Muscular fatigue limits athletic performance as well as activities of daily living that require repetitive or sustained contractile activity. The decrease in force output or inability to maintain a given force level during fatigue occurs as the result of neural and muscle physiological factors. In contrast to muscle fatigue, potentiation is an increase in muscle force following voluntary muscle activity. The simultaneously occurring processes of potentiation and fatigue influence force output. The aims of this research were to investigate parameters used to potentiate muscle via electrical stimulation and voluntary contraction, and to better understand how muscle force is sustained, we studied single motor unit firing patterns and force potentiation following muscular endurance training. In study 1, electrical stimulation trains matched for pulse number of various frequencies and of increasing pulse number at a given frequency were administered to determine the effects of these stimulation parameters and of the force-time integral (FTI) produced during the train on potentiation magnitude. No difference in potentiation magnitude was found across trains of matched pulse number for frequencies of 15, 25, 30 and 50 Hz. Potentiation increased as pulse number increased and there was a positive correlation between potentiation and the FTI. In study 2, we measured maximal potentiation following conditioning contractions (CC) of 25%, 50% and 100% maximal voluntary contraction (MVC) and during a 25% MVC fatigue task, pre-post 8 weeks of muscular endurance training. Results showed significant potentiation for all CC intensities. Potentiation increased as CC intensity increased and CC duration required to achieve maximal potentiation decreased as CC intensity increased. Muscular endurance training resulted in increased maximal potentiation, and potentiation was greater during the fatigue task after training. Potentiation was also correlated to endurance time. In study 3, the effects of muscular endurance training on motor unit firing rates were investigated. There was a small increase in mean motor unit firing rates during the course of the fatigue task after training. This research contributes to our understanding of muscular force production and muscular endurance. The findings suggest that motor unit firing frequency and force potentiation may contribute to enhanced muscular endurance. / text

The objective of this dissertation was to evaluate the changes in preparedness over the course of training for a marathon in two well-trained runners. The athletes completed periodized strength training or a periodized concurrent training. This dissertation consisted of two separate investigations: Study 1 – The purpose of this study was to monitor changes in force production ability and running performance in one sub-elite marathon runner before, during, and after undertaking a short-term block periodized strength training program. The athlete ceased strength training during the off-seasons and resumed testing after 10. The athlete experienced likely true, meaningful changes in force production characteristics during the taper after the training program. Improvements in force production characteristics coincided with improvements in running economy. Both force production characteristics and running economy reversed after the withdraw from strength training. However, both measures remained improved from initial baseline. The improvement in running economy and force production likely coincided with a cardiovascular de-training period, due to a reduction in aerobic training during the off-season. Therefore, strength training may have independent effects on running economy and running performance. These results indicate that endurance runners may better optimize performance by improving force production characteristics via periodized strength training program, and should avoid prolonged periods without strength training. Study 2 – The purpose of this study was to monitor the concurrent and divergent changes in athlete preparedness and performance over a competitive training cycle in two marathon athletes. One athlete added a block periodized strength training program to a non-periodized endurance training program (NBP Athlete). The other athlete (BP Athlete) completed an integrated, concurrent block periodized program using HIT over-reach endurance training. Both athlete displayed improvements in running performance and running economy over the duration of the monitoring program. The BP Athlete displayed earlier and greater magnitudes of performance improvements. These results indicate that strength training can enhance running economy in marathon athletes, performance may be better optimized through periodized integration of strength and endurance training, and the use of HIT over-reach blocks may improve marathon relevant fitness characteristic within the ecologically valid context of an athlete’s training cycle.

