INTRODUCTION Assessment of running economy (RE) is important for training monitoring in endurance running. Aim of this study is to investigate the validity of a continuous incremental test for assessing RE, a useful and economic tool to evaluate RE at different post-selected speeds. METHODS Four middle-distance runners (26,8 1,48 yr; 178,2 6,27 cm; 66,9 5,66 kg; VO2max: 66,8 4,85 mlxmin-1xkg-1 ) were recruited. Subjects performed two RE tests on a synthetic outdoor track: a continuous incremental test (CONT) and a constant-load incremental test (KLOAD). VO2 was monitored with a portable gas analyser (K4b2, Cosmed, Italy). In CONT initial running speed was set at 12 kmxh-1 and increased by 1 kmxh-1 every 400 m until exhaustion. VO2max and the velocity associated with it (MAV) were determined. The linear VO2 versus time relationship and its parameters were determined by fitting VO2 filtered data. In KLOAD subjects completed three 5-min stages at a speed of 70%, 80% and 90% of MAV. Validity of CONT was investigated with correlation analyses. RESULTS The relationship between running speeds in KLOAD and speeds eliciting the same VO2 in CONT appears to be strong (R2=0,93). The fitting line is parallel to the identity line, but shifted on the left, with an intercept of about 0,6 km/h. This indicates a delay of about 40-45 s in the response of VO2 to speed increase in CONT, probably due to the latency in adaptation of the aerobic system to increasing loads. This finding suggests to associate the speed of a stage with VO2 values elicited in the second half of that stage. Therefore, we performed two correlation analyses to relate VO2 associated with each stage of CONT with VO2 elicited by the same speeds in KLOAD. In the first analysis VO2 was computed as the mean of data in a 20-s period beginning from the middle of the stage. In the second analysis the mean VO2 value in the entire second half of the stage was considered, while the mean VO2 in the first half of the stage was associated with a velocity equal to vSTAGE -0,5 km/h. R2 was 0,92 in the first analysis and 0,94 in the second. The unexplained variance in this relationships may be due to sinusoidal oscillations in the linear course of VO2 versus running speed in CONT. CONCLUSIONS Our results show that the correct procedure to assess RE with CONT is to associate a stage’s speed to VO2 values averaged on the 2nd half of the same stage. The validity of this procedure is confirmed by correlation analyses.
A preliminary investigation of methods to determine running economy through a continuous incremental test
MERNI, FRANCO;DI MICHELE, ROCCO;
2009
Abstract
INTRODUCTION Assessment of running economy (RE) is important for training monitoring in endurance running. Aim of this study is to investigate the validity of a continuous incremental test for assessing RE, a useful and economic tool to evaluate RE at different post-selected speeds. METHODS Four middle-distance runners (26,8 1,48 yr; 178,2 6,27 cm; 66,9 5,66 kg; VO2max: 66,8 4,85 mlxmin-1xkg-1 ) were recruited. Subjects performed two RE tests on a synthetic outdoor track: a continuous incremental test (CONT) and a constant-load incremental test (KLOAD). VO2 was monitored with a portable gas analyser (K4b2, Cosmed, Italy). In CONT initial running speed was set at 12 kmxh-1 and increased by 1 kmxh-1 every 400 m until exhaustion. VO2max and the velocity associated with it (MAV) were determined. The linear VO2 versus time relationship and its parameters were determined by fitting VO2 filtered data. In KLOAD subjects completed three 5-min stages at a speed of 70%, 80% and 90% of MAV. Validity of CONT was investigated with correlation analyses. RESULTS The relationship between running speeds in KLOAD and speeds eliciting the same VO2 in CONT appears to be strong (R2=0,93). The fitting line is parallel to the identity line, but shifted on the left, with an intercept of about 0,6 km/h. This indicates a delay of about 40-45 s in the response of VO2 to speed increase in CONT, probably due to the latency in adaptation of the aerobic system to increasing loads. This finding suggests to associate the speed of a stage with VO2 values elicited in the second half of that stage. Therefore, we performed two correlation analyses to relate VO2 associated with each stage of CONT with VO2 elicited by the same speeds in KLOAD. In the first analysis VO2 was computed as the mean of data in a 20-s period beginning from the middle of the stage. In the second analysis the mean VO2 value in the entire second half of the stage was considered, while the mean VO2 in the first half of the stage was associated with a velocity equal to vSTAGE -0,5 km/h. R2 was 0,92 in the first analysis and 0,94 in the second. The unexplained variance in this relationships may be due to sinusoidal oscillations in the linear course of VO2 versus running speed in CONT. CONCLUSIONS Our results show that the correct procedure to assess RE with CONT is to associate a stage’s speed to VO2 values averaged on the 2nd half of the same stage. The validity of this procedure is confirmed by correlation analyses.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
