Kerem Tuncay Özgünen

Effect of hot environmental conditions on physical activity patterns and temperature response of football players

Heat stress may contribute to decreased match performance when football is played in extreme heat. This study evaluated activity patterns and thermal responses of players during soccer matches played in different environmental conditions. Non‐acclimatized soccer players (n=11, 20±2 years) played two matches in conditions of moderate heat (MH) and high heat (HH) index. Core temperature (Tc) and physical performance were measured using a telemetric sensor and a global positioning system, respectively. The average ambient temperature and relative humidity were MH 34±1 °C and 38±2%; HH 36±0 °C and 61±1%. Peak Tc in the MH match was 39.1±0.4 °C and in the HH match it was 39.6±0.3 °C. The total distance covered in the first and second halves was 4386±367 and 4227±292 m for the MH match and 4301±487 and 3761±358 m for the HH match. Players covered more distance (P<0.001) in the first half of the HH match than in the second half. In football matches played at high environmental temperature and humidity, the physical performance of the players may decrease due to high thermal stress.

The effects of exercise, heat, cooling and rehydration strategies on cognitive function in football players

We investigated the cognitive effects of exercising in the heat on the field players of two football teams in a series of three matches. Different rehydration and cooling strategies were used for one of the teams during the last two games. Cognitive functions were measured before, during and immediately after each football match, as well as core temperature, body mass, plasma osmolality and glucose levels, allowing an estimate of their differential impacts on cognition. The pattern of results suggests that mild–moderate dehydration during exercise in the heat (up to 2.5%) has no clear effect on cognitive function. Instead, plasma glucose and core temperature changes appear to be the main determinants: higher glucose was related to faster and less accurate performance, whereas core temperature rises had the opposite effect. The 50% correlation between plasma glucose and core temperatures observed during exercise in the heat may help to stabilize cognitive performance via their opposing effects. The glucose‐like effects of sports drinks appear to be mediated by increased plasma glucose levels, because drinks effects became non‐significant when plasma glucose levels were added to the models. The cooling intervention had only a beneficial effect on complex visuo‐motor speed.

Hydration and sweating responses to hot-weather football competition

During a football match played in warm (34.3 ± 0.6 °C), humid (64 ± 2% rh) conditions, 22 male players had their pre‐match hydration status, body mass change, sweat loss and drinking behavior assessed. Pre‐match urine specific gravity (1.012 ± 0.006) suggested that all but three players commenced the match euhydrated. Players lost 3.1 ± 0.6 L of sweat and 45 ± 9 mmol of sodium during the 90‐min match and replaced 55 ± 19% of their sweat losses and hence by the end of the game were 2.2 ± 0.9% lighter. The water volume consumed during the game was highly variable (1653 ± 487 mL; 741–2387 mL) but there was a stronger relationship between the estimated pre‐game hydration status and water volume consumed, than between sweat rate and water volume consumed. In a second match, with the same players 2 weeks later in 34.4 ± 0.6 °C, 65 ± 3% rh, 11 players had a sports drink available to them before and during the match in addition to water. Total drink volume consumed during the match was the same, but approximately half the volume was consumed as sports drink. The results indicate that substantial sweat water and electrolyte losses can occur during match play in hot conditions and a substantial water and sodium deficit can occur in many players even when water or sports drink is freely available.

Living, training and playing in the heat: challenges to the football player and strategies for coping with environmental extremes

Dehydration and hyperthermia both, if sufficiently severe, will impair exercise performance. Dehydration can also impair performance of tasks requiring cognition and skill. Body temperature may exceed 40 °C in competitive games played in hot weather, but limited data are available. Football played in the heat, therefore, poses a challenge, and effects on some aspects of performance become apparent as environmental temperature increases above about 12–15 °C. Prior acclimatization will reduce the impact of high environmental temperatures but provides limited protection when humidity is also high. Ingestion of fluids is effective in limiting the detrimental effects on performance: drinks with added carbohydrate and electrolytes are generally more effective than plain water and drinks may be more effective if taken cold than if taken at ambient temperature. Pre‐exercise lowering of body temperature may aid some aspects of performance, but the efficacy has not been demonstrated in football.

DIFFERENTIAL CONTRIBUTIONS OF RIGHT AND LEFT BRAINS TO PAW SKILL IN RIGHT- AND LEFT-PAWED FEMALE RATS

Paw preference and paw frequency was studied in female rats. Paw preference was assessed using a modified version of food reaching task in quadrupedal position. Of 68 rats, 56 (82.4%) were right-handed, 7 (10.3%) were left-handed, and 5 (7.4%) were mixed-handed. There were significantly more right-handers than left-handers. The distribution of right minus left (L) paw reach (R + L = 50) was not U-shaped, it was J-shaped like in humans. Estrus cycle was a significant factor influencing the right-paw entry scores: most of left-handers were in estrus and proestrus, most of left-handers were in estrus, and most of mixed-handers were in postestrus. In right- and non-right-handers, the frequency of right-paw usage (right-hand skill) increased linearly with testing days, but the frequency of left-hand usage (left-hand skill) did not show significant changes with the successive testing days. Controlling for body weight and estrus only accentuated these results. It was concluded that distribution of hand preference in rats is J-shaped and there is a right-sided population bias in handedness in rats like in humans. The results suggested that motor learning in paw skill is mainly involved the left brain in right- and mixed-handed rats, not the right brain: only the left brain has the inbuilt capacity for motor learning in female rats. Such an asymmetric cognitive control in an animal model may have a major impact in many aspects of biology in respect to normal functioning, superior talents, and disease (see Geschwind, 1985).