Thesis Title: Enhancing rehabilitation following anterior cruciate ligament reconstruction. Context: Physical training with a neuromuscular focus has been shown to reduce anterior cruciate ligament (ACL) injury. However, ACL injury remains prevalent and often leads to joint instability, which requires surgical reconstruction. Following reconstructive surgery, a minimum of 6 months supervised rehabilitation is recommended with associated with financial cost implications to the National Health Service (NHS), the patient and society. Traditionally rehabilitation is offered in a concurrent format, whereby strength and cardio-vascular endurance exercises are performed in the same session. However, accumulating evidence from healthy populations, suggests that the development of strength might be attenuated by cardio-vascular endurance conditioning performed in close temporal proximity. This thesis comprises an entirely novel investigation of potential attenuation of strength gains in rehabilitating clinical populations that is associated with temporal incompatibility of physiological conditioning stimuli. No study has previously investigated this phenomenon, whether it might compromise the efficacy of treatment or recovery, or its potential influence on objectively-measured and patients’ perception of functional, musculoskeletal and neuromuscular performance capabilities. Objectives: The purpose of this thesis was to assess the effects of reconstruction surgery and 24 weeks of non-concurrent strength and endurance rehabilitation (with 48 week post-operative follow-up) on (a) subjective (IKDC; KOOS; PP [Chapter 4]) and objective measures of function (HOP [Chapter 5]) (primary outcome measures for this thesis), and (b) objective measures of musculoskeletal (ATFD) and neuromuscular performance (PF, EMD, RFD, SMP [Chapter 5]) (secondary outcome measures), in patients with anterior cruciate ligament deficiency. The secondary aim was to evaluate the relationships amongst a subjective outcome of function (IKDC), an objective outcome of function (HOP), and the secondary objective outcomes of musculoskeletal (ATFD) and neuromuscular (PF, RFD, EMD, SMP) performance at pre-surgery and at 24 weeks post-surgery (Chapter 6). Setting: Orthopaedic Hospital NHS Foundation Trust. Design: Prospective random-allocation to group trial involving iso-volume rehabilitative intervention versus contemporary practice, using contralateral limb assessment and clinico-social approbation controls. The design compared the effects of experimental post-surgical rehabilitation comprising non-concurrent strength and endurance conditioning with two conditions of control reflecting contemporary clinical practice (matched versus minimal assessment interaction). Participants: Eighty two patients (69♂, 13♀, age: 35.4 ± 8.6 yr; time from injury to surgery 9.4 ± 6.9 months [mean ± SD]) electing to undergo unilateral ACL reconstructive surgery (semitendinosus and gracilis graft [n = 57]; central third, bone-patella tendon-bone graft [n = 25]); were allocated to groups (2:2:1 purposive sampling ratio, respectively). Nineteen patients were lost to follow-up. Intervention: A standardised traditional concurrent (CON) ACL rehabilitation programme acted as the control versus an experimental non-concurrent (NCON) ACL rehabilitation programme that involved separation of strength and cardio-vascular endurance conditioning. An additional control group (Limited testing CON) matched the CON group rehabilitation applied within contemporary clinical practice. Outcome Measures: Chapter 4: The self-perceived primary outcome measures of function IKDC, KOOS and PP were assessed on five separate occasions (pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery). However, assessment occasions were purposefully reduced to pre-operative and 48 weeks post-operative for the Limited testing CON group. Chapter 5: The primary objective outcome of function was HOP; the secondary outcomes were ATFD, PF, RFD, EMD and SMP associated with the knee extensors and flexors of the injured and non-injured legs. These objective outcomes were assessed on five separate occasions (pre-surgery, and at 6, 12, 24 and 48 weeks post-surgery). However, assessment occasions were purposefully reduced to pre-operative and at 48 weeks post-operative only for the Limited testing CON group. Chapter 6 Self-perceived (IKDC) subjective knee evaluation and the objective outcome of function (HOP), and selected objective outcomes of musculoskeletal and neuromuscular performance including ATFD, PF, RFD, EMD and SMP of the knee extensors and flexors of the injured and non-injured legs where applicable; measured at pre-surgery and at 24 weeks post-surgery were analysed for association, using Pearson product-moment correlation coefficients. A priori alpha levels were set at p<0.05. Results: Chapter 4: Factorial analyses of variance (ANOVAs) with repeated-measures investigating the primary aim showed significant group (NCON; CON) by test occasion (pre-surgery, 6, 12. 