Soy protein and recovery after speed-endurance training in soccer players
What it found
In 10 male soccer players, raising daily protein to 1.5 g/kg with either soy or whey protein helped them keep up high-intensity running during a second speed-endurance session 48 hours later.
Neither protein changed most markers of muscle damage or recovery.
What they found
Studies in people
Field performance
During the second speed-endurance session, high-intensity running and high-speed running dropped in all trials, but the drops were smaller with whey and soy protein than with placebo. Maximum speed also fell less with both proteins.
Muscle damage markers
Delayed-onset muscle soreness and creatine kinase rose similarly in all trials after training and stayed elevated at 48 hours, with no differences between whey, soy and placebo.
Performance recovery
Isokinetic strength, maximal voluntary isometric contraction, 30-m speed, repeated sprint ability and countermovement jump all worsened similarly in all trials during recovery. Only 10-m speed was impaired at 24 hours in the placebo trial but not in the protein trials.
Redox status
Glutathione fell and total antioxidant capacity and protein carbonyls rose in all trials after training. Soy protein led to a faster recovery of protein carbonyls at 48 hours compared with whey and placebo.
Protein intake
Increasing daily protein to 1.5 g/kg through either whey or soy supplements helped maintain field performance during a second training session, but did not affect muscle damage or redox markers.
What the authors conclude
“In conclusion, increasing daily protein intake to 1.5 g/kg/day through either whey or soy protein supplementation facilitates recovery of field performance following speed-endurance training, in soccer players.”
Also in their conclusions
- They conclude that increasing daily protein intake to 1.5 g/kg/day through either whey or soy protein supplementation facilitates recovery of field performance following speed-endurance training in soccer players.
- They state that this effect was not related to an attenuation of exercise-induced muscle damage indices or oxidative stress.
- They propose that soy protein consumption may represent an efficient and cost-effective alternative to dairy proteins for recovery from soccer-specific high-intensity training.
How it was done
The authors wanted to see whether protein supplements could reduce muscle damage and speed up recovery after speed-endurance training in soccer players. They also wanted to compare whey protein with soy protein, since soy is a more sustainable option.
Ten well-trained male soccer players completed three trials in random order: whey protein, soy protein, or a placebo (maltodextrin). In each trial they pre-loaded for 7 days to reach a total protein intake of 1.5 g/kg/day (or 0.8-1 g/kg/day for placebo), then did two speed-endurance training sessions 48 hours apart, with performance, muscle damage and blood redox markers measured before, during and after.
What it can’t tell you
- This was a small study in 10 well-trained male soccer players, so the results may not apply to other people or to other types of training.
- The participants' total energy and protein intake were lower than recommended for soccer players during the in-season, which may have influenced the findings.
- The study cannot show whether these effects would be the same over a longer period or with different protein doses.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- University of Thessaly, Greece; Democritus University of Thrace, Greece; University of Southern Denmark, Denmark
The paper
- Title
- Effect of whey vs. soy protein supplementation on recovery kinetics following speed endurance training in competitive male soccer players: a randomized controlled trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Kritikos S, Papanikolaou K, Draganidis D, et al (2021). Effect of whey vs. soy protein supplementation on recovery kinetics following speed endurance training in competitive male soccer players: a randomized controlled trial. Journal of the International Society of Sports Nutrition. doi:10.1186/s12970-021-00420-wFree full textPubMed 33726784DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error