Ingesta aguda de p-sinefrina: efectos sobre el rendimiento físico, oxidación de sustratos energéticos y respuesta cardiovascular en reposo y ejercicio

La p-sinefrina (PS) es un protoalcaloide presente en algunas de las plantas de la familia Rutaceae popularmente denominado como citrus. Esta sustancia puede ser ingerida a través de productos naturales como los zumos de cítricos, mandarinas, naranjas de Sevilla, pomelos, etc. Por otro lado, la PS también puede ser sintetizada en el laboratorio para ser incluida en suplementos alimenticios en dosis mayores a las encontradas naturalmente en las frutas. En la actualidad, este alcaloide se incluye comúnmente en productos destinados a incrementar el rendimiento deportivo para el control del peso corporal. Sin embargo, la información científica disponible hasta la fecha sobre la eficacia y seguridad de la PS en humanos es muy limitada. El objetivo de la presente Tesis Doctoral fue investigar los efectos de la ingesta aguda de PS en el rendimiento físico, en la oxidación de los sustratos energéticos y en la respuesta cardiovascular en el reposo y el ejercicio. Para cumplir este objetivo se plantearon seis investigaciones con un diseño experimental de medidas repetidas, doble-ciego y con orden aleatorizado en las que la PS fue ingerida 45 minutos antes del inicio de las pruebas y fue comparada a una sustancia placebo (PLAC). En total, 89 deportistas jóvenes y sanos participaron en las investigaciones. En el Estudio 1 se investigó el efecto de una dosis de 3 mg·kg-1 de PS en pruebas de velocidad en atletismo (60 metros lisos, 100 metros lisos), la potencia de salto y posibles efectos secundarios en 13 velocistas experimentados. En esta investigación, la PS no fue efectiva para incrementar el rendimiento físico en las pruebas de velocidad y salto mientras que tampoco se encontraron efectos secundarios en las 24 horas siguientes a la ingesta en comparación con el PLAC. En el Estudio 2 se investigó los efectos de una dosis de 3 mg·kg-1 de PS sobre la oxidación de los sustratos energéticos, la presión arterial (PA) y la frecuencia cardíaca (FC) en reposo y durante un ejercicio de intensidad incremental en un total de 18 participantes. Se observó que la PS aumentó el ritmo de oxidación de grasas, mientras redujo el ritmo de oxidación de carbohidratos (CHO) durante el ejercicio de intensidad baja/moderada. La PS no modificó la respuesta cardiovascular ni en el reposo ni en el ejercicio, ni produjo efectos secundarios en las 24 horas siguientes a la ingesta en comparación con el PLAC. En el Estudio 3 se investigó el efecto dosis-respuesta de la PS sobre la oxidación de sustratos energéticos y la FC en el reposo y durante el ejercicio. Para ello, se administraron 1, 2 o 3 mg·kg-1 de PS antes de un ejercicio de intensidad creciente a un total de 17 participantes activos. En esta investigación se observó un efecto dosis respuesta desde 1 hasta 2 mg·kg-1 mientras que la dosis de 3 mg·kg-1 no produjo efectos superiores. No se encontró ningún efecto en la FC en reposo ni durante el ejercicio en ninguna de las dosis utilizadas. En el Estudio 4 se investigó los efectos de la combinación de la PS y cafeína sobre el efecto en variables cardiovasculares medidas en reposo y sobre la oxidación de sustratos energéticos durante el ejercicio de intensidad incremental en el cicloergómetro. 