24 and 48 weeks post-surgery) interactions for self-perceived outcomes of function IKDC, KOOS and PP confirmed increased clinical effectiveness of NCON conditioning (F(2.0, 82.9)GG = 4.0 p<0.05, F(2.2, 134.7)GG = 5.5 p<0.001, F(1.9, 121.4)GG = 14.6 p<0.001, respectively) and the group mean peak relative difference in improvement for NCON was ~5.9% - 12.7% superior to CON. The greatest interaction effect was found to occur between pre-surgery and the 12 weeks post-operative test occasion for IKDC and KOOS, and between pre-surgery and the 24 week test occasion for PP. Patterns of improvements in self-perceived fitness over time were represented by a relative effect size range of 0.71 to 1.92. Improvement patterns were not significantly different between control groups offering matched or minimised assessor-patient interaction (CON vs. Limited testing CON; pre-surgery vs. 48 weeks post-surgery) indicating that clinical approbation by patients had not contributed to the outcome. Chapter 5: Factorial analyses of variance (ANOVAs) with repeated-measures showed significant group (NCON; CON) by leg (injured/non-injured) by test occasion (pre-surgery, 6, 12, 24 and 48 weeks post-surgery) interactions of the objective measure of function (HOP) together with the secondary outcomes of ATFD, PF, RFD, EMD and SMP. Similar responses were noted for the knee extensors and flexors of the injured and non-injured legs (F(2.1, 248) GG = 4.5 to 6.6; p<0.01) and confirmed increased clinical effectiveness of NCON conditioning (range ~4.7% - 15.3% [10.8%]) better than CON between 12 and 48 weeks. Patterns of improvements in physical fitness capabilities over time were represented by a relative effect size range of 1.92 to 2.89. Improvement patterns were not significantly different between control groups offering matched or minimised assessor-patient interaction (CON vs. Limited testing CON; pre-surgery versus 48 weeks post-surgery) indicating that clinical approbation by patients had not contributed to the outcome. Chapter 6: Two-tailed probabilities were used due to the exploratory nature of this study. A limited number of weak to moderate statistically significant correlations were confirmed (ranging from r = 0.262 – 0.404; p<0.05; n=48 [amalgamated NCON and CON groups] ) between IKDC and most notably, the neuromuscular performance outcome of EMD. Conclusion: Overall, the patterning and extent of changes amongst self-perceived, functional, musculoskeletal and neuromuscular performance scores offer support for the efficacy of using non-concurrent strength and endurance conditioning to enhance post-surgery rehabilitation. The limited robustness of relationships amongst the validated and frequently-used self-perceived outcome of function [IKDC], and objectively-measured outcomes of function and musculoskeletal and neuromuscular performance suggested that each might properly reflect an important but separate aspect of clinical response and should be deployed to detect change.

O objetivo da presente dissertação foi avaliar e comparar as possíveis diferenças nas adaptações cardiovasculares e funcionais ao treinamento concorrente com e sem a execução de séries com repetições até a falha concêntrica em homens idosos. Trinta e dois homens idosos saudáveis (67,4 ± 4,1) foram alocados randomicamente em três grupos diferentes de treinamento concorrente: Treinamento de força utilizando repetições máximas (GRM, n = 12), Treinamento de força com repetições submáximas (GRNM, n = 11) e Treinamento de força com repetições submáximas com volume equalizado ao realizado pelo GRM (GRNMV, n = 9). Os participantes treinavam duas vezes por semana, durante doze semanas, executando o treinamento aeróbico imediatamente após o treinamento de força. Antes e após a intervenção foi avaliado o Vo2pico através de ergoespirometria, o desempenho funcional utilizando os testes timed up and go (TUG), sentar e levantar 5 vezes (SeL) e preensão manual (PM). Coletou-se amostras de sangue para análise da glicemia, colesterol total, HDL, LDL e triglicerídeos. A pressão arterial sistólica (PAS) e pressão arterial diastólica (PAD) foram mensuradas através de método auscultatório, o desempenho de saltos através do salto agachado (SJ) e salto com contra movimento (CMJ) e a composição corporal avaliada a partir de antropometria. Após a intervenção, foi observado um efeito tempo significativo (P<0,05) no Vo2pico, sem diferenças entre os grupos. No desempenho funcional não foram observadas mudanças em nenhum dos testes. A análise sanguínea demonstrou um efeito tempo significativo (p<0,01) no HDL, sem diferenças entre os grupos, enquanto não houve variações para glicemia, LDL e triglicerídeos. Na altura dos saltos, foi verificado um efeito tempo significativo (p<0,01) no SJ e uma tendência a incremento (p<0,056) no CMJ, sem diferenças entre os protocolos de treinamento. A composição corporal foi alterada pelo treinamento, com efeito significativo na massa de gordura relativa (p<0,001), na massa livre de gordura relativa (p<0,001) e no somatório de dobras cutâneas (p<0,001), sem diferenças entre os grupos. Desta forma, foi observado que todos os protocolos de treinamento foram eficazes para promover mudanças na capacidade aeróbica, no perfil lipídico, no desempenho de saltos e na composição corporal, porém, o GRNM foi mais eficiente, pois promoveu tais adaptações com um volume de treino menor. / The aim of this study was to evaluate and compare the possible differences in cardiovascular and functional adaptations to concurrent training with and without the execution of series with repetitions until concentric failure in elderly men. Thirty-two healthy elderly men (67,4 ± 4,1) were randomly assigned to three different groups of concurrent training: strength training using maximal repetitions (GRM, n = 12), Strength training with submaximal repetitions (GRNM, n = 11), and strength training with submaximal repetitions with volume equalized to that performed by GRM (GRNMV, n = 9). Participants trained twice a week for twelve weeks, performing aerobic training immediately after strength training. Before and after the intervention, VO2peak was evaluated using a metabolic cart, functional performance using the timed up and go (TUG), sit and up 5 times (SUp) and handgrip strength (HS) tests. Blood samples were collected for analysis of glycemia, total cholesterol, HDL, LDL, and triglycerides. The systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured using the auscultatory method, the jump performance determined by squat jump (SJ) and counter-movement jump (CMJ). Body composition are evaluated through anthropometry. After the intervention, a significant time effect (P <0.05) was observed on VO2peak, with no differences between groups. In functional performance, no changes were observed in any of the tests. Blood analysis showed a significant increase (p <0.01) in HDL, with no differences between groups, whereas there were no changes for glycemia, LDL and triglycerides. In the jump performance, a significant time effect (p <0.01) was observed in the SJ and a trend toward significant increase (p <0.057) in the CMJ, without differences between the training protocols. Body composition was changed by training, with a significant time effect on the relative fat mass (p <0.001), relative fat free mass (p <0.001), and on the sum of skinfolds (p <0.001), with no differences between groups. In this way, it was observed that all training protocols were effective to promote changes in aerobic capacity, lipid profile, jumping performance and body composition, but the GRNM was more efficient, as it induced such adaptations with a lower training volume.

This study examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on left ventricular (LV) function in young, healthy men. Sixteen untrained men were randomly assigned to HIT (8-12 X 60:75 seconds cycling at 95-100%:10% V˙O2peak) and CMT (90-120 minutes cycling at 65% V˙O2peak) and assessed before and after six sessions of training. LV function was determined at rest and during submaximal exercise using two-dimensional and Doppler echocardiography. HIT and CMT improved V˙O2peak and induced plasma volume expansion to a similar magnitude. Although resting LV function did not change, increased exercise stroke volume and cardiac output was observed, secondary to increases in end-diastolic volume. Numerous ECHO-derived indices of diastolic performance were similarly enhanced during exercise in both groups. Short-term HIT and CMT elicit rapid increases in V˙O2peak and LV filling without global changes in systolic performance or cardiac morphology at rest.