Effect of pulsed magnetic field on regenerating rat sciatic nerve: an in-vitro electrophysiologic study.

Some experimental studies report that low-frequency pulsed electromagnetic field (PEMF) stimulation may accelerate regeneration in peripheral nerves. In the present study, effects of PEMF on the regeneration of the crushed rat sciatic nerves were investigated with histological and in-vitro electrophysiological methods (sucrose-gap). After crush injury of the sciatic nerves, rats were divided into 5, 15, 25, 38 day-groups and exposed to PEMF (1.5 h/day, intensity; 1.5 mT, consecutive frequency; 10-10-100 Hz). In the 15th day post crush, compound action potential (CAP) amplitude was measured as 5.5 ± 1 mV (crush group) and 5.4 ± 1.2 mV (crush + PEMF group). In addition, half width of CAP extended ∼ 3 fold in both groups and frequency-dependent amplitude inhibition (FDI) decreased -20% at 100 Hz. In the 38th day, amplitude of CAP, half width of CAP and FDI were measured nearly intact nerve values in both groups. In histological examinations, Wallerian degeneration was observed similar progress between both groups. The results were compared between crush and crush + PEMF groups, it was found that the effect of PEMF was not significant. The authors conclude that PEMF were ineffective on rat sciatic nerve regeneration.

Support vector machines for aerobic fitness prediction of athletes

Support vector machine is a statistical learning classifier, based on the principle of structural risk minimization, which performs well when applied to data outside the training set. This paper presents a new approach based on support vector machines to predict whether an athlete is aerobically fit or not. The input data set contains physical properties of athletes as well as their cardiopulmonary exercise testing results which were obtained at Cukurova University Sports Physiology Laboratory. According to the exercise test protocol, speed and grade of the treadmill were increased at certain times and the input variables of time, speed and grade of the treadmill, and oxygen uptake, carbon dioxide output, minute ventilation and heart rate of athletes were recorded. The average of the exercise test data was taken over certain time intervals and a curve fitting algorithm was applied to remove the spikes in the data and make it more suitable to use with support vector machines. Experiments with several different training and test data show that curve-fitted data has better performance measures, such as higher prediction rate, sensitivity, specificity, and shorter training time.

CONDUCTION BLOCKS OF LIDOCAINE ON CRUSHED RAT SCIATIC NERVE: AN IN-VITRO STUDY

The effects of lidocaine on the action potential of crushed sciatic nerves were investigated. The sciatic nerves of the rats were removed 5, 15, 25, and 38 days after the crushing and the compound action potentials were recorded with sucrose gap technique. The nerves were treated with 1 mM lidocaine and the conduction blocks of nonfrequency dependent block (NFDB) and frequency depended block (FDB) at 10, 40, and 100 Hz were determined. In intact nerves, the NFDB effect of lidocaine was 38.4 ± 0.7 %. On the 15th day after the crush, the NFDB was increased to 60.1 ± 1.3%. On the 38th day NFDB was decreased to 46.0 ± 0.8%. The following days after the crushing, lidocaine caused a very high rate of FDB with 10, 40, and 100 Hz stimulation. The high NFDB ratios approached normal levels with the improvement of regeneration, but FDB ratios continued to stay at high levels. The results showed that the ratios of FDB and NFDB were increased on the crushed nerve. It was concluded that, in the regeneration conditions of crushed rat sciatic nerves, the sensitivity to local anesthetic increases more than in intact nerves.

Şiddetli Hemofili A Hastalarında Sınırlanmış Eklem Açıklığı ile İlişkili Atrofik Kaslarda Su İçi Egzersizlerin Etkisi: Bir Pilot Çalışma

Amac: Hemofili tekrarlayan kanama ataklarina sekonder olarak kas- iskelet sorunlarina neden olmaktadir. Bu calismada, su ici egzersizlerinin, kas ve eklem problemleri olan siddetli hemofili A hastalarinda etkilerinin arastirilmasi amaclanmistir. Materyal ve Metod: Proflaksi alan, siddetli hemofili A hastasi (n=11) duzenli olarak egzersiz uygulamasina alinmistir. Bulgular: Calismaya katilan hastalarin, sag bacaklarinda ust bacak, orta bacak ve calf cevrelerinde (42.0 ± 2.4, 43.0 ±2.1 ; 37.1 ±1.9, 39.0 ±1.8; 28.1 ± 1.4, 28.9 ±1.3 respectively) (mean ± SE), sol bacaklarinda ust ve orta bacak cevrelerinde (36.9 ± 1.5 , 38.9 ± 1.5 ; 41.2 ± 2.2 , 42.9 ± 2) egzersiz oncesi degerlerine gore istatistiksel olarak anlamli farklilik bulunmustur (p