Efectos de la ingesta aguda y prolongada de cafeína sobre el rendimiento neuromuscular

La cafeína (1,3,7 trimetilxantina) es una de las sustancias más consumidas en el mundo, a pesar de carecer de valor nutricional. En el ámbito deportivo, la administración de suplementos de cafeína es una estrategia muy utilizada para mejorar el rendimiento físico. Aproximadamente, 3 de cada 4 atletas de alto rendimiento tienen cafeína en la orina post-competición, indicativo de que utilizan suplementos de cafeína antes o durante la competición. Gran parte de la bibliografía sobre los efectos beneficiosos de esta sustancia en el ejercicio se ha centrado históricamente en el rendimiento aeróbico. Sin embargo, existe una falta de consistencia sobre la existencia de beneficios de la cafeína y su magnitud en el rendimiento neuromuscular que llega incluso a las revisiones sistemáticas, donde se han observado resultados contradictorios del beneficio de la cafeína a pesar de meta-analizar las mismas variables neuromusculares. Además, el análisis del efecto de la cafeína en el rendimiento neuromuscular se ha basado en investigaciones con una ingesta aguda mientras se desconoce el efecto de la ingesta prolongada de cafeína y la posible tolerancia desarrollada a esta sustancia. Asimismo, la literatura científica en este tema se ha basado en test neuromusculares y se desconoce el beneficio real de la suplementación con cafeína en situaciones de expresión de fuerza próximas a la situación deportiva real, como los entrenamientos de fuerza. Por ello, es necesario más información acerca del efecto de la cafeína en el rendimiento neuromuscular con el uso de una ingesta prolongada y en un contexto más ecológico, ya que rara vez se ha investigado el efecto de esta sustancia en deportes con una clara expresión de fuerza como son los saltos o los lanzamientos atléticos. El objetivo principal de esta Tesis Doctoral fue investigar y evaluar los efectos de la cafeína en el rendimiento neuromuscular, utilizando una ingesta aguda y prolongada de esta sustancia. Para cumplir este objetivo se planteó una revisión general de la literatura científica y cuatro investigaciones experimentales con un diseño de medidas repetidas mediante protocolos controlados con placebo, empleando una metodología doble ciego, aleatorizada y contrabalanceada

Acute caffeine supplementation enhances several aspects of shot put performance in trained athletes.

The aim of this investigation was to determine the effect of a moderate dose of caffeine (3 mg/kg/b.m.) on muscular power and strength and shot put performance in trained athletes. Methods. Thirteen shot putters (eight men and five women) participated in a double-blind, placebo-controlled, randomized experiment. In two different trials, participants ingested either 3 mg/kg/b.m. of caffeine or a placebo. Forty-five min after substance ingestion, athletes performed a handgrip dynamometry test, a countermovement jump (CMJ), a squat jump (SJ), and a maximum-velocity push-up. The athletes also performed three types of throws: a backwards throw, a standing shot put and a complete shot put. Results. In comparison with the placebo, caffeine ingestion increased CMJ height (32.25 ± 7.26 vs. 33.83 ± 7.72 cm, respectively; effect size (ES) = 0.82, p = 0.012; +5.0%;) and SJ height (29.93 ± 7.88 vs. 31.40 ± 7.16 cm; ES = 0.63, p = 0.042; +6.4%) and distance in the standing shot put (10.27 ± 1.77 m vs. 10.55 ± 1.94 m; ES = 0.87, p = 0.009; +2.6%). However, caffeine ingestion did not increase strength in the handgrip test, power in the ballistic push-up, or distance in the backwards throw (all p > 0.05). Shot put performance changed from 11.24 ± 2.54 to 11.35 ± . 2.57 m (ES = 0.33, p = 0.26; +1.0%), although the difference did not reach statistically significant differences. Caffeine ingestion did not increase the prevalence of side effects (nervousness, gastrointestinal problems, activeness, irritability, muscular pain, headache, and diuresis) in comparison with the placebo (p > 0.05). Conclusion. In summary, caffeine ingestion with a dose equivalent to 3 mg/kg/b.m. elicited moderate improvements in several aspects of physical performance in trained shot putters but with a small effect on distance in a complete shot put.post-print838 K

Effect of ambient temperature on fat oxidation during an incremental cycling exercise test.