This study examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on left ventricular (LV) function in young, healthy men. Sixteen untrained men were randomly assigned to HIT (8-12 X 60:75 seconds cycling at 95-100%:10% V˙O2peak) and CMT (90-120 minutes cycling at 65% V˙O2peak) and assessed before and after six sessions of training. LV function was determined at rest and during submaximal exercise using two-dimensional and Doppler echocardiography. HIT and CMT improved V˙O2peak and induced plasma volume expansion to a similar magnitude. Although resting LV function did not change, increased exercise stroke volume and cardiac output was observed, secondary to increases in end-diastolic volume. Numerous ECHO-derived indices of diastolic performance were similarly enhanced during exercise in both groups. Short-term HIT and CMT elicit rapid increases in V˙O2peak and LV filling without global changes in systolic performance or cardiac morphology at rest.

Ischemia-reperfusion (IR) injury occurs during myocardial infarction and during some cardiovascular surgeries. Animal studies support the role of endurance exercise training in preventing myocardial IR injury and coronary endothelial dysfunction. In human and animal studies, habitual exercise has been shown to attenuate endothelial dysfunction caused by aging and disease. It is unknown; however, if exercise can protect against vascular IR injury in humans and if so, whether these effects persist with advancing age. Using 20 minutes of forearm ischemia and the response of the brachial artery as a noninvasive surrogate model for the heart, the association between the mode of exercise training (endurance versus resistance) and vascular IR injury was examined in young healthy adults in the first study. Endothelial function, as measured by flow-mediated dilation (FMD) in the brachial artery, decreased significantly after forearm ischemia, suggesting that this noninvasive model of the heart produces significant and measureable vascular injury. These measures returned to baseline levels within 30 minutes following ischemia, illustrating the transient nature of this form of IR injury. The magnitude of injury and recovery from ischemia were not significantly different among young sedentary, endurance-trained, and resistance-trained subjects, suggesting that exercise training is not associated with protection from vascular IR injury in a young, healthy population. In the second study, the association between aging, endurance exercise training, and vascular IR injury was studied. Twenty minutes of forearm ischemia was associated with a transient fall in brachial FMD in young and older sedentary and endurance-trained subjects. Young subjects recovered more quickly from IR injury than older subjects. Within 30 minutes of injury, the endothelial function of the young group was back to baseline while blunted endothelial function persisted in older subjects for greater than 45 minutes after injury. There was no association between endurance exercise training and enhanced recovery from IR injury. These findings suggest that aging is associated with delayed recovery from vascular IR injury and that endurance training does not appear to modulate the vascular IR injury responses. / text

The potential role of lower limb blood pooling in reducing venous return to the heart during orthostasis and elevated venous pressure is investigated. This study compares lower limb capacitance, microvascular filtration, and peripheral resistance between a group of highly trained endurance athletes and a group of their sedentary peers. Seven endurance trained males were selected between the ages of 23-33 [(29.1 4.1 yr), mean SD]. The subjects weekly cycling mileage ranged from 80 to 150 miles per week with an average of 125 8.5 miles/week. Nine healthy, age-matched sedentary subjects (25.8 4.8 yr.) were selected for the control group, based upon their reporting they had not participated in repeated lower-body or cardiovascular exercise in the months prior to their study. Results show that both subject groups had similar calf venous capacitances, rates of capillary fluid filtration, and local flow shunting (vascular resistance change) in response to venous thigh occlusion and 70 head-up tilt (HUT). The only significant difference found between groups was the cyclist groups smaller rise in heart rate in response to HUT. The findings of this study suggest that cyclists are not predisposed to orthostatic intolerance due to any changes in lower limb function.

