The effects of general fatigue induced by incremental exercise test and active recovery modes on energy cost, gait variability and stability in male soccer players Mohammadreza Mahaki a,b,⇑ , Raghad Mimar a , Heydar Sadeghi a,c , Mehdi Khaleghi Tazji a , Marcus Fraga Vieira d a Faculty of Physical Education and Sport Sciences, Kharazmi University of Tehran, Tehran, Iran b Faculty of Behavioural and Movement Sciences, VU University of Amsterdam, Amsterdam, The Netherlands c Kinesiology Research Center, Kharazmi University of Tehran, Tehran, Iran d Bioengineering and Biomechanics Laboratory, Federal University of Goiás, Goiânia, Brazil article info Article history: Accepted 5 May 2020 Keywords: General fatigue Maximum Lyapunov exponent Energy cost Active recovery Gait Soccer abstract The aerobic endurance is considered an important physiological capacity of soccer players which is examined by Incremental Exercise Test (IET). However, it is not clear how general fatigue induced by IET influences physiological and biomechanical gait features in soccer players and how players recover optimally at post-IET. Here, the effect of general fatigue induced by IET on energy cost, gait variability and stability in soccer players was investigated. To identify an optimal recovery mode, the effect of walking at Preferred Walking Speed (PWS), running at Individual Ventilation Threshold (IVT) (two active recovery modes), and Rest (a passive recovery mode) on aforementioned features were studied. Nine male players walked 4-min at PWS on a treadmill prior IET (PreT), which was followed by four 4-min walking trials (PosT-0, 1, 2, and 3) with three 4-min recovery intervals (PWS, IVT, or Rest) between them, in three sessions (one for each recovery mode) in a random order. Energy cost, gait variability and stability were examined at PreT (baseline), and at PosT-0, 1, 2, and 3 (intervals of respectively 0–4, 8–12, 16–20, 24–28 min at post-IET). Gait variabil- ity was assessed by the standard deviation of trunk angle and gait stability was assessed by the local dynamic stability of trunk angular velocity. Gait stability was not affected by IET, despite increases in gait variability and energy cost. Different from IVT, PWS and Rest recovery modes reduced energy cost at post-IET. Gait variability and energy cost recovered at PosT-1 and PosT-2, suggesting that 8–12 and 16–20 min recovery intervals, respectively, were required for returning to their baselines. No preference for active over passive recovery was found in terms of gait vari- ability and energy cost. Ó 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/). 1. Introduction There is no consensus on whether active or passive recovery modes are more effective after general fatigue. Passive recovery means recovery by resting (Van Hooren and Peake, 2018). Yet, could active recovery, i.e. recovery by submaximal exercise (Baldari et al., 2004; Menzies et al., 2010; Van Hooren and Peake, 2018), decrease recovery time? This is an important question for high level athletes who need to recover fast in order to continue their training. In this study, we looked at the effect of active and passive recovery modes after general fatigue in soccer players. Soccer players are examined by numerous tests and there has been an increasing focus on their physical capacities, such as endurance, isokinetic peak torque, and muscle strength and power in pre-season tests (Kalapotharakos et al., 2006; Wisloeff et al., 1998). _ VO 2max is considered to be the most important component of aerobic endurance performance and it has been reported that in elite soccer, _ VO 2max values greater than 60 ml.kg À1 .min À1 are required to play in-season matches (Wisloeff et al., 1998). https://doi.org/10.1016/j.jbiomech.2020.109823 0021-9290/Ó 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). ⇑ Corresponding author at: Faculty of Physical Education and Sport Sciences, Kharazmi University, Tehran, Iran. Faculty of Behavioural and Movement Sciences, VU University Amsterdam, Amsterdam, The Netherlands. E-mail addresses: mahaki.mr@gmail.com, m.mahaki@vu.nl (M. Mahaki). Journal of Biomechanics 106 (2020) 109823 Contents lists available at ScienceDirect Journal of Biomechanics journal homepage: www.elsevier.com/locate/jbiomech www.JBiomech.com