberosity-trochlear groove distance (TT-TG) is ascertained by axial CT scanning, with an increased value associated with patellar instability. This study aimed to determine whether the Q-angle correlates with the TT-TG distance in patients with patellar instability. METHODS: Q-angles were measured in 34 knees that had previously undergone CT scanning for assessment of patellar instability. Measurements were made with the patient supine, the knee extended and the lower limbs in neutral rotation with the quadriceps relaxed and contracted. TT-TG distance was measured on CT scanning in an identical position. RESULTS: Of the 34 knees measured, 24 had symptoms of patellar instability, and 10 were normal. A significant negative correlation between relaxed Q-angle and TT-TG in all knees was demonstrated (p = 0.028). In symptomatic knees, contracted Q-angle also demonstrated a significant negative correlation with TT-TG (p = 0.037). CONCLUSIONS: If TT-TG distance is regarded as the gold standard measurement, Q-angle is not a reliable indicator of patellar instability. There is a clear need to develop methods to more fully characterise the knee and factors contributing to patellar instability. LEVEL OF EVIDENCE: II.


Assuntos
Instabilidade Articular/diagnóstico por imagem , Articulação do Joelho/anatomia & histologia , Luxação Patelar/diagnóstico por imagem , Músculo Quadríceps/anatomia & histologia , Tíbia/anatomia & histologia , Feminino , Humanos , Articulação do Joelho/diagnóstico por imagem , Masculino , Músculo Quadríceps/diagnóstico por imagem , Tíbia/diagnóstico por imagem , Tomografia Computadorizada por Raios X
3.
J Orthop Traumatol ; 13(2): 97-103, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22391943

RESUMO

BACKGROUND: Pelvic osteoporotic fractures (POFs) are often associated with considerable morbidity and mortality mainly as a result of infections and cardiovascular events. Patients usually need prolonged institutionalization, rehabilitation, and follow-up, with a high rate of dependency and cost. The most common sites of POFs include the pubic rami, sacrum, ilium, and acetabulum. Combined pubic rami (PROFs) and sacral osteoporotic fractures (SOFs) have been reported, mostly in retrospective studies, describing the mechanism of injury and incidence. The aim of this study was to evaluate the association between PROFs and SOFs and to assess the effect of combined PROFs and SOFs on patients' mobility, discharge destination, and length of stay. MATERIALS AND METHODS: We prospectively studied 67 patients with low-impact PROFs and/or SOFs. There were 54 (80.4%) female and 13 (19.6%) male patients, and the average age was 87.5 (range 65-96) years. All patients were assessed by the fracture liaison service. Patients had magnetic resonance imaging or bone scan when there was history of low back pain following the injury or lumbosacral tenderness on clinical examination. RESULTS: The mean length of stay for all patients was 45 (± 35) days. Mortality rate was 10.4%. A significant relationship was found between low back pain and a positive finding of sacral fracture. Patients with combined PROFs and SOFs showed significantly longer length of stay than those with isolated PROFs. CONCLUSIONS: The presence of low back pain and tenderness in patients who had low-impact pelvic injuries was highly suggestive of the presence of an associated SOF. There was a high association between sacral and PROFs. The length of stay of patients with PROFs associated with sacral osteoporotic fractures was significantly longer than that of patients with PROFs only. Therefore, we recommend considering the high association between SOFs and PROFs in planning the management and rehabilitation of patients with POFs.