A small number of previous cross-sectional studies have examined the relationship between endurance training status on recovery of performance and metabolites from sprinting. However, no longitudinal studies have been undertaken. In addition, there is a dearth of information on female subjects and on running exercise which prompted the need, in the present thesis, to address the effect of menstrual cycle phase on performance and metabolic responses during a repeated sprint run. Thus, the overall purpose of the present thesis was to examine the effect of short-term endurance training on a repeated sprint in female subjects. A number of methodological studies (for which 25 subjects volunteered) were undertaken as preparation for the main experimental chapters of the thesis (Chapter 3). The first methodological study examined the reliability of performance during a 30-s sprint on the non-motorised treadmill. Performance was reproducible as indicated by the 95% limits of agreement for PPO (5 ± 42 W) and by the ratio limits of agreement for MPO (1.01 */÷1.06) during the 30 s sprint. In the second methodological study it was found that capillary lactate concentrations were significantly higher than venous blood lactate after a 30 s sprint (P < 0.05). The third methodological study revealed that a repeated sprint run caused an additional plasma volume loss when compared with the loss caused by a change in posture alone (12.7 % vs 7.5 % for sprint and posture change, respectively, P < 0.05). Finally, it seems that prolonged freezing (up to 13 months) does not have a detrimental influence on whole blood lactate concentration, but repeated defrosting may result in errors in the determination of blood lactate at high lactate concentrations (methodological study 4). The first mam experiment examined the effects of menstrual cycle phase on performance and metabolic responses during a repeated sprint run (2x30 s, with a 2 min passive recovery) in 8 volunteers (chapter 4). Performance was unaltered during the follicular, mid-cycle and luteal phase of the menstrual cycle as reflected by PPO (461 ± 51 and 395 ± 48, 443 ± 43 and 359 ± 44, 449 ± 52 and 397 ± 48 W, for the first and second sprint, during the follicular, mid-cycle and luteal phase, respectively, P > 0.05) and MPO (302 ± 41 and 252 ± 29, 298 ± 37 and 248 ± 29, 298 ± 39 and 252 ± 35 W, for the first and second sprint, at follicular, mid-cycle and luteal phases, respectively, P > 0.05). Similarly, blood metabolic responses were unaffected by menstrual cycle phase as reflected by the unchanged metabolic profile of blood lactate, plasma' ammonia, blood pH and % changes in plasma volume across menstrual cycle. These results suggest that the hormonal fluctuations of 17-,β-estradiol (estradiol) and progesterone, due to menstrual cycle phase, have no effect on repeated sprint performance and possibly on the metabolic responses as reflected by the blood metabolic responses. The second main experiment examined the effects of short-term endurance training on power output recovery and metabolic responses to a repeated sprint run (2x30 s with a 2 min passive recovery) (chapter 5, n = 16). Six weeks of endurance training resulted in a 3% increase (P < 0.05) in V̇ 0₂ max (from 48.7 ± 4.4 before training to 50.17 ± 5.1 mL.kg⁻¹·min⁻¹ after training) in the training group (n = 8) in comparison with 1.9% decrease (from 50.4 ± 1.3 to 49.4 ± 1.2 mL.kg⁻¹·min⁻¹ post-trial) in the control group (n = 7). In addition, % V̇ 0₂ max @ 4 mmol·L⁻¹ [the relative intensity (% V̇ 0₂ max) corresponding to blood lactate concentration of 4 mmol·L⁻¹] was 3% higher (from 82 to 84%) in the training group as compared with the 1% decrease in the control group (from 81 to 80%) (P < 0.05). These endurance adaptations were accompanied by a 7% improvement in MPO recovery (in the second of two 30 s sprints) in the training group in comparison with 2% increases in the control group after training (P < 0.05). Metabolic responses to sprints were unaltered after training, but there was a tendency for higher pH immediately after sprint 1 in the training group in comparison with the control group (7.12 ± 0.07 vs 7.19 ± 0.06 and 7.09 ± 0.07 vs 7.10 ± 0.06, before and after training, in the training and control group, respectively, P = 0.082). These findings suggest that endurance training can be beneficial in terms of quicker recovery of performance during a repeated sprint run. The third main experiment