Pseudoephedrine and circadian rhythm interaction on neuromuscular performance.

This study analyzed the effects of pseudoephedrine (PSE) provided at different time of day on neuromuscular performance, side effects, and violation of the current doping cut-off threshold [World Anti-Doping Agency (WADA)]. Nine resistance-trained males carried out bench press and full squat exercises against four incremental loads (25%, 50%, 75%, and 90% one repetition maximum [1RM]), in a randomized, double-blind, cross-over design. Participants ingested either 180 mg of PSE (supra-therapeutic dose) or placebo in the morning (7:00 h; AM(PLAC) and AM(PSE)) and in the afternoon (17:00 h; PM(PLAC) and PM(PSE)). PSE enhanced muscle contraction velocity against 25% and 50% 1RM loads, only when it was ingested in the mornings, and only in the full squat exercise (4.4-8.7%; P < 0.05). PSE ingestion raised urine and plasma PSE concentrations (P < 0.05) regardless of time of day; however, cathine only increased in the urine samples. PSE ingestion resulted in positive tests occurring in 11% of samples, and it rose some adverse side effects such us tachycardia and heart palpitations. Ingestion of a single dose of 180 mg of PSE results in enhanced lower body muscle contraction velocity against low and moderate loads only in the mornings. These mild performance improvements are accompanied by undesirable side effects and an 11% risk of surpassing the doping threshold.

Infrared tympanic thermometry in a hot environment.

The purpose of this study was to compare tympanic (measured by infrared thermometry; Tty- (IRED)) with rectal and esophageal temperatures (T(REC) and T(ES)) during exercise in the heat. During Experiment 1, nine subjects pedaled for 55 min in a hot-dry environment (37 degrees C; 27% humidity) in still-air (<0.2 m/s) and for 10 additional min using water ingestion, wind and ice to cool them down. During Experiment 2, subjects pedaled for 90 min in a similar environment but with airflow at 2.5 m/s. Pearson correlation coefficients (r) and Bland-Altman plots were calculated. In Experiment 1, Tty-(IRED) and T (REC) were highly correlated (r=0.83; p<0.001) with close agreement (-0.08+/-0.4 degrees C). Overall Tty-(IRED) was significantly correlated with T(ES) (r=0.91; p<0.001). Cold water ingestion did not affect Tty-(IRED) or T(REC) but lowered T(ES). Wind and ice application lowered Tty- (IRED) below T(REC) (p<0.05). During Experiment 2, Tty-(IRED) was lower than T(REC) (p<0.05) and the difference increased throughout exercise as hyperthermia developed resulting in low agreement (-1.01+/-1.1 degrees C). In conclusion, Tty- (IRED) dangerously underestimates T(REC) when exercising in a hot environment with airflow or during a cooling treatment. However, it could correctly detect hyperthermia during exercise in a hot still-air environment.

Influencia del calor ambiental en un test incrernental de umbral de lactato / The effect of environmental heat on lactate threshold testing

Ocho estudiantes de educación fisica sanos, moderadamente entrenados (VO2 max:57ñ4ml-kg-1-min-1)y no aclimatados al calor,completaron dos test de umbral de lactato en un cicloergómetro. Los participantes pedalearon durante 5 estadios incrementales hasta los 225 vatios en el CALOR (38 ñ I'C; 28 ñ 3 por ciento de humedad relativa) y a las mismas cargas de trabajo en un ambiente NEUTRAL (21 + 2ºC; 43 ñ 4 por ciento de humedad relativa). El orden de los test (CALOR o NEUTRAL) fue aleatorio y separados por al menos 45 minutos de descanso en ambiente termoneutral (21º C). La pérdida de peso por sudor fue de 0,41 ñ 0,02 kg y la temperatura timpánica al final de cada test era similar en el CALOR que en NEUTRAL (37.6 ñ 0.3 Ys. 37.5 ñ 0.3 º C). Sin embargo, en el último estadio del test (225 vatios) en el CALOR la frecuencia cardiaca era 8 latidos/minuto, la ventilación pulmonar era 6 litros/minuto y la percepción del esfuerzo (escala de Borg) era 13 por ciento mayor que en el test NEUTRAL (todos ellos p<0,05). Asimismo, durante el último estadio del test la concentración de lactato sanguíneo era un 30 por ciento mayor en el CALOR que en NEUTRAL (4,6 + 1,0 vs 3,5 ñ 0,6 mmol/L,respectivamente p<0.05). En el CALOR, el ritmo de acumulación de lactato sanguíneo se aceleró apareciendo el umbral de lactato a los 75 vatios en comparación a los 200 vatios en el test NEUTRAL. Debido al incremento en la frecuencia cardiaca en el CALOR, la frecuencia cardiaca en el umbral de lactalo fue similar en el CALOR y en NEUTRAL (1 50 ñ 1 latidos/minuto). En conclusión, el CALOR ambiental en atletas no aclimatados reduce el umbral de lactato y podría infravalorar las adaptaciones metabólicas y cardiovasculares derivadas del entrenamiento (AU)