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Biomedical subjects

Archie Young

Publications and source records attributed to Archie Young.

8 recordsLinked to original sources
PubMed2006

Skeletal muscle IGF-I isoform expression in healthy women after isometric exercise.

CONTEXT: Little is known about the expression of skeletal muscle-specific isoforms of the insulin-like growth factor-I (IGF-I) gene in response to exercise in humans. Data for women are sparse and the influences of age and physical training status are unknown. Here we aimed to describe the expression of mRNA for the IGF-I isoforms in the quadriceps muscles of women at rest and after isometric exercise. OBJECTIVE: To categorize mRNA expression of the IGF-I splice variants IGF-IEa and IGF-IEc (MGF) in healthy women, determine whether isometric exercise stimulates expression, and to determine the duration of the response. DESIGN: Observational study. SETTING: Clinical research facility. PARTICIPANTS: Six healthy women (median age 38 years, range 25-43 years). INTERVENTION: Single bout of maximal isometric knee extension undertaken as 20 sets of 6 contractions. Muscle samples from the lateral mass of the quadriceps were obtained by needle biopsy at baseline, 2.5h and 50h after exercise. MAIN OUTCOME MEASURES: Quantification of mRNAs for IGF-IEa and MGF. RESULTS: mRNA for the IGF-IEa transcript was significantly elevated by 50h post-exercise compared to baseline (p=0.005) and mRNA for MGF was significantly elevated by 2.5h (p=0.026). There were no statistically significant differences between measurements at 2.5h and 50h for either transcript. CONCLUSIONS: We have shown that the upregulation of the muscle specific IGF-IEa and MGF isoforms occurs within 2.5h of a single bout of isometric exercise in women. The upregulation persists for at least 2 days after exercise. We have also demonstrated a potentially safe and effective way of studying the responsiveness of these isoforms to resistance exercise in future studies of older and/or frail individuals.

Adult↗
PubMed2006

Longitudinal changes in muscle strength and mass after acute stroke.

BACKGROUND: Reduced mobility after stroke may cause a loss of muscle mass which may, in theory, contribute to disability. We investigated longitudinal changes in muscle strength, lean cross-sectional area and muscle mass in all limbs after acute stroke. METHODS: We recruited 17 patients within 72 h of hospital admission and measured (a) hand grip strength, (b) knee extensor strength and (c) arm and leg lean cross-sectional area on 6 occasions over 6 months. Appendicular and total muscle mass (dual-energy X-ray absorptiometry) were measured at 3 weeks and 6 months. RESULTS: There was no significant change over time in the strength, lean cross-sectional area and muscle mass of the arms or legs. We noted that muscle strength was substantially lower in all limbs compared with population norms. CONCLUSION: We found no evidence of a decline in muscle strength or mass in any limb after the stroke, which could have been attributed to reduced mobility. The observed muscle weakness in the ipsilateral side may have pre-dated the stroke.

Absorptiometry, Photon↗
PubMed2005

Responses to walking-speed instructions: implications for health promotion for older adults.

This study examined the effect of age on descriptive walking-speed instructions commonly used in health promotion. Participants were 9 young (20-23 years) and 9 older (75-83 years) women. Oxygen uptake and walking speed were measured in response to descriptive walking instructions ("slow," "comfortable," "brisk," and "fast"). Although the older women walked approximately 20% slower in response to all walking instructions and with significantly lower oxygen costs for brisk and fast, the intensity of the exercise represented a much greater percentage of VO2max and showed greater interindividual variation. When asked to walk at a brisk pace, the older women averaged 67% VO2max (SD 20.6), whereas the young women averaged only 45% VO2max (SD 4.5). With older people, brisk might elicit an exercise intensity unnecessarily high for physiological benefit and that might compromise safety and adherence, which emphasizes the need for validation of carefully worded exercise and training guidance for older adults.

Aged↗
PubMed2003

Cycling as a novel approach to resistance training increases muscle strength, power, and selected functional abilities in healthy older women.

Cycling on a mechanically braked cycle ergometer was used as a novel approach to compare the effects of three different 16-wk resistance-training programs on isometric force, power output, and selected functional abilities in 31 healthy 65- to 74-yr-old women. Training was conducted three times per week. During each session, individuals of the speed group performed 8 sets of 16 pedal revolutions at 40% of the maximal resistance to complete two revolutions (2 RM); strength group performed 8 sets of 8 revolutions at 80% of 2 RM; and combination group performed 4 sets of 16 revolutions at 40% and 4 sets of 8 revolutions at 80% of 2 RM. During each set, all participants were required to pedal as fast as possible with a 2-min interval between sets. All training groups significantly increased force, power, and functional abilities (maximal treadmill walking speed, vertical jumping, and box stepping) at week 8 (in the range from 6.5 to 20.8%) with no further improvement at week 16 (except maximal treadmill walking speed), but no significant differences were observed between the three groups. The novel approach to performing both low- and high-resistance training, based on the use of a cycle ergometer, has been shown to be effective in improving strength, power, and functional abilities in a group of healthy women. Even fit older women can still improve in functional abilities. Interestingly, the "high-speed" and "low-speed" programs induced an increase in both power and strength of similar magnitude.

Adaptation, Physiological↗
PubMed2002

Aerobic training in the 'oldest old': the effect of 24 weeks of training.

OBJECTIVE: to determine the effects of aerobic training on the maximal aerobic power of healthy, very elderly people. DESIGN: a 12-week control period followed by 24 weeks of progressive, weight bearing, aerobic training. SUBJECTS: 26 men and women aged 79 to 91 years conforming to pre-determined health criteria. METHODS: we took measurements before and after a 12 week control period and following 24 weeks of training. These were maximal aerobic power (VO(2)max), heart rate at an oxygen consumption of 10 ml x kg(-1) x min(-1) (HR at VO(2)10), resting heart rate, isometric knee extensor strength, isometric elbow flexor strength and lower limb extensor power. MAIN RESULTS: pre-control values of VO(2)max for the women and men were 14.1 (SD 2.79) and 22.0 (5.12) ml.kg(-1).min(-1) respectively. There was no significant change in the VO(2)max of either group over the control period. After training, there was a 15% increase in the VO(2)max of the women (P<0.01) but no change was observed in the men. In the women, there was no significant change in HR at VO(2)10 over the control period but a 14% decrease (P<0.01) after training. In the men there was a 7% (P<0.05) increase in HR at VO(2)10 over the control period and a 5% (P<0.05) decrease after training. No effect of training was seen on isometric knee extensor strength, isometric elbow flexor strength or lower limb extensor power of either group. CONCLUSION: progressive aerobic training can increase the maximal aerobic power of very elderly women. A 15% increase in VO(2)max may prevent many elderly women from crossing functionally important thresholds, thereby helping to maintain independence.

Aged↗
PubMed2002

Muscle function in elite master weightlifters.

PURPOSE: To determine whether explosive power and isometric strength of the lower-limb muscles in elite master Olympic weightlifters declines at a similar rate to nontrained healthy controls with increasing age. METHODS: 54 elite level masters weightlifters (aged 40-87), who were competitors at the World Masters Weightlifting Championships (1999), were compared with a similar number of aged-matched, healthy untrained individuals. Isometric knee extensor strength and lower-limb explosive power were tested. Extent of antagonist co-contraction during isometric knee extension was determined by EMG and power loading characteristics by using a variable inertial system. Muscle volume was estimated using anthropometry. RESULTS: On average, the weightlifters were able to generate 32% more peak power (P < 0.05) in the lower limbs and 32% more isometric knee extensor force (P < 0.05) than the control subjects. No significant differences in lower-leg volume were observed between the two groups. Peak power declined at a similar rate with increasing age in the weightlifters and controls (1.2 and 1.3% of a 45-yr-old's value per year), as did strength, but at a lower rate (0.6 and 0.5% per year). The inertial load at which the weightlifters achieved their maximal peak power output was greater (P < 0.05) than the controls. The torque generated at this optimal inertia was also greater in the weightlifters (P < 0.05), whereas the time taken for the weightlifters to reach their maximal peak power was on average 13% shorter (P < 0.05). No differences in antagonist co-contraction during isometric knee extension were observed between the two groups. CONCLUSIONS: Muscle power and isometric strength decline at a similar rate with increasing age in elite master weightlifters and healthy controls. In spite of inertial load optimization, muscle power declined in both groups at approximately twice the rate of isometric strength. Although similar rates of decline were observed, the absolute differences between the weightlifters and controls were such that an 85-yr-old weightlifter was as powerful as a 65-yr-old control subject. This would therefore represent an apparent age advantage of approximately 20 yr for the weightlifters.

Adult↗