Assuntos
Fraturas por Osteoporose/epidemiologia , Osso Púbico/lesões , Sacro/lesões , Acidentes por Quedas , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Feminino , Seguimentos , Humanos , Incidência , Imageamento por Ressonância Magnética , Masculino , Fraturas por Osteoporose/diagnóstico , Fraturas por Osteoporose/etiologia , Estudos Prospectivos , Fatores de Risco , Reino Unido/epidemiologia
4.
Appetite ; 57(2): 443-7, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21726590

RESUMO

The accuracy of a combined dietary data collection method (self-reported, weighed food diary and 24-h recall technique) in 13 female, adolescent netball players (14-16 years) was explored. The girls were observed for a 12 h period (08:00-20:00), during which food and drink items were available ad libitum throughout the day and for the period between 20:00 and 08:00 the following morning. All items were covertly weighed before and after consumption to calculate observed energy intake. To calculate participant reported energy intake, food and drink items were weighed and recorded in a food diary by the participants, which was then supplemented with information from the 24-h recall the following morning. Agreement between observed and participant reported energy intake was calculated using the Bland and Altman technique. The mean difference between observed and participant reported energy intake was 0.46 MJ d(-1) (change in mean of 4.2%) indicating a slight bias towards over-reporting using the combined dietary data collection method. There was good agreement at the group level with the confidence interval for bias ranging from 0.00 to 0.92 MJ d(-1). The combined dietary data collection method is an effective technique to employ in 14-16-year old, female adolescent netball players when quantifying energy intake.


Assuntos
Atletas , Coleta de Dados/métodos , Registros de Dieta , Ingestão de Energia , Rememoração Mental , Adolescente , Dieta , Feminino , Alimentos , Humanos , Entrevistas como Assunto , Autorrelato , Esportes , Inquéritos e Questionários
5.
Appetite ; 56(3): 621-8, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21352880

RESUMO

Free-living energy intake and subjective appetite were monitored in a group of eleven 13-15-year old trained adolescent netball players. During preliminary visits, a FLEX heart rate calibration and resting metabolic test were conducted. Heart rate data were collected during a netball exercise session and sedentary period and during the waking hours of all study days, to enable exercise-induced and 24-h energy expenditure to be quantified. The girls completed two 5-day treatment weeks, interspersed with a 2-week 'wash out' period. A 47-min bout of netball exercise or an equivalent sedentary period was carried out on day 3 of each treatment week. Energy intake was measured over each 5-day period using a combined self-reported, weighed, food diary and 24-h recall interview technique. Subjective appetite (hunger, prospective food consumption, fullness) and mood were rated by subjects immediately before and after meals each day, and before and after the netball exercise and the sedentary period. Forty eight hour energy intake was significantly higher following the netball exercise compared to the sedentary period. The girls felt significantly more hungry immediately following the netball exercise compared to immediately before. In conclusion, a single intermittent exercise bout alters subsequent appetite and energy intake in trained 13-15-year old girls.


Assuntos
Apetite/fisiologia , Ingestão de Energia/fisiologia , Exercício Físico/fisiologia , Comportamento Alimentar/fisiologia , Esportes/fisiologia , Adolescente , Comportamento do Adolescente/fisiologia , Afeto/fisiologia , Estudos Cross-Over , Registros de Dieta , Metabolismo Energético/fisiologia , Feminino , Frequência Cardíaca/fisiologia , Humanos , Fome/fisiologia , Estudos Longitudinais
6.
Knee Surg Sports Traumatol Arthrosc ; 19(10): 1699-703, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21409465

RESUMO

PURPOSE: This study reports the specific interactions between the different grades and locations of chondral lesions found in symptomatic knees requiring arthroscopy. The associations between meniscal tears and chondral lesions were also investigated. METHODS: Data were analysed for 141 knee arthroscopies (87 males and 54 females), with a mean patient age of 45.9 years. Chondral lesions were defined according to the modified Outerbridge classification system by a single surgeon immediately following arthroscopic surgery. RESULTS: The most common clinical findings were medial meniscal tears (47%) and medial femoral condyle lesions (57%). Compared to other locations within the knee, the medial femoral condyle was the most commonly affected location for a chondral lesion and 75% of these lesions were graded as III (32%) or IV (43%). Similarly, 77% of knees with a trochlea lesion were affected by high-grade chondral lesions (grade III = 12%; grade IV = 65%). The trochlea presented with the greatest percentage of grade IV chondral lesions. Eighty percent of patients with a meniscal tear also had a chondral lesion. Medial meniscal tears were most commonly observed with medial femoral condyle lesion. Lateral meniscal tears were most commonly observed with lateral tibial plateau lesions. Twenty-nine percent of patients had corresponding lesions on the medial femoral condyle and medial tibial plateau, and this was the most commonly found interaction between chondral lesion locations. CONCLUSION: Patients with medial meniscal tears are likely to also have a chondral lesion on the same side of the knee. LEVEL OF EVIDENCE: II.


