Timing Nutrient Intake With Traditional High-load Or Low-load Blood Flow Restricted Exercise During Unloading

Date of Award

8-20-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Exercise Science

Advisor(s)

Lori Ploutz-Snyder

Keywords

Anabolic Resistance;Nutrient Timing;Resistance Exercise;Skeletal Muscle;Spaceflight

Subject Categories

Kinesiology | Life Sciences

Abstract

The manuscripts represented within this collection were developed in cooperation with Graduate Student Researcher Program training grant (NNX08AW71H) sponsored by the National Aeronautics and Space Administration (NASA). The first manuscript titled, "Unilateral Lower-Limb Suspension (ULLS): Integrative Physiological Knowledge from the Past Twenty Years (1991-2011)," is a review exploring ULLS as a ground based musculoskeletal unloading analog used in spaceflight research. The work synthesizes the physiological findings across various durations of unloading and multiple body systems. The second manuscript titled, "Blood Flow Restricted Exercise in Space" is a review article discussing the potential application of a novel exercise countermeasure to combat neuromuscular and cardiovascular dysfunction during prolonged exposure to microgravity. This article evaluates how this method of exercise may be implemented during long duration space missions. The third manuscript is a quantitative research study conducted for the Exercise Science requirement titled, "Blood Flow Restricted and High-Load Resistance Exercise Coupled with Pre/Post-Exercise Protein-Carbohydrate Intake During 28 Days of Unilateral Limb Suspension". Over the past ten years a wealth of evidence has been published to suggest pre and/or post-exercise intake of protein-carbohydrate is an effective strategy to optimize resistance exercise training for muscle hypertrophy. However, few studies have explored this type of strategy to prevent losses of muscle cross-sectional area (CSA) and function with prolonged musculoskeletal unloading. In this study, thirteen subjects completed 28 days of ULLS, where the left limb was unloaded and the right limb remained weight-bearing. During ULLS, subjects performed leg press and plantar flexor exercise training three days per week. Of the thirteen subjects, seven performed blood flow restricted exercise training and six performed high-load resistance exercise training. Immediately (<10 minutes) before and after exercise both groups consumed liquid protein-carbohydrate (total amount- 54g carbohydrate, 16g protein). Pre and Post-ULLS, muscle CSA, strength, central activation capacity, rate of force development, force steadiness, and dynamic endurance were evaluated to determine the skeletal muscle adaptations in both the unloaded and weight-bearing limbs. Muscle biopsies were also obtained from the vastus lateralis and lateral gastrocnemius pre and post-ULLS on a subset of subjects (N=6) to determine if basal mammalian target of rapamycin signaling (mTOR) was related to the changes in muscle size. Overall, given equivalent nutritional support for muscle anabolism, high-load resistance training was more effective than blood flow restricted exercise training as a countermeasure during unloading. Alternatively, both methods of resistance exercise training showed similar training adaptations when daily weight-bearing was present. The final project titled, "Misconceptions Regarding Protein Supplement Effectiveness in Undergraduate, Kinesiology Students, reflects the Science Education requirement. Although additional intake of protein above the Recommended Daily Allowance (RDA) has been promoted for individuals participating in endurance or resistance training there is no evidence to suggest protein from dietary supplements are superior to whole food sources. This study is a qualitative research investigation performed in senior Kinesiology students to determine if there is a belief that protein supplements are superior to whole food sources for promoting exercise training adaptations. We hypothesized male students that used protein supplements would have the greatest misconceptions about protein supplement effectiveness. Data from one hundred and twenty five senior- level Kinesiology students that responded to a protein supplement knowledge survey (which included a protein misconception index) were analyzed. These data suggest protein supplement effectiveness misconceptions were apparent in senior Kinesiology students based on supplement use; however, gender was not a factor. Teaching strategies and curriculum or course requirements may need to be modified to target the identified protein misconceptions.

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