Consistency of sex-based differences between treadmill and overground running using an inertial measurement unit (IMU).

Differences in running gait between treadmill and overground running has been subject of study, while consistency of group differences between running surfaces has not been previously analysed. This study examined both the differences between running surfaces and the consistency of sex-based differences between surfaces in some spatiotemporal and kinematic variables measured by an inertial measurement unit fastened over the lumbar spine. Thirty-two (sixteen females) endurance runners firstly performed overground and then treadmill (1 % inclination) runs at speeds between 9-21 km∙h-1. Males showed lower flight time (FT) [moderate effect size (ES)] during treadmill running compared to overground, while females showed greater stride frequency (SF) (moderate ES), lower stride length (SL) (moderate ES), FT (moderate ES), and vertical (VT) trunk displacement (moderate ES), as well as greater medio-lateral (ML) trunk displacement (moderate ES). No differences in CT between surfaces were found (trivial to small). Furthermore, all the sex-differences were consistent between treadmill and overground running: Males showed lower SF (large and moderate ES, respectively), greater SL (large and moderate ES) and CT (moderate and large ES), lower FT (large ES), greater VT displacement (moderate to large ES), and lower ML displacement (moderate ES) than females. These results may be of interest to carefully transfer the running gait analyses between surfaces depending on sex.

Reliability of Xsens inertial measurement unit in measuring trunk accelerations: a sex-based differences study during incremental treadmill running.

Introduction: Inertial measurement units (IMUs) are utilized to measure trunk acceleration variables related to both running performances and rehabilitation purposes. This study examined both the reliability and sex-based differences of these variables during an incremental treadmill running test. Methods: Eighteen endurance runners performed a test-retest on different days, and 30 runners (15 females) were recruited to analyze sex-based differences. Mediolateral (ML) and vertical (VT) trunk displacement and root mean square (RMS) accelerations were analyzed at 9, 15, and 21 km·h-1. Results: No significant differences were found between test-retests [effect size (ES)<0.50)]. Higher intraclass correlation coefficients (ICCs) were found in the trunk displacement (0.85-0.96) compared to the RMS-based variables (0.71-0.94). Male runners showed greater VT displacement (ES = 0.90-1.0), while female runners displayed greater ML displacement, RMS ML and anteroposterior (AP), and resultant euclidean scalar (RES) (ES = 0.83-1.9). Discussion: The IMU was found reliable for the analysis of the studied trunk acceleration-based variables. This is the first study that reports different results concerning acceleration (RMS) and trunk displacement variables for a same axis in the analysis of sex-based differences.

Elovanoids Counteract Inflammatory Signaling, Autophagy, Endoplasmic Reticulum Stress, and Senescence Gene Programming in Human Nasal Epithelial Cells Exposed to Allergens.

To contribute to further understanding the cellular and molecular complexities of inflammatory-immune responses in allergic disorders, we have tested the pro-homeostatic elovanoids (ELV) in human nasal epithelial cells (HNEpC) in culture challenged by several allergens. ELV are novel bioactive lipid mediators synthesized from the omega-3 very-long-chain polyunsaturated fatty acids (VLC-PUFA,n-3). We ask if: (a) several critical signaling events that sustain the integrity of the human nasal epithelium and other organ barriers are perturbed by house dust mites (HDM) and other allergens, and (b) if ELV would participate in beneficially modulating these events. HDM is a prevalent indoor allergen that frequently causes allergic respiratory diseases, including allergic rhinitis and allergic asthma, in HDM-sensitized individuals. Our study used HNEpC as an in vitro model to study the effects of ELV in counteracting HDM sensitization resulting in inflammation, endoplasmic reticulum (ER) stress, autophagy, and senescence. HNEpC were challenged with the following allergy inducers: LPS, poly(I:C), or Dermatophagoides farinae plus Dermatophagoides pteronyssinus extract (HDM) (30 µg/mL), with either phosphate-buffered saline (PBS) (vehicle) or ELVN-34 (500 nM). Results show that ELVN-34 promotes cell viability and reduces cytotoxicity upon HDM sensitization of HNEpC. This lipid mediator remarkably reduces the abundance of pro-inflammatory cytokines and chemokines IL-1ß, IL-8, VEGF, IL-6, CXCL1, CCL2, and cell adhesion molecule ICAM1 and restores the levels of the pleiotropic anti-inflammatory IL-10. ELVN-34 also lessens the expression of senescence gene programming as well as of gene transcription engaged in pro-inflammatory responses. Our data also uncovered that HDM triggered the expression of key genes that drive autophagy, unfolded protein response (UPR), and matrix metalloproteinases (MMP). ELVN-34 has been shown to counteract these effects effectively. Together, our data reveal a novel, pro-homeostatic, cell-protective lipid-signaling mechanism in HNEpC as potential therapeutic targets for allergies.