13 sujetos activos participaron en esta investigación. Tanto la PS como la cafeína, ingeridas de manera aislada, fueron efectivas para incrementar la oxidación de grasas durante el ejercicio. Sin embargo, la adición de 3 mg·kg-1 de cafeína, no potenció el efecto sobre la oxidación de grasas que mostro la ingesta aislada de PS. Tampoco se encontraron efectos secundarios tras la ingesta aislada de PS, mientras que la cafeína aumentó las puntuaciones de potencia muscular y resistencia percibidas, pero redujo el nivel de esfuerzo percibido (RPE) en comparación con el PLAC. El Estudio 5 tuvo por objetivo determinar los efectos agudos de la ingesta de 3 mg·kg-1 de PS en el ritmo de oxidación de grasas y CHO durante el ejercicio de intensidad incremental en ciclistas de élite. Para ello se reclutaron 15 participantes altamente entrenados que realizaron un test incremental. La ingesta aguda de 3 mg·kg-1 de PS no modificó la FC ni las presiones arteriales medidas en reposo ni mostró una mayor potencia alcanzada durante el test de intensidad incremental en el cicloergómetro. Sin embargo, esta dosis incrementó la oxidación de grasas durante el ejercicio en intensidades de moderadas a altas. Finalmente, el Estudio 6 tuvo por objetivo analizar el efecto de la ingesta aguda de 3 mg·kg-1 de PS sobre el ritmo de oxidación de grasas durante 60 minutos de ejercicio al Fatmax en el cicloergómetro. Para este objetivo se reclutaron 13 participantes jóvenes y sanos. Los resultados obtenidos mostraron que la ingesta aguda de 3 mg·kg-1 no modificó ninguna de las variables medida en reposo (FC ni PAsistólica ni diastólica). Sin embargo, la ingesta de 3 mg·kg-1 PS incrementó la oxidación de grasas en comparación con el PLAC en 60 minutos de ejercicio a una intensidad mantenida (Fatmax) reduciendo la oxidación de CHO en comparación con el PLAC. En conclusión, la ingesta aguda de PS no incrementó el rendimiento físico en pruebas de potencia/velocidad, pero fue efectiva para incrementar el ritmo de oxidación de grasas durante el ejercicio de intensidad de baja a moderada, a expensas del ritmo de oxidación de CHO. Por otro lado, la PS no modificó la PA ni la FC en el reposo ni durante el ejercicio, ni produjo efectos secundarios en las 24 horas siguientes a su ingesta. Por tanto, la PS ingerida de manera aguda, y al menos con una dosis de 2 mg·kg-1, puede ser considerada como una sustancia efectiva para incrementar la oxidación de grasas durante el ejercicio a intensidades bajas/ moderadas y segura en términos de ausencia de efectos secundarios. Sin embargo, los efectos de la PS deben ser investigados cuando se utiliza en dosis mayores y tras su consumo a largo plazo

