Creatine and Resistance Training for Older Adults
By Dónal P. O'Mathúna
Donal O'Mathuna is a lecturer in Health Care Ethics, School of Nursing, Dublin City University, Ireland. He reports no financial relationship relevant to this field of study.
Creatine remains one of the most popular supplements for athletes, especially those lifting weights.1 Much evidence supports claims that creatine enhances power output during short maximal bursts of exercise, such as power lifting or sprinting.2 The benefit is noted particularly when the bursts are repeated intermittently in what is called interval training.
Building muscle strength and endurance is important in other arenas. Aging is associated with reduced muscle mass and strength, which can lead to functional impairment and reduced quality of life. Sarcopenia refers to the condition when fat-free mass is more than 2 standard deviations below normal.3 Numerous studies have demonstrated that resistance exercise counteracts sarcopenia, leading to investigation of complementary strategies to supplement those gains.
Because of encouraging results in athletes who were supplementing with creatine while resistance training, suggestions have been made that non-athletes might benefit similarly. Creatine supplementation could be beneficial if it hastened strength gains or reduced the number of repetitions necessary to get desired improvements after injuries.4 Resistance training is also suggested for age- and disease-related loss of muscle mass, strength, and function.5 Such exercise, along with supplementation, might be preferable to exercise alone, or other invasive or pharmacological alternatives. This article will review the evidence available to date regarding creatine supplementation for those who are recommended resistance training for age or disease reasons, as opposed to athletic reasons.
Creatine is made from three amino acids common to protein. On average, people require about 2 g of creatine daily, obtained equally from exogenous and endogenous sources.6 Humans store 95% of their creatine in skeletal muscle, with more found in fast twitch muscle fibers than slow twitch ones.7
About 60% of the creatine in skeletal muscle exists as creatine phosphate (CP). Adenosine triphosphate (ATP) supplies energy for muscle contraction when it is converted into adenosine diphosphate (ADP). Muscles normally store enough ATP for only a few seconds of exertion, after which CP replenishes ATP. Muscle CP can provide fuel for an additional 4-6 seconds of intense exercise, and its rate of replenishment depends on free creatine concentrations.8 Creatine is, thus, essential for short, intense, anaerobic exercise like power-lifting, sprinting, and jumping. Thirty seconds of rest will half-replenish CP levels, though complete recovery may take up to 3-4 minutes.9
Mechanism of Action
The mechanism of action by which creatine supplementation could increase muscle strength and exercise performance is only partly understood. However, a number of physiological mechanisms have been proposed and are being investigated.2 Studies have provided evidence that up to 40% of the ergogenic effect could be due to a direct consequence of making more creatine and CP available for muscle energy production. Increased free plasma creatine could allow faster replenishment of CP stores and, thus, shorten the recovery periods needed during repeated bouts of intense exercise. In addition to these direct effects on exercise performance, creatine has been proposed to contribute to muscle protein growth both directly and via gene activation. Evidence here is lacking.10 Body mass does increase with creatine, but this is more likely due to increased accumulation of body water.10
These different mechanisms could contribute to increased muscle mass and strength. Variation in their influence could account for one of the ongoing controversies regarding creatine supplementation; namely, the great variability found in individual responses to supplementation.
The first double-blind study to examine creatine use with resistance training in elderly sedentary adults was published in 1998.11 Thirty-two men and women (67-80 years old) were randomized into four groups: creatine with resistance training, placebo with training, creatine without training, and placebo without training. None of the participants did weight-lifting before the study and were sedentary to moderately active. Creatine dose was 20 g/day for 5 days, followed by 3 g/day for a total of 8 weeks. Resistance training was carried out 3 times a week. No significant changes in body mass or body fat were found in any group. Training groups had significantly increased strength and endurance compared to those not training (P < 0.02). Creatine supplementation did not provide any additional benefit.
