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Growing evidence has shown that acute exercise impairs erythrocyte membrane structure and function as a consequence of increased physical and chemical stress. Erythrocyte-synthesized nitric oxide (NO) is known to modulate membrane fluidity, and its bioavailability depends on the balance between its production and scavenging by reactive oxygen species. Here, we investigated whether a maximal exercise test could affect erythrocyte NO bioavailability and oxidative stress. Twelve men (26±4 years old, V̇O2peak 44.1±4.3 mL·kg-1·min-1) performed a treadmill maximal cardiopulmonary exercise test. Blood was collected at rest and immediately after exercise for erythrocytes isolation. Maximal exercise caused an increase in erythrocytes count, haemoglobin and haematocrit levels. There was no change in L-arginine influx into erythrocytes after exercise. Yet, nitric oxide synthase activity, and thus, NO production, was increased after maximal test, as well cyclic GMP levels. In relation to biomarkers of oxidative stress, maximal test resulted in increased levels of lipid peroxidation, and diminished superoxide dismutase activity. Neither glutathione peroxidase nor catalase activity was affected by maximal test. Our findings demonstrate that the increased erythrocyte membrane rigidity caused by an acute bout of exercise may be caused, in part, by an increased lipid oxidative damage caused by ROS produced exogenously.

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BACKGROUND: the control of cardiovascular responses during resistance exercise (RE) is important for patient safety. OBJECTIVE: to investigate the influence of repetition maximum (RM) and rest interval between sets (RI) on heart rate (HR), systolic blood pressure (SBP) and rate-pressure product (RPP) during RE. METHODS: twenty healthy subjects (26 ± 5 years of age) underwent RE protocols involving three sets of leg press (6 and 12 RM) and RI proportional to the contraction time (1:3 and 1:5). The HR was checked on a continuous basis by using a cardiotachometer and the SBP was checked at the end of the sets, via a protocol validated by the auscultatory method. RESULTS: the HR was influenced by the workload (p = 0.008) and sets (p < 0.001), but not by the RI (p = 0.087). The SBP suffered from the isolated effect of the number of sets (p < 0.001) and RI (p = 0.017), but not from the workload (p = 0.95). The RPP rose in direct proportion to the workload (p = 0.036) and sets (p < 0.001), but in inverse proportion to the RI (p = 0.006). In 6 RM protocols, the variation in the HR was higher for RI = 1:3 (Δ = 11.2 ± 1.1 bpm) than for RI = 1:5 (Δ = 4.5 ± 0.2 bpm; p = 0.002), but there was no difference for 12 RM (Δ 1:3 = 21.1 ± 2.2 bpm; Δ 1:5 = 18.9 ± 2.0 bpm, p = 0.83). The RI influenced the variation in SBP in all loads (6 RM - Δ 1:3 = 10.6 ± 0.9 mmHg, Δ 1:5 = 6.6 ± 0.7 mmHg; p = 0.02 and 12 RM - Δ 1:3 = 15.2 ± 1.1 mmHg, Δ 1:5 = 8.4 ± 0.7 mmHg; p = 0.04). The RPP rose in proportion to the workload (p = 0.036) and to the sets (p < 0.001), but in inverse proportion to the RI (p = 0.006). With RI = 1:3, there was difference in RPP for 6 RM (Δ = 2,892 ± 189 mmHg.bpm) and 12 RM (Δ = 4,587 ± 300 mmHg.bpm; p = 0.018), but not with RI = 1:5 (6 RM: Δ = 1,224 ± 141 mmHg.bpm, 12 RM: Δ = 2,332 ± 194 mmHg.bpm; p = 0.58). CONCLUSION: regardless of the workload, an increased RI was associated with lower cardiovascular responses during RE, especially of SBP.

