We thank the reviewers for their positive comments. We improved the manuscript according to the they suggestions. All the changes are underline with the yellow colour in the manuscript. =====================Commento 1 ===================== General comment (originality, scientific accuracy, strengths and/or weaknesses): Originality: the aim is not new; good scientific accuracy. Strengths: attention to supplementation of athletes.Weaknesses: CUS in the evaluation of bone quality, and in the same time is useless in soccer players for at least two reasons: first they are very young (<24 yrs old) and second is well known that soccer is a protective factors for bone quality. Major corrections (main criticisms): No major criticismMinor corrections (page, paragraph, line where the author must make the corrections): Minor: please discuss the role of soccer in preventing bone quality and geometric properties. ANSWER: Thanks to the reviewer for this positive comment. As suggested, we added the role of soccer in preventing bone quality and geometric properties (page 3, lines 14-20).===================== Commento 2 ===================== General comment (originality, scientific accuracy, strengths and/or weaknesses): Overall this is a straightforward and well carried out pilot study of bone biochemical measures (i.e., serum parathyroid hormone, urinary calcium, serum Vitamin D etc.) in relation to joint, musculoskeletal injuries in 16 young adult male professional football players from October -May. Samples were obtained at the beginning (Oct) and end (May) of the season.Major corrections (main criticisms): the researchers indicate the participants had less than 10 hours/week of sunlight. This is not verified nor are the methods to determine sunlight exposure given (i.e., self-report, direct observation). Please provide these details in the manuscript methodology section. ANSWER:The sunlight exposure has been evaluated by using a self-report questionnaire

In competitive sports is important optimizing and improving the recovery-stress state. We aimed to investigate the overtraining syndrome in the football, modulating the agonistic training and evaluating the nutritional status of the young amateur soccer players, thought monitoring of the capacity of endurance and strength in a sample of twenty athletes between the ages of 18 and 33 (mean 22 +/-4.43 SD). Overtraining syndrome is a condition of physical, behavioural and emotional stress in sports and occurs when the physical activity is so intense as to prevent the athlete from performing a correct recovery totally eliminating the sense of fatigue. The athletes, from September 2016 to April 2017 were monitored with anthropometric tests (BMI calculation), nutritional tests (Recall test) and sportive (Cooper and Sargent test) to prevention of the overtraining syndrome with initial, intermediate and final measurements. Each player, during the observational period, performed normal athletic training sessions and participating two additional monthly sessions, for a total of sixteen sessions, with free overloads and, after intermediate verification, the exercises has been modified to reduce overtraining phenomenon. Tests initial results have been positive for defenders and midfielders while at the end of the search goalkeepers and forwards have significantly improved the performances. The total percentage increase of sample is around +/-4% and the study confirmed that by modulating the intensity of training and controlling the athletes' diet, it is possible to reduce or eliminate overtraining effects.

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