Energy Drinks and Sports Performance, Cardiovascular Risk, and Genetic Associations; Future Prospects

The consumption of energy drinks (e.g., containing caffeine and taurine) has increased over the last decade among adolescents and athletes to enhance their cognitive level and improve intellectual and athletic performance. Numerous studies have shown that drinking moderate doses of such drinks produces beneficial effects, as they considerably boost the sporting performance of elite athletes in various sports, including both endurance and explosive events. However, apart from their ergogenic effects, the regular consumption of energy drinks also increases blood pressure and consequently incites problems such as hypertension, tachycardia, and nervousness, all of which can lead to cardiovascular disorders. A potential positive correlation between genetics and the moderate consumption of energy drinks and athletic performance has recently been reported; notwithstanding, a better understanding of the genetic variants involved in metabolism is a key area for future research to optimize the dose of energy drink consumed and obtain the maximal ergogenic effect in elite sports. The aim of this literature review, therefore, is to present the results of recent studies, classifying them according to the differences in the associations between energy drinks and: (i) Athletic performance; (ii) cardiovascular risk factors while practicing sports; and (iii) genetic associations and future prospects between the consumption of energy drinks and performance.post-print429 K

Effect of p-Synephrine on Fat Oxidation Rate during Exercise of Increasing Intensity in Healthy Active Women

p-Synephrine is the principal alkaloid of bitter orange (Citrus aurantium). Several recent investigations have found that the intake of 2-3 mg/kg of p-synephrine raises fat oxidation rate during exercise of low-to-moderate intensity. However, these investigations have been carried out only with samples of male participants or mixed men/women samples. Therefore, the aim of this investigation was to study the effect of p-synephrine intake on fat oxidation during exercise of increasing intensity in healthy women. Using a double-blind, randomized experiment, 18 healthy recreationally active women performed two identical exercise trials after the ingestion of (a) 3 mg/kg of p-synephrine and (b) 3 mg/kg of a placebo (cellulose). The exercise trials consisted of a ramp test (from 30 to 80% of maximal oxygen uptake; VO(2)max) on a cycle ergometer while substrate oxidation rates were measured at each workload by indirect calorimetry. In comparison to the placebo, the intake of p-synephrine increased resting tympanic temperature (36.1 +/- 0.5 vs. 36.4 +/- 0.4 degrees C p = 0.033, d = 0.87) with no effect on resting heart rate (p = 0.111) and systolic (p = 0.994) and diastolic blood pressure (p = 0.751). During exercise, there was no significant effect of p-synephrine on fat oxidation rate (F = 0.517; p = 0.484), carbohydrate oxidation rate (F = 0.730; p = 0.795), energy expenditure rate (F = 0.480; p = 0.833), heart rate (F = 4.269; p = 0.068) and participant's perceived exertion (F = 0.337; p = 0.580). The maximal rate of fat oxidation with placebo was 0.26 +/- 0.10 g/min and it was similar with p-synephrine (0.28 +/- 0.08 g/min, p = 0.449, d = 0.21). An acute intake of 3 mg/kg of p-synephrine before exercise did not modify energy expenditure and substrate oxidation during submaximal aerobic exercise in healthy active women. It is likely that the increase in resting tympanic temperature induced by p-synephrine hindered the effect of this substance on fat utilization during exercise in healthy active women.Francisco de Vitoria University UFV-18/202

Does the Time of Day Play a Role in the Acute Effect of p-Synephrine on Fat Oxidation Rate during Exercise in Women? A Randomized, Crossover and Double-Blind Study

p-Synephrine is deemed a safe and effective substance to increase fat utilization during exercise of low-to-moderate intensity in men but not in women. Additionally, the existence of a diurnal variation in substrate utilization has been documented during exercise with enhanced fat oxidation in the evening compared with early morning. However, it remains unknown whether there is an interaction between the effect of p-synephrine and the time of the day on fat oxidation during exercise. This study aimed to evaluate the effect of the acute ingestion of 3 milligram of p-synephrine per kilogram of body mass (mg/kg) on fat oxidation during exercise of increasing intensity when the exercise is performed in the morning vs. the evening. Using a randomized, double-blind, placebo-controlled experimental design, 16 healthy and active women performed four identical exercise trials after the ingestion of 3 mg/kg of p-synephrine and 3 mg/kg of a placebo (cellulose) both in the morning (8-10 am) and in the evening (5-7 pm). In the exercise trials, the substances were ingested 60 min before an incremental test on a cycle ergometer with 3 min stages at workloads from 30 to 80% of maximal oxygen uptake (VO(2)max). Substrate oxidation rates were measured by indirect calorimetry. In each trial, the maximum rate of fat oxidation (MFO) and the intensity that elicited MFO (Fatmax) were measured. A two-way analysis of variance (time-of-the day x substance) was used to detect differences among the trials. With the placebo, MFO was 0.25 +/- 0.11 g/min in the morning and 0.24 +/- 0.07 g/min in the evening. With p-synephrine, MFO was 0.26 +/- 0.09 g/min in the morning and 0.21 +/- 0.07 g/min in the evening. There was no main effect of substance (p = 0.349), time of day (p = 0.186) and the substance x time of day (p = 0.365) on MFO. Additionally, Fatmax was reached at a similar exercise intensity with the placebo (41.33 +/- 8.34% VO(2)max in the morning and 44.38 +/- 7.37% VO(2)max in the evening) and with p-synephrine (43.33 +/- 7.24% VO(2)max in the morning and 45.00 +/- 7.43% VO(2)max in the evening), irrespective of the time of day with no main effect of substance (p = 0.633), time of day (p = 0.191), or interaction (p = 0.580). In summary, the acute intake of 3 mg/kg of p-synephrine before exercise did not increase MFO and Fatmax, independently of the time of day, in female athletes. This indicates that the time of day is not a factor explaining the lack of effectiveness of this substance to enhance fat oxidation during aerobic exercise in women.Francisco de Vitoria University, grant number UFV-18/202

Acute p-synephrine ingestion increases whole-body fat oxidation during 1-h of cycling at Fatmax.