Aim: The objective of this current research was to compare fat oxidation rates during an incremental cycling exercise test in a temperate vs. hot environment. Methods: Twelve healthy young participants were recruited for a randomised crossover experimental design. Each participant performed a VO2max test in a thermoneutral environment followed by two cycling ramp test trials, one in a temperate environment (18.3°C) and another in a hot environment (36.3°C). The ramp test consisted of 3-min stages of increasing intensity (+10% of VO2max) while gas exchange, heart rate and perceived exertion were measured. Results: During exercise, there was a main effect of the environment temperature on fat oxidation rate (F = 9.35, P = 0.014). The rate of fat oxidation was lower in the heat at 30% VO2max (0.42 ± 0.15 vs.0.37 ± 0.13 g/min; P = 0.042), 60% VO2max (0.37 ± 0.27 vs.0.23 ± 0.23 g/min; P = 0.018) and 70% VO2max (0.22 ± 0.26 vs.0.12 ± 0.26 g/min; P = 0.007). In addition, there was a tendency for a lower maximal fat oxidation rate in the heat (0.55 ± 0.2 vs.0.48 ± 0.2 g/min; P = 0.052) and it occurred at a lower exercise intensity (44 ± 14 vs.38% ± 8% VO2max; P = 0.004). The total amount of fat oxidised was lower in the heat (5.8 ± 2.6 vs 4.6 ± 2.8 g; P = 0.002). The ambient temperature also produced main effects on heart rate (F = 15.18, P = 0.005) and tympanic temperature (F = 25.23, P = 0.001) with no effect on energy expenditure (F = 0.01, P = 0.945). Conclusion: A hot environment notably reduced fat oxidation rates during a ramp exercise test. Exercising in the heat should not be recommended for those individuals seeking to increase fat oxidation during exercise.pre-print375 K

Caffeine Doses of 3 mg/kg Increase Unilateral and Bilateral Vertical Jump Outcomes in Elite Traditional Jiu-Jitsu Athletes.

Caffeine increases vertical jump, although its effects on kinetics and kinematics during different phases of bilateral and unilateral jumps remain unclear. The aim of this study was to identify the effects of 3 mg/kg on kinetic, kinematic and temporal variables in the concentric and eccentric phases of bilateral and unilateral countermovement jumps. A total of 16 Spanish national team traditional Jiu-Jitsu athletes took part in two experimental trials (3 mg/kg caffeine or placebo) in a randomized, double-blind crossover study. Sixty minutes after ingestion, bilateral and unilateral jumps were performed on a force platform. Compared to the placebo, caffeine increased bilateral jump height (p = 0.008; D% = 4.40), flight time (p = 0.008; D% = 2.20), flight time:contraction time (p = 0.029; D% = 8.90), concentric impulse (p = 0.018; D% = 1.80), peak power (p = 0.049; D% = 2.50), RSI-modified (p = 0.011; D% = 11.50) and eccentric mean braking force (p = 0.045; D% = 4.00). Additionally, caffeine increased unilateral RSI-mod in both legs (Left: p = 0.034; D% = 7.65; Right: p = 0.004; D% = 11.83), left leg flight time (p = 0.044; D% = 1.91), left leg jump height (p = 0.039; D% = 3.75) and right leg FT:CT (p = 0.040; D% = 9.72). Caffeine in a dose of 3 mg/kg BM in elite Jiu- Jitsu athletes is a recommended ergogenic aid as it increased performance of bilateral and unilateral vertical jumps. These increases were also accompanied by modified jump execution during the different phases of the countermovement prior to take-off.post-print746 K

Effects of 3 mg/kg Body Mass of Caffeine on the Performance of Jiu-Jitsu Elite Athletes.

