Influence of Reduced Daily Step Count and Anabolic Interventions on Muscle Protein Metabolism in Older Persons

Not Applicable

Completed

• Conditions: Reduced Physical Activity; Older Adults; Muscle Protein Synthetic Response to Protein
• Interventions: Other: step-reduction; Other: step-reduction plus resistance exercise

• Registration Number: NCT02347137
• Lead Sponsor: McMaster University

Brief Summary

As the loss of muscle mass with aging is associated with a dysregulation of muscle protein synthesis (MPS) that is generally characterized by an 'anabolic resistance' to nutrients, the primary outcome of the trial is to investigate the effect of a mixed macronutrient beverage on post-prandial myofibrillar MPS. However, the 'anabolic resistance' of aging may be predominantly influenced by the contractile activity of skeletal muscle; for example, the investigators have demonstrated that 2 weeks of reduced habitual activity (i.e. daily step count) induces anabolic resistance in otherwise healthy older adults. In contrast, resistance exercise is well-known to enhance muscle mass and can increase the sensitivity of skeletal muscle to dietary amino acids. Therefore, all participants will undergo a 2-week reduced step count intervention combined with a unilateral leg resistance exercise protocol to induce an 'unhealthy' or 'anabolically resistant' leg and a relatively 'healthy' or 'anabolically sensitive' leg, respectively; this within subject model will be utilized to investigate the effect of the mixed macronutrient beverage in both relatively 'healthy' and 'unhealthy' older muscle. The investigators will also measure changes in muscle mass, muscle function, and cardiovascular health of both legs before and after the 2-week intervention to determine the effect of reduced activity and the protective effect of minimal, low-intensity exercise on these outcomes.

Detailed Description

Not available

Study Timeline

• Study Start: 2012-07
• Primary Completion: 2013-05
• Study Completion: 2013-05
• Status Verified: 2015-01
• Study First Submitted: 2015-01-06
• Study First Submitted QC: 2015-01-21
• Last Update Submitted: 2015-01-21
• Study First Posted: 2015-01-27
• Last Update Posted: 2015-01-27

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Male
• Target Recruitment: 30

Inclusion Criteria

• Non-smoker

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Exclusion Criteria

• Health problems such as: heart disease, rheumatoid arthritis, diabetes, poor lung function, uncontrolled hypertension, or any health conditions that might put the participant at risk for this study
• Failed clearance for exercise participation by the participants family physician/medical doctor
• Failed an exercise strength test.
• Regular consumption of any analgesic or anti-inflammatory drug(s), prescription or non-prescription, chronically will be excluded.
• Taking any medications known to affect protein metabolism (i.e. corticosteroids, non-steroidal anti-inflammatories, or prescription strength acne medications).
• Factors that may exclude a participant from an MRI scan (i.e. various implants, metal in the eyes etc)
• Participants who complete fewer than 5000 steps per day (as assessed by pedometer prior to the study).

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Micellar Whey Protein + Citrulline	step-reduction	20 g micellar whey protein + 5 g citrulline
Micellar Whey Protein + Citrulline	step-reduction plus resistance exercise	20 g micellar whey protein + 5 g citrulline
Isolated Whey Protein	step-reduction	20 g isolated whey protein + 15 g non-essential amino acids
Micellar Whey Protein	step-reduction	20 g micellar whey protein + 15 g non-essential amino acids
Isolated Whey Protein	step-reduction plus resistance exercise	20 g isolated whey protein + 15 g non-essential amino acids
Micellar Whey Protein	step-reduction plus resistance exercise	20 g micellar whey protein + 15 g non-essential amino acids

Primary Outcome Measures

Name	Time	Method
Myofibrillar fractional synthetic rate will be measured using 13C6 ring phenylalanine	7 hours	analysis

Secondary Outcome Measures

Name	Time	Method
body composition (lean body mass, fat mass, leg lean mass, leg fat mass) will be measured using dual energy xray absorptiometry	14 days	analysis
vascular function (femoral blood flow, femoral artery diameter, leg pulse) will be measured using doppler ultrasound	14 days	analysis
leg muscle strength (leg press and leg extension 1 repetition maximum [1-RM], peak knee extensor torque) will be measured using a dynamometer	14 days	analysis

Trial Locations

Locations (1)

Exercise Metabolism Research Laboratory, McMaster Univeristy; 🇨🇦 Hamilton, Ontario, Canada