Assuntos
Artroscopia , Traumatismos do Joelho/patologia , Lesões do Menisco Tibial , Adolescente , Adulto , Idoso , Cartilagem/patologia , Feminino , Fêmur/patologia , Humanos , Articulação do Joelho/patologia , Masculino , Meniscos Tibiais/patologia , Pessoa de Meia-Idade , Patela/patologia , Estudos Retrospectivos , Tíbia/patologia , Adulto Jovem
7.
Eur J Appl Physiol ; 110(3): 619-25, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20574676

RESUMO

Interleukin-6 (IL-6) is a cytokine that can mediate numerous biological actions including fatigue. Circulating IL-6 increases during prolonged exercise, and furthermore, the signalling receptors sIL-6R and sgp130 are also increased. The variability of the response of these markers to exercise is unknown; therefore, we examined the changes in these markers to a preloaded time trial bout of running. Nine males performed three identical trials where participants ran at 60% vVO2max for 2 h interspersed with 30 s at 90% vVO2max every 10 min, followed by a 5-km time trial. Blood samples were drawn at baseline, following the 2-h bout, post time trial, 1 h post time trial and the following morning. Results showed that between-subject variability (CVg) was greater than within-subject variation (CVi) for the three markers. IL-6, sIL-6R and sgp130 demonstrated a CVi of 15.3-25.5%, 15.0-17.6% and 6.2-9.4% variation, respectively, across the time points. When the data from the second and third trials were analysed independently, CVi was reduced which is supported by the time trial results for which CVi improve (4.7-2.4%). In conclusion, the results indicate that a large variation in response to exercise can be reduced following a habituation trial.


Assuntos
Atletas , Receptor gp130 de Citocina/sangue , Teste de Esforço/métodos , Interleucina-6/sangue , Receptores de Interleucina-6/sangue , Corrida/fisiologia , Adulto , Glicemia/metabolismo , Proteína C-Reativa/metabolismo , Frequência Cardíaca/fisiologia , Humanos , Hidrocortisona/sangue , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Esforço Físico/fisiologia , Troca Gasosa Pulmonar/fisiologia , Adulto Jovem
8.
Br J Sports Med ; 43(10): 782-8, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19052141

RESUMO

OBJECTIVE: The purpose of this study was to measure the effects of an amphetamine (methylphenidate) on exercise performance at a fixed rating of perceived exertion of 16. METHODS: Eight elite cyclists ingested 10 mg methylphenidate in a randomised, placebo-controlled crossover trial. RESULTS: Compared with placebo, subjects receiving methylphenidate cycled for approximately 32% longer before power output fell to 70% of the starting value. At the equivalent time at which the placebo trial terminated, subjects receiving methylphenidate had significantly higher power outputs, oxygen consumptions, heart rates, ventilatory volumes and blood lactate concentrations although electromyographic activity remained unchanged. The ingestion of a centrally acting stimulant thus allowed subjects to exercise for longer at higher cardiorespiratory and metabolic stress indicating the presence of a muscular reserve in the natural state. CONCLUSIONS: This suggests that endurance performance is not only "limited" by mechanical failure of the exercising muscles ("peripheral fatigue"). Rather performance during prolonged endurance exercise under normal conditions is highly regulated by the central nervous system to ensure that whole-body homeostasis is protected and an emergency reserve is always present.