The effects of caffeine were investigated in judo, boxing, taekwondo and Brazilian jiu-jitsu. However, this substance was never investigated regarding traditional jiu-jitsu. Therefore, the aim of this research was to analyze the effects of caffeine in the Special Judo Fitness Test (SJFT) and technical variables during combat in traditional jiu-jitsu elite athletes. Methods: Twenty-two young professionals of traditional jiu-jitsu, 11 men and 11 women (age = 22 ± 4 (18–33) years, body mass = 66.6 ± 10.8 (46.2–86.1) kg, height = 1.70 ± 0.9 (1.55–1.85) m) with 15 ± 7 years of experience in traditional jiu-jitsu, participated in a double-blind, counterbalanced, crossover study. In two different conditions, the traditional jiu-jitsu athletes ingested 3 mg/kg body mass of caffeine or a placebo. After 60 min, they performed the SJFT test to measure throwing performance, and subsequently, combat to analyze offensive and defensive hitting techniques. Results: Caffeine had a main effect on the number of throws during the SJFT test (P < 0.01). In addition, it was effective in sets 2 (13 ± 2 vs. 14 ± 2; p = 0.01) and 3 (12 ± 2 vs. 13 ± 1; p = 0.03). There was also a main effect during the test on heart rate when caffeine was ingested (F = 12.48, p < 0.01). The effects of caffeine were similar compared to the placebo condition regarding performance during combat both in offensive and defensive fighting variables Conclusions: the pre-exercise ingestion of 3 mg/kg body mass of caffeine increased performance in the SJFT test, decreased fatigue perception, and increased power and endurance perception in professionally traditional jiu-jitsu athletes. However, it did not seem to improve offensive and defensive technical actions during combat.post-print1054 K

Effects of p-Synephrine during Exercise: A Brief Narrative Review

p-Synephrine is the principal phytochemical found in bitter orange (Citrus aurantium). This substance is widely included in dietary supplements for weight loss/body fat reduction due to its potential benefits of increasing fat oxidation. For years, p-synephrine-containing dietary supplements have been marketed without proper knowledge of their true effectiveness to enhance fat utilization, especially when combined with exercise. However, the effects of p-synephrine on fat oxidation during exercise have been investigated in the last few years. The aim of the current discussion is to summarize the evidence on the effects of p-synephrine intake on fat oxidation and performance during exercise. Previous investigations have demonstrated that the acute intake of p-synephrine does not modify running sprint performance, jumping capacity, or aerobic capacity. However, the acute intake of p-synephrine, in a dose of 2–3 mg/kg of body mass, has been effective to enhance the rate of fat oxidation during incremental and continuous exercise. This effect has been observed in a range of exercise workloads between 30% and 80% of VO2peak. p-Synephrine has the ability to increase the maximal rate of fat oxidation during exercise of increasing intensity without affecting the workload at which maximal fat oxidation is obtained (Fatmax). The effect of p-synephrine of fat oxidation is normally accompanied by a concomitant reduction of carbohydrate utilization during exercise, without modifying the energy expended during exercise. The shifting in substrate oxidation is obtained without any effect on heart rate during exercise and the prevalence of adverse effects is negligible. Thus, the acute use of p-synephrine, or p-synephrine containing products, might offer some benefits for those individuals seeking higher fat utilisation during exercise at low-to-moderate intensities. However, more research is still necessary to determine if the effect of p-synephrine on fat oxidation during exercise is maintained with chronic ingestion, in order to ascertain the utility of this substance in conjunction with exercise pro-grammes to produce an effective body fat/weight loss reduction

Caffeine increases exercise intensity and energy expenditure but does not modify substrate oxidation during 1 h of self-paced cycling.