examined the effects of endurance training on performance recovery and muscle metabolites (chapter 6, n=14). Endurance training resulted in a tendency towards lower blood lactate concentrations during sub-maximal exercise in the training group in comparison with the control group (P = 0.063) whilst time to exhaustion for the incremental V̇ 0₂ max test was 12.7% longer for the training group in comparison with 4.1% decrease in the control group (P = 0.095). These endurance training adaptations were accompanied by a 7% improvement (77 ± 7 to 84 ± 5 W) in MPO recovery in the second of two 30 s sprints in the training group while in the control group MPO recovery improved by just 2% (87 ± 8 to 89 ± 8%) (P < 0.05). In addition, similar increases in the recovery of peak speed (3.4% vs 1%, P < 0.05), and mean speed (5% vs 0.9%, P < 0.05) were also evident in the training in comparison with control group. Endurance training resulted in 5.6% decrease in ATP provision from PCr degradation ≈ 14 s post-sprint 1 (P < 0.05) while glycogen degradation was 10% lower (P = 0.063). The latter alterations, in turn, resulted in a tendency towards less reliance on anaerobic energy resources for energy supply after training in the training group (11%, P = 0.098). These results corroborate the findings of chapter 5, but it is still unclear which physiological mechanisms were instrumental in enhancing recovery of performance. It is possible that a faster initial PCr resynthesis or an improved mechanical efficiency or an increased reliance on aerobic metabolism, independently, all together, or in any combination, could have contributed to these improvements in performance recovery. In conclusion the present thesis has shown that: the non-motorised treadmill is a reliable tool for the examination of sprint running performance in the laboratory; that performance and metabolic responses during a repeated sprint run are unaffected by menstrual cycle phase and; that endurance training enhances the recovery of power in female subjects during a repeated sprint run of 2 x 30 s duration with a 2 min passive recovery. The mechanisms underlying the performance improvement following endurance training are unknown, but it is possible that faster PCr resynthesis during the initial phase of recovery (< 1 min) after the sprint is the dominant factor, while greater reliance on aerobic metabolism and improved mechanical efficiency can not be excluded.

O objetivo desse estudo foi determinar se a ordem de execução dos exercícios de força e aeróbio no treinamento concorrente (TC) afeta as adaptações neuromusculares, funcionais e cardiovasculares de idosos. Para isso, 24 homens idosos sedentários e saudáveis foram divididos em dois grupos de TC. O grupo aeróbio-força (n=11; 63,1±3,3 anos; 1,76±0,07 m; 84,0±12,2 kg) realizou o exercício aeróbio no início das sessões de TC; o grupo força-aeróbio (n=13, 67,0±6,0 anos; 1,77±0,05 m; 80,9±10,5 kg) executou os exercícios de força no começo das sessões de TC. Ambos os grupos treinaram duas vezes por semana durante 12 semanas. A força máxima dos sujeitos foi testada pelo testes de uma repetição máxima (1RM) e pela contração isométrica voluntária máxima (CIVM) de extensão de joelho. A taxa de produção de força (TPF) em 50, 100, 150 e 200 ms, a potência de extensão de joelho produzido com 60% de 1RM pré-treinamento e a altura do salto com contra movimento (SCM) foram utilizados como medida de produção de potência muscular. A ativação muscular máxima do vasto lateral (VL) e do reto femoral (RF) foi obtida por eletromiografia de superfície durante a CIVM e durante a extensão de joelho com a carga de 1RM, enquanto que a ativação muscular submáxima foi obtida no movimento de extensão de joelho com 60% de 1RM pré-treinamento e durante o movimento de levantar da cadeira. A ultrassonografia muscular foi realizada para a determinação da espessura muscular do quadríceps femoral e a echo intensity do RF. O teste de sentar e levantar da cadeira em 30 segundos o teste get up and go foram realizados para avaliar as adaptações funcionais. A capacidade aeróbia máxima foi determinada pelo o consumo de oxigênio de pico (VO2pico) e a função endotelial foi avaliada pela dilatação mediada por fluxo (DMF) da artéria braquial. A comparação entre valores pré e pós-treinamento foi realizada pela ANOVA para medidas repetidas de dois fatores (tempo vs grupo), com grupo como um fator intersujeitos e assumindo α≤0,05 como