Assuntos
Estimulantes do Sistema Nervoso Central/farmacologia , Sistema Nervoso Central/efeitos dos fármacos , Exercício Físico/fisiologia , Adulto , Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Glicemia/metabolismo , Sistema Nervoso Central/fisiologia , Estudos Cross-Over , Eletromiografia , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Humanos , Lactatos/sangue , Metilfenidato/farmacologia , Consumo de Oxigênio/efeitos dos fármacos , Consumo de Oxigênio/fisiologia , Resistência Física/efeitos dos fármacos , Resistência Física/fisiologia , Esforço Físico/efeitos dos fármacos , Esforço Físico/fisiologia
9.
Eur J Sport Sci ; 18(1): 25-36, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28478704

RESUMO

Either central (brain) or peripheral (body physiological system) control mechanisms, or a combination of these, have been championed in the last few decades in the field of Exercise Sciences as how physiological activity and fatigue processes are regulated. In this review, we suggest that the concept of 'central' or 'peripheral' mechanisms are both artificial constructs that have 'straight-jacketed' research in the field, and rather that competition between psychological and physiological homeostatic drives is central to the regulation of both, and that governing principles, rather than distinct physical processes, underpin all physical system and exercise regulation. As part of the Integrative Governor theory we develop in this review, we suggest that both psychological and physiological drives and requirements are underpinned by homeostatic principles, and that regulation of the relative activity of each is by dynamic negative feedback activity, as the fundamental general operational controller. Because of this competitive, dynamic interplay, we propose that the activity in all systems will oscillate, that these oscillations create information, and comparison of this oscillatory information with either prior information, current activity, or activity templates create efferent responses that change the activity in the different systems in a similarly dynamic manner. Changes in a particular system are always the result of perturbations occurring outside the system itself, the behavioural causative 'history' of this external activity will be evident in the pattern of the oscillations, and awareness of change occurs as a result of unexpected rather than planned change in physiological activity or psychological state.


Assuntos
Exercício Físico/fisiologia , Exercício Físico/psicologia , Fadiga , Retroalimentação Fisiológica , Homeostase , Humanos , Teoria Psicológica
10.
Br J Sports Med ; 41(1): 2-7, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17062658

RESUMO

BACKGROUND: The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear. AIMS: To determine whether the perceived effort of ventilation is altered through substituting a less dense gas for normal ambient air and whether this substitution affects performance of maximal incremental exercise in trained athletes. METHODS: Eight highly trained cyclists (mean SD) maximal oxygen consumption (VO(2)max) = 69.9 (7.9) (mlO(2)/kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O(2)/65% N(2) (nitrox) or 35% O(2)/65% He (heliox). A ramp protocol was used in which power output was incremented at 0.5 W/s. The trials were separated by at least 48 h. The perceived effort of breathing was obtained via Borg Category Ratio Scales at 3-min intervals and at fatigue. Oxygen consumption (VO(2)) and minute ventilation (V(E)) were monitored continuously. RESULTS: Breathing heliox did not change the sensation of dyspnoea: there were no differences between trials for the Borg scales at any time point. Exercise performance was not different between the nitrox and heliox trials (peak power output = 451 (58) and 453 (56) W), nor was VO(2)max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal V(E) (157 (24) and 163 (22) l/min). Between-trial variability in peak power output was less than either VO(2)max or maximal V(E). CONCLUSION: Breathing a less dense gas does not improve maximal performance of exercise or reduce the perception of breathing effort in highly trained athletes, although an attenuated submaximal tidal volume and V(E) with a concomitant reduction in VO(2) suggests an improved gas exchange and reduced O(2) cost of ventilation when breathing heliox.


