Strength and Fitness - The Impartial Guide to strength, fitness, endurance and nutrition

Whey protein isolate improves recovery following endurance exercise

Posted on Monday, 1 April, 2013 by anthony

One area of nutrition often overlooked by endurance athletes is the importance of adequate protein consumption for effective recovery between and after endurance training workouts. Recently researchers (Hill et al., 2013) looked at the effect of consuming either a high or normal amount of protein on markers of endurance training adaptations and recovery, following endurance exercise in a group of six healthy endurance trained cyclists and triathletes (age 29 ± 4 years, weight 74 ± 2 kg, VO2 max 63 ± 3 ml/kg/min, height 183 ± 5 cm;).

 About the research:

The dietary intervention: The researchers divided the subjects into two groups and both underwent a 16-day dietary intervention in which they were provided with all their meals and snacks. The two dietary interventions contained the same total calories and amount of carbohydrate (8g per kg/bodyweight/day), the only differences were the proportions of protein and fat in the diet – the high protein diet group consumed twice the amount of protein (2.4g vs 1.2g per kg/bodyweight/day) whilst the normal protein intake group had increased fat intake to ensure they consumed the same total calories as the high protein group (1.7g vs 1.1g per kg/bodyweight/day). The extra 1.2g kg/bw/day protein was provided through a sports drink containing whey protein isolate. Following 14-days of dietary intervention both groups underwent a 2-day carbohydrate loading phase in which carbohydrate intake was increased to 10g per kg/bw/day (both groups) – the protein and fat intakes were maintained at the same level as the first 14-days of the dietary intervention.

The two dietary interventions:

Whey protein isolate endurance training




The exercise tests: Prior to the dietary intervention subjects undertook a laboratory test, consisting of 3 sub-maximal workloads followed by an incremental test (25-watt increments every minute) to establish workloads for the post dietary intervention exercise trial. The exercise trial consisted of 60 minutes at 70% VO2max followed by 2mins rest and then exercise to failure at 90% of VO2max. Following the completion of the exercise trial subjects remained in the lab for a 6-hour recovery period. During the recovery period they consumed a recovery drink containing the same amount of carbohydrate (4g kg/bw) but different amounts of protein (1.1g vs 0.4g kg/bw in the high and normal protein groups respectively) and fat (0.4g vs 0.6g kg/bw in the high and normal protein groups respectively).

What the researchers found:

  • Muscle glycogen levels were not significantly different between the two groups either before during or after exercise. However, the rate of glycogen re-synthesis was enhanced after 6hours recovery in the whey protein isolate group but not the carbohydrate group.
  • There was increased plasma insulin levels during the recovery phase in the whey protein isolate group compared with the carbohydrate group.
  • The researchers observed significantly increased PGC-1α mRNA expression – an indicator of mitochondrial biogenesis which is an important adaptation associated with endurance training - during recovery in the whey protein isolate group compared with the carbohydrate group. Another indicator or mitochondrial biogenesis (AMPK-α2 mRNA expression) was decreased in the carbohydrate group but not the whey protein isolate group at the 6hour recovery point.

Insulin whey protein isolate

Mitochondrial adaptation whey protein


The researchers conclusions about whey protein and endurance training recovery

The researchers concluded that co-ingestion of carbohydrate and whey protein isolate appears to be important for endurance training adaptations, through increasing plasma insulin and may enhance mitochondrial biogenesis.

Whey protein for endurance recovery summary:

Consuming additional protein (whey protein isolate), along with adequate carbohydrate, as part of your daily diet and as a post exercise recovery drink appears to be beneficial for increased rates of recovery.


The amount of additional whey protein used in this study was fairly high with an additional 1.2g kg/bw of whey protein isolate consumed in the high protein dietary intervention phase – equivalent to 84g for a 70kg athlete which equates to just over three normal size servings of whey protein isolate. It’s not clear whether similar results would have been achieved if a smaller amount of whey protein was consumed daily (e.g. 25-50g whey protein isolate).

The high protein post exercise drink also contained a fairly significant amount of protein (1.1g kg/bw – equivalent to around 77g of whey protein isolate for a 70kg athlete). Whilst the higher post exercise protein consumption was more beneficial, it’s not clear whether a slightly lower protein intake may prove equally effective and more cost effective. There was quite a large difference in the amount of protein used in the two groups (1.1g vs 0.4g kg/bw – equivalent to 77g vs 28g in a 70kg athlete) and it may be that somewhere between the two (e.g. 50g of whey protein isolate) may prove to be equally effective and significantly more cost effective than consuming 3 or more servings. It’s also important to consider that muscle protein synthesis is maximally stimulated following consumption of around 25g of whey protein and therefore consuming more in one dose may not be beneficial. In view of this you should consider splitting the protein intake into two smaller doses e.g. consume 25g of protein immediately following endurance exercise and a separate 25g dose 2-3hours later.

A further consideration is the intensity or duration of exercise – a single 25 serving of whey protein may be equally effective following low intensity (<80% HR max) short duration exercise (<60 minutes duration). Whereas taking two 25g whey protein servings (separated by 2-3 hours) may prove to be more effective following higher intensity training (e.g. lactate threshold training or high intensity interval training) or prolonged exercise (e.g. 2+ hours duration).

Whey protein endurance recovery reference:

Hill KM, Stathis CG, Grinfeld E, Hayes A, McAinch AJ. (2013) Co-ingestion of carbohydrate and whey protein isolates enhance PGC-1α mRNA expression: a randomised, single blind, cross over study. J Int Soc Sports Nutr. 2013 Feb 12;10(1):8. doi: 10.1186/1550-2783-10-8.

Back to Endurance Training News