Prior Low- or High-Intensity Exercise Alters Pacing Strategy, Energy System Contribution and Performance during a 4-km Cycling Time Trial

We analyzed the influence of prior exercise designed to reduce predominantly muscle glycogen in either type I or II fibers on pacing and performance during a 4-km cycling time trial (TT). After preliminary and familiarization trials, in a randomized, repeated-measures crossover design, ten amateur cyclists performed: 1) an exercise designed to reduce glycogen of type I muscle fibers, followed by a 4-km TT (EX-FIB I); 2) an exercise designed to reduce glycogen of type II muscle fibers, followed by a 4-km TT (EX-FIB II) and; 3) a 4-km TT, without the prior exercise (CONT). the muscle-glycogen-reducing exercise in both EX-FIB I and EX-FIB II was performed in the evening, similar to 12 h before the 4-km TT. Performance time was increased and power output (PO) was reduced in EX-FIB I (432.8 +/- 8.3 s and 204.9 +/- 10.9 W) and EX-FIB II (428.7 +/- 6.7 s and 207.5 +/- 9.1 W) compared to CONT (420.8 +/- 6.4 s and 218.4 +/- 9.3 W; P0.05). the PO was lower in EX-FIB I than in CONT at the beginning and middle of the trial (P0.05). the integrated electromyography was unchanged between conditions (P>0.05). Performance may have been impaired in EX-FIB I due a more conservative pacing at the beginning and middle, which was associated with a reduced aerobic contribution. in turn, the PO profile adopted in EX-FIB II was also reduced throughout the trial, but the impairment in performance may be attributed to a reduced glycolytic contribution (i.e. reduced lactate accumulation).Foundation of Aids to Scientific Research of the State of Alagoas (FAPEAL)Univ Fed Pernambuco, CAV, Dept Phys Educ & Sports Sci, Sports Sci Res Grp, Vitoria de Santo Antao, Pernambuco, BrazilUniv São Paulo, Sch Phys Educ & Sport, Endurance Performance Res Grp, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilVictoria Univ, Coll Sport & Exercise Sci, Inst Sport Exercise & Active Living, Melbourne, Vic 8001, AustraliaUniversidade Federal de São Paulo, Dept Med, Div Nephrol, São Paulo, BrazilWeb of Scienc

Influência do treinamento físico aeróbio ou resistido no desenvolvimento da cardiomiopatia diabética: aspectos metabólicos e hormonais

Diabetic patients may present myocardial dysfunction, named diabetic cardiomyopathy (DCMP). Considering the beneficial effects of physical training (PT) on the cardiovascular system, the objective of the study was to compare the influence of aerobic physical training (APT) and resistance (RPT) on the development of the DCMP, evaluating the modulation of both modalities of exercise on hormonal systems and myocardial metabolism. Male Wistar rats were randomly assigned into control, control + RPT, control + APT, diabetic, diabetic + RPT and diabetic + APT. Diabetes was induced by streptozotocin (50 mg / kg, i.v.) and trained animals were submitted to RPT (vertical ladder climbing) or APT (treadmill running) for 8 consecutive weeks (5 days per week). At the end of experimental protocol, diabetic rats presented significantly increased functional capacity in response to physical training. Diabetic animals submitted to APT or RPT presented a decrease in serum triglycerides, free fatty acids and VLDL, with no significant effect on HDL and LDL. In addition, diabetic trained animals (APT or RPT) presented a reduction on abnormal accumulation of cardiac glycogen as compared with sedentary diabetic group, without any training effect on the expression of glucose transporter GLUT-4. Serum corticosterone concentration was significantly higher in diabetic groups compared to controls. DM also significantly increased plasma concentration of adrenaline and noradrenaline, and both exercise modalities induced a significant reduction on these parameters. APT significantly reduced the concentration of noradrenaline in left ventricle (LV) of diabetic group, as compared with sedentary diabetic animals and diabetic + RPT. Diabetic animals presented increased serum and LV concentration of (serotonin) 5-HT. RPT significantly reduced serum concentration of 5-HT in the diabetic group, while APT significantly increased its concentration in both control and diabetic groups. In LV, the concentration of 5-HT was reduced in response to both modalities of PT DM significantly increased PPAR? protein expression in the sedentary group, and both training modalities reduced the expression of this protein in diabetic groups. The expression of PGC-1? decreased significantly in response to DM, and this response was not observed in diabetic groups submitted to APT and RPT. There was no significant influence of DM or PT on LV CPT-1A protein expression. The results of this study show that the DCMP induces hormonal and metabolic changes of cardiac tissue, which can be reduced or minimized, by exercise, including the RPT. Thus, the RPT can be considered as an additional important non-pharmacological tool for the treatment of cardiac disorders induced by diabetes.Indivíduos diabéticos apresentam disfunção do miocárdio, denominada cardiomiopatia diabética (CMPD). Considerando os efeitos benéficos do treinamento físico (TF) sobre o sistema cardiovascular, o objetivo do estudo foi comparar a influência do treinamento físico aeróbio (TFA) e resistido (TFR) sobre o desenvolvimento da CMPD, avaliando a modulação de ambas modalidades sobre sistemas hormonais e metabólicos. Ratos Wistar machos foram aleatoriamente separados em: controle, controle + TFR, controle + TFA, diabético, diabético + TFR e diabético + TFA. Para indução do DM, foi utilizada a estreptozotocina (50 mg/Kg, e.v.) e os animais treinados foram submetidos ao TFR (escalada vertical) ou ao TFA (esteira), por 8 semanas consecutivas (5 dias por semana). Ao final do protocolo experimental, a capacidade funcional dos animais diabéticos aumentou significativamente em resposta ao treinamento físico. Animais diabéticos submetidos ao TFA e TFR apresentaram redução na concentração sérica de triglicerídeos, ácidos graxos livres e VLDL, sem efeito significativo sobre o HDL e LDL. Além disto, animais treinados (TFA e TFR) diabéticos apresentaram redução na concentração cardíaca de glicogênio em comparação ao diabético sedentário, sem efeito do treinamento sobre a expressão do transportador de glicose GLUT-4. A concentração sérica de corticosterona foi significativamente maior nos grupos diabéticos, em comparação aos controles. O DM aumentou significativamente a concentração plasmática de adrenalina e noradrenalina, e ambas modalidades de exercício induziram redução significativa. No ventrículo esquerdo (VE) o TFA reduziu significativamente a concentração de noradrenalina no grupo diabético em relação ao sedentário e o TFR. Animais diabéticos apresentaram aumento da concentração sérica e cardíaca de serotonina (5-HT). O TFR reduziu significantemente a 5-HT sérica no grupo diabético, enquanto o TFA aumentou significantemente no grupo controle, e no diabético. No VE, ambas as modalidades de TF levaram à redução da concentração de 5-HT. O DM aumentou significativamente a expressão proteica do PPAR? nos animais sedentários, e ambas modalidades de treinamento reduziram a expressão desta proteína nos grupos diabéticos. A expressão do PGC-1? diminuiu significativamente em resposta ao DM, resposta não observada nos grupos diabéticos submetidos ao TFA e TFR. Não foi observada influência significativa do DM ou do exercício sobre a expressão proteica da CPT-1A cardíaco. Os resultados do presente estudo mostram que a CMPD induz alterações hormonais e metabólicas do tecido cardíaco, que podem ser atenuadas ou minimizadas pelo exercício físico, inclusive pelo TFR. Sendo assim, o TFR mostra-se como uma ferramenta não-farmacológica adicional importante para o tratamento de alterações cardíacas induzidas pelo DM.Dados abertos - Sucupira - Teses e dissertações (2013 a 2016