Aim Oral caffeine intake has been deemed as an effective supplementation strategy to enhance fat oxidation during aerobic exercise with a steady-state intensity. However, in real exercise scenarios, individuals habitually train with autoregulation of exercise intensity. This study aimed to analyze the effect of oral caffeine intake during self-paced cycling on autoregulated exercise intensity and substrate oxidation. Methods Fifteen young and healthy participants (11 men and 4 women) participated in a double-blind, randomized, cross-over investigation. Each participant took part in 2 experimental days consisting of pedaling for 1 h with a self-selected wattage. Participants were told that they had to exercise at a moderate intensity to maximize fat oxidation. On one occasion participants ingested 3 mg/kg of caffeine and on the other occasion ingested a placebo. Energy expenditure, fat oxidation rate, and carbohydrate oxidation rate were continuously measured during exercise by indirect calorimetry. Results In comparison to the placebo, caffeine intake increased the self-selected wattage (on average, 105 ± 44 vs 117 ± 45 W, respectively, P < 0.001) which represented a higher total work during the cycling session (377 ± 157 vs 422 ± 160 kJ, P < 0.001). Caffeine increased total energy expenditure (543 ± 161 vs 587 ± 155 kcal, P = 0.042) but it did not affect total fat oxidation (24.7 ± 12.2 vs 22.9 ± 11.5 g, P = 0.509) or total carbohydrate oxidation (87.4 ± 22.4 vs 97.8 ± 32.3 g, P = 0.101). Conclusion Acute caffeine ingestion before an exercise session with an individual's freedom to regulate intensity induces a higher self-selected exercise intensity and total work. The selection of a higher exercise intensity augments total energy expenditure but eliminates the effect of caffeine on substrate oxidation during exercise.pre-print418 K

Pre-exercise Caffeine Intake Enhances Bench Press Strength Training Adaptations

Previous research has identified acute caffeine intake as an effective ergogenic aid to enhance velocity and power during bench press exercise. However, no previous investigation has analyzed the effects of chronic intake of caffeine on training adaptations induced by bench press strength training. Thus, the aim of this investigation was to determine the effects of pre-exercise caffeine intake on training adaptations induced by a bench press training protocol. Using a double-blind, randomized experimental design, 16 healthy participants underwent a bench press training protocol for 4 weeks (12 sessions). Seven participants ingested a placebo and nine participants ingested 3 mg/kg/BM of caffeine before each training session. Three days before, and 3 days after the completion of the training protocol, participants performed a one-repetition maximum (1RM) bench press and force-velocity test (from 10 to 100% 1RM). From comparable pre-training values, the strength training similarly increased 1RM in the caffeine and placebo groups (+13.5 ± 7.8% vs. +11.3 ± 5.3%, respectively; p = 0.53). In the caffeine group, the strength training induced a higher mean velocity at 40%, (0.81 ± 0.08 vs. 0.90 ± 0.14 m/s), 60% (0.60 ± 0.06 vs. 0.65 ± 0.06 m/s), 70% (0.47 ± 0.05 vs. 0.55 ± 0.06 m/s), 80% (0.37 ± 0.06 vs. 0.45 ± 0.05 m/s), 90% (0.26 ± 0.07 vs. 0.34 ± 0.06 m/s), and 100% 1RM (0.14 ± 0.04 vs. 0.25 ± 0.05 m/s; p < 0.05) while the increases in the placebo group were evident only at 30 (0.95 ± 0.06 vs. 1.03 ± 0.07 m/s), 70% (0.51 ± 0.03 vs. 0.57 ± 0.05 m/s) and 80% 1RM (0.37 ± 0.06 vs. 0.45 ± 0.05 m/s) (p < 0.05). The placebo group only increased peak velocity at 60 and 70% 1RM (p < 0.05) while peak velocity increased at 10%, and from 30 to 100% 1RM in the caffeine group (p < 0.05). The use of 3 mg/kg/BM of caffeine before exercise did not modify improvements in 1RM obtained during a 4 week bench press strength training program but induced more muscle performance adaptations over a wider range of load

Positional differences in the most demanding conditional phases in female football competition