significante. Após o treinamento os dois grupos aumentaram os valores de 1RM, CIVM, potência de extensão de joelho e de TPF em 150 e 200 ms (p≤0,05), sem diferença entre os grupos (p>0,05). Entretanto, nenhum grupo aumentou a TPF em 50 e 100 ms e nem a altura do SCM (p>0,05). A ativação muscular do VL e do RF aumentou similarmente em ambos os grupos na CIVM e no 1RM (p≤0,05), e ativação submáxima reduziu nos dois grupos apenas na extensão de joelho com 60% de 1RM pré-treinamento, sem diferença entre eles (p>0,05). A espessura muscular quadríceps femoral aumentou de maneira similar nos dois grupos (p≤0,05) e a echo intensity do RF reduziu significativamente (p≤0,05), sem diferença entre os grupos (p>0,05). O número de repetições no teste de sentar e levantar de 30 segundos aumentou após o TC (p≤0,05), sem diferença entre os grupos (p>0,05). Nenhuma diferença foi encontrada no tempo do teste get up and go (p>0,05). O VO2pico não foi alterado após o treinamento (p>0,05), mas a DMF aumentou após as 12 semanas nos dois grupos (p≤0,05). Esses resultados demonstram que o TC é benéfico para idosos e a que a ordem dos exercícios de força e aeróbio do TC não tem influência as adaptações neuromusculares, cardiovasculares e funcionais dessa população. / The aim of this study was to determine whether the concurrent training (CT) endurance and strength exercise sequence affects the neuromuscular, functional and cardiovascular adaptations of elderly people. Twenty-four healthy sedentary elderly men were divided into two CT groups. The endurance-strength group (n=11; 63.1±3.3 years; 1.76±0.07 m; 84.0±12.2 kg) performed the endurance exercise in the beginning of the CT sessions; the strength-endurance group (n=13; 67.0±6.0 years; 1.77±0.05 m; 80.9±10.5 kg) performed the strength exercises in the beginning of the CT sessions. Both groups trained two times per week for 12 weeks. The maximal strength of the subjects was tested by the knee extension one repetition maximum test (1RM) and by the knee extension maximal isometric voluntary contraction (MIVC). The rate of force development (RFD) in 50, 100, 150 and 200 ms, the knee extension power with 60% of pre-training 1RM, and the countermovement jump (CMJ) height were used as a measure of muscular power. Maximal muscle activation of the vastus lateralis (VL) and rectus femoris (RF) was obtained by surface electromyography during the MIVC and during the knee extension with the 1RM load, while the submaximal activation was obtained during the knee extension with 60% of pre-training 1RM and during the sit to stand movement. Muscular ultrassonography was performed to determine the muscle thickness of the quadriceps femoris, and the echo intensity of the RF. The 30-s chair stand test and the get up and go test were performed to evaluate the functional adaptations. The maximal aerobic capacity was determined by the peak oxygen uptake (VO2peak) and the endothelial function was evaluated by the brachial artery flow mediated dilation (FMD). Pre and post-training values were compared by the two way repeated measures ANOVA (time vs group), with group as inter-subject factor and accepting α≤0.05 as significant. After the training period both groups improved the values of 1RM, MIVC, knee extension power and RFD at 150 and 200 ms (p≤0.05), without difference between them. However, no improvement was observed in the RFD at 50 and 100 ms, and in the CMJ height (p>0.05). The VL and RF muscular activation increased similarly in both groups in the MIVC and in the 1RM (p≤0.05), and the submaximal activation was reduced in the two groups only in the knee extension performed with 60% of pretraining 1RM (p≤0.05), without differences between them (p>0.05). The muscle thickness quadriceps femoris increased similarly in the two groups (p≤0.05) and the RF echo intensity reduced significantly (p≤0.05), without difference between groups (p>0,05). The number of repetitions in the 30-s chair stand test increased after the CT (p≤0.05), without difference between groups (p>0.05). No difference was observed in the time to perform the get up and go test (p>0,05). The VO2peak did not change after the training (p>0,05), but the FMD enhanced after the 12 weeks in both groups (p≤0.05). These results demonstrated that CT is beneficial for elderly people and the endurance and strength exercise sequence in the CT do not affect the neuromuscular, cardiovascular and functional adaptations in this population.