A comparison between the cardiorespiratory responses of motorized and non-motorized treadmill protocols

Abstract

Maximal aerobic capacity (VO2max) can be considered an important performance determinant of distance runners’ performance due to endurance events being performed at high percentages of one’s VO2max. The protocol and running modality incorporated into the graded exercise test (GXT) needs to be considered when performing VOX2max tests on distance runners. The first objective of this study was thus to determine which motorized treadmill (MT) GXT protocol would allow elite male university-level distance runners to attain the highest cardiorespiratory responses (2maxOV•, time to exhaustion (Tlim), ventilatory threshold (VT), and respiratory compensation point (RCP)). Two GXT protocols were identified for this research study namely, the Adapted Incremental Speed Protocol (AISP) and the Incremental Speed and Incline Protocol (ISIP). The second objective of this research study was to determine which running modality, namely the MT or the Curve non-motorized treadmill (NMT), would elicit the highest cardiorespiratory responses. The AISP was compared to the Adapted Non-Motorized Incremental Speed Protocol (ANMIP). These objectives were achieved through a cross-sectional design by using elite male university-level distance runners. In order to fulfill these objectives, elite male university-level distance runners were recruited. Twelve runners (age: 21.8 ± 3.0 yrs.; stature: 178.2 ± 6.5 cm; and body weight: 66.7 ± 4.7 kg) from a university of the North West Province in South Africa participated in this research study. For the first objective of this study, results obtained by the two GXT protocols performed on the MT were compared. Maximal cardiorespiratory responses obtained, as well as all cardiorespiratory responses of each corresponding minute, were compared. The VO2max values attained by the ISIP (67.6 ± 5.0 vs. 65.0 ± 4.4 ml/kg/min) was statistically significantly higher (p<0.05) than the AISP despite the longer Tlim (11.4 ± 1.2 vs. 13.6 ± 1.2 min). Consequently the ISIP is recommended to be used for the determination of elite male university-level distance runners’ highest cardiorespiratory responses. Furthermore, GXT protocols with 1 km/h increases cannot be directly compared to GXT protocols with 1% increases in gradient and increments are advised to be adapted to enable more accurate comparison. For the second objective of this study, results obtained by the AISP and ANMIP, performed on the MT and Curve NMT respectively, were compared. Maximal cardiorespiratory responses, as well as all cardiorespiratory responses of each corresponding speed, were compared. From the results obtained, the ANMIP attained statistically significantly higher (p<0.05) VO2max values (66.7 ± 4.0 vs. 65.0 ± 4.4 ml/kg/min) than the AISP. These values were also attained within a significantly shorter time (8.31 ± 0.87 vs. 11.42 ± 1.19 min). Unfortunately, when determining the ANMIP’s intensity markers for exercise prescription, unrealistic VT and RCP values were attained. These values are not recommended for exercise prescription owing to the manifestation of the VO2max “slow component”. From results obtained by this study, it is clear that the ISIP is considered the more appropriate GXT protocol for elite male university-level distance runners. Use of the ISIP as standardized sport-specific GXT protocol by future coaches, elite male university-level distance runners and athletes’ supporting staff will make more accurate determination of VO2max values possible