Heat dissipating upper body compression garment: Thermoregulatory, cardiovascular, and perceptual responses.

PURPOSE: The aim of the present study was to determine the effects of an upper body compression garment (UBCG) on thermoregulatory responses during cycling in a controlled laboratory thermoneutral environment (~23°C). A secondary aim was to determine the cardiovascular and perceptual responses when wearing the garment. METHODS: Sixteen untrained participants (age: 21.3 ± 5.7 years; peak oxygen consumption (VO2peak): 50.88 ± 8.00 mL/min/kg; mean ± SD) performed 2 cycling trials in a thermoneutral environment (~23°C) wearing either UBCG or control (Con) garment. Testing consisted of a 5-min rest on a cycle ergometer, followed by 4 bouts of cycling for 14-min at ~50%VO2peak, with 1-min rest between each bout. At the end of these bouts there was 10-min of passive recovery. During the entire protocol rectal temperature (T rec), skin temperature (T skin), mean body temperature (T body), and heat storage (HS) were measured. Heart rate (HR), VO2, pH, hematocrit (Hct), plasma electrolytes, weight loss (W loss), and perceptual responses were also measured. RESULTS: There were no significant differences between garments for T skin, HS, HR, VO2, pH, Hct, plasma electrolyte concentration, W loss, and perceptual responses during the trial. T rec did not differ between garment conditions during rest, exercise, or recovery although a greater reduction in T rec wearing UBCG (p = 0.01) was observed during recovery. Lower T body during recovery was found when wearing UBCG (36.82°C ± 0.30°C vs. 36.99°C ± 0.24°C). CONCLUSION: Wearing a UBCG did not benefit thermoregulatory, cardiovascular, and perceptual responses during exercise although it was found to lower Tbody during recovery, which suggests that it could be used as a recovery tool after exercise.

Effects of Suspension Versus Traditional Resistance Training on Explosive Strength in Elementary School-Aged Boys.

PURPOSE: The aim of this study was to determine the effects of an 8-week program of resistance training (RT) or suspension training (ST) on explosive strength in prepubescent boys. METHODS: Fifty-seven boys aged 10-11 years were assigned to 2 training groups, RT or ST or a control group (no training program). Boys trained twice weekly for 8 weeks. RESULTS: A significant interaction was reported with a large (P < .001, ηp2=.463), medium (P < .001, ηp2=.395), and small effect sized (P ≤ .001, ηp2=.218) in the 1-kg ball throw, 3-kg ball throw, and time-at-20-m test, respectively. There was no significant interaction in the countermovement vertical jump or the standing long jump. Changes from preintervention to postintervention for the 1-kg ball throw were 5.94% and 5.82% for the ST and RT, respectively, and 8.82% and 8.14% in the 3-kg ball throw for the ST and RT, respectively. The improvement in the 20-m sprint was 1.19% for the ST and 2.33% for the RT. CONCLUSION: Traditional RT and ST seem to be effective methods for improving explosive strength in prepubescent boys. ST could be considered as an alternative modality to optimize explosive strength training in school-based programs.

Schoolbag weight carriage in Portuguese children and adolescents: a cross-sectional study comparing possible influencing factors.

