The study athlete was a 36-year-old, elite wheelchair marathoner, functional class T52 (upper limb involvement category). Some of his accolades include winning a silver medal at the Paralympic Games and 106 victories in assorted road events, including a win at the 2016 Boston Marathon, ten weeks after returning to sea level from Los Andes (Peruvian Altiplano). Our participant’s height = 1.76 m; body mass = 52.6 ± 0.4 kg; power output at second ventilatory threshold = 62 W; training 8000 km per year; former world record holder in the T52 division in 800 m (1 min:56 s); 1500 m (3 min:36 s); world record holder in 5000 m (12 min:37 s); half marathon (50 min:28 s) and fourth best ever time in marathon (1 h:42 min:05 s). Additionally, he has more than ten years of altitude training experience, with training camps performed in Boulder, CO (1655 m), Navacerrada, Spain (1858 m), Flagstaff, AZ (2106 m), Sierra Nevada, Spain (2320 m), Keystone, CO (2796 m) and Breckenridge, CO (2926 m), performing both altitude models: Live-High-Train-High (LHTH) and Live-High-Train-Low (LHTL) and has been exposed to more than 8000 h of normobaric-hypoxia. For the last five seasons prior to the current study, the athletes trained at moderate altitudes (1655 up to 2926 m) for: 78, 82, 101, 79 and 62 days.
The research participant provided written consent prior to participation in the current study and read the manuscript before submission. Research was approved by the Ethics Research Committee of the University Miguel Hernandez.
Training protocol
Both pre-altitude (B
N), at 16 m and acclimatization (B
H) at 3900 m incorporated identical training loads (128 km of mileage each). However, the first two days of B
H incorporated no training to minimize the effects of jet-lag, and acute mountain symptoms (AMS), like headache [
33]. Two daily training sessions were performed from Wednesday to Friday under the first ventilatory threshold (<VT1). The morning session involved 20 km of distance training and the afternoon session 16 km. A 20 km workout was performed on Saturday <VT1. Sunday was a rest day. Specific training weeks “W
1, W
2, W
3 & W
4” were based on a day-to-day basis periodization, according to level of heart rate variability (HRV) [
34]. When the HRV reached a reference value (RV), the subject completed a specific session in the morning, followed by an evening off. If the RV was not reached, two workouts <VT1 were performed: 20 km in the morning and 16 km in the afternoon. On three days the training was fixed; On Mondays and Thursdays the AM sessions were 16 km < VT1, while the PM sessions involved resistance training and Sundays were off. The specific sessions were known as: A (20 × 400 m at ~ second ventilatory threshold (VT2) in a plateau at 4090 m altitude; recovery reps: 75 s); B (30 km ~ VT1) and C (6 × 2000 m ~ VT2 in a plateau at 4090 m altitude; recovery reps: 120 s).
As a way to induce muscle hypertrophy, resistance sessions were performed at 80% of 1 RM [
35] with 4 sets of 8 reps with 150 s recovery, aimed at avoiding loss of muscle mass induced by chronic hypoxia. RM test was not performed under altitude conditions due to high risk of injury, so it was done four days before flying to Peru. More details on the experimental design have been reported previously [
11].
Nutritional program
The athlete was instructed by a nutritionist to prepare all meals which included weighing both ingredients prior to cooking and left overs prior to disposal. On days when the athlete ate at restaurants, which occurred on four occasions, he was instructed to send pictures of these meals to the research team [
37]. A personal chef was contacted to buy and cook all foods/ingredients for the athlete on a daily basis according to athlete instructions while the weighing and cooking process occurred under the athlete’s supervision. Additionally, the athlete was instructed to prepare all training drinks and post-training recovery solutions. To prevent contamination, the athlete did not eat raw foods or unpeeled fruits or vegetables and no water from the tap was consumed [
38]. At sea level the athlete cooked all meals at home.
Daily energy intake was increased ~ 20% from pre-altitude (B
N), to arrival at altitude (B
H) to avoid body mass loss from increased RMR which is common while living and training at higher altitudes [
2,
22]. Moreover, main meals were designed according to the type of training session performed (Fig.