El objetivo de este estudio fue analizar las demandas de los períodos de máxima exigencia condicional (PMI) en partidos de competición oficial de fútbol femenino. 18 jugadoras profesionales (1ª División española, Liga Iberdrola) participaron en este estudio. Las jugadoras fueron analizadas en función del puesto específico: defensas centrales (DC), defensas laterales (DL), medios centros (MC), medios de banda (MB) y delanteras (DE). Se registraron los PMI en 3 ventanas temporales (1, 5, y 10 minutos), durante 15 partidos de competición oficial por medio de dispositivos GPS (10 Hz), y en función de cuatro variables de estudio: distancia total recorrida (DR), distancia sprint (D-SP>21km·h-1), distancia recorrida a alta potencia metabólica (D-APM>20w·kg-1) y acceleration density (AD). Además, se valoró el número de ocurrencias sub-máximas (intensidad>85% del PMI) en cada ventana temporal. Las DC y DE alcanzaron valores de DR significativamente menores que MC en todas las ventanas temporales. Mientras que las MC reflejaron valores de D-SP significativamente inferiores a DL, MB y DE en todas las ventanas temporales. Además, las DC obtuvieron valores significativamente menores de D-APM que DL, MC, MB y DE (ventanas temporales de 5´ y 10´). Respecto a AD, las DC, MC y DE alcanzaron valores significativamente inferiores a DL y MB (ventana temporal 1´). El número de ocurrencias sub-máximas en competición fue significativamente menor en las variables D-SP y D-APM en comparación con DR y AD en todas las ventanas temporales. Estos resultados podrían servir como referencia en el diseño de tareas de entrenamiento, que tengan como objetivo la simulación de los requerimientos condicionales de PMI.The purpose of this study was to analyze the demands of maximum conditional requirements periods (PMI) in official women’s competition football matches.18 professional players (1ª Spanish Division, Liga Iberdrola) participated in this study. Players were analyzed depending on their specific position: central defender (DC), lateral defender (DL), midfield player (MC), midband (MB) and forward (DE). PMI were registered in 3 time windows (1, 5 and 10 minutes), in 15 official competition matches by GPS devices (10 Hz) and based on four study variables: total distance covered (DR), sprint-distance (D-SP>21km·h-1), high metabolic load distance (D-APM>20w·kg-1) and acceleration density (AD). In addition, the number of sub-maximal occurrences (intensity >85% PMI) in each time window was assessed. DC and DE reached values significantly lower than MC in all analyzed time windows. While the MC reflected D-SP values significantly lower than DL, MB and DE in all time windows. Moreover, the DC reached D-APM values significantly lower than DL, MC, MB and DE (time windows 5’ and 10’). Regarding AD, the DC, MC and DE reached values significantly lower than DL and MB (time window 1’). The number of sub-maximal occurrences in competition was significantly lower in the D-SP and D-APM variables, compared to DR and AD in all time windows. These results could serve as a reference in the design of training tasks, aimed at simulating of PMI conditional requirement

The Long Way to Establish the Ergogenic Effect of Caffeine on Strength Performance: An Overview Review

This overview review aimed to describe the evolution of the characteristics of the research on caffeine effects on strength. A total of 189 experimental studies with 3459 participants were included. The median sample size was 15 participants, with an over-representation of men vs. women (79.4 vs. 20.6%). Studies on young participants and elders were scarce (4.2%). Most studies tested a single dose of caffeine (87.3%), while 72.0% used doses adjusted to body mass. Single-dose studies ranged from 1.7 to 7 mg/kg (4.8 &plusmn; 1.4 mg/kg), while dose&ndash;response studies ranged from 1 to 12 mg/kg. Caffeine was mixed with other substances in 27.0% of studies, although only 10.1% of studies analyzed the caffeine interaction with these substances. Capsules (51.9%) and beverages (41.3%) were the most common forms of caffeine administration. Similar proportions of studies focused on upper (24.9%) or lower body strength 37.6% (37.6% both). Participants&rsquo; daily intake of caffeine was reported in 68.3% of studies. Overall, the pattern in the study of caffeine&rsquo;s effects on strength performance has been carried out with experiments including 11&ndash;15 adults, using a single and moderate dose of caffeine adjusted to participants&rsquo; body mass in the form of a capsule