Healthy
Conditions
Keywords
Strength/resistance training, Glucose supplementation, Skeletal muscle
Brief summary
The aim of the study is to investigate the effects of ingesting glucose during five bouts of resistance exercise on muscle biological charateristics in m. vastus lateralis of moderately trained healthy individuals (20-45 years of age, n=20)
Detailed description
Muscular responses to resistance training vary extensively between humans, with many showing impaired growth. In such individuals, cellular plasticity is compromised, leading to reduced functional and health-beneficial outcomes of training. While this is likely due to a range of determinants, including epigenetic, genetic and physiological variables, recent studies suggest that it involves reduced ability to produce novel ribosomes in response to training. This eventually leads to less pronounced increases in protein synthesis, and thus decreased growth rates, and makes ribosomal content in muscle a potential proxy marker for training-associated muscle hypertrophy. In a recent study, the investigators showed that increased resistance training volume was associated with more pronounced muscle growth, a trait that was associated with increased ribosomal biogenesis. Despite this, \ 50 % of the participants did not exhibit true beneficial effects of increased training volume, which in turn coincided with reduced abilities to accumulate ribosomes. In such individuals, other means are likely necessary to circumvent the negative influence of genetic and epigenetic predispositions on muscle plasticity. Nutrient supplementation stand out as a potential therapy. However, at present, knowledge with regard to this perspective is limited to a selected few nutrients, with protein ingestion being the best studied potential adjuvant, for which adequate intake seems to be essential for achieving optimal muscle growth, potentially being interconnected with ribosomal synthesis. For other nutrients, such as glucose, little is know about their importance for muscle plasticity and ribosomal biogenesis. In cell types such as cultivated kidney cells, exposure to high levels of glucose is an efficient mean to increase ribosomal biogenesis (and growth rates). This suggests that glucose is an important signaling molecule for increasing ribosomal production per se, perhaps acting as a ligand for signaling proteins or by acting to increase energy availability. In the human body (as opposed to cultured cells), glucose may also exert growth-stimulating effects by increasing insulin levels in blood. Overall, it thus seems plausible that glucose intake during resistance training may stimulate ribosomal biogenesis, in turn having beneficial effects for protein synthesis and muscle plasticity, perhaps acting in an additive manner to protein supplementation. At present, we do not know if this is the case, though studies have suggested that glucose ingestion during acute resistance training sessions may reduce training-induced muscle damage without affecting within-session work output (i.e. volume). This lack of knowledge is surprising given the long-standing appreciation of the beneficial effects of glucose intake for endurance performance, acting to delay muscular fatigue.
Interventions
To investigate the effects of glucose intake during resistance training on muscle biological adaptations
Sponsors
Study design
Masking description
On each intervention day, participants will receive boluses of supplements in accordance with his or her study ID number. The list that links this ID number to the randomization code will be kept with the person who generated the randomization code (and stored on a safe server) until completion of data sampling and cleaning of data on main outcome measures. The person resonsible for generating the randomization code will not be involved in any aspects of data sampling or handling. None of the project collaborators/participants will have access to this list during the intervention or during data handling. Half the participants (n=10) will commence the intervention with GLU on Day 1, while the other half will commence with PLAC (randomized). For participants starting with GLU, half will perform training on their dominant leg, while the other half will perform training on their non-dominant leg. The same will be the case for participants starting with PLAC.
Intervention model description
The study will be conducted as a 12-day placebo-controlled randomized clinical trial. Each day will consist of concomitant dietary intervention and resistance training. The dietary intervention consists of alternating days of ingesting glucose (GLU, 90 g) or placebo (PLAC) in connection with training. Likewise, training consists of alternating days of resistance training of the two legs (using identical training protocols), with Day 1 involving training of the first leg, Day 2 involving training of the second leg, Day 3 involving training of the first leg, etc. In this way, each of the two dietary interventions will be associated with training of one particular leg, allowing within-subject comparisons of the effects of GLU vs PLAC on muscle biology and recovery.