BACKGROUND: Schoolbags and the consequences of carrying them, particularly those associated with overload, are often studied as a health concern. Modifications in gait and posture were reported when children carried loads that corresponded to more than 10% of their body weight (BW). The aims of this study were to verify the load that is carried by Portuguese students and how it is influenced by factors such as school grade, school schedule, lunch site, physical education, sex and body mass index (BMI). Acquiring a more specific knowledge of the Portuguese context and understanding the influence of these factors may allow us to generate proposals to control them in ways that benefit students. METHODS: The load carried by students in the 5th grade (10.6 ± 0.4 years) and 9th grade (14.7 ± 0.6 years) were weighed with a luggage scale on all days of the week, resulting in 680 evaluations. Data related to the school day were also collected, such as the student's lunch site, how he or she got to school and his or her school schedule for that day. Individual height and weight were also assessed. RESULTS: The 5th grade students carried greater loads than the 9th grade students, resulting in a substantial difference relative to their BW. The school loads of the 5th grade students were mostly greater than 10% of their BWs. Girls tended to carry heavier loads than boys, and overweight students also tended to carry heavier loads. Students who could eat lunch at home carried less weight, and on physical education days, the total load carried increased, but the backpacks of the 5th grade students were lighter. CONCLUSIONS: The results of the current study describe excessive schoolbag weight among Portuguese students and expound on some of the factors that influence it, which can help researchers and professionals design a solution to decrease children's schoolbag loads.

Upper Body Compression Garment: Physiological Effects While Cycling in a Hot Environment.

OBJECTIVE: The purpose of the present study was to investigate the effects of an upper body compression garment (UBCG) on physiologic and perceptual responses while cycling in a hot environment. METHODS: Twenty recreational road cyclists were pair-matched for age, anthropometric data, and fitness level (V̇O2max) and randomly assigned to a control (CON) group (n=10) of cyclists who wore a conventional t-shirt or to a group (n=10) of cyclists who wore UBCG. Test session consisted of cycling at a fixed load (~50% V̇O2max) for 30 minutes at an ambient temperature of ~40ºC (39.9±0.4ºC), followed by 10 minutes of recovery. RESULTS: Significantly greater (P = .002) rectal temperature (Trec) was observed at the end of exercise in the UBCG group (38.3±0.2ºC) versus CON group (37.9±0.3ºC). Significantly greater heart rate (HR) was observed in the UBCG group at minute 15 (P = .01) and at the end of exercise (187±9 vs 173±10 beats/min; P = .004) for UBCG and CON, respectively. Furthermore, participants who wore UBCG perceived a significantly greater (P = .03) thermal sensation at the end of exercise. During recovery HR and Trec remained significantly greater (P < .05) in the UBCG group. CONCLUSIONS: The use of an UBCG increased cardiovascular and thermoregulatory strain during cycling in a hot environment and did not aid during recovery.

Increased Thermoregulatory Strain When Wearing an Upper Body Compression Garment During Moderate Exercise in Trained Older Adults.

The efficacy of the use of an upper body compression garment (UBCG) as an ergogenic aid to reduce thermoregulatory strain in older adults remains unknown. The aim of this study was to evaluate the effects of UBCG on thermoregulatory, cardiorespiratory, and perceptual responses during cycling in a temperate environment (~25 °C, 66% rh) in trained older adults. Twelve cyclists aged 66 ± 2 years performed an intermittent 1-hr cycling trial at 50% of the peak power output followed by 10 min of passive recovery. Participants were provided with either commercially available UBCG or a control garment in a randomized order. UBCG increased thermoregulatory strain during exercise, as indicated by a significantly higher core temperature (38.1 ± 0.3 °C vs. 37.9 ± 0.3 °C; p = .04), body temperature (36.9 ± 0.2 °C vs. 36.7 ± 0.2 °C; p = .01), and thermal sensation (8.0 ± 0.4 vs. 7.5 ± 1.0; p = .02). These results suggest that the use of UBCG in trained older adults does not reduce the thermoregulatory strain during moderate exercise.

Running Performance While Wearing a Heat Dissipating Compression Garment in Male Recreational Runners.

