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Athletic Performance
Published in Clete A. Kushida, Sleep Deprivation, 2004
Roger S. Smith, Thomas P. Reilly
Endurance and time to exhaustion are also important components of athletic performance. Decreases in either measure were observed in several studies (19,21,38–42). Holland (38) noted a 10% reduction in work performed during all-out cycle ergometer exercise after 24 hr of sleep deprivation. Brodan and Kuhn (39) evaluated subjects (n = 7, sleep debt = 120 hr) with the Harvard step test (reflects cardiorespiratory endurance and recovery) and revealed adaptation during the test but impaired recovery. Martin (41) utilized treadmill testing at 80% and found decreased time to exhaustion, increased perceived exertion, and increased minute ventilation (n = 8, sleep debt = 36 hr). Martin and Chen (42) revealed a 20% reduction in time to exhaustion after 50 hr of sleep deprivation. Decreased time to exhaustion after 30 hr of sleep deprivation has been demonstrated even when subjects were allowed caffeine intake (21).
Guanidinoacetic acid in health, sport and exercise
Published in Jay R Hoffman, Dietary Supplementation in Sport and Exercise, 2019
The idea that the addition of GAA to food will stimulate creatine synthesis and boost energy levels was first reported in 1951. Borsook and Borsook (5) described a biochemical basis of betaine-glycocyamine therapy in the course of six to 12 months in over 200 patients with heart disease. The daily oral dose of GAA in this seminal study was 30 mg per pound of body weight while betaine hydrate was added in the amount four to five times the dose of GAA, with betaine “given because of the insufficiency of the methylation process.” GAA dosage after methylation to creatine was calculated to be approximately three times the normal production of creatine; the mixture was divided into four to five portions through the day. Within several weeks of beginning the treatment, many patients reported an improved sense of well-being, less fatigue and an increased desire for performance of physical and mental work. This so called “asthenic effect” appeared early and persisted throughout the study, regardless the degree of the specific disease, with the authors suggesting a possible involvement of the nervous system. In the follow-up paper in the same issue of the journal Annals of Western Medicine and Surgery, another research group from the United States Naval School of Aviation Medicine confirmed the beneficial effects of GAA in a case study (9), describing 16 hospital and outpatient cardiac patients who received 30 mg of GAA per pound body weight. Most patients experienced an asthenic effect, along with an increase in exercise tolerance (as measured with the Harvard step test) and a tendency toward improvements in electrocardiographic findings. Both studies indicated that there were no side effects and toxicity from the treatment, as determined by the participants’ subjective symptoms and extensive blood and urine analyses. Those pioneering studies were followed by a number of trails in the 1950s that evaluated GAA supplementation in patients with acute and chronic anterior poliomyelitis (2, 6, 8, 28), arthritis (10), myopathic muscular dystrophy (3), anxiety states and anxiety complicated by depression (7), myasthenia gravis (4) and motor-neuron disease (1, 11). Although not all studies found that GAA was clinically beneficial, most demonstrated its potential for building up the energy reserves of the body. However, those studies were non-randomized and open-label trials with no comparator group, using few biomarkers to evaluate cellular bioenergetics and/or creatine synthesis after treatment.
Ascorbic Acid
Published in Judy A. Driskell, Ira Wolinsky, Sports Nutrition, 2005
Several studies performed since 1960 also have reported positive performance changes in subjects given additional ascorbic acid. Hoogerwerf and Hoitink74 worked 33 untrained male students on a cycle ergometer at 120 watts for 10 minutes. The study was performed in a double-blind manner with 15 students receiving 1,000 mg of ascorbic a day for 5 days while the rest of the students received a placebo. Blood ascorbate concentrations in the subjects were within normal range at the beginning of the study. The researchers found that excess metabolism due to work decreased and mechanical efficiency increased significantly in the group receiving ascorbic acid as compared with the placebo group. Margolis75 studied 40 adult male workers; half of the subjects received a vitamin C supplement of 100 mg while the other subjects served as controls. The authors concluded that the vitamin C supplement was helpful in reducing fatigue and in increasing or preventing a decrease in muscular endurance. Spioch et al.76 gave 30 healthy men 500 mg of ascorbic acid intravenously prior to a 5-minute step test. Oxygen consumption was reduced by 12%, oxygen debt by 40%, total energy output by 18% and pulse rate by 11% compared with the same test without ascorbic acid. Mechanical efficiency also improved in the subjects when they received the ascorbic acid. Meyer et al.77 investigated the effect of a predominately fruit diet containing 500–1000 mg of vitamin C on the athletic performance of six male and three female university and high school students. All students performed 1 hour of exercise and a 20-km run each day. Measurements were taken before, during and after the diet, which was continued for 14 days. Running times of the students were reduced following the diet but no changes were noted for resting heart rate. Howald et al.78 studied 13 athletes undergoing a moderately intense continuous training program. The athletes were initially given a placebo for 14 days. This was followed by a vitamin C supplement of 1,000 mg/day for the next 14 days. Exercise tests were performed at the end of each dietary period. The exercise test was a progressive cycle ergometer test starting at a workload of 30 watts and increasing in 40-watt increments every 4 minutes until the subject reached exhaustion. Subjects exhibited a significantly greater physical working capacity at a heart rate of 170 beats/minute. In addition, heart rates were consistently lower at each workload throughout the progressive test when the subjects were receiving the vitamin C. Finally, the addition of vitamin C to the diets of a group of trained Indian university women also resulted in an improvement in their VO2max and work efficiency in the Harvard step test.79
The effect of using activity workstations on heart rate variability during complex cognitive tasks
Published in Journal of American College Health, 2022
June J. Pilcher, Drew M. Morris, Sarah E. Limyansky, Stewart A. Bryant
Participants were tested in a campus laboratory facility with constant room temperature of approximately 70 °F in a secluded, quiet area. Participants first completed the screening survey described previously and then relaxed for five minutes prior to starting the tasks. Each participant then completed the Harvard Step Test at a rate of 30 steps per minute for five minutes to ensure a standard level of cardiac fitness.48 Participants were then given a 5-minute break to return to a resting heart rate before physiological recordings began. An HRV sensor was attached to the participants who met the screening and fitness criteria and participants were assigned the order of type of desk (traditional desk or FitDesk) in a block random fashion. When working on the activity workstation, participants were instructed to pedal the FitDesk at a comfortable pace.
Effectiveness of a physical activity program on weight, physical fitness, occupational stress, job satisfaction and quality of life of overweight employees in high-tech industries: a randomized controlled study
Published in International Journal of Occupational Safety and Ergonomics, 2019
Yun-Ya Fang, Chien-Yuan Huang, Mei-Chi Hsu
Evaluations of physical fitness included: flexibility measured by sit and reach test; muscular strength and endurance measured by 1-min sit-ups; cardiorespiratory endurance measured by heart rate (HR), BP and 3-min modified Harvard step test (MHST). The fitness index (FI) of the MHST was calculated based on the equation: