Five Days of Tart Cherry Supplementation Improves Exercise Performance in Normobaric Hypoxia.

Previous studies have shown tart cherry (TC) to improve exercise performance in normoxia. The effect of TC on hypoxic exercise performance is unknown. This study investigated the effects of 5 days of tart cherry (TC) or placebo (PL) supplementation on hypoxic exercise performance. Thirteen healthy participants completed an incremental cycle exercise test to exhaustion (TTE) under two conditions: (i) hypoxia (13% O2) with PL and (ii) hypoxia with TC (200 mg anthocyanin per day for 4 days and 100 mg on day 5). Pulmonary gas exchange variables, peripheral arterial oxygen saturation (SpO2), deoxygenated hemoglobin (HHb), and tissue oxygen saturation (StO2) assessed by near-infrared spectroscopy in the vastus lateralis muscle were measured at rest and during exercise. Urinary 8-hydro-2' deoxyguanosine (8-OHdG) excretion was evaluated pre-exercise and 1 and 5 h post-exercise. The TTE after TC (940 ± 84 s, mean ± standard deviation) was longer than after PL (912 ± 63 s, p < 0.05). During submaximal hypoxic exercise, HHb was lower and StO2 and SpO2 were higher after TC than PL. Moreover, a significant interaction (supplements × time) in urinary 8-OHdG excretion was found (p < 0.05), whereby 1 h post-exercise increases in urinary 8-OHdG excretion tended to be attenuated after TC. These findings indicate that short-term dietary TC supplementation improved hypoxic exercise tolerance, perhaps due to lower HHb and higher StO2 in the working muscles during submaximal exercise.

Ukemi Technique Prevents the Elevation of Head Acceleration of a Person Thrown by the Judo Technique 'Osoto-gari'.

Biomechanical analysis was performed to evaluate the effectiveness of mastering ukemi in preventing severe head injury in judo. One judo expert (tori) threw another judo expert (uke) with a skilled break-fall (ukemi) four times. We obtained kinematic data of uke with a digital video camera. Both translational and rotational accelerations were measured with a six-degree-of-freedom sensor affixed to uke's forehead. When Osoto-gari was performed, uke fell backward and his arm made contact with the tatami; the translational and rotational accelerations rose to peak values. The peak resultant translational and rotational accelerations were respectively 10.3 ± 1.6 G and 679.4 ± 173.6 rad/s2 (mean ± standard deviation). Furthermore, when comparing the values obtained for the judo experts with those obtained using an anthropomorphic test device (ATD: the POLAR dummy) that did not perform ukemi, both the peak resultant translational (P = 0.021) and rotational (P = 0.021) accelerations of uke were significantly lower than those for the ATD, whose head struck the tatami. Additionally, there was no significant difference among the three axis directions for either translational (ax: 7.4 ± 0.2, ay: 8.5 ± 2.1, az: 7.2 ± 0.8 G) or rotational (αx: 576.7 ± 132.7, αy: 401.0 ± 101.6, αz: 487.8 ± 66.6 rad/s2) acceleration. We confirmed that performing correct ukemi prevented the elevation of head acceleration by avoiding head contact with the tatami when a judoka is thrown by Osoto-gari. Judoka should therefore undertake intensive practice after they have acquired ukemi skills.

Biomechanical Analysis of the Head Movements of a Person Thrown by the Judo Technique 'Seoi-nage'.

The present study examined the kinematics and biomechanical parameters of the head of a person thrown forward by the judo technique 'Seoi-nage'. A judo expert threw an anthropomorphic test device (the POLAR dummy) five times. Kinematics data were obtained with a high-speed digital video camera. Linear and angular accelerations of the head were measured by accelerometers mounted at the center of gravity of the dummy's head. When Seoi-nage was performed, the dummy fell forward accompanied by contacting the anterior parietal regions of the head to the tatami, and the linear and angular accelerations of most axes reached peak values when the head contacted the tatami. Peak resultant linear and angular accelerations were 20.3 ± 9.8 G and 1890.1 ± 1151.9 rad/s2, respectively (means ± standard deviation). Peak values in linear and angular acceleration did not significantly differ between the three directional axes. Absolute angular accelerations in all axes observed in Seoi-nage were high and the resultant value was approximately equal to the already reported in Ouchi-gari, one of the predominant techniques causing judo-related acute subdural hematoma. However, the remarkable increase of linear acceleration in the longitudinal direction and/or angular acceleration in the sagittal plane, as previously reported in techniques being thrown backward (i.e., Ouchi-gari and Osoto-gari), was not detected. The likely mechanism of acute subdural hematoma caused by Seoi-nage is that a large angular acceleration causes large strains and deformations of the brain surface and subsequent rupture of cortical vessels.

Impact of Dietary Nitrate Supplementation on Executive Function During Hypoxic Exercise.

We investigated the effects of 4-day dietary beetroot (BR) juice supplementation on executive function assessed by color-word Stroop task (CWST) in hypoxia (fraction of inspired oxygen [FiO2] = 0.1395). Eight healthy young men performed 25-minute leg cycling exercise (target heart rate, 140 bpm) randomly with placebo (PL) juice or BR supplementation. The CWST was evaluated at resting hypoxic condition (after 30 minutes of hypoxic exposure) and at 15 minutes during exercise. During exercise, the correct response time in the CWST was significantly shortened compared with those at rest with no differences between PL and BR. The response accuracy in the CWST with BR was marginally lower than that with PL during exercise (p = 0.066). There were no significant differences in all physiological values, including pulmonary ventilation, arterial oxygen saturation, partial pressure of end-tidal carbon dioxide output, and tissue oxygenation in the left frontal lobe, assessed by near-infrared spectroscopy during exercise conditions involving PL and BR supplementation. These results suggest that moderate exercise in hypoxia partially improved executive function; however, 4-day dietary BR supplementation did not improve executive function during hypoxic exercise.

