Whey and Soy Protein Supplementation in Football Players
Condition: Skeletal Muscle Damage; Muscle Damage; Athletic Performance
Study type: Interventional

Summary: 
      In a constant effort to find ways to make a quicker recovery between demanding workouts and
      football matches, this study is the first to investigate the benefits of protein
      supplementation, and compares two types of proteins, an animal-derived (whey) and a
      plant-derived (soy) protein, after an exercise-induced muscle injury caused by a speed
      endurance training protocol. Soy protein could be a cheaper and more environment-friendly
      alternative for athletes involved in high-velocity strength training.
    

Detailed description: 
      A randomized, three-trial (placebo vs. whey protein isolate vs. soy protein isolate
      consumption), cross-over, double-blind design.

        1. Baseline performance testing: Initially, volunteers will participate in a performance
           testing procedure at University facilities. These measurements include:

           A) measurement of descriptor variables: a) body composition (DXA), b) VO2max, c) Yo-Yo
           intermittent endurance level 2 (Yo-Yo IE2), d) Yo-Yo intermittent recovery test level 2
           (Yo-Yo IR2), e) technical skill level, f) daily dietary intake profile (over a 7-day
           period), g) gabitual physical activity level (over a 7-day period) and h) resting
           mtabolic rate (RMR).

           B) Measurement of dependent variables: a) isokinetic strength (concentric, eccentric)
           and maximal voluntary isometric contraction (MVIC) of knee extensors and flexors of both
           lower limbs, b) counter movement jump height (CMJ), c) repeated sprint ability (RSA), d)
           speed (10 and 30 m), e) delayed onset of muscle soreness (DOMS), f) blood sampling for
           measurement of lactate concentration, creatine kinase activity (CK) and inflammatory
           markers [i.e.Glutathione (GSH), total antioxidant capacity (TAC) and protein carbonyls
           (PC)].

        2. A 1-week adaptive period: based on a dietary analysis, participants will be given a
           dietary plan [taking into account the resting metabolic rate (RMR) and total daily
           physical activity related energy expenditure], providing a standard protein intake of
           0.8-1 g protein/kg/day over the 1-week adaptive period. This protein intake is accepted
           as the average and population-safe protein intake during periods of very low physical
           activity and/or exercise levels. RMR, daily dietary intake and physical activity will be
           measured before the adaptive period. Familiarization with the training protocol will
           take place during this phase.

        3. Participants will randomly participate in three trials including: whey protein (WP), soy
           protein (SP) and placebo (PL) supplementation:

             -  A 7-day pre-loading phase: A 7-day pre-loading phase will be applied prior to each
                trial, during which volunteers will receive the respective supplement (placebo,
                whey protein or soy protein). In WP and SP trials, participants will consume daily
                the appropriate amount of protein to reach a total protein intake of 1.5 g
                protein/kg body weight (BW).

             -  On the 7th day (end of pre-loading phase), participants will repeat performance
                testing (assessment of all dependent variables according to baseline testing) and
                blood sampling.

             -  On the 8th day, participants will perform the speed-endurance production training
                (SEPT) session 1 (1st trial). During training, participants internal (heart rate)
                and external load (total distance, speed zones, acceleration and decelerations,
                impacts) will be continuously monitored using heart rate monitors and global
                positioning system (GPS) instrumentation.

             -  Immediately after the training protocol: Determination of blood lactate
                concentration (3-4 minutes post-training) and assessment of MVIC (1 hour, 2 hours
                and 3 hours post-training).

             -  1-Day post-training (9th day; 24 hours post-training): Blood sampling (for the
                determination of CK, GSH, TAC and PC) and measurement of dependent variables (i.e.
                isokinetic strength, MVIC, Speed, RSA, CMJ and DOMS).

             -  2-Days post-training (10th day; 48 hours post-training): Blood sampling (for the
                determination of CK, GSH, TAC and PC) and assessment of DOMS. Thereafter, the SEPT
                session 2 will take place during which the particpants' internal and external load
                will be continuously monitored (as described in SEPT session 1).

        4. Wash-out period: 2-week without any activity or supplementation.

        5. 2nd trial: repeat of stages 3 and 4.

        6. 3rd trial: repeat of stage 3.
    

Intervention name(s): Whey protein; Soy protein; Placebo (maltodextrin)
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): Whey protein isolate supplementation, individually adjusted to reach a total protein intake of 1.5 g/kg body weight/day for 10 days (7 days pre-loading and 3 days during trials 1 and 2); Soy protein isolate supplementation, individually adjusted to reach a total protein intake of 1.5 g/kg body weight/day for 10 days (7 days pre-loading and 3 days during trials 1 and 2); Isoenergetic placebo (maltodextrin) for 10 days (7 days pre-loading and 3 days during trials 1 and 2
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double (Participant, Investigator)
Primary purpose: Basic Science