Assuntos
Ciclismo/fisiologia , Hélio/administração & dosagem , Nitrogênio/administração & dosagem , Consumo de Oxigênio/fisiologia , Oxigênio/administração & dosagem , Adulto , Limiar Anaeróbio/fisiologia , Análise de Variância , Ergometria , Teste de Esforço/métodos , Humanos , Troca Gasosa Pulmonar/fisiologia , Respiração , Método Simples-Cego
11.
Percept Mot Skills ; 105(3 Pt 2): 1227-41, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-18380123

RESUMO

In this study the effect of complete visual stimulus deprivation and manipulation of auditory timing signals during this deprivation on pacing strategy during an exercise bout were examined. 7 moderately trained men completed four 40-km cycling time trials under laboratory conditions in either normal light or absolute darkness, with either correct or manipulated auditory timing signals and without any other timing cues. The subjects were told to perform the time trial in the fastest time possible. There was no significant difference among trials for time to perform the trial, power output, heart rate, or ratings of perceived exertion, indicating that brain-control mechanisms responsible for pacing are not affected by manipulation of light or auditory signals.


Assuntos
Percepção Auditiva/fisiologia , Ciclismo/fisiologia , Exercício Físico/fisiologia , Privação Sensorial/fisiologia , Estimulação Acústica/métodos , Ciclismo/psicologia , Encéfalo/fisiologia , Sinais (Psicologia) , Escuridão , Frequência Cardíaca/fisiologia , Humanos , Luz , Masculino , Estimulação Luminosa , Esforço Físico/fisiologia , Análise e Desempenho de Tarefas , Percepção Visual/fisiologia
12.
Sports Med ; 47(11): 2375-2393, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28283993

RESUMO

OBJECTIVE: The purpose of these experiments was to develop a rating-of-fatigue (ROF) scale capable of tracking the intensity of perceived fatigue in a variety of contexts. METHODS: Four experiments were carried out. The first provided the evidential basis for the construction of the ROF scale. The second tested the face validity of the ROF, and the third tested the convergent and divergent validity of the ROF scale during ramped cycling to exhaustion and 30 min of resting recovery. The final experiment tested the convergent validity of the ROF scale with time of day and physical activity (accelerometer counts) across a whole week. RESULTS: Modal selections of descriptions and diagrams at different levels of exertion and recovery were found during Experiment 1 upon which the ROF scale was constructed and finalised. In Experiment 2, a high level of face validity was indicated, in that ROF was reported to represent fatigue rather than exertion. Descriptor and diagrammatic elements of ROF reportedly added to the coherence and ease of use of the scale. In Experiment 3, high convergence between ROF and various physiological measures were found during exercise and recovery (heart rate, blood lactate concentration, oxygen uptake, carbon dioxide production, respiratory exchange ratio and ventilation rate were all P < 0.001). During ramped cycling to exhaustion ROF and RPE did correspond (P < 0.0001) but not during recovery, demonstrating discriminant validity. Experiment 4 found ROF to correspond with waking time during each day (Mon-Sun all P < 0.0001) and with physical activity (accelerometer count) (Mon-Sun all P < 0.001). CONCLUSIONS: The ROF scale has good face validity and high levels of convergent validity during ramped cycling to exhaustion, resting recovery and daily living activities. The ROF scale has both theoretical and applied potential in understanding changes in fatigue in a variety of contexts.


Assuntos
Exercício Físico , Fadiga , Esforço Físico/fisiologia , Adulto , Teste de Esforço , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Reprodutibilidade dos Testes , Adulto Jovem
13.
Acta Physiol (Oxf) ; 220(4): 486-500, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-27981782