Leoz-Abaurrea, I, Santos-Concejero, J, Grobler, L, Engelbrecht, L, and Aguado-Jiménez, R. Running performance while wearing a heat dissipating compression garment in male recreational runners. J Strength Cond Res 30(12): 3367-3372, 2016-The aim of this study was to investigate the effects of a heat dissipating compression garment (CG) during a running performance test. Ten male recreational runners (mean ± SD: age 23 ± 3 years; V[Combining Dot Above]O2max 55.8 ± 4.8 ml·kg·min) completed 2 identical sessions wearing either CG or conventional t-shirt (CON). Each trial included a 45-minute run at 60% of the peak treadmill speed (PTS) followed by a time to exhaustion (TTE) run at 80% of the PTS and a 10-minute recovery period. During the tests, thermoregulatory and cardiovascular responses were monitored. Participants wearing the CG displayed an impaired running performance (508 ± 281 vs. 580 ± 314 seconds, p = 0.046; effect size [ES] = 0.24). In addition, a higher respiratory exchange ratio (1.06 ± 0.04 vs. 1.02 ± 0.07, p = 0.01; ES = 0.70) was observed at TTE when wearing the CG in comparison to CON. Changes in core temperature did not differ between garments after the 45-minute run (p = 0.96; ES = 0.03) or TTE (1.97 ± 0.32 vs. 1.98 ± 0.38° C; p = 0.93; ES = 0.02) for CG and CON, respectively. During recovery, significantly higher heart rate and blood lactate values were observed when wearing CG (p ≤ 0.05). These findings suggest that the use of a heat dissipating CG may not improve running performance in male recreational runners during a running performance test to exhaustion.

Impaired cardiorespiratory responses when wearing an upper body compression garment during recovery in a hot environment (40 ºC).

BACKGROUND: Previous studies have not investigated the effects of a heat dissipating upper body compression garment (UBCG) during cycling in a hot environment. The present study examined the effects of a heat dissipating UBCG on thermoregulatory, cardiorespiratory and perceptual responses (thermal sensation and exertion scales), during cycling at a fixed workload (~50% VO2peak) and during active recovery (~25% VO2peak). METHODS: Thirteen untrained males (mean±SD; age 21±6 years, VO2peak 53.7±5.0 ml·kg-1·min-1) completed two randomized cycling trials consisting of a 5 min rest on a cycling ergometer, followed by 4 bouts of 14 min at a fixed load + 1 min active recovery. Followed further by 10 min of active recovery. Testing occurred in a hot environment (~40±0.4 ºC, 35±2 % relative humidity, ~2.5 m·s-1 air velocity) and volunteers wore either a UBCG or non-UBCG (CON). RESULTS: Wearing UBCG resulted in significantly smaller reduction in heart rate (31±11 bpm vs. 46±15 bpm) and higher VO2 and VCO2 values (P<0.05) during 10 min recovery period. No differences in rectal, skin and body temperature were observed during the trial between garment conditions. Clothing wetness sensation remained significantly higher wearing CON (P<0.05) during exercise although no significant differences in weight loss or in sweat rate were observed. CONCLUSIONS: These results suggest that wearing heat dissipating UBCG had no thermoregulatory benefits during exercise and it had impaired cardiorespiratory responses during active recovery when exercising in a hot environment.

A standard blood bank donation alters the thermal and cardiovascular responses during subsequent exercise.

BACKGROUND: The fear for adverse effects of blood donation on subsequent exercise may prevent physically active people from donating. We studied the impact of a standard blood bank donation (i.e., 450-mL blood withdrawal) on the thermoregulatory and cardiovascular responses to prolonged exercise in the heat. STUDY DESIGN AND METHODS: Eight moderately trained, heat-acclimated males cycled for 1 hour at 60% in a hot environment (34.9±0.6 °C) on four occasions: 1) 2 days before blood donation (CON), 2) 2 hours after donation (DON), 3) 2 days after donation (2 DAYS), and 4) 7 days after donation (7 DAYS). RESULTS: Two-thirds of the blood volume withdrawn was endogenously restored before exercise in the DON trial (p<0.05). DON started with increased preexercise rectal temperature (TRE; 0.42±0.1 °C above CON; p<0.05), which resulted in high levels of hyperthermia (i.e., 39.0±0.2 °C) after 1 hour of exercise. Skin temperature (34.5±0.1 °C) and sweat rate (1.15±0.1 L/h) were not affected by DON. However, DON lowered the skin blood flow:TRE relationship and elevated heart rate (HR) above CON (12±4 beats/min; p<0.05) maintaining cardiac output. After 2 DAYS, TRE and HR were restored to CON levels while cardiac output increased above CON (6%; p<0.05) in association with reduced hemoglobin concentration (i.e., peak hemodilution). CONCLUSION: A blood bank donation increases preexercise TRE. Subsequent exercise in a hot environment results in high levels of hyperthermia and HR. These thermoregulatory and cardiovascular perturbations observed during exercise disappear 2 days after donation.

Restoration of blood pH between repeated bouts of high-intensity exercise: effects of various active-recovery protocols.

