Relevant Research

in the Field of Strength Training and Sports #12

Written by: Joachim Bartoll, January/February 2016
Classic Muscle Newsletter, March 2016 (issue #18)


In this ongoing series, I will summarize recent and relevant studies within our field of Strength and Performance Sports – including topics such as Strength Training, Hypertrophy, Nutrition, Weight Loss and more. I will wade through all the new published research and pick out the gems – so you don’t have to. If warranted, I will also add my opinion on the findings and/or the methodology of the study. No matter if you’re an Athlete, a Coach or a Personal Trainer, this series will keep you up to date with the latest research in a manageable and easily accessible way.

Effects of protein dosage, timing, quality, and co-ingestion with carbohydrates on muscle protein synthesis

In the last issue of Relevant research in the field of Strength Training and Sports (#11) we looked at a narrative review of measurement methods for muscle protein synthesis (MPS). In all simplicity, skeletal muscle mass is regulated by a balance between muscle protein synthesis and muscle protein breakdown (MPB). In healthy humans, MPS is more sensitive (varying 4–5 times more than MPB) to changes in protein feeding, rendering it the primary focus of determining gains in muscle mass. Performing resistance exercise (RE) followed by the consumption of protein results in an augmentation of MPS and, over time, can lead to muscle hypertrophy.
The researchers in this study wanted to review the effects of protein dosage, timing, quality and co-ingestion with carbohydrates on acute muscle protein synthesis rates. Their goal was to provide nutritional recommendations for optimal skeletal muscle adaptation.

The findings

Protein dosage: The researchers came to the conclusion that just 20g of protein seems to be almost as effective at elevating MPS as 40g of protein in both untrained and trained individuals. The researchers explain that protein above this amount oxidizes more quickly and a lot of it is turned into urea.

Protein timing: The researchers came to the conclusion that there are indications to support the use of a moderately frequent timing pattern of whey protein ingestion, in which 20g of protein is consumed 4 times over a 12-hour period, with each dose consumed every 3 hours. This has been found to elevate MPS more than a less frequent timing pattern (40g of protein consumed 2 times, every 6 hours) or a higher frequency (10g of protein consumed 8 times, every 1.5 hours).

Protein quality: The researchers concluded that three types of protein are consumed regularly by individuals involved in regular resistance training, these are whey, casein, and soy. They note that whey and soy are digested more rapidly than casein and this leads to a shorter but much larger rise in MPS. However, the reduction in muscle protein breakdown (MPB) seems to be greater with casein.
Finally, they note that the size of the rise in MPS is greater with whey than with the inferior soy. They suggest that this may be because of differences in leucine levels. If soy, whey and casein blends are matched for identical leucine levels, there are no differences in the resulting MPS.

Co-ingestion with carbohydrates (CHO): It has been suggested that raising insulin levels may enhance increases in MPS when consumed together with protein, as infusing insulin at rest in isolation does increase MPS. Indeed, the researchers note that when combined with amino acids, infusion of insulin does elevate MPS above levels observed following administration of amino acids alone and also reduces MPB.
When considering consumption of CHO (rather than administration of insulin), the researchers note that, when consumed in isolation, CHO does not affect MPS but does reduce the negative effects on MPB.
When consumed together with amino acids, CHO similarly does not have any additive effect on MPS and also fails to have any additional benefit

My thoughts

The researchers looked at several studies; some including whole-eggs, others consuming lean beef, and a few studies with whey protein. As we already know, about 20 grams (depending on protein quality, rate of absorption and leucine content) is enough to stimulate protein synthesis. They also found that the best timing pattern for maximum stimulation of protein synthesis was roughly every three hours, as two hours was too often (this is also dependent on the absorption rate). These facts has been a cornerstone of my Anabolic Pulse Protocol since 2006/2007 - and was used in my second book The Maximum Muscle Guide from 2008. So nothing new there.
They also found that about 40 grams protein per meal is the limit for the average person, as more protein than that will mostly be oxidized and turned into urea. This limit will probably depend on intestine health, the hormonal environment and perhaps even muscle mass and how the person has been conditioned to a high protein diet.

Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy.
Morton, McGlory, and Phillips.
Front. Physiol., 03 September 2015

High protein diet combined with heavy resistance training on body composition

In this follow-up study the researchers wanted to assess the effects of a high protein diet (3.4g of protein per kg of bodyweight per day) in combination with a long-term program of resistance training on body composition (measured by whole body densitometry using air displacement with the Bod Pod device), strength (as measured by 1RM back squat and bench press), and athletic performance (as measured by vertical jump height, broad jump distance, and total number of pull ups in a single set).