Muscle oxygenation profiles between active and inactive muscles with nitrate supplementation under hypoxic exercise.

Whether dietary nitrate supplementation improves exercise performance or not is still controversial. While redistribution of sufficient oxygen from inactive to active muscles is essential for optimal exercise performance, no study investigated the effects of nitrate supplementation on muscle oxygenation profiles between active and inactive muscles. Nine healthy males performed 25 min of submaximal (heart rate ~140 bpm; EXsub) and incremental cycling (EXmax) until exhaustion under three conditions: (A) normoxia without drink; (B) hypoxia (FiO2 = 13.95%) with placebo (PL); and (c) hypoxia with beetroot juice (BR). PL and BR were provided for 4 days. Oxygenated and deoxygenated hemoglobin (HbO2 and HHb) were measured in vastus lateralis (active) and biceps brachii (inactive) muscles, and the oxygen saturation of skeletal muscle (StO2; HbO2/total Hb) were calculated. During EXsub, BR suppressed the HHb increases in active muscles during the last 5 min of exercise. During EXmax, time to exhaustion with BR (513 ± 24 sec) was significantly longer than with PL (490 ± 39 sec, P < 0.05). In active muscles, BR suppressed the HHb increases at moderate work rates during EXmax compared to PL (P < 0.05). In addition, BR supplementation was associated with greater reductions in HbO2 and StO2 at higher work rates in inactive muscles during EXmax Collectively, these findings indicate that short-term dietary nitrate supplementation improved hypoxic exercise tolerance, perhaps, due to suppressed increases in HHb in active muscles at moderate work rates. Moreover, nitrate supplementation caused greater reductions in oxygenation in inactive muscle at higher work rates during hypoxic exercise.

Biomechanical analysis of acute subdural hematoma resulting from judo.

This study investigated biomechanical mechanisms of acute subdural hematoma caused by judo and sought preventive measures to reduce injury. A Japanese judo expert repeatedly threw an anthropometric test device using two throwing techniques, Osoto-gari and Ouchi-gari. Linear and angular accelerations of the head were measured. Both throwing techniques resulted in the dummy falling backwards, with the occipital area of the head contacting the mat, and peak linear and angular accelerations being observed when the head contacted the mat. For linear acceleration, the posterior-anterior direction showed the greatest force (41.0 ± 2.6 G using Osoto-gari, and 86.5 ±4.3 G using Ouchi-gari). For angular acceleration, values for sagittal plane rotation were greatest among the three directions measured (3315 ± 168 rad/s(2) using Osoto-gari, and 1328 ± 201 rad/s(2) using Ouchi-gari). We concluded that occipital head contact produced the most forceful longitudinal linear and sagittal plane angular accelerations; subsequent stretches and ruptures of parasagittal bridging veins resulting in acute subdural hematoma. As severe head injuries can result if a person's head comes into contact with the mat, offensive throwing techniques should be restricted to participants able to sufficiently demonstrate the Ukemi technique.

Rotational acceleration during head impact resulting from different judo throwing techniques.

Most severe head injuries in judo are reported as acute subdural hematoma. It is thus necessary to examine the rotational acceleration of the head to clarify the mechanism of head injuries. We determined the rotational acceleration of the head when the subject is thrown by judo techniques. One Japanese male judo expert threw an anthropomorphic test device using two throwing techniques, Osoto-gari and Ouchi-gari. Rotational and translational head accelerations were measured with and without an under-mat. For Osoto-gari, peak resultant rotational acceleration ranged from 4,284.2 rad/s(2) to 5,525.9 rad/s(2) and peak resultant translational acceleration ranged from 64.3 g to 87.2 g; for Ouchi-gari, the accelerations respectively ranged from 1,708.0 rad/s(2) to 2,104.1 rad/s(2) and from 120.2 g to 149.4 g. The resultant rotational acceleration did not decrease with installation of an under-mat for both Ouchi-gari and Osoto-gari. We found that head contact with the tatami could result in the peak values of translational and rotational accelerations, respectively. In general, because kinematics of the body strongly affects translational and rotational accelerations of the head, both accelerations should be measured to analyze the underlying mechanism of head injury. As a primary preventative measure, throwing techniques should be restricted to participants demonstrating ability in ukemi techniques to avoid head contact with the tatami.

Simple strategy to prevent severe head trauma in Judo.

To determine whether the use of an under-mat has an effect on impact forces to the head in Judo, a Judo expert threw an anthropomorphic test device using the Osoto-gari and Ouchi-gari techniques onto a tatami (judo mat) with and without an under-mat. Head acceleration was measured and the head injury criterion (HIC) values with or without under-mat were compared. The use of an under-mat significantly decreased (p = 0.021) the HIC values from 1174.7 ± 246.7 (without under-mat) to 539.3 ± 43.5 in Ouchi-gari and from 330.0 ± 78.3 (without under-mat) to 156.1 ± 30.4 in Osoto-gari. The use of an under-mat simply reduces impact forces to the head in Judo. Rule changes are not necessary and the enjoyment and health benefits of Judo are maintained.