Introduction
There is a lack of information regarding the slow component of oxygen uptake (VO
2
sc) and efficiency/economy in resistance exercises despite the crucial role played in endurance performance.
Purpose
this study aimed to compare the VO
2
sc, efficiency/economy, metabolic, cardiorespiratory responses, rating of perceived effort and mechanical fatigue between cycling and half-squat (HS) exercises during a constant-load test at lactate threshold (LT
1
) intensity.
Methods
Twenty-one healthy men were randomly assigned in a crossover design to perform cycle-ergometer or HS tests. The order of the two cycle ergometer tests was an incremental test for determining load-intensity in watts (W) at LT
1
, followed by a constant-load test at the LT
1
intensity. For the three HS tests, the order was a 1RM test to determine the load (kg) corresponding to the 1RM percentages to be used during the second test, incremental HS exercise to establish the load (kg) at the LT
1
intensity, and finally, a constant-load HS test at the LT
1
intensity. A rest period of 48 h between each test was established. During the HS and cycle-ergometer constant-load tests, cardiorespiratory and metabolic responses were recorded. Lower limbs fatigue was determined by a jump test before and after the constant-load tests.
Results
A significant exercise mode × time interaction effect was detected in VO
2
, heart rate, energy expenditure (EE), gross efficiency (GE), and economy (
p
< 0.05). A significant and sustained VO
2
raise was confirmed in HS exercise (
p
< 0.05) and a steady-state VO
2
was revealed in cycle-ergometer. A higher GE and economy were obtained in HS test than in cycle-ergometer exercise (
p
< 0.001). In both exercises, a non-significant decrease was observed in GE and economy (
p
> 0.05). Lower limbs fatigue was only detected after constant-load HS test.
Conclusion
Although the VO
2
, heart rate and EE responses were higher in cycling exercise, the constant-load HS test induced a greater VO
2
sc and EE raise than the cycling test in a predominantly aerobic metabolism. These results could explain a decrease observed in jump performance only after HS test. GE and economy could benefit from the eccentric phase of the HS exercise.