Strength, flexibility and heart rate in women practicing karate

Introduction It is known that the longitudinal training of muscle tendon flexibility (Mtf) improves range of motion. On the contrary it is not clear if static stretching (SS) can reduce muscle-joint damage and have any effect on warm-up. Moreover, if SS is used before competition it can reduce the physical capacity of the athlete. A number of researchers have studied different stretching method effects, the relationship between Mtf and body temperature, the circadian rhythm, and range of motion variations. The aim of this work was to investigate, in a group of women performing high-level karate, whether the flexibility of the extensor muscles of the spinal column and the posterior area of the leg were subjected to modifications during a typical specific training session, and whether they were correlated with explosive elastic force and heart rate (HR). Method Seven subjects (age 238 years, weight 565 kg, and height 1623 cm) who had practiced karate for 10±6 years were enrolled. This group did the following Mtf and strength tests during the training session: - Mtf test from a standing position (stand and reach); - Mtf test from a sitting position (sit and reach); - The countermovement jump test (CMJ) to evaluate the explosive-elastic force of a vertical jump (OPTOJUMP Microgate, Italy). The tests were conducted at fixed moments of the training session: 1) 10 minutes before warm-up (TPre-R); 2) immediately after warm-up (TPost-R), 3) immediately after the central phase of training lasting 30 minutes (TPost-Tr); 4) immediately after the recovery phase lasting 15 minutes (TPost-D); 5) 15 minutes after the Post-D test, about 30 minutes after the end of TPost-Tr (Tpost-D15). At the end of each phase HR was measured (Polar 710 I, Polar Electro, Finland). Results Data analyzed by the Friedman test showed a dependence on the time factor of the muscle-tendon flexibility measured in the standing position (P<0.001). Post-hoc procedure found Post-D Mtf greater than Pre-R Mtf (P<0,01, +47%); Post-D15 Mtf greater than Pre-R Mtf (P<0,05, +38%); Post-D Mtf greater than Post-R (P<0,05, +22%). No significant variations were observed in sit and reach test. No significant correlations between CMJ and Mtf were observed. The stand and sit tests were correlated in all phases of the training session (P<0.05, r>0,7). Negative correlations were observed between CMJ in the TPost-Tr and HR in the Post-D (P<0,05, r= -0,821) and post D15 (P<0,05, r= -0,785), highlighting a reduction in HR The HR in the TPost-R test was correlated with HR in the TPost-Tr test (P<0,05, R=0,857). Data showed that the central phase of training led to an increase in HR due to the intensity of the exercise that produced cardiovascular fatigue in all athletes. Conclusion This study confirms that the warm-up is essential to increase Mtf, and suggests that it could contribute to a reduction in muscle damage. However, the activity of stretching in itself, as confirmed by other researchers, is not necessarily useful for reducing muscle damage in high-level competition. Muscle-tendon flexibility data measured in the sitting position did not show significant variations. This finding may be due to an existing level of Mtf in the athletes, which did not obtain any further benefit from an increase in exercise intensity. The CMJ was not related to Mtf in any phase of the training. This indicates that those who are more flexible are not necessarily able to return elastic energy. The increase in CMJ had the same trend as HR, but the latter was negatively correlated with the explosive-elastic force in the TPost-D and TPost-D15 tests, indicating that the values of HR return at the basal level after the TPost-Tr. This last result can indicate an efficient cardiovascular system. The Mtf measured in the Tpost-D15 showed the highest values of TPre-R Mtf. This indicates that the biomechanics of Karate increased the range of motion of the vertebral column.