Purpose p-Synephrine, the principal alkaloid of bitter orange (Citrus aurantium), is widely used in dietary supplements for weight loss due to its purported effect of increasing fat oxidation. However, there is a paucity of scientific information about its effectiveness in enhancing fat oxidation during exercise. The aim of this investigation was to determine the effect of an acute dose of p-synephrine on substrate oxidation during prolonged and constant intensity exercise. Methods In a double-blind and randomized experiment, 14 healthy subjects performed two acute experimental trials after ingesting either p-synephrine (3 mg kg−1) or a placebo (cellulose). Energy expenditure and fat oxidation rates were continuously measured by indirect calorimetry during 1 h of continuous cycling at Fatmax, the intensity that induces maximal fat oxidation rate. Results In comparison to the placebo, energy expenditure during 1 h of cycling remained unchanged with p-synephrine (698 ± 129 vs. 686 ± 123 kcal, P = 0.08). However, p-synephrine increased whole-body fat oxidation (33.6 ± 10.4 vs. 37.3 ± 9.8 g, P < 0.01) while also reducing carbohydrate oxidation (99.5 ± 30.4 vs. 85.0 ± 28.4 g, P < 0.01). However, the magnitude of the shift on substrate oxidation induced by p-synephrine was small. Conclusion Acute ingestion of p-synephrine augments fat oxidation during prolonged and constant-intensity exercise.pre-print193 K

The Effect of Caffeine on the Velocity of Half-Squat Exercise during the Menstrual Cycle: A Randomized Controlled Trial

Recent literature confirms the ergogenic effect of acute caffeine intake to increase muscle strength and power in men. However, the information about the effect of caffeine on muscle performance in women is uncertain and it is unknown whether its ergogenicity is similar during the menstrual cycle. The goal of this investigation was to assess the effect of acute caffeine intake on mean and peak velocity of half-squat exercise during three different phases of the menstrual cycle. Thirteen trained eumenorrheic athletes (age = 31 ± 6 years; body mass = 58.6 ± 7.8 kg) participated in a double-blind, crossover and randomized experimental trial. In the early follicular (EFP), late follicular (LFP) and mid luteal phases (MLP), participants either ingested a placebo (cellulose) or 3 mg/kg/bm of caffeine in an opaque and unidentifiable capsule. In each trial, participants performed a half-squat exercise at maximal velocity with loads equivalent to 20%, 40% 60% and 80% of one repetition maximum (1RM). In each load, mean and peak velocity were measured during the concentric phase of the exercise using a rotatory encoder. In comparison to the placebo, a two-way ANOVA showed that the ingestion of 3 mg/kg/bm of caffeine increased mean velocity at 60% 1RM in EFP (Δ = 1.4 ± 2.7%, p = 0.04; ES: 0.2 ± 0.2) and LFP (Δ = 5.0 ± 10.4%, p = 0.04; ES: 0.3 ± 0.4). No other statistical differences were found for the caffeine-placebo comparison for mean velocity, but caffeine induced an ergogenic effect of small magnitude in all of the menstrual cycle phases. These results suggest that the acute intake of 3 mg/kg/bm of caffeine induces a small effect to increase movement velocity during resistance exercise in eumenorrheic female athletes. The positive effect of caffeine was of similar magnitude in all the three phases of the menstrual cycle.post-print559 K

Effect of caffeine on muscle oxygen saturation during short‑term all‑out exercise: a double‑blind randomized crossover study.