A double-blind, randomized trial assigned 30 men (mean age 70 years) to receive either creatine (0.3 g/kg for 5 days followed by 0.07 g/kg daily) or placebo.12 Both groups engaged in three sessions of resistance training per week for 12 weeks. Both groups had significantly increased fat-free mass (FFM), with the increase being significantly greater in the creatine group (P < 0.05). Fat mass did not differ between the two groups. With two of the three muscle groups trained, the creatine group had significantly greater improvements in strength and endurance. The training volumes were 31 percent higher in the creatine group (P = 0.05).
Thirty-nine community dwelling, healthy adults (aged 65-85 years) were randomized to receive either creatine (5 g/day) with conjugated linoleic acid (CLA, 6 g/day) or placebo for 6 months.3 No participants had participated in an exercise program during the previous 2 years, and all participated in supervised resistance training twice a week for the duration of the study. All measures of strength increased for both groups. Isokinetic (resistance at a constant speed) strength increased significantly more in the supplement group (P < 0.05), but isometric (performed at static position) strength gains did not differ between the groups. The supplement group had significantly better increases in FFM and decreases in total fat mass (P < 0.05). These changes were suggested to arise from creatine because CLA is not known to enhance FFM.
Parkinson's disease (PD) is accompanied by loss of muscle mass, strength, and endurance, along with loss of function in the lower extremities. Twenty patients, aged 62 years, with mild-to-moderate PD were randomized to receive either creatine (20 g/day for 5 days followed by 5 g/day) or placebo.5 Participants had not been involved in regular exercise, and both groups participated in twice weekly progressive resistance training for 12 weeks. At the end of the study, participants in both groups had significantly increased muscle strength, with the creatine group showing significantly greater improvements than placebo for two of three muscle groups (P < 0.05). Both groups had increased muscle endurance and FFM, with no differences between the groups. Functional performance was measured by timing participants rising from a chair three times without using their arms. The creatine group showed a significant 11% reduction in total time, while the placebo group had a non-significant change.
Creatine frequently leads to weight-gain of 1-3 kg, probable due to intramuscular water retention resulting from an osmotic effect.13 Numerous anecdotal reports from athletes claim creatine supplementation causes gastrointestinal problems, muscle cramping, and renal problems. One study with older men found significantly more reports of loose stools during creatine loading than with placebo.12 Also, after 3-5 weeks, muscle cramping and strains were more frequent with creatine than placebo. Whether creatine adversely effects renal function remains controversial and unclear, suggesting that those at high risk for renal disease should be monitored medically.14 Patients with McArdle disease experience exercise intolerance, premature muscle fatigue, and exercise-induced muscle pain. Beneficial effects of creatine supplementation alone were demonstrated at 60 mg/kg, but at 150 mg/kg, muscle pain severity and intensity were significantly higher (P < 0.05).15
No drug interactions are known, although concerns about the potential for renal toxicity raise issues about drugs metabolized through the kidneys.
Creatine is readily available from meat and fish (containing roughly 4-5 g/kg) and, therefore, is classified as a dietary supplement, not a drug. It is most commonly available as the monohydrate in powder, candy, gum, and liquid. Numerous products combine it with vitamins, nutrients, and supplements, with no evidence of added benefits. Athletes usually "load" with 20 g creatine per day for 4-6 days (usually 5 g qid), followed by one 2 g daily dose. This approach has been adopted in some studies with older people.
Oral creatine supplementation has been studied extensively in athletes. Beneficial effects occur with high-intensity exertion lasting short periods of time. Much less research has been conducted in older people. Where resistance training has shown itself to be beneficial, there is some evidence to support the use of creatine supplements. However, the early stage of this research must be noted, especially given the potential for complications, in the elderly, especially those with co-morbidities.
Creatine supplementation may enhance the effects of resistance training in older adults. However, the functional benefits of this have, for the most part, not been examined in studies. If creatine allows people to gain in strength or endurance with fewer repetitions, their willingness to train may increase. However, such an approach could lead to the neglect of cardiovascular or social dimensions of training. For those interested in taking creatine, it may augment resistance training, and appears to be well tolerated, but given the small number of studies available at this point, creatine supplementation cannot be confidently promoted for older adults.
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