 
 
 1 
S6 Table. Results of round 2. 
Table A. Factors rated as ‘relevant’ in round 2 (level of agreement 70-100%), n=24. 
 
Factor 
Level of agreement 
(%) 
Training 
Maximal oxygen consumption 
94,4 
Economy of movement (=energy utilization) 
88,9 
Lactate threshold 
88,9 
Metabolism 
Glycolysis capacity (=break down of glucose) 
100,0 
Mitochondrial biogenesis (=growth of pre-existing 
mitochondria) 
88,9 
Lactate buffering system (=regulation of lactate level) 
88,9 
Fat metabolism (break down of fat for energy) 
88,9 
Body 
Number of red blood cells (=erythrocytes) 
100,0 
Muscle fibres - type 1 vs. type 2a/x (=slow vs. fast twitch 
fibres) 
94,4 
Hormones 
Testosterone level 
94,4 
Cortisol level 
77,8 
Erythropoietin (EPO) level 
83,3 
Nutrition 
Carbohydrate metabolism 
100,0 
Iron deficiency 
94,4 
Electrolyte balance/ hydration status 
77,8 
Vitamin D deficiency 
72,2 
Immune 
system 
Healing function of skeletal tissue 
88,9 
Injuries 
Risk of non-functional overreaching 
88,9 
Risk of stress fractures 
77,8 
Psychological 
Stress resistance 
88,9 
Motivation capacity 
94,4 
Self-confidence 
72,2 
Environment 
Sleep quality 
94,4 
Level of fatigue 
77,8 
 
 
 
2 
Table B. Factors rated as ‘moderate’ in round 2 (level of agreement 40-69%), n=22. 
 
Factor 
Level of agreement 
(%) 
Training 
Endurance capacity 
61,1 
Recovery speed 
61,1 
Metabolism 
Angiogenesis (=formation of new blood vessels) 
50,0 
Body 
Muscle fibres - transformation capacity (type 1 vs. type 
2) 
55,6 
Weight / BMI 
44,4 
Total fat mass 
50,0 
Lean mass (=mass of all organs except body fat 
including bones, muscles, blood, skin) 
44,4 
Tendon stiffness 
55,6 
Hormones 
Insulin-like growth factor-1 (IGF-1) level 
55,6 
Growth hormone level 
66,7 
Nutrition 
Vitamin B complex vitamins (B1-12) deficiency 
50,0 
Immune 
system 
Blood pressure regulation 
50,0 
Healing function of soft tissue 
50,0 
Injuries 
Risk of joint injuries 
66,7 
Risk of upper respiratory tract infections 
61,1 
Psychological 
Emotion regulation 
66,7 
Pain sensitivity 
44,4 
Self-control 
50,0 
Resilience capacity 
50,0 
Concentration capacity 
44,4 
Environment 
Heat resistance capacity 
50,0 
Altitude training sensitivity 
55,6 
 
 
 
3 
Table C. Factors rated as ‘not relevant’ in round 2 (level of agreement 0-39%), n=54. 
 
Factor 
Level of agreement 
(%) 
Training 
Power capacity 
33,3 
Heart volume 
33,3 
Lung volume 
16,7 
Strength capacity 
16,7 
Metabolism 
Myoglobin storage capacity (=iron/ oxygen-binding 
protein) 
33,3 
Lactate dehydrogenase metabolism 
33,3 
Thermogenesis (=production of heat in the body) 
5,6 
Body 
Muscle fibres – contraction velocity capacity 
11,1 
Subcutaneous adipose tissue (=fat under the skin) 
16,7 
Muscle fibres – hypertrophy capacity (=muscle growth) 
11,1 
Hormones 
Dihydrotestosterone level 
11,1 
Oestradiol level 
33,3 
Thyroid hormones level 
27,8 
Epinephrine level 
11,1 
Norepinephrine level 
11,1 
Progesterone level 
11,1 
Gonadocorticoids level 
11,1 
Gonadotropin-releasing hormone level 
22,2 
Androstenedione level 
11,1 
Ghrelin level 
5,6 
Dehydroepiandrosterone level 
5,6 
Follicle-stimulating hormone level 
11,1 
Human chorionic gonadotropin level 
5,6 
Nutrition 
Steroid metabolism 
33,3 
Cell hydration status 
33,3 
Leucine level 
22,2 
Zinc deficiency 
27,8 
Magnesium deficiency 
38,9 
L-carnitine level 
5,6 
Creatine level 
22,2 
Caffeine metabolism 
33,3 
Antioxidant level 
22,2 
Carnosine level 
16,7 
Saturated fat metabolism 
11,1 
Beta carotene deficiency 
11,1 
 
4 
Vitamin C deficiency 
22,2 
Folic acid deficiency 
16,7 
Bicarbonate level 
27,8 
Unsaturated fat metabolism 
16,7 
Cholesterol level 
22,2 
Omega 3 level 
16,7 
Vitamin A deficiency 
11,1 
Vitamin E deficiency 
11,1 
Selenium deficiency 
11,1 
Valine level 
5,6 
Omega 6 level 
11,1 
Immune 
system 
Cytokine responses 
27,8 
Detoxification process 
11,1 
Injuries 
Risk of left ventricular hypertrophy 
27,8 
Risk of metabolic myopathy 
11,1 
Psychological 
Risk of eating disorders 
16,7 
Environment 
Alcohol usage 
22,2 
Smoking behaviour 
11,1 
Proposed item 
(Sedentary) lifestyle in amateur athletes 
16,7 
 

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