The design

48 healthy subjects was recruited and allocated into a normal protein (NP) group (17 subjects; 4 females and 13 males; aged 24.8 ± 6.9 years; 2.4 ± 1.7 years of resistance training) and a high protein (HP) group (31 subjects; 7 females and 24 males; 22.9 ± 3.1 years; 4.9 ± 4.1 years of resistance training).
All participants performed a body part split training program, 5 days per week for 8 weeks. The NP and HP groups were instructed to consume approximately 2g and 3g of protein per kg of bodyweight per day, respectively.

The findings

When analyzing the subjects dietary records, the researchers found that NP and HP groups consumed 2.3g and 3.4g of protein per kg of bodyweight per day, respectively. And more importantly, the HP group consumed significantly more total energy and protein compared to baseline and compared to the NP group.

Effects on body composition: The researchers found that the NP group gained significantly more bodyweight than the HP group (+1.3 ± 1.3 vs. −0.1 ± 2.5kg) but lost less fat mass (−0.3 ± 2.2 vs. −1.7 ± 2.3kg). Both the NP and HP groups gained similar amounts of lean body mass, with the HP group marginally better (+1.5 ± 1.8 +1.5 ± 2.2kg).

Effects on strength and performance gains: The researchers found that both NP and HP groups significantly increased their 1RM back squat and 1RM bench press, as well as vertical jump height, broad jump distance, and total number of pull ups in a single set. There were no significant differences between the two groups.

The conclusion

The researchers concluded that consuming protein of around 3.4g per kg of bodyweight per day appears to produce superior changes in body composition (specifically reductions in fat mass) to consuming protein of 2.3g per kg of bodyweight per day.

My thoughts

This study was limited to the fact that only two levels of protein consumption were measured. It would have been interesting with at least four levels of protein intake.
The interesting part, which goes hand in hand with findings in previous studies, is that a higher protein intake leads to fat loss despite a higher overall energy intake. Once again, the old dogma that a calorie is a calorie, gets another nail in the coffin.
The high protein group only gained a non-significant amount of muscle mass more than the normal group, which gives indications to that an ideal protein intake is within the neighborhood of 2.4 to 3 grams when the objective is to gain muscle mass in natural subjects.
As for muscle growth, one should also note that the subjects in the HP group had far more weight training experience (almost the double), which should make it harder to gain more muscle mass. Despite this fact, the results were similar with a small advantage to the HP group. The researchers should have blended the two groups with more care.
As for fat loss, a higher protein intake seems more beneficial. As other studies has shown superior results with close to 4 grams of protein per kilogram of body weight, one should also consider the subjects, their level of body fat and insulin resistance. Still, a higher protein intake when trying to lose body fat is warranted. Depending on the subject, about 3 to 3.5 grams of protein per kilogram of bodyweight seems ideal.

A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women – a follow-up investigation.
Jose Antonio , Anya Ellerbroek, Tobin Silver, Steve Orris, Max Scheiner, Adriana Gonzalez, Corey A Peacock.
Journal of the International Society of Sports Nutrition. December 2015, 12:39

Kettlebell interval training versus sprint interval cycling

The researchers of this study wanted to compare the effects of a “high-intensity” interval training workout using kettlebells (KB-HIIT) to a similar sprint interval cycling (SIC) workout on heart rates, oxygen consumption (VO2), and total energy expended (all measured using a metabolic analyzer).

The design

8 athletic males were recruited for the study; with an average maximal aerobic capacity (VO2-max) of 52.16 ± 6.55 ml/kg/min.
All of the 8 subjects performed the two 12-minute workouts on different days. The KB-HITT workout involved 3 circuits of 4 exercises using a Tabata protocol, which involves 20 seconds of exercising and 10 seconds of rest, repeated 8 times over 4 minutes. The 4 exercises were the sumo squat singlehanded or two-handed), two-handed swings, clean and press (dominant arm), and sumo deadlifts (singlehanded or two-handed). The weight of the kettlebells ranged between 10 to 22kg across subjects and exercises.
The SIC workout involved 3 bouts of 30-second Wingate sprints with 4 minutes of rest between the first two sprints and 2.5 minutes of recovery after the third sprint.

The findings

Heart rate: The researchers found that the average heart rate was significantly higher during the KB-HIIT workout than during the SIC workout (149.16 ± 7.4 vs. 139.69 ± 7.85bpm). However, peak heart rates appeared higher in the SIC workout than in the KB-HIIT workout.

Oxygen consumption: The researchers found that the average oxygen consumption was significantly greater in the KB-HIIT workout than in the SIC workout (22.6 ± 1.48 vs. 19.9 ± 1.01 ml/kg/min). However, peak oxygen consumption appeared higher in the SIC workout than in the KB-HIIT workout.

Energy expenditure: The researchers found that total caloric expenditure in the KB-HIIT workout was significantly greater than in the SIC workout (144.9 ± 6.6 vs. 122.0 ± 7.3 kcal).