Eligibility
Inclusion criteria
* Non-smoking * Moderately trained (i.e. having performed 2-8 resistance training sessions per 14 days for the last six months)
Exclusion criteria
* Not able to understand Norwegian * Unstable cardiovascular disease * Illness or injury contradicting heavy strength training * Disabling musculoskeletal disease * Serious mental illness * Allergy to local anaesthesia * Impaired glucose tolerance
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Total RNA in muscle tissue | Before the intervention and immediately after the intervention (i.e. after 5 training sessions of each leg) | Total RNA content in m. vastus lateralis (ug per mg tissue) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Glucose in blood, after glucose/placebo intake | Immediately before glucose/placebo intake and 30 min, 45 min, 60 min and 195 min after initial glucose/placebo intake | Glucose concentrations in blood (area under the curve), measured before and after intake of glucose/placebo on the two final days of the intervention (one day = glucose; one day = placebo) |
| Hormone concentrations in blood (after protein intake) | Immediately before protein intake and 90 min after protein intake | Abundances of insulin, c-peptide, testosterone, growth hormone, cortisol and inflammatory markers in blood, measured after intake of protein on the two final days of the intervention |
| Unilateral lower body isokinetic muscle strength (during the intervention) | Before the intervention and after the second, fourth and sixth training session | The ability of the knee extensors to exert maximal force during isokinetic movements (recovery/strength), measured before the intervention and at three time points during the intervention (\ 24 hours after training sessions) |
| Unilateral lower body isokinetic muscle strength (last days of the intervention) | Before the last training session and 30 min, 120 min and 24 hours after the last training session | The ability of the knee extensors to exert maximal force during isokinetic movements (recovery/strength), measured before and at three time points after the last two training sessions (one day = glucose; one day = placebo) |
| Unilateral lower body isometric muscle strength (during the intervention) | Before the intervention and after the second, fourth and sixth training session | The ability of the knee extensors to exert maximal force during isometric actions (recovery/strength), measured before the intervention and at three time points during the intervention (\ 24 hours after training sessions) |
| Unilateral lower body isometric muscle strength (last days of the intervention) | Before the last training session and 30 min, 120 min and 24 hours after the last training session | The ability of the knee extensors to exert maximal force during isometric actions (recovery/strength), measured before and at three time points after the last two training sessions (one day = glucose; one day = placebo) |
| Perceived muscle soreness (during the intervention) | Before the intervention and 24 hours after each training session | Muscular soreness measured before the intervention and at three time points during the intervention (\ 24 hours after training sessions) using a VAS-scale from 0 to 10 (0 = no soreness; 10 = maximal soreness) |
| Perceived feeling of the legs (during the intervention) | 30 min after each training session | Feeling of the legs measured immediately after each training session using a 9-point scale (1 = very very good, 9 = very very heavy) |
| Muscle fractional synthesis rate | Immediately after the intervention | Protein synthesis rate measured using heavy water (deuterium) and chromatography/spectrometry |
| Ribosomal RNA in skeletal muscle | Before the intervention and immediately after the intervention (i.e. after 5 training sessions of each leg) | Abundances of ribosomal RNA species in m. vastus lateralis measured using qPCR |
| Protein in skeletal muscle | Before the intervention and immediately after the intervention (i.e. after 5 training sessions of each leg) | Abundances of protein species in m. vastus lateralis measured using Western blotting (e.g. ECM proteins) |
| Gene expression in skeletal muscle | Before the intervention and immediately after the intervention (i.e. after 5 training sessions of each leg) | Abundances of mRNA species in m. vastus lateralis measured using qPCR |
| Glucose in blood (after protein intake) | Immediately before protein intake and 45 min and 90 min after protein intake | Glucose concentrations in blood (area under the curve), measured before and after intake of protein on the two final days of the intervention |
| Hormone concentrations in blood (after glucose/placebo intake) | Immediately before glucose/placebo intake and 30 min and 60 min after the initial glucose/placebo intake | Abundances of insulin, c-peptide, testosterone, growth hormone, cortisol and inflammatory markers in blood (area under the curve), measured before and after intake of glucose/placebo on the two final days of the intervention (one day = glucose; one day = placebo) |
Other
| Measure | Time frame | Description |
|---|---|---|
| Dietary registration | During each day of the intervention | Nutritional intake during each day of the intervention, tracked using MyFitnessPal |
| Unilateral lower body maximal strength | Before the intervention | The ability of muscles of the lower body to exert maximal force during dynamic movements |
| Blind test glucose vs placebo comparators | Immediately after the intervention | The ability to discriminate between glucose and placebo beverages, tested after the training intervention using a blinded randomized design: each participant will ingest six beverages (3 x glucose and 3 x placebo) and will be asked to identify theam as either glucose or placebo. The ability to discriminate will be determined based on analyses of the full study population |
| Deuterium in spit | On each day of the intervention | Deuterium levels in spit on each day during the intervention measured using chromatography/spectrometry (sampled prior to each training session) |
| Fasting blood glucose | Before the intervention and immediately after the intervention | Fasting blood glucose measured in serum, measured before the intervention and prior to training on the last two days of the intervention |
| Training diary | During each training session of the intervention | Training volume (total kg lifted) during each day of the intervention |
| Body mass composition | Prior to the intervention | Body mass composition measured using DXA |
Countries
Norway