Purpose The ergogenic effect of oral caffeine administration on short-term all-out exercise performance is well established. However, the potential mechanisms associated with caffeine’s ergogenicity in this type of exercise are poorly understood. The aim of this study was to investigate whether caffeine intake modifies muscle oxygen saturation during the 15-s Wingate Anaerobic Test. Methods Fifteen moderately trained individuals (body mass = 67.4 ± 12.3 kg; height 171.3 ± 6.9 cm; age 31 ± 6 years) took part in two identical experimental trials after the ingestion of (a) 3 mg/kg of caffeine or (b) 3 mg/kg of cellulose (placebo). After 60 min for substances absorption, participants performed a 15-s Wingate test on a cycle ergometer against a load representing 7.5% of participant’s body mass. Muscle oxygen saturation was continuously measured during exercise with near-infrared spectroscopy and blood lactate concentration was measured 1 min after exercise. Results In comparison to the placebo, the oral administration of caffeine increased peak power by 2.9 ± 4.5% (from 9.65 ± 1.38 to. 9.92 ± 1.40 W/kg, P = 0.038; effect size (ES), 95% confidence intervals = 0.28, 0.05–0.51), mean power by 3.5 ± 6.2% (from 8.30 ± 1.08 to 8.57 ± 1.12 W/kg, P = 0.044; ES = 0.36, 0.01–0.71) and blood lactate concentration by 20.9 ± 24.7% (from 12.4 ± 2.6 to 14.8 ± 4.0 mmol/L, P = 0.005; ES = 0.59, 0.16–1.02). However, caffeine did not modify the curve of muscle oxygen desaturation during exercise (lowest value was 23.1 ± 14.1 and 23.4 ± 14.1%, P = 0.940). Conclusion Caffeine’s ergogenic effect during short-term all-out exercise seems to be associated with an increased glycolytic metabolism with no influence of enhanced muscle oxygen saturation.post-print839 K

Acute p‑synephrine ingestion increases whole‑body fat oxidation during 1‑h of cycling at Fatmax

Purpose: p-Synephrine, the principal alkaloid of bitter orange (Citrus aurantium), is widely used in dietary supplements for weight loss due to its purported effect of increasing fat oxidation. However, there is a paucity of scientific information about its effectiveness in enhancing fat oxidation during exercise. The aim of this investigation was to determine the effect of an acute dose of p-synephrine on substrate oxidation during prolonged and constant intensity exercise. Methods: In a double-blind and randomized experiment, 14 healthy subjects performed two acute experimental trials after ingesting either p-synephrine (3 mg kg-1) or a placebo (cellulose). Energy expenditure and fat oxidation rates were continuously measured by indirect calorimetry during 1 h of continuous cycling at Fatmax, the intensity that induces maximal fat oxidation rate. Results: In comparison to the placebo, energy expenditure during 1 h of cycling remained unchanged with p-synephrine (698 ± 129 vs. 686 ± 123 kcal, P = 0.08). However, p-synephrine increased whole-body fat oxidation (33.6 ± 10.4 vs. 37.3 ± 9.8 g, P < 0.01) while also reducing carbohydrate oxidation (99.5 ± 30.4 vs. 85.0 ± 28.4 g, P < 0.01). However, the magnitude of the shift on substrate oxidation induced by p-synephrine was small. Conclusion: Acute ingestion of p-synephrine augments fat oxidation during prolonged and constant-intensity exercise

Time Course and Magnitude of Tolerance to the Ergogenic Effect of Caffeine on the Second Ventilatory Threshold.

