Cardiorespiratory and Metabolic Responses to Loaded Half Squat Exercise Executed at an Intensity Corresponding to the Lactate Threshold.

This study was designed to identify the blood lactate threshold (LT2) for the half squat (HS) and to examine cardiorespiratory and metabolic variables during a HS test performed at a work intensity corresponding to the LT2. Twenty-four healthy men completed 3 test sessions. In the first, their one-repetition maximum (1RM) was determined for the HS. In the second session, a resistance HS incremental-load test was performed to determine LT2. Finally, in the third session, subjects performed a constant-load HS exercise at the load corresponding to the LT2 (21 sets of 15 repetitions with 1 min of rest between sets). In this last test, blood samples were collected for lactate determination before the test and 30 s after the end of set (S) 3, S6, S9, S12, S15, S18 and S21. During the test, heart rate (HR) was telemetrically monitored and oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), respiratory exchange ratio (RER), ventilatory equivalent for O2 (VE·VO2 (-1)) and ventilatory equivalent for CO2 (VE·VCO2 (-1)) were monitored using a breath-by-breath respiratory gas analyzer. The mean LT2 for the participants was 24.8 ± 4.8% 1RM. Blood lactate concentrations showed no significant differences between sets 3 and 21 of exercise (p = 1.000). HR failed to vary between S6 and S21 (p > 1.000). The respiratory variables VO2, VCO2, and VE·VCO2 (-1) stabilized from S3 to the end of the constant-load HS test (p = 0.471, p = 0.136, p = 1.000), while VE and VE·VO2 (-1) stabilized from S6 to S21. RER did not vary significantly across exercise sets (p = 0.103). The LT2 was readily identified in the incremental HS test. Cardiorespiratory and metabolic variables remained stable during this resistance exercise conducted at an exercise intensity corresponding to the LT2. These responses need to be confirmed for other resistance exercises and adaptations in these responses after a training program also need to be addressed. Key pointsIt can be identified lactate threshold at half-squat.Exercise intensity is predominantly aerobic.The duration of the half-squat can be maintained over time, ~30 min of discontinuous exercise (21 sets, 15 repetitions, 1 min rest).Lactate threshold intensity may be suitable for older adults, sedentary individuals, patients or subjects with a lower functional capacity and even for resistance sports athletes.

Acute Physiological and Mechanical Responses During Resistance Exercise at the Lactate Threshold Intensity.

The purpose of this study was to examine acute metabolic, mechanical, and cardiac responses to half-squat (HS) resistance exercise performed at a workload corresponding to the lactate threshold (LT). Thirteen healthy subjects completed 3 HS exercise tests separated by 48-hour rest periods: a maximal strength or 1 repetition maximum (1RM) test, an incremental load test to establish the % 1RM at which the LT was reached, and a constant load test at the LT intensity. During the last test, metabolic, mechanical, and cardiac responses were monitored respectively through blood lactate concentrations, height (H), average power (AP) and peak power (PP) recorded in a countermovement jump test, and heart rate (HR). During the constant load test, lactate concentrations and HR remained stable whereas significant reductions were detected in H, AP, and PP (p ≤ 0.05). Only low correlation was observed between lactate concentrations and the H (r = 0.028), AP (r = 0.072), and PP (r = 0.359) losses produced. Half-squat exercise at the LT elicits stable HR and blood lactate responses within a predominantly aerobic metabolism, although this exercise modality induces significant mechanical fatigue.

Respuestas cardiorrespiratorias y metabólicas al ejercicio realizado sobre una plataforma de disipación de aire / Cardiorespiratory and metabolic responses to exercise performed on an air dissipation platform

Introducción: El objetivo del estudio fue analizar el efecto del ejercicio realizado sobre una plataforma de disipación de aire comparado con el mismo ejercicio en suelo en un grupo de mujeres sanas. Material y métodos: En un estudio cuasi-experimental 14 mujeres sanas de entre 20 y 25 años realizaron un mismo ejercicio en 2 condiciones diferentes separados entre sí por una semana; uno fue sobre una plataforma de disipación de aire y otro sobre el suelo. Durante las 2 pruebas se recolectaron los datos del intercambio respiratorio por un analizador de gases de circuito abierto. La frecuencia cardíaca (FC) fue registrada mediante telemetría. Muestras de sangre capilar (5 μl) fueron extraídas cada 10 min de ejercicio utilizando un analizador de lactato portátil. La percepción subjetiva del esfuerzo (RPE) fue registrada cada 10 min de ejercicio mediante la escala de Borg. Resultados: Hubo diferencias significativas en las variables de FC media (plataforma: 173,1 ± 13,6 lpm; suelo: 166,7 ± 14,1 lpm; z = 1,9; p < 0,05), ventilación (VE) media (plataforma: 58 ± 8,6 l/min; suelo: 54,4 ± 12,4 l/min; z = 1,7; p < 0,05), lactato en el minuto 20 (plataforma: 6,9 ± 2,4 mmol/l; suelo: 4,4 ± 1,9 mmol/l; z = 2,9; p < 0,01), en el minuto 30 (plataforma 7,1 ± 2,6 mmol/l; suelo: 5,0 ± 2,3 mmol/l; z = 2,4; p < 0,01) y en el minuto 40 (plataforma: 5,0 ± 1,9 mmol/l; suelo: 3,6 ± 1,6 mmol/l; z = 1,9; p < 0,05), sin encontrar diferencias significativas en el RPE durante toda la prueba. Conclusiones: La intensidad del ejercicio realizado sobre la plataforma de disipación de aire ante una misma sesión de ejercicio es mayor que la realizada sobre el suelo, teniendo unos valores similares en la percepción de esfuerzo

Introduction: The aim of the study was to analyze the effect of exercise performed on an air dissipation platform compared to the same exercise on the floor in a group of healthy women. Material and methods: In a quasi-experimental study 14 healthy women between 20 and 25 years performed exercises under two different conditions separated by one week, one was on an air dissipation platform and another on the floor. Respiratory exchange data were collected during the two tests using an open-circuit gas analyzer. Heart rate (HR) was recorded via telemetry. Capillary blood samples (5 μl) were taken every 10 minutes during the exercises using a portable lactate analyzer. The rated perceived exertion (RPE) was recorded every 10 minutes during the exercises using the Borg scale. Results: There were significant differences in mean HR variables (platform: 173.1 ± 13.6 bpm; floor: 166.7 ± 14.1 bpm; z = 1.9; P < 0.05), average ventilation (VE) (platform: 58 ± 8.6 L/min; floor: 54.4 ± 12.4 L/min; z = 1.7; P < 0.05), lactate in the 20th minute (platform: 6.9 ± 2.4 mmol/L; floor: 4.4 ± 1.9 mmol/L, z = 2.9; P < 0.01), 30th minute (platform: 7.1 ± 2.6 mmol/L; floor: 5.0 ± 2.3 mmol/L; z = 2.4; P < 0.01) and 40th (platform: 5.0 ± 1.9 mmol/L; floor: 3.6 ± 1,6 mmol/L; z = 1.9; P < 0.05), with no significant differences in RPE throughout the test. Conclusions: The intensity of exercise on the air dissipation platform with the same session of exercises is greater than that performed on the floor, with similar values in the perceived exertion