Contents lists available at ScienceDirect Physiology & Behavior journal homepage: www.elsevier.com/locate/physbeh Internal training load and its longitudinal relationship with seasonal player wellness in elite professional soccer Filipe Manuel Clemente a,b,⁎ , Bruno Mendes c , Pantelis Theodoros Nikolaidis d , Francisco Calvete c , Sandro Carriço c , Adam Lee Owen c,e a Instituto Politécnico de Viana do Castelo, Escola Superior de Desporto e Lazer, Melgaço, Portugal b Instituto de Telecomunicações, Delegação da Covilhã, Portugal c Benfica LAB, Sport Lisboa e Benfica, Lisbon, Portugal d Exercise Physiology Laboratory, Nikaia, Greece e Centre de Recherche et d'Innovation sur le Sport, Université Claude Bernard Lyon.1, Lyon, France ARTICLE INFO Keywords: Soccer Congested fixture Training RPE Monitoring ABSTRACT Monitoring internal training load has been extensively used and described within team sport environments, however when compared to internal physiological measures such as heart rate (HR) and rating of perceived exertion (RPE), the literature is sparse. The primary aim of this investigation study was to assess differences of playing position on ITL, session-RPE and wellness across two different training microcycles (1 vs. 2 competitive games), in addition with examining the relationship between ITL and Hooper's Index across an entire season. Thirty-five professional soccer players from the Portuguese premier league participated in the study (25.7 ± 5.0 years; 182.3 ± 6.4 cm; 79.1 ± 7.0 kg). Analysis of variance revealed higher values of DOMS (Means(M): 3.33 vs. 3.10; p = 0.001; effect Size (ES) = 0.087), fatigue (M: 3.18 vs. 2.99; p = 0.001; ES = 0.060) and HI (M: 11.85 vs. 11.56; p = 0.045; ES = 0.034) in 2-game weeks compared with 1-game weeks. Correlation between ITL and HI levels found significant negative correlations between ITL and DOMS (ρ = -0.156), ITL and sleep (ρ = -0.109), ITL and fatigue (ρ = -0.225), ITL and stress (ρ = -0.188), and ITL and HI (ρ = -0.238) in 2-game weeks. Results from 1-game microcycle only highlighted negative corre- lations between ITL and stress (ρ = -0.080). It was concluded from the study that greater fatigue potential, muscle soreness, stress and ITL was significantly more apparent within a 2-game microcycle. As a result, care should be taken when planning the lead into and out of a 2-game fixture microcycle highlighting key specific recovery strategies to damped the increased stress effect. Additionally, the potential utilization of squad rotation strategies may be a positive approach with aim of managing the fatigue effect. 1. Introduction Monitoring internal training load has been used extensively and well discussed in sports, especially in team sports [1]. Additionally, compared to internal physiological measures, such as heart rate (HR) and rate of perceived exertion (RPE), other measures of physiological status are less known. Recent literature has reported the use of the Hooper index [2] as a reliable method for the monitoring of athlete wellness providing further information concerning the detail of player fatigue, stress, muscle soreness and sleep perception. The Hooper index has recently been utilized to monitor player wellness during a 4-day FIFA international futsal tournament [2] in addition with a 2-month study on cycling performance [3]. However, apart from the aforemen- tioned studies, the relationship between use of the Hooper index and session-RPE is limited amongst the research. One investigation ob- served no association between the Hooper index and RPE [4], however, further research is needed in this subject to validate the findings fur- ther. Recent literature using team sport players competing in one game microcycle have shown that internal training load might be more in- tense towards the beginning of the microcycle as a way to ensure fa- tigue is minimal close to competitive match play [5–7] and a one- month mesocycle [8]. However, competing in 2-game microcycles oc- curs often in team sports such as soccer, when teams are more suc- cessful based on their need for domestic and European competition [6,9]. A recent study also suggests that there are evidences of a negative impact of a longitudinal fixture congestions cross the season [10]. Only a few studies have so far investigated the quantification of training of http://dx.doi.org/10.1016/j.physbeh.2017.06.021 Received 19 November 2016; Received in revised form 7 June 2017; Accepted 28 June 2017 ⁎ Corresponding author at: Complexo Desportivo e Lazer de Melgaço – Monte de Prado, 4960-320 Melgaço, Portugal. E-mail address: filipe.clemente5@gmail.com (F.M. Clemente). Physiology & Behavior 179 (2017) 262–267 Available online 28 June 2017 0031-9384/ © 2017 Elsevier Inc. All rights reserved. MARK