Effects of lower and upper body fatigue in striking response time of amateur karate athletes.

In combat sports, strikes or counter-strikes response time (RT) can be related to performance and sporting success. Moreover, training sessions are usually highly fatiguing, which is expected to impair basic skills, such as RT. Thus, this study aimed to investigate the effect of fatigue on punch and kick RTs of karate practitioners. Twelve individuals of both sexes from different levels (three yellow belts, three red belts, two orange belts, two green belts, one brown belt, and one black belt) were selected. Participants were aged 22 ± 3 years old, with a stature of 169.1 ± 6.5 cm, and a body mass of 65.5 ± 10 kg. Six visits were held with each participant. On the first 2 days, the RT of punches and kicks was measured by a validated smartphone app (TReaction). For the subsequent visits, a randomized incremental test for the upper or lower body was adopted as motor fatigue protocol, immediately followed by punches and kicks RT tests, also in random order. For induction of lower and upper body-specific muscle fatigue, the ITStriker app was used, which operates by emitting sound signals transmitted by a smartphone. One-way repeated measures ANOVA was performed, and significance was set at p ≤ 0.05. Regarding the mean punches RT, significant effects between situations for the upper (F(2,22) = 11.5; ω2 = 0.23; p < 0.001) and lower body (F(2,22) = 14.2; ω2 = 0.18; p < 0.001) fatigue protocols were found. The negative effect of the lower body fatigue protocol in punches RT was evident regardless of the order of the tests (punch RT first: Δ = 10.5%; t = 4.4; p < 0.001; d = 1.0; kick RT first: Δ = 11.4%; t = 4.8; p < 0.001; d = 1.1). Regarding mean kicks RT, significant effects were found between situations for the lower (F(2,22) = 16.6; ω2 = 0.27; p < 0.001) but not for the upper (F(2,22) = 2.3; ω2 = 0.02; p = 0.12) body fatigue protocols. Kick RTs were negatively affected by the lower body fatigue protocol regardless of the RT order applied (punch RT first: Δ = 7.5%; t = 3.0; p = 0.01; d = 0.8; kick RT first: Δ = 14.3%; t = 5.7; p < 0.001; d = 1.5). Upper body fatigue does not impair punch or kick RTs. Thus, it is concluded that the specificity of fatigue protocols and striking order should be considered while performing RT demanding techniques in karate practice. Specifically, lower body motor fatigue may impair both kicks and punches RT, which highlights the role of lower limbs in punches performance. Otherwise, upper body motor fatigue seems to induce impairments that are limited to the specific motor actions of this body segment.

Development of a Mobile Phone App for Measuring Striking Response Time in Combat Sports: Cross-Sectional Validation Study.

BACKGROUND: TReaction is a mobile app developed to determine strike response time at low cost and with easy application in combat sports. However, the validity and accuracy of the response time obtained by the TReaction app has not yet been evaluated. OBJECTIVE: This study aimed to test the validity and reliability of the TReaction app in measuring motor response time in combat sports. METHODS: A total of two athletes performed 59 strikes to assess the response time upon visual stimulus using the TReaction app simultaneously with a high-speed camera. Accuracy of the measure was verified using a computer simulator programmed to discharge visual stimuli and obtain the response time. Pearson correlation, Student t test for dependent samples, and the Bland-Altman analysis were performed. Accuracy was verified using the intraclass correlation coefficient. Effect size (g) and the typical error of measurement (TEM) were calculated. The significance level was set at P<.05. RESULTS: No significant difference (P=.56) was found between both systems. The methods presented a very strong correlation (r=0.993). The magnitude of differences was trivial (g<0.25), and TEM was 1.4%. These findings indicate a high accuracy between the computer screen and the mobile app measures to determine the beginning of the task and the response time. CONCLUSIONS: Our findings suggest that the TReaction app is a valid tool to evaluate the response time in combat sports athletes.

Effect of fatigue on reaction time, response time, performance time, and kick impact in taekwondo roundhouse kick.

Reaction time and response time are considered important abilities and can potentially affect combat performance. This study investigated the effect of a specific fatigue protocol on reaction time, response time, performance time, and kick impact. Seven male athletes reported to the laboratory on two different days. During day one, athletes performed a specific progressive taekwondo test, and on day two, a protocol for determining reaction time, response time, performance time, and kick impact before and after a time to exhaustion test at an intensity level corresponding to the maximal kick frequency obtained during the specific progressive taekwondo test. Muscle activation from rectus femoris and kick impact of the preferred limb were assessed. No differences were observed for response time and performance time. However, kick impact decreased (43 ± 27 to 13 ± 10 g, p < 0.01) while reaction time increased (145 ± 51 to 223 ± 133 ms, p < 0.05). Moderate correlation was observed between kick impact and response time (r = 0.565; p < 0.01), and kick impact and performance time (r = 0.494; p < 0.05). Results indicate that coaches and athletes may use taekwondo training programmes on coordination-based exercises leading to improve response time and to reduce fatigue effects in order to improve technique effectiveness and enhance the possibilities of scoring in a competitive situation.

Variáveis fisiológicas identificadas em teste progressivo específico para taekwondo / Physiological variables identified in progressive specific test for taekwondo

A avaliação fisiológica, a partir de testes específicos, é fundamental para predição do desempenho, prescrição da intensidade e volume de treinamento e, principalmente, verificar os efeitos destes. O objetivo deste estudo foi investigar a possibilidade de predizer o Limiar Anaeróbio (LAn) a partir do Ponto de Deflexão da Frequência Cardíaca (PDFC) a partir de teste específico. Doze atletas masculinos(25,2 ± 2,7 anos; 71,3 ± 9,5 kg; 176 ± 7 cm; 11,7 ± 2,1 %G; 9,8 ± 2,9 anos de treinamento) realizaram Teste Progressivo Específico para Taekwondo (TET) e Teste de Carga Constante (TCC). Foram obtidas medidas de lactato (La) e registrado a Frequência Cardíaca (FC) por meio de um POLAR® S610. O teste "t de Student" foi utilizado para comparar as Frequências de Chute (FCH) e FC do PDFC, com as do LAn.Adotou-se p< 0,05. A Frequência de Chutes de Limiar Anaeróbio (FCHLAn), (19 ± 4) não apresentou diferença significativa da Frequência de Chutes de Ponto de Deflexão da Frequência Cardíaca (FCHpdfc), (18 ± 3) altamente correlacionadas (r = 0,845). O TET demonstrou-se como uma metodologia alternativa para avaliar o LAn em atletas de taekwondo, a partir do PDFC.

The physiological assessment from specific tests, is essential to predicting the performance, the prescription of training intensity and volume, and, especially to verify the effect of them. The aim of this study was to verify the possibility to predict the anaerobic threshold (AT) from Heart Rate Deflection of Point (HRDP) from specific test. Twelve male athletes (age 25.2 ± 2.7; weight 71.3 ± 9.5 kg; height 176 ± 7 cm, percent body fat 11.7 ± 2.1%; 9.8 ± 2.9 years of training) performed Specific Test for Progressive Taekwondo (STT) and Test of Constant Loads (TCL). It was obtained the measures of lactate (La) and recorded heart rate (HR) using a Polar ® S610. To compare kick frequency (KF) and heart rate (HR) of HRDP with the TAn. It was adopted the p <0.05. The kick frequency of the aerobic threshold (KFTAn), (19 ± 4) showed no significant difference in the kick frequency of the Heart Rate Deflection of Point (KFhrdp), (18± 3) highly correlated (r = 0.845). The STT proved itself as an alternative methodology for assessing the (TAn) in the Taekwondo athletes from the HRDP.