To determine which active-recovery protocol would reduce faster the high blood H(+) and lactate concentrations produced by repeated bouts of high-intensity exercise (HIE). On three occasions, 11 moderately trained males performed 4 bouts (1.5 min) at 163% of their respiratory compensation threshold (RCT) interspersed with active-recovery: (1) 4.5 min pedalling at 24% RCT (S(HORT)); (2) 6 min at 18% RCT (M(EDIUM)); (3) 9 min at 12% RCT (L(ONG)). The total work completed during recovery was the same in all three trials. Respiratory gases and arterialized-blood samples were obtained during exercise. At the end of exercise, L(ONG) in comparison to S(HORT) and M(EDIUM) increased plasma pH (7.32 +/- 0.02 vs. approximately 7.22 +/- 0.03; P < 0.05), while reduced lactate concentration (8.5 +/- 0.9 vs. approximately 10.9 +/- 0.8 mM; P < 0.05). Ventilatory equivalent for CO(2) was higher in L(ONG) than S(HORT) and M(EDIUM) (31.4 +/- 0.5 vs. approximately 29.6 +/- 0.5; P < 0.05). Low-intensity prolonged recovery between repeated bouts of HIE maximized H(+) and lactate removal likely by enhancing CO(2) unloading.

Respiratory compensation and blood pH regulation during variable intensity exercise in trained versus untrained subjects.

To determine whether endurance-trained cyclists (T; n = 10) have a superior blood-respiratory buffering for metabolic acidosis relative to untrained subjects (UT; n = 10) during variable intensity exercise (VAR). On three occasions, T and UT pedaled for 24 min alternating high- and low-intensities as percentage of their second ventilatory threshold (VT2): VAR(LOW) 87.5-37.5% VT2, VAR(MODERATE) 125-25% VT2, and VAR(HIGH) 162.5-12.5% VT2 to complete the same amount of work. Before and just after each VAR trial, maximal cycling power (P(MAX)) was assessed. For each trial, the respiratory compensation for exercise acidosis (ventilatory equivalent for CO2) and the final blood pH, lactate and bicarbonate concentrations were similar for T and UT subjects. However, after VAR(HIGH), UT reduced P(MAX) (-14 +/- 1%; P < 0.05) while T did not. Our data suggest that endurance training confers adaptations to withstand the low pH provoked by VAR without losing cycling power, although this response is not due to differences in blood-respiratory buffering.

Separate and combined effects of airflow and rehydration during exercise in the heat.

PURPOSE: To determine whether airflow is required to obtain the beneficial effects of rehydration (thermoregulatory and cardiovascular) during exercise in dry heat. METHODS: Ten moderately trained (VO2max = 55 +/- 8 mL.kg(-1).min(-1)) heat acclimated males pedaled for 60 min at 60% VO2max in a hot-dry environment (36 +/- 1 degrees C; 29 +/- 2% relative humidity) on four different occasions: 1) without rehydration or forced airflow (control trial; CON); 2) rehydrating 100% of sweat losses by ingestion of a 6% carbohydrate-electrolyte solution (rehydration trial; REH); 3) receiving airflow at a velocity of 2.55 m.s(-1) (wind trial; WIND); and 4) combining airflow and rehydration (W + R). RESULTS: Without airflow, rehydration alone (REH) did not lower rectal temperature below CON (39.0 +/- 0.1 vs 39.1 +/- 0.1 degrees C at 60 min; respectively). However, with airflow, rehydration reduced final rectal temperature (38.8 +/- 0.1 vs 38.5 +/- 0.1 degrees C; P < 0.05; WIND vs W + R). In the trials with wind (WIND and W + R), skin temperature was reduced by about 0.6 degrees C (P < 0.05), and heart rate drift was prevented. In the trials with rehydration (REH and W + R trials), cardiac output (CO2-rebreathing technique) was maintained higher than CON (16.5 +/- 0.4 and 17.0 +/- 0.7 vs 15.4 +/- 0.4 L.min(-1), respectively; P < 0.05). CONCLUSION: When exercising in a hot-dry environment, airflow is required for rehydration to improve thermoregulation and cardiovascular function.

Performance at high pedaling cadences in well-trained cyclists.