RESUMO

INTRODUCTION: An initial bout of eccentric exercise is known to protect against muscle damage following a repeated bout of the same exercise; however, the neuromuscular adaptations owing to this phenomenon are unknown. AIM: To determine whether neuromuscular disturbances are modulated following a repeated bout of eccentric exercise. METHODS: Following eccentric exercise performed with the elbow flexors, we measured maximal voluntary force, resting twitch force, muscle soreness, creatine kinase (CK) and voluntary activation (VA) using motor point and motor cortex stimulation at baseline, immediately post-exercise and at 1, 2, 3, 4 and 7 days post-exercise on two occasions, separated by 3 weeks. RESULTS: Significant muscle damage and fatigue were evident following the first exercise bout; maximal voluntary contraction (MVC) was reduced immediately by 35% and remained depressed at 7 days post-exercise. Soreness and CK release peaked at 3 and 4 days post-exercise respectively. Resting twitch force remained significantly reduced at 7 days (-48%), whilst VA measured with motor point and motor cortex stimulation was reduced until 2 and 3 days respectively. A repeated bout effect (RBE) was observed with attenuated soreness and CK release and a quicker recovery of MVC and resting twitch force. A similar decrement in VA was observed following both bouts; however, following the repeated bout there was a significantly smaller reduction in, and a faster recovery of, VA measured using motor cortical stimulation. CONCLUSION: Our data suggest that the RBE may be explained, partly, by a modification in motor corticospinal drive.


Assuntos
Adaptação Fisiológica/fisiologia , Exercício Físico/fisiologia , Músculo Esquelético/fisiologia , Eletromiografia , Humanos , Masculino , Contração Muscular/fisiologia , Mialgia , Adulto Jovem
14.
J Appl Physiol (1985) ; 100(1): 194-202, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16141377

RESUMO

The aim of this study was to investigate the effect of a high-fat diet (HFD) followed by 1 day of carbohydrate (CHO) loading on substrate utilization, heart rate variability (HRV), effort perception [rating or perceived exertion (RPE)], muscle recruitment [electromyograph (EMG)], and performance during a 100-km cycling time trial. In this randomized single-blind crossover study, eight well-trained cyclists completed two trials, ingesting either a high-CHO diet (HCD) (68% CHO energy) or an isoenergetic HFD (68% fat energy) for 6 days, followed by 1 day of CHO loading (8-10 g CHO/kg). Subjects completed a 100-km time trial on day 1 and a 1-h cycle at 70% of peak oxygen consumption on days 3, 5, and 7, during which resting HRV and resting and exercising respiratory exchange ratio (RER) were measured. On day 8, subjects completed a 100-km performance time trial, during which blood samples were drawn and EMG was recorded. Ingestion of the HFD reduced RER at rest (P < 0.005) and during exercise (P < 0.01) and increased plasma free fatty acid levels (P < 0.01), indicating increased fat utilization. There was a tendency for the low-frequency power component of HRV to be greater for HFD-CHO (P = 0.056), suggestive of increased sympathetic activation. Overall 100-km time-trial performance was not different between diets; however, 1-km sprint power output after HFD-CHO was lower (P < 0.05) compared with HCD-CHO. Despite a reduced power output with HFD-CHO, RPE, heart rate, and EMG were not different between trials. In conclusion, the HFD-CHO dietary strategy increased fat oxidation, but compromised high intensity sprint performance, possibly by increased sympathetic activation or altered contractile function.


Assuntos
Carboidratos da Dieta/metabolismo , Gorduras na Dieta/metabolismo , Músculo Esquelético/fisiologia , Resistência Física/fisiologia , Esforço Físico/fisiologia , Desempenho Psicomotor , Corrida/fisiologia , Adaptação Fisiológica/fisiologia , Adulto , Estudos Cross-Over , Teste de Esforço , Frequência Cardíaca/fisiologia , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Método Simples-Cego
15.
Br J Sports Med ; 40(11): 912-7; discussion 917, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16980537