Mean plasma lactate concentration at rest, immediately before and 1 min after the 4-km cycling time trial in the control and reduced muscle glycogen conditions.

<p>Values are mean ± SEM. Pre-TT: plasma lactate concentration immediately before the time trial. Post-TT: plasma lactate concentration 1 min after the time trial. CONT: control condition. EX-FIB I and EX-FIB II: time trial performed after a carbohydrate-manipulation protocol designed to predominantly reduce muscle glycogen content in type I or II fibers, respectively. # Significantly higher than Rest and Pre-TT (P<0.05). * Significantly lower than CONT (P<0.05).</p><p>Mean plasma lactate concentration at rest, immediately before and 1 min after the 4-km cycling time trial in the control and reduced muscle glycogen conditions.</p

Mean and SEM for normalized integrated electromyography (% maximal voluntary contraction) during the 4-km cycling time trial in control (CONT) and reduced muscle glycogen conditions.

<p>EX-FIB I and EX-FIB II: time trial performed after a type I or type II muscle fibers glycogen-lowering exercise protocol, respectively.</p

Mean performance time, power output, aerobic and anaerobic power output, and integrated electromyographic activity during the 4-km cycling time trial in the control and reduced muscle glycogen conditions.

<p>Values are means ± SEM. PO: power output. P_aer: aerobic power output. P_an: anaerobic power output. iEMG: integrated electromyographic activity expressed as a percentage of their EMG value obtained during the maximal voluntary contraction. CONT: control condition. EX-FIB I and EX-FIB II: time trial performed after a carbohydrate-manipulation protocol designed to predominantly reduce muscle glycogen content in type I or II fibers, respectively. * Significantly different from CONT (P<0.05).</p><p>Mean performance time, power output, aerobic and anaerobic power output, and integrated electromyographic activity during the 4-km cycling time trial in the control and reduced muscle glycogen conditions.</p

Characteristics of the participants.

<p>Values are mean ± SD. PO_max: maximal power output achieved in the incremental test; VO_2max: maximal oxygen consumption; HR_max: maximal heart rate.</p

Effect of order for performance and physiological parameters during the 4000-m cycling time-trial.

<p>Values are means ± SD. Anaerobic power (P_an), aerobic power (P_aer), oxygen consumption (VO₂), integrated electromyography (iEMG), maximal voluntary contraction (MVC), heart rate (HR) and rating of perceived exertion (RPE).</p

Mean and SEM for power output during the 4-km cycling time trial in the control (CONT) and reduced muscle glycogen conditions.

<p>EX-FIB I and EX-FIB II: time trial performed after a type I or type II muscle fibers glycogen-lowering exercise protocol, respectively. * CONT significantly higher than EX-FIB I for the same interval (P<0.05).</p