2), as we have recently reported that during specific training weeks (W
1,2,3,4) number of A,B,C, sessions differed between specific training weeks, according to a training program based in HRV [
11], which explains why at W
2 the greatest amount of CHO was ingested (9.9 ± 1.2 g · kg
− 1 body mass), and why during B
H and W
4 the total amount of CHO tended to be lower than W
1,2,3 (
Table 2). Moreover, main meals were accompanied by two rich-carbohydrate snacks, based on reports that the inclusion of several rich carbohydrate snacks, more optimally covers increased energy requirements than three standalone main meals [
38]. Furthermore, regarding proteins, a minimum intake of 2.4 g · kg
− 1 body mass was targeted in the current nutritional design to avoid loss of lean mass [
39]. To avoid gastrointestinal issues (GI) and fullness [
40], a low protein/fat intake was provided for breakfast and PM sessions, however the percentage of lipids at lunch was lower than dinner. Protein intake at lunch and dinner were ≈ 1 g · kg
− 1, given that specific and, more demanding sessions (A,B,C) were performed in the morning, and muscle tissue repair is a main meal target. The ingestion of lipids was set at a minimum of 1 g · kg
− 1 body mass throughout the sea level and altitude camps, as fat cells increase their sensitivity to hormonal stimulation after training, resulting in a greater mobilization of fatty acids [
41]. Moreover, an Iso-Lyn Isotonic (AMIX) sports drink was used for workouts < VT1 shorter than 65 min (20 and 16 km). The athlete was instructed to drink a solution with 750 ml of water and 56.4 g of CHO, while a solution of 1250 ml with 80 g of CHO was recommended for specific sessions. The CHO rate was 0.5 to 1 g · kg
− 1 body mass per hour [
42]. Despite these recommendations, the athlete and team elected to preserve his natural drinking habits that involved consuming drinks every 10 min. This decision was made because fluid consumption for a wheelchair racer can be precarious during propulsion, as they must come out of their natural prone/kneeling body position to drink. This action can force loss of vision, which increases the risk of collision or crashing. Because our participant never experienced GI in his career with the use of carb gels [
43], he drank a 42 g CHO (Glucose + Fructose) Iso-Gel carbo snack (AMIX) during specific sessions workouts [
44]. Gels were consumed in the A session after fourteen 400 m rep, in the B session 90 min after starting, and in the C session after four 2000 m rep. Both types of carbs used in the solution and gels were multiple transportable carbohydrates, as directed by Jeukendrup [
45].
During gym sessions water was consumed ad libitum and immediately after gym sessions the athlete co-ingested a rich leucine whey protein (23.6 g) (Whey Fussion, AMIX) dissolved in 400 ml of water and a carbohydrate gel (Iso-Gel Recovery, AMIX) (37.6 g maltodextrin + fructose + Vitargo®) as directed for speeding up to 25% glycogen synthesis [
46]. For refueling purposes carbohydrate guidelines [
42], suggest aiming for post-exercise rapid recovery of muscle glycogen deposits, with 1 g · kg
− 1 body mass of CHO, repeated every 2–3 h. After specific sessions, a carbohydrate shake was taken with a carbohydrate gel, providing 1.4 g · kg
− 1 body mass. In the hour immediately after 16 km and 20 km < VT1, the subject drank a carbohydrate solution (Carbojet Gain, AMIX) (34 g CHO, 7.5 g prot, 1.8 g fat) dissolved in 400 ml of water, and after specific sessions he ingested a combination of the same drink plus Iso-Gel Recovery. To consider, 2.4 g · kg
− 1 body mass, CHO were consumed (Fig.
1) at lunch which occurred approximately two hours post-exercise meal, in order to achieve 3.1 g · kg
− 1 body mass of CHO 3 h post-exercise for our athlete vs. 3 g · kg
− 1 body mass as suggested by Burke and colleagues [
42].
On specific session days, rest was provided in the evenings along with a snack at 5:30 PM, to meet increased energy requirements [
38]. This snack included two 30 g cereal bars (Tri-Fit Bar, AMIX) (34.9 g CHO, 3.9 g prot, and 10.1 g fat).
In a manner to avoid loss of body mass [
32] and enhance muscle protein synthesis [
47] the athlete consumed 2.5 g leucine, 1.5 g isoleucine, and 1.5 g valine) immediately after each session (BCAA Elite Rate, AMIX). Before bedtime, 30 g of casein protein (Micellar Casein, AMIX) (1.7 g CHO, 24 g prot, 0.6 g fat) was ingested as suggested by Snijders and colleagues [
48].
Finally, the athlete maintained iron levels through a daily intake of 105 mg of ferrous sulphate (Ferogradumet®, Ross, Abbott Científica), as ferrous sulphate intake has been related to the production of Hemoglobin and red cells [
49,
50]. To comply with World Anti-Doping Agency (WADA) regulations, none of the aforementioned supplements contain prohibited substance.
For a description of the macronutrients intake during main meals in each session see Fig.
1.