RESUMO

OBJECTIVES: To analyse the power output measured during a self-paced 20-km cycling time trial, during which power output was free to vary, in order to assess the level and characteristics of the variability in power output that occurred during the exercise bout. METHODS: Eleven well-trained cyclists performed a 20-km cycling time trial, during which power output was sampled every 200 m. Power spectrum analysis was performed on the power output data, and a fractal dimension was calculated for each trial using the Higuchi method. RESULTS: In all subjects, power output was maintained throughout the trial until the final kilometre, when it increased significantly, indicating the presence of a global pacing strategy. The power spectrum revealed the presence of 1/f-like scaling of power output and multiple frequency peaks during each trial, with the values of the frequency peaks changing over the course of the trial. The fractal dimension (D-score) was similar for all subjects over the 20-km trial and ranged between 1.5 and 1.9. CONCLUSIONS: The presence of an end spurt in all subjects, 1/f-like scaling and multiple frequency peaks in the power output data indicate that the measured oscillations in power output during cycling exercise activity may not be system noise, but may rather be associated with system control mechanisms that are similar in different individuals.


Assuntos
Ciclismo/fisiologia , Aptidão Física/fisiologia , Adulto , Ergometria , Teste de Esforço/métodos , Análise de Fourier , Fractais , Humanos , Masculino , Análise e Desempenho de Tarefas
16.
Br J Sports Med ; 39(2): 120-4, 2005 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15665213

RESUMO

It is hypothesised that physical activity is controlled by a central governor in the brain and that the human body functions as a complex system during exercise. Using feed forward control in response to afferent feedback from different physiological systems, the extent of skeletal muscle recruitment is controlled as part of a continuously altering pacing strategy, with the sensation of fatigue being the conscious interpretation of these homoeostatic, central governor control mechanisms.


Assuntos
Sistema Nervoso Central/fisiologia , Exercício Físico/fisiologia , Fadiga Muscular/fisiologia , Metabolismo Energético/fisiologia , Humanos , Atividade Motora/fisiologia , Resistência Física/fisiologia , Esforço Físico/fisiologia
17.
Br J Sports Med ; 39(1): 52-62, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15618343

RESUMO

Fatigue is hypothesised as being the result of the complex interaction of multiple peripheral physiological systems and the brain. In this new model, all changes in peripheral physiological systems such as substrate depletion or metabolite accumulation act as afferent signallers which modulate control processes in the brain in a dynamic, non-linear, integrative manner.


Assuntos
Exercício Físico/fisiologia , Fadiga Muscular/fisiologia , Eletromiografia/métodos , Homeostase/fisiologia , Humanos , Hipoglicemia/fisiopatologia , Percepção
18.
Br J Sports Med ; 39(10): 742-6; discussion 742-6, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16183771

RESUMO

OBJECTIVES: To determine the effect of unknown exercise duration and an unexpected increase in exercise duration on rating of perceived exertion (RPE), affect, and running economy during treadmill running. METHODS: Sixteen well trained male and female runners completed three bouts of treadmill running at 75% of their peak treadmill running speed. In the first trial, they were told to run for 20 minutes and were stopped at 20 minutes (20 MIN). In another trial, they were told to run for 10 minutes, but at 10 minutes were told to run for a further 10 minutes (10 MIN). In the final trial, they were not told for how long they would be running but were stopped after 20 minutes (unknown, UN). During each of the running bouts, RPE, oxygen consumption (ml/kg/min), heart rate (beats/min), stride frequency (min(-1)), affect scores (arbitrary units), and attentional focus (percentage associative thought scores) were recorded. RESULTS: RPE increased significantly between 10 and 11 minutes in the 10 MIN compared with the 20 MIN and UN trials (p<0.05). The affect score decreased significantly between 10 and 11 minutes in the 10 MIN compared with the 20 MIN trial (p<0.05). Running economy, as measured by oxygen consumption, was significantly lower in the UN compared with the 20 MIN trial from 10 to 19 minutes (p<0.05). CONCLUSIONS: The change in RPE between 10 and 11 minutes in the 10 MIN trial suggests that RPE is not purely a measure of physical exertion, as treadmill speed was maintained at a constant pace both before and after the unexpected increase in exercise duration. The associated changes in affect score at similar times in the 10 MIN trial supports the hypothesis that RPE has an affective component.


