 
 
 1 
S5 Table. Results of round 1. 
 
Table A. Factors rated as ‘relevant’ in round 1 (level of agreement 70-100%), n=99. 
 
Factor 
Level of agreement 
(%) 
Training 
Endurance capacity 
96,3 
Maximal oxygen consumption 
100,0 
Economy of movement (=energy utilization) 
96,3 
Strength capacity 
70,4 
Power capacity 
85,2 
Lactate threshold 
96,3 
Lung volume 
77,8 
Heart volume 
85,2 
Recovery speed 
88,9 
Metabolism 
Glycolysis capacity (=break down of glucose) 
100,0 
Mitochondrial biogenesis (=growth of pre-existing 
mitochondria) 
100,0 
Myoglobin storage capacity (=iron/ oxygen-binding 
protein) 
88,9 
Thermogenesis (=production of heat in the body) 
70,4 
Angiogenesis (=formation of new blood vessels) 
85,2 
Fat metabolism (break down of fat for energy) 
88,9 
Lactate dehydrogenase metabolism 
85,2 
Lactate buffering system (=regulation of lactate level) 
96,3 
Body 
Weight / BMI 
88,9 
Total fat mass 
88,9 
Subcutaneous adipose tissue (=fat under the skin) 
70,4 
Lean mass (=mass of all organs except body fat 
including bones, muscles, blood, skin) 
88,9 
Tendon stiffness 
88,9 
Number of red blood cells (=erythrocytes) 
100,0 
Muscle fibres - hypertrophy capacity (=muscle growth) 
70,4 
Muscle fibres - type 1 vs. type 2a/b (=slow vs. fast twitch 
fibres) 
100,0 
Muscle fibres - transformation capacity (type 1 vs. type 
2) 
92,6 
Muscle fibres - contraction velocity capacity 
74,1 
Hormones 
Erythropoietin (EPO) level 
92,6 
Insulin-like growth factor-1 (IGF-1) level 
92,6 
 
2 
Growth hormone level 
92,6 
Cortisol level 
96,3 
Epinephrine level 
77,8 
Norepinephrine level 
77,8 
Testosterone level 
100,0 
Dihydrotestosterone level 
88,9 
Oestradiol level 
85,2 
Dehydroepiandrosterone level 
70,4 
Ghrelin level 
74,1 
Progesterone level 
77,8 
Follicle-stimulating hormone level 
70,4 
Gonadocorticoids level 
77,8 
Human chorionic gonadotropin level 
70,4 
Gonadotropin-releasing hormone level 
77,8 
Thyroid hormones level 
81,5 
Androstenedione level 
77,8 
Nutrition 
Valine level 
70,4 
Leucine level 
85,2 
L-carnitine level 
81,5 
Carnosine level 
77,8 
Creatine level 
81,5 
Carbohydrate metabolism 
100,0 
Saturated fat metabolism 
77,8 
Unsaturated fat metabolism 
74,1 
Cholesterol level 
74,1 
Omega 3 level 
74,1 
Omega 6 level 
70,4 
Vitamin A deficiency 
74,1 
Beta carotene deficiency 
77,8 
Vitamin B complex vitamins (B1-12) deficiency 
88,9 
Vitamin C deficiency 
77,8 
Vitamin D deficiency 
92,6 
Vitamin E deficiency 
74,1 
Folic acid deficiency 
77,8 
Iron deficiency 
100,0 
Zinc deficiency 
85,2 
Magnesium deficiency 
85,2 
Selenium deficiency 
74,1 
Caffeine metabolism 
81,5 
 
3 
Antioxidant level 
81,5 
Bicarbonate level 
77,8 
Cell hydration status 
88,9 
Electrolyte balance/ hydration status 
96,3 
Steroid metabolism 
92,6 
Immune 
system 
Detoxification process 
81,5 
Cytokine responses 
85,2 
Healing function of skeletal tissue 
88,9 
Healing function of soft tissue 
81,5 
Blood pressure regulation 
85,2 
Injuries 
Risk of left ventricular hypertrophy 
74,1 
Risk of metabolic myopathy 
70,4 
Risk of stress fractures 
85,2 
Risk of upper respiratory tract infections 
85,2 
Risk of non-functional overreaching 
88,9 
Risk of joint injuries 
88,9 
Psychological 
Stress resistance 
100,0 
Motivation capacity 
100,0 
Resilience capacity 
92,6 
Concentration capacity 
92,6 
Emotion regulation 
96,3 
Pain sensitivity 
96,3 
Self-control 
96,3 
Self-confidence 
100,0 
Risk of eating disorders 
85,2 
Environment 
Smoking behaviour 
74,1 
Alcohol usage 
85,2 
Sleep quality 
96,3 
Level of fatigue 
96,3 
Heat resistance capacity 
85,2 
Altitude training sensitivity 
85,2 
 
 
 
4 
Table B. Factors rated as ‘moderate’ in round 1 (level of agreement 40-69%), n=19. 
 
Factor 
Level of agreement 
(%) 
Training 
Speed capacity 
51,9 
Coordination capacity 
63,0 
Flexibility capacity 
59,3 
Metabolism 
Basal metabolism rate (=calories required to keep the 
body functioning at rest) 
59,3 
Creatine kinase metabolism 
55,6 
Body 
Regional fat mass 
66,7 
Visceral adipose tissue (=fat around internal organs) 
55,6 
Bone mineral density 
51,9 
Hormones 
Anti-Müllerian hormone level 
55,6 
Nutrition 
Vitamin K deficiency 
66,7 
Gluten intolerance 
55,6 
Lactose intolerance 
59,3 
Alcohol metabolism 
48,1 
Injuries 
Injuries Risk of lumbar disk degeneration 
59,3 
Injuries Risk of inguinal hernia 
55,6 
Psychological 
Aggression regulation 
66,7 
Risk of addiction 
66,7 
Intro vs. extroverted personality 
59,3 
Ability to differentiate 
66,7 
 
 
 
 
5 
Table C. Factors rated as ‘not relevant’ in round 1 (level of agreement 0-39%), n=2. 
 
Factor 
Level of agreement 
(%) 
Training 
Agility capacity 
25,9 
Reaction time 
14,8 
 
 
Table D. Proposed factors from round 1. 
(Sedentary) lifestyle in amateur athletes 
 
 
Table E. Free text comments from round 1. 
“For my studies, human muscle fibers are classified in 1, 2a and 2x. 2b fibers are present only in 
some animals, but not in human. Feel free to accept or not my suggestion, just a thought.” 
“List is complete” 
“Since I'm not an expert in hormonal function, my opinion of these factors might not be very 
accurate.” 
“Without incorporating a number of people, it would have taken some time to come to this list. On 
the opposite end, the list is very comprehensive, or is it just very long.” 
 

Factors associated with high-level endurance performance: An expert consensus derived via the Delphi technique.
Konopka, Magdalena J,Zeegers, Maurice P,Solberg, Paul A,Delhaije, Louis,Meeusen, Romain,Ruigrok, Geert,Rietjens, Gerard,Sperlich, Billy