PURPOSE: This study was conducted to determine the effect of high pedaling cadences on maximal cycling power output (W(max)). METHODS: Nine well-trained cyclists performed a continuous, incremental cycle-ergometer test to exhaustion (25 W increases every 3 min) either at 80, 100, or 120 rpm on three different occasions. RESULTS: W(max) was approximately 9% lower during 120 rpm in comparison with 80 and 100 rpm (335 +/- 9, 363 +/- 7, and 370 +/- 12 W, respectively; P < 0.05). During 120 rpm, ventilation rate (V(E)) increased above the increases in expired CO(2), which reduced the power output (PO) at the ventilatory anaerobic threshold (VT(2)) by 11% (P < 0.05). Gross efficiency (GE) did not differ among trials. At 120 rpm, capillary blood lactate concentration ([Lac]) increased above the 80-rpm trial (5.3 +/- 1.2 vs 3.0 +/- 0.7 mM at 300 W; P < 0.05), although pH was not reduced. At 120 rpm, expired CO(2) increased and reduced blood bicarbonate concentration ([HCO(3)(-)]) was reduced, maintaining blood pH similar to the other trials. CONCLUSION: A high pedaling cadence (i.e., 120 rpm) reduces performance (i.e., W(max)) and anaerobic threshold during an incremental test in well-trained cyclists. The data suggest that ventilatory anaerobic threshold (VT(2)) is a sensitive predictor of optimal pedaling cadence for performance, whereas blood pH or efficiency is not.

Mejora la biomecánica en el sprint en ciclismo: sistema bielas rotor(r) vs. sistema tradicional / Biomechanical improvement in sprint cycling: rotor(r) crank system vs. tradictional system

El propósito de este estudio fue examinar las diferencias entre el sistema de bielas Rotor® y el sistema tradicional (NOR) en la potencia, distancia recorrida y velocidad alcanzada durante un sprint de ciclismo. El sprint consistía en vencer desde el reposo la carga inercial del cicloergómetro Monark® (CI=8,72 Kgm2) acelerándola al máximo en 4 segundos. Reclutamos a 20 sujetos jóvenes, sanos y físicamente activos no ciclistas. Cada sujeto realizó dos días de test de familiarización previos a dos días de test experimental. Cada test (familiarización o experimental) consistía en 5 sprints de 4 segundos de duración con 2 minutos de recuperación activa entre ellos. En orden aleatorio, en uno de los días de test experimental se utilizaba NOR y en el otro Rotor® en 2 posiciones distintas. En una posición el eje de giro de las bielas se situó 7,75 mm por delante del eje de giro del plato, permitiendo así aumentar el par ejercido en la parte positiva de la pedalada (R+ PAR). En otra ocasión el eje de bielas se situó 7,75 mm por detrás del eje del plato, reduciendo el par (R-PAR). Un encoder absoluto conectado a la rueda midió los grados incrementados en cada milisegundo del test y con estos datos se calculó la potencia. La diferencia entre el máximo y el mínimo valor de potencia en cada pedalada fue menor con R-PAR que con NORy R+PAR. Con R-PAR se alcanzó una menor potencia instantánea máxima (Pi max) que con NOR y R+ PAR, pero la potencia media en la revolución más potente (Prev max) fue igual que NOR y ambas superiores a R+ PAR. Con R+ PAR se consigue alcanzar Pi y Prev max en menor tiempo pero se reduce la velocidad final alcanzada en comparación a los otros sistemas. En conclusión, el sistema Rotor® colocado en R-PAR permite desarrollar una Prev max y una velocidad máxima similar al sistema NOR en sujetos sin previa experiencia en ciclismo. Además Rotor® en R-PAR produce un efecto de suavizado en la aplicación de potencia en cada pedalada, pudiendo esto reducir la solicitación muscular durante sprints repetidos (AU)

the purpose of this study was to examine the differences between the new crank-set Rotor and the traditional system (NOR) in power, distance traveled and velocity achieved during a all-out cycling sprint. Starting from rest subjects were asked to sprint to overcame in 4 seconds the Monark cycloergometer´s inertial load (IL = 8m72 kgm2). We recruited 20 young, healthy and active males with no previous cycling experience. Each subject underwent two days of familiarization with the sprints prior to the two days of familiarization with the sprints prior to the two experimental days (...) (AU)

Efecto de la cadencia de pedaleo en el equilibrio ácido-base / Effect of pedaling rate on acid-base balance