Assuntos
Afeto/fisiologia , Exercício Físico/psicologia , Esforço Físico/fisiologia , Corrida/psicologia , Exercício Físico/fisiologia , Teste de Esforço/métodos , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia , Corrida/fisiologia
19.
Br J Sports Med ; 39(1): 34-8, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15618337

RESUMO

INTRODUCTION: In this study we examined the pacing strategy and the end muscle glycogen contents in eight cyclists, once when they were carbohydrate loaded and once when they were non-loaded. METHODS: Cyclists completed 2 hours of cycling at approximately 73% of maximum oxygen consumption, which included five sprints at 100% of peak sustained power output every 20 minutes, followed immediately by a 1 hour time trial. Muscle biopsies were performed before and immediately after exercise, while blood samples were taken during the 2 hour steady state rides and immediately after exercise. RESULTS: Carbohydrate loading improved mean power output during the 1 hour time trial (mean (SEM) 219 (17) v 233 (15) W; p<0.05) and enabled subjects to use significantly more muscle glycogen than during the trial following their normal diet. Significantly, the subjects, kept blind to all feedback except for time, started both time trials at similar workloads ( approximately 30 W), but after 1 minute of cycling, the workload average 14 W higher throughout the loaded compared with the non-loaded time trial. There were no differences in subjects' plasma glucose and lactate concentrations and heart rates in the carbohydrate loaded versus the non-loaded trial. Of the eight subjects, seven improved their time trial performance after carbohydrate loading. Finishing muscle glycogen concentrations in these seven subjects were remarkably similar in both trials (18 (3) v 20 (3) mmol/kg w/w), despite significantly different starting values and time trial performances (36.55 (1.47) v 38.14 (1.27) km/h; p<0.05). The intra-subject coefficient of variation (CV) for end glycogen content in these seven subjects was 10%, compared with an inter-subject CV of 43%. CONCLUSIONS: As seven subjects completed the time trials with the same end exercise muscle glycogen concentrations, diet induced changes in pacing strategies during the time trials in these subjects may have resulted from integrated feedback from the periphery, perhaps from glycogen content in exercising muscles.


Assuntos
Ciclismo/fisiologia , Exercício Físico/fisiologia , Glicogênio/metabolismo , Músculo Esquelético/metabolismo , Adulto , Biópsia/métodos , Glicemia/análise , Carboidratos da Dieta/administração & dosagem , Teste de Esforço/métodos , Frequência Cardíaca/fisiologia , Humanos , Ácido Láctico/sangue , Masculino , Consumo de Oxigênio/fisiologia , Resistência Física/fisiologia
20.
S Afr Med J ; 106(1): 76-81, 2015 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-26792312

RESUMO

BACKGROUND: Selection of medical students at South African (SA) medical schools must promote equitable and fair access to students from all population groups, while ensuring optimal student throughput and success, and training future healthcare practitioners who will fulfil the needs of the local society. In keeping with international practices, a variety of academic and non-academic measures are used to select applicants for medical training programmes in SA medical schools. OBJECTIVES: To provide an overview of the selection procedures used by all eight medical schools in SA, and the student demographics (race and gender) at these medical schools, and to determine to what extent collective practices are achieving the goals of student diversity and inclusivity. METHODS: A retrospective, quantitative, descriptive study design was used. All eight medical schools in SA provided information regarding selection criteria, selection procedures, and student demographics (race and gender). Descriptive analysis of data was done by calculating frequencies and percentages of the variables measured. RESULTS: Medical schools in SA make use of academic and non-academic criteria in their selection processes. The latter include indices of socioeconomic disadvantage. Most undergraduate medical students in SA are black (38.7%), followed by white (33.0%), coloured (13.4%) and Indian/Asian (13.6%). The majority of students are female (62.2%). The number of black students is still proportionately lower than in the general population, while other groups are overrepresented. CONCLUSION: Selection policies for undergraduate medical programmes aimed at redress should be continued and further refined, along with the provision of support to ensure student success.

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