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BACKGROUND:
Many observational studies have shown a protective effect of physical activity on cognitive ageing, but interventional studies have been less convincing. This may be due to short time scales of interventions, suboptimal interventional regimes or lack of lasting effect. Confounding through common genetic and developmental causes is also possible.
OBJECTIVES:
We aimed to test whether muscle fitness (measured by leg power) could predict cognitive change in a healthy older population over a 10-year time interval, how this performed alongside other predictors of cognitive ageing, and whether this effect was confounded by factors shared by twins. In addition, we investigated whether differences in leg power were predictive of differences in brain structure and function after 12 years of follow-up in identical twin pairs.
METHODS:
A total of 324 healthy female twins (average age at baseline 55, range 43-73) performed the Cambridge Neuropsychological Test Automated Battery (CANTAB) at two time points 10 years apart. Linear regression modelling was used to assess the relationships between baseline leg power, physical activity and subsequent cognitive change, adjusting comprehensively for baseline covariates (including heart disease, diabetes, blood pressure, fasting blood glucose, lipids, diet, body habitus, smoking and alcohol habits, reading IQ, socioeconomic status and birthweight). A discordant twin approach was used to adjust for factors shared by twins. A subset of monozygotic pairs then underwent magnetic resonance imaging. The relationship between muscle fitness and brain structure and function was assessed using linear regression modelling and paired t tests.
RESULTS:
A striking protective relationship was found between muscle fitness (leg power) and both 10-year cognitive change [fully adjusted model standardised β-coefficient (Stdβ) = 0.174, p = 0.002] and subsequent total grey matter (Stdβ = 0.362, p = 0.005). These effects were robust in discordant twin analyses, where within-pair difference in physical fitness was also predictive of within-pair difference in lateral ventricle size. There was a weak independent effect of self-reported physical activity.
CONCLUSION:
Leg power predicts both cognitive ageing and global brain structure, despite controlling for common genetics and early life environment shared by twins. Interventions targeted to improve leg power in the long term may help reach a universal goal of healthy cognitive ageing.
W50-54 60 Meter: Sandy Triolo, 8.64 seconds
W75-79 60 Meter: Rose Green, 10.82 American Record
M50-54 60 Meter: Lonnie Hooker, 7.32
M90-94 60 Meter: Dixon Hemphill, 17.72
M95-99 60 Meter: Orville Rogers, 16.92
W75-79 200 Meter: Rose Green, 36.83
M50-54 200 Meter: Lonnie Hooker, 24.08
M60-64 200 Meter: Oscar Peyton, 25.25
M90-94 200 Meter: Dixon Hemphill, 1:05.86
M95-99 200 Meter: Orville Rogers, 1:16.77
M95-99 400 Meter: Orville Rogers, 3:25.88
M70-74 800 Meter: John Brittain, 2:52.98
M90-94 800 Meter: Dixon Hemphill, 7:03.86
W65-69 1 Mile: Joanie McMullan, 8:22.79
M90-94 1 Mile: Roy Englert, 11:52.34
W75-79 3000 Meter: Tami Graf, 20:36.95
M80-84 3000 Meter: Robert Gurtler, 21:52.62
W65-69 4x200 Meter: Joanie McMullan, Lynnea Salvo, Tami Graf, Rose Green, 2:54.84
M80-84 4x200 Meter: Darrell Dempster, Robert Gurtler, Lawrence Dickerson, Ino Cantu, 4:03.05
M90-99 4x200 Meter: Orville Rogers, Charles Ross, Roy Englert