Pre‐exercise caffeine ingestion has been shown to increase the workload at ventilatory threshold, suggesting an ergogenic effect of this stimulant on submaximal aerobic exercise. However, the time course of tolerance to the effect of caffeine on ventilatory threshold is unknown. This study aimed to determine the evolution of tolerance to the ergogenic effect of caffeine on the ventilatory threshold. Methods: Eleven participants (age 32.3 ± 4.9 yrs, height 171 ± 8 cm, body mass 66.6 ± 13.6 kg, VO2max = 48.0 ± 3.8 mL/kg/min) took part in a longitudinal, double‐blind, placebocontrolled, randomized, crossover experimental design. Each participant took part in two identical treatments: in one treatment, participants ingested a capsule containing 3 mg of caffeine per kg of body mass per day (mg/kg/day) for twenty consecutive days; in the other treatment, participants ingested a capsule filled with a placebo for the same duration and frequency. During these treatments, participants performed a maximal ramp test on a cycle ergometer three times per week and the second ventilatory threshold (VT2) was assessed by using the ventilatory equivalents for oxygen and carbon dioxide. Results: A two‐way ANOVA with repeated measures (substance x time) revealed statistically significant main effects of caffeine (p < 0.01) and time (p = 0.04) on the wattage obtained at VT2, although there was no interaction (p = 0.09). In comparison to the placebo, caffeine increased the workload at VT2 on days 1, 4, 6 and 15 of ingestion (p < 0.05). The size of the ergogenic effect of caffeine over the placebo on the workload at VT2 was progressively reduced with the duration of the treatment. In addition, there were main effects of caffeine (p = 0.03) and time (p = 0.16) on VO2 obtained at VT2, with no interaction (p = 0.49). Specifically, caffeine increased oxygen uptake at VT2 on days 1 and 4 (p < 0.05), with no other caffeine–placebo differences afterwards. For heart rate obtained at VT2, there was a main effect of substance (p < 0.01), while the overall effect of time (p = 0.13) and the interaction (p = 0.22) did not reach statistical significance. Heart rate at VT2 was higher with caffeine than with the placebo on days 1 and 4 (p < 0.05). The size of the effect of caffeine on VO2 and heart at VT2 tended to decline over time. Conclusion: Pre‐exercise intake of 3 mg/kg/day of caffeine for twenty days enhanced the wattage obtained at VT2 during cycling ramp tests for ~15 days of ingestion, while there was a progressive attenuation of the size of the ergogenic effect of caffeine on this performance variable. Therefore, habituation to caffeine through daily ingestion may reduce the ergogenic effect of this stimulant on aerobic exercise of submaximal intensity.post-print501 K

The Effect of Caffeine on the Velocity of Half-Squat Exercise during the Menstrual Cycle: A Randomized Controlled Trial

Recent literature confirms the ergogenic effect of acute caffeine intake to increase muscle strength and power in men. However, the information about the effect of caffeine on muscle performance in women is uncertain and it is unknown whether its ergogenicity is similar during the menstrual cycle. The goal of this investigation was to assess the effect of acute caffeine intake on mean and peak velocity of half-squat exercise during three different phases of the menstrual cycle. Thirteen trained eumenorrheic athletes (age = 31 ± 6 years; body mass = 58.6 ± 7.8 kg) participated in a double-blind, crossover and randomized experimental trial. In the early follicular (EFP), late follicular (LFP) and mid luteal phases (MLP), participants either ingested a placebo (cellulose) or 3 mg/kg/bm of caffeine in an opaque and unidentifiable capsule. In each trial, participants performed a half-squat exercise at maximal velocity with loads equivalent to 20%, 40% 60% and 80% of one repetition maximum (1RM). In each load, mean and peak velocity were measured during the concentric phase of the exercise using a rotatory encoder. In comparison to the placebo, a two-way ANOVA showed that the ingestion of 3 mg/kg/bm of caffeine increased mean velocity at 60% 1RM in EFP (Δ = 1.4 ± 2.7%, p = 0.04; ES: 0.2 ± 0.2) and LFP (Δ = 5.0 ± 10.4%, p = 0.04; ES: 0.3 ± 0.4). No other statistical differences were found for the caffeine-placebo comparison for mean velocity, but caffeine induced an ergogenic effect of small magnitude in all of the menstrual cycle phases. These results suggest that the acute intake of 3 mg/kg/bm of caffeine induces a small effect to increase movement velocity during resistance exercise in eumenorrheic female athletes. The positive effect of caffeine was of similar magnitude in all the three phases of the menstrual cycle