Differences between indoor and outdoor field cycling tests in triathletes are associated with training environment history and BMI: analysis and prediction formula.

Abstract

Background: Patients underwent cyclists and triathletes test, train, and race both indoors and outdoors. However, the differences between indoor and outdoor performance remain understudied. This study aimed to analyze the relationship between indoor and outdoor performance in cycling. We investigated the influence of training environment history (indoor vs. outdoor) and application of e-sport platform on the aforementioned relationship.

Methods: Forty-three well-trained triathletes performed indoor and outdoor field tests to establish maximum sprint power (MSP) and functional threshold power (FTP). The main effects for FTP and MSP were assessed by repeated-measures ANOVA to analyze the differences between power output obtained indoors and outdoors. Multiple covariates, including training environment history and application of ZWIFT e-sport platform, were applied. Multiple linear regression was performed to investigate outdoor FTP prediction based on indoor testing.

Results: No significant differences were found for MSP and FTP obtained indoors and outdoors. However, the high individual variability in the disparity between indoor and outdoor power output (PO) in triathletes was observed. There was a statistically significant interaction between FTP and training environment history (P<0.001 for FTP expressed in W*kg^-1 and W) and FTP and BMI (P=0.042 and P=0.034 for FTP expressed in W*kg^-1 and W, respectively). The prediction formulas to establish outdoor FTP based on indoor testing had high accuracy (R2 0.80 and 0.68 for full and simple model, respectively).

Conclusions: The study underlines the crucial role of the appropriate testing environment, corresponding to the training environment and racing demands. A high individual variability in the disparity between indoor and outdoor PO at FTP are associated with training environment history and BMI. No such interactions were found for MSP.