The conclusion

The researchers draw the conclusion that their KB-HIIT workout produced greater average heart rate, higher oxygen consumption, and a higher energy expenditure than a traditional SIC workout. They also noted that peak heart rates and oxygen consumption were lower in the KB-HIIT workout.

My thoughts

It should be noted that while both workouts took 12 minutes, the KB-HIIT consisted of 240 seconds of actual exercise while the SIC-workout only consisted of 90 seconds of exercise.
This means that the KB-HIIT workout “burned” 0.6 kcal per second of exercise and the SIC-workout burned 1.35 kcal per second of exercise.
While the SIC-workout seems more efficient when calculating for actual work done, we don’t know how hard the subject pushed themselves during the KB-HIIT workout, nor how many repetitions they did in each 20 second bout. While a SIC-workout is an “all-out burst”, doing sumo squats and deadlifts with a kettlebell is far from “all-out”. It’s also unclear how much energy the subject “burned” after the workouts while recuperating. Since more muscle mass was involved in the KB-HIIT workout, my guess is that the “after burn” was greater after that workout. Also, it’s unclear what hormonal benefits each workout would give in a longer perspective.

Comparison of cardiorespiratory and metabolic responses in kettlebell high-intensity interval training versus sprint interval cycling.
Williams, Brian M.; Kraemer, Robert R.
Journal of Strength & Conditioning Research: September 08, 2015. doi: 10.1519/JSC.0000000000001193

Insulin and its role in regulation of muscle protein synthesis and breakdown

In this study the researchers performed a meta-analysis to find out to which extent insulin plays a role in regulating Muscle Protein Synthesis (MPS) and Muscle Protein Breakdown (MPB), using a random effects model to compare weighted mean differences between a condition with an insulin infusion and a control condition, as well as subgroup analyses according to the levels of amino acid (AA) delivery to the muscle.

The design

The researchers decided to pick studies that reported changes in muscle protein metabolism (either MPS or MPB) in humans in response to interventions with insulin.
Within this criteria, they identified 13 articles that included 25 studies, involving a total of 173 subjects. Of these 25 studies, 13 assessed effects in young adults, 3 in people with diabetes, and 8 looked at older adults.

The findings

Effects of insulin infusion on MPS and MPB: Looking at all the collected data, the researchers found that insulin did not really affect MPS but significantly reduced MPB and thereby significantly increased net balance protein acquisition.
The heterogeneity for the effect of insulin on MPS was substantial and also significant (I-squared = 49%) and this variability seemed to stem from the effect of amino acids (AA) delivery. A meta-regression analysis identified that there was no effect of anthropometric or population-specific variables (such as age, lean body mass etc.) on this variability. In contrast, the heterogeneity for the effect of insulin on MPB was not substantial or significant (I-squared = 13%).

Effect of insulin infusion by amount of Amino Acids delivery: From the collected data, the researchers found that there was a significant effect of insulin depending on AA availability. MPS was in fact significantly increased when AA availability increased but not when AA availability was reduced or unchanged.

The conclusion

The researchers concluded that the release of insulin does not have any significant effect on MPS unless the delivery of AA is simultaneously maintained or increased. In contrast, they found that the release of insulin does appear to reduce MPB, irrespective of the availability of AA at the same time. They therefore suggested that under most circumstances, any anabolic effect of insulin will be exerted via its ability to reduce MPB and not by change of MPS.

My thoughts

The fact that muscle protein synthesis is significantly increased when amino acid availability is increased above normal and in the presence of extra insulin, is one of the many reasons for taking protein or amino acids together with carbohydrates before a training session to spike insulin levels, increase nutrition uptake, and stimulate MPS as much as possible (para workout nutrition) - as described in my second book The Maximum Muscle Guide from 2009 and in my third book, Träningsnutrition from 2015.
One of the limits of this meta-analysis is that some of the studies analyzed used artificial infusion of insulin under controlled conditions with simultaneous control over the AA delivery.
In real life, we can only control insulin by the nutrition we consume – primarily carbohydrates and, to some effect, by insulinogenic amino acids.

Role of insulin in the regulation of human skeletal muscle protein synthesis and breakdown: a systematic review and meta-analysis.
Haitham Abdulla, Kenneth Smith, Philip J. Atherton, Iskandar Idris.
Diabetologia, January 2016, Volume 59, Issue 1, pp 44-55

This was an excerpt from Relevant Research in the Field of Strength Training and Sports #12. For more reviewed studies (6 to 7 each month) and 4 to 5 additional articles each month, please subscribe by clicking the button below. By becoming a subscriber, you'll also get instant access to the archives, featuring more than 250 articles and +20 training programs.