El propósito de este estudio fue determinar el efecto de una frecuencia alta de pedaleo en el equilibrio ácido-base durante el ejercicio intenso. Para ello reclutarnos a 10 ciclistas sanos y entrenados aeróbicamente que realizaron tres pruebas incrementales (175 a 300 vatios aumentando 25 vatios cada 3 minutos) a una frecuencia de pedalada de 8O, 100 ó 120 revoluciones por minuto (rpm). El orden de las pruebas fue aleatorio y estuvieron separadas al menos por 48 horas entre ellas. Durante el último minuto de cada carga de trabajo se extrajo sangre capilar mediante punción en el dedo midiendo inmediatamente la concentración de bicarbonato ([HCO 3-1)1 lactato sanguíneo (Lac), pH y presión capilar de C02 (Pcap CO,). Durante toda la prueba se determinaron, el ritmo de ventilación (Ve), consumo de oxigeno(V02) producción de CO2 (VC02) y fracción de C02 al final de la espiración (FetCO 2) . A 120 rpm la Ve, fue significativamente mayor (P<0,05) que a 80 (todas las cargas) y 100 rpm (desde 225 a 300 vatios) debido a una mayor frecuencia respiratoria (Fr); (P<0,05). Pedalear a 120 rpm tendió a disminuir la Pcap CO2 y disminuyó la PaCO2 calculada (P<0,05). A 120 rpm el [La) el fue mayor que durante 100 y 80 rpm a 300 vatios (P<0,05), mientras que la concentracion de bicarbonato mostró una tendencia a disminuir evitando reducciones significativas del pH. En conclusión, frecuencias de pedaleo de 120 rpm aumentan la V, en comparación a 100 rpm y 80 rpm a cargas iguales. El incremento en Ve aumentó la excreción respiratoria de CO2 por encima de la producción metabólica, disminuyendo el nivel de Pcap CO2 (Hipernea- hipocápnica). Estos resultados sugieren que las contracciones a cadencias altas de pedaleo (120 rpm) generan señales que incrementan la Ve por encima del estímulo metabólico del CO2 posiblemente para prevenir descensos en el pH (AU)

Influencia del lugar de muestreo (DEDO-VENA) en los resultados de un test de lactato / Influence of sampling site (VEIN vs. CAPILLARY) on lactate threshold testing

El propósito de este estudio fue examinar las diferencias en la concentración de lactato durante un test de pedaleo incremental en intensidad entre la sangre extraída de una vena antecubital (VENA) y la sangre extraída de los capilares cutáneos de un dedo (DEDO) del mismo brazo. Para llevar a cabo el propósito del estudio se empleó una muestra de ocho sujetos sanos y activos con capacidades aeróbicas máximas similares (VOZ— de 57ñ4 ml.kg-1.min-1), todos ellos habituados al ejercicio físico en bicicleta. Cada uno de los sujetos realizó dos test de umbral de lactato en cicloergómetro, uno en ambiente caluroso (39ñ 1° C) y otro en un ambiente termoneutral (21 ñ2° C). El orden de la realización de las pruebas fue aleatorio. Partiendo del reposo en cada prueba se realizaron 5 estadios de pedaleo en cicloergómetro contra una resistencia creciente en 25 vatios cada 4 minutos hasta alcanzar una carga que provocase la aparición del umbral de lactato (225 vatios). Durante los últimos 30 segundos de cada estadio se extrajo sangre de la VENA y del DEDO de manera simultanea, y se procesaron y analizaron de manera idéntica. Se observó que para la misma intensidad de ejercicio, la concentración de lactato en DEDO era más elevada que la obtenida en VENA en todas las cargas de ejercicio (P<0.05). El ambiente caluroso disminuyó las diferencias entre DEDO y VENA y a 225 vatios solamente en la prueba termoneutral hubo una diferencia significativa (Figura 4). Los incrementos en carga de trabajo durante los primeros estadios de ejercicio (125,150 y 175 vatios) no consiguieron aumentar la concentración del lactato del DEDO que se mantuvo estable. Sin embargo, la concentración de lactato en VENA durante estos tres primeros estadios claramente aumentó en consonancia con el aumento de la carga. En conclusión, el lugar de extracción dela muestra de sangre (DEDO VENA) influye en la determinación gráfica del umbral de lactato (AU)