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FUNDAMENTO: O controle das respostas cardiovasculares durante exercício resistido (ER) é importante para a segurança do paciente. OBJETIVO: Investigar a influência do número de repetições máximas (RM) e dos intervalos de recuperação entre séries (IR) sobre a frequência cardíaca (FC), pressão arterial sistólica (PAS) e duplo produto (DP) durante ER. MÉTODOS: Vinte sujeitos saudáveis (26 ± 5 anos) realizaram protocolos de ER envolvendo três séries do leg press (6 e 12 RM) e IR proporcional ao tempo de contração (1:3 e 1:5). Aferiu-se a FC continuamente com cardiofrequencímetro e a PAS foi verificada ao final das séries, por meio de protocolo validado com método auscultatório. RESULTADOS: A FC sofreu influência da carga (p = 0,008) e das séries (p < 0,001), mas não do IR (p = 0,087). A PAS sofreu efeito isolado do número de séries (p < 0,001) e do IR (p = 0,017), mas não da carga (p = 0,95). O DP elevou-se em relação direta com a carga (p = 0,036) e com as séries (p < 0,001), mas inversamente ao IR (p = 0,006). Nos protocolos de 6 RM, a variação da FC foi maior para IR = 1:3 (Δ = 11,2 ± 1,1 bpm) do que para IR = 1:5 (Δ = 4,5 ± 0,2 bpm; p = 0,002), mas não houve diferença para 12 RM (Δ 1:3 = 21,1 ± 2,2 bpm; Δ 1:5 = 18,9 ± 2,0 bpm, p = 0,83). O IR influenciou a variação da PAS em todas as cargas (6 RM - Δ 1:3 = 10,6 ± 0,9 mmHg, Δ 1:5 = 6,6 ± 0,7 mmHg; p = 0,02 e 12 RM - Δ 1:3 = 15,2 ± 1,1 mmHg, Δ 1:5 = 8,4 ± 0,7 mmHg; p = 0,04). O DP elevou-se proporcionalmente à carga (p = 0,036) e para séries (p < 0,001), mas inversamente ao IR (p = 0,006). Com IR = 1:3, houve diferença de DP para 6 RM (Δ = 2.892 ± 189 mmHg.bpm) e 12 RM (Δ = 4.587 ± 300 mmHg.bpm; p = 0,018), mas não com IR = 1:5 (6 RM: Δ = 1.224 ± 141 mmHg.bpm, 12 RM: Δ = 2.332 ± 194 mmHg.bpm; p = 0,58). CONCLUSÃO: Independentemente da carga, um maior IR associou-se a menores respostas cardiovasculares durante ER, especialmente de PAS.

BACKGROUND: The control of cardiovascular responses during resistance exercise (RE) is important for patient safety. OBJECTIVE: To investigate the influence of repetition maximum (RM) and rest interval between sets (RI) on heart rate (HR), systolic blood pressure (SBP) and rate-pressure product (RPP) during RE. METHODS: Twenty healthy subjects (26 ± 5 years of age) underwent RE protocols involving three sets of leg press (6 and 12 RM) and RI proportional to the contraction time (1:3 and 1:5). The HR was checked on a continuous basis by using a cardiotachometer and the SBP was checked at the end of the sets, via a protocol validated by the auscultatory method. RESULTS: The HR was influenced by the workload (p = 0.008) and sets (p < 0.001), but not by the RI (p = 0.087). The SBP suffered from the isolated effect of the number of sets (p < 0.001) and RI (p = 0.017), but not from the workload (p = 0.95). The RPP rose in direct proportion to the workload (p = 0.036) and sets (p < 0.001), but in inverse proportion to the RI (p = 0.006). In 6 RM protocols, the variation in the HR was higher for RI = 1:3 (Δ = 11.2 ± 1.1 bpm) than for RI = 1:5 (Δ = 4.5 ± 0.2 bpm; p = 0.002), but there was no difference for 12 RM (Δ 1:3 = 21.1 ± 2.2 bpm; Δ 1:5 = 18.9 ± 2.0 bpm, p = 0.83). The RI influenced the variation in SBP in all loads (6 RM - Δ 1:3 = 10.6 ± 0.9 mmHg, Δ 1:5 = 6.6 ± 0.7 mmHg; p = 0.02 and 12 RM - Δ 1:3 = 15.2 ± 1.1 mmHg, Δ 1:5 = 8.4 ± 0.7 mmHg; p = 0.04). The RPP rose in proportion to the workload (p = 0.036) and to the sets (p < 0.001), but in inverse proportion to the RI (p = 0.006). With RI = 1:3, there was difference in RPP for 6 RM (Δ = 2,892 ± 189 mmHg.bpm) and 12 RM (Δ = 4,587 ± 300 mmHg.bpm; p = 0.018), but not with RI = 1:5 (6 RM: Δ = 1,224 ± 141 mmHg.bpm, 12 RM: Δ = 2,332 ± 194 mmHg.bpm; p = 0.58). CONCLUSION: Regardless of the workload, an increased RI was associated with lower cardiovascular responses during RE, especially of SBP.

