Does the combination of resistance training and stretching increase cardiac overload?

OBJECTIVES: To compare the effects of combinations of resistance training (RT) and static stretching (SS) on heart rate (HR), systolic pressure (SBP), diastolic pressure (DBP), rate pressure product (RPP), oxygen saturation (SpO2), rating of perceived effort (RPE), and heart rate variability (HRV) in men. METHODS: Twelve normotensive healthy men participated in four protocols: a) SS+RT, b) RT+SS, c) RT, and d) SS. Variables were measured before, immediately after, and 15, 30, and 45 min after the sessions. RESULTS: The combination of SS and RT increased (p<0.001) HR when compared to the effects of the noncombined protocols (from 2.38 to 11.02%), and this result indicated metabolic compensation. Regarding DBP, there were differences (p<0.001) between the RT and SS groups (53.93±8.59 vs. 67.00±7.01 mmHg). SS has been shown to be able to reduce (p<0.001) SpO2 (4.67%) due to the occlusion caused by a reduction in the caliber of the blood vessels during SS compared to during rest. The increase in RPP (6.88% between RT and SS+RT) along with the HR results indicated higher metabolic stress than that reflected by the RPE (combined protocols increased RPE from 21.63 to 43.25%). The HRV analysis confirmed these results, showing increases (p<0.01) in the LF index between the combined and noncombined protocols. Compared to the effect of RT, the combination of SS and RT promoted a vagal suppression root mean square of the successive differences (RMSSD) index (from 9.51 to 21.52%) between the RT and SS+RT groups (p<0.01) and between the RT and RT+SS groups (p<0.001). CONCLUSION: Static stretching increases cardiac overload and RPE, reducing oxygen supply, especially when performed in combination with RT.

Low intensity static stretching does not modulate heart rate variability in trained men / Alongamento estático de baixa intensidade não modula a variabilidade da frequência cardíaca em homens treinados

OBJECTIVE: To investigate the acute effect of static stretching on heart rate variability in trained men. METHODS: Eight subjects were randomly submitted to two situations, as follows: a static stretch protocol and 20 minutes at rest. The stretch protocol consisted of two sets of 30 seconds of static stretch of the chest muscles with a 40 second of interval between them. After 48 hours, the procedures were reversed so that all the subjects should were submitted to the two situations. The values of heart rate variability were measured before and after the experimental and control situation (stretch vs. rest). We registered the following cardiac variables: root mean square of standard deviation (rMSSD), the number of pairs of successive beats that differ by more than 50 ms (pNN50), low frequency (LF) and high frequency (HF). The Shapiro-Wilk and the paired Student's test were used for statistical analysis; a critical level of significance of p < 0.05 was adopted. RESULTS: No significant differences (p > 0.05) were found (stretching vs. control) to the RMSSD, pNN50, LF and HF indices. However, although no statistical differences were observed, the figures show large changes on mean values, suggesting an unclear effect on the sympathetic-vagal modulation. CONCLUSION: The present results suggest that a low intensity (motion range until discomfort point) and volume (1 minute) of static stretching does not significantly affect the acute sympathetic-vagal control in trained men. Because the protocol did not show differences regarding the studied variables, we suggest that there is not a sufficient level of physiological basis to perform this type of exercise in a traditional pre-exercise setting, if the purpose is obtain gains in physical performance.

OBJETIVO: Nosso objetivo foi verificar o efeito agudo do alongamento estático sobre a variabilidade da frequência cardíaca (VFC) em homens treinados. MÉTODOS: Oito voluntários (n = 8) foram randomicamente submetidos a duas situações, a saber: alongamento estático (AE) ou 20 minutos em repouso (CTRL). O protocolo de alongamento consistiu em duas séries de 30 segundos para musculatura do peitoral (40 segundos de intervalo). Após 48 horas, os procedimentos foram realizados de maneira reversa, de forma que todos os participantes realizaram as duas situações (ALONGAMENTO e CRTL) ao final do estudo. Os valores de VFC foram medidos antes e imediatamente depois das situações experimental e controle (alongamento vs. repouso). Para registro das variáveis cardíacas coletadas (rMSSD, pNN50, LF e HF) no presente estudo, nós utilizamos um relógio Polar RS800CX (Polar Electro OY, Finland). As análises estatísticas realizadas foram feitas através da aplicação do teste de Shapiro-Wilk seguido pelo teste t de Student pareado, sendo adotado um nível crítico de significância de p < 0.05. RESULTADOS: Nenhuma diferença significativa (p > 0.05) foi observada (alongamento vs. controle) quando as variáveis foram analisadas. CONCLUSÃO: O presente estudo sugere que o alongamento estático com baixo volume de aplicação não altera significativamente o controle simpato-vagal em homens treinados. Na medida em que o protocolo utilizado não resultou em diferenças significativas nas variáveis estudadas, nós inferimos que não há fundamento fisiologicamente válido para a realização deste tipo de exercício em sua forma tradicional pré-exercício quando o objetivo for a obtenção de ganhos na performance física.