FUNDAMENTO: El control de las respuestas cardiovasculares durante ejercicio de resistencia (ER) es importante para la seguridad del paciente. OBJETIVO: Investigar la influencia del número de repeticiones máximas (RM) y de los intervalos de recuperación entre series (IR) sobre la frecuencia cardíaca (FC), presión arterial sistólica (PAS) y doble producto (DP) durante ER. MÉTODOS: Veinte sujetos sanos (26 ± 5 años) realizaron protocolos de ER comprendiendo tres series del leg press (6 y 12 RM) y IR proporcional al tiempo de contracción (1:3 y 1:5). Se midió la FC continuamente con cardiofrecuencímetro y la PAS fue verificada al final de las series, por medio de protocolo validado con método auscultatorio. RESULTADOS: La FC sufrió influencia de la carga (p = 0,008) y de las series (p < 0,001), pero no del IR (p = 0,087). La PAS sufrió efecto aislado del número de series (p < 0,001) y del IR (p = 0,017), pero no de la carga (p = 0,95). El DP se elevó en relación directa con la carga (p = 0,036) y con las series (p < 0,001), pero inversamente al IR (p = 0,006). En los protocolos de 6 RM, la variación de la FC fue mayor para IR = 1:3 (Δ = 11,2 ± 1,1 lpm) que para IR = 1:5 (Δ = 4,5 ± 0,2 lpm; p = 0,002), pero no hubo diferencia para 12 RM (Δ 1:3 = 21,1 ± 2,2 lpm; Δ 1:5 = 18,9 ± 2,0 lpm, p = 0,83). El IR influenció la variación de la PAS en todas las cargas (6 RM - Δ 1:3 = 10,6 ± 0,9 mmHg, Δ 1:5 = 6,6 ± 0,7 mmHg; p = 0,02 y 12 RM - Δ 1:3 = 15,2 ± 1,1 mmHg, Δ 1:5 = 8,4 ± 0,7 mmHg; p = 0,04). El DP se elevó proporcionalmente a la carga (p = 0,036) y para series (p < 0,001), pero inversamente al IR (p = 0,006). Con IR = 1:3, hubo diferencia de DP para 6 RM (Δ = 2.892 ± 189 mmHg.lpm) y 12 RM (Δ = 4.587 ± 300 mmHg.lpm; p = 0,018), pero no con IR = 1:5 (6 RM: Δ = 1.224 ± 141 mmHg.lpm, 12 RM: Δ = 2.332 ± 194 mmHg.lpm; p = 0,58). CONCLUSIÓN: Independientemente de la carga, un mayor IR se asoció a menores respuestas cardiovasculares durante ER, especialmente de PAS.

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BACKGROUND: The control of cardiovascular responses during resistance exercise (RE) is important for patient safety. OBJECTIVE: To investigate the influence of repetition maximum (RM) and rest interval between sets (RI) on heart rate (HR), systolic blood pressure (SBP) and rate-pressure product (RPP) during RE. METHODS: Twenty healthy subjects (26 +/- 5 years of age) underwent RE protocols involving three sets of leg press (6 and 12 RM) and RI proportional to the contraction time (1:3 and 1:5). The HR was checked on a continuous basis by using a cardiotachometer and the SBP was checked at the end of the sets, via a protocol validated by the auscultatory method. RESULTS: The HR was influenced by the workload (p = 0.008) and sets (p < 0.001), but not by the RI (p = 0.087). The SBP suffered from the isolated effect of the number of sets (p < 0.001) and RI (p = 0.017), but not from the workload (p = 0.95). The RPP rose in direct proportion to the workload (p = 0.036) and sets (p < 0.001), but in inverse proportion to the RI (p = 0.006). In 6 RM protocols, the variation in the HR was higher for RI = 1:3 (Delta = 11.2 +/- 1.1 bpm) than for RI = 1:5 (Delta = 4.5 +/- 0.2 bpm; p = 0.002), but there was no difference for 12 RM (Delta 1:3 = 21.1 +/- 2.2 bpm; Delta 1:5 = 18.9 +/- 2.0 bpm, p = 0.83). The RI influenced the variation in SBP in all loads (6 RM - Delta 1:3 = 10.6 +/- 0.9 mmHg, Delta 1:5 = 6.6 +/- 0.7 mmHg; p = 0.02 and 12 RM - Delta 1:3 = 15.2 +/- 1.1 mmHg, Delta 1:5 = 8.4 +/- 0.7 mmHg; p = 0.04). The RPP rose in proportion to the workload (p = 0.036) and to the sets (p < 0.001), but in inverse proportion to the RI (p = 0.006). With RI = 1:3, there was difference in RPP for 6 RM (Delta = 2,892 +/- 189 mmHg.bpm) and 12 RM (Delta = 4,587 +/- 300 mmHg.bpm; p = 0.018), but not with RI = 1:5 (6 RM: Delta = 1,224 +/- 141 mmHg.bpm, 12 RM: Delta = 2,332 +/- 194 mmHg.bpm; p = 0.58). CONCLUSION: Regardless of the workload, an increased RI was associated with lower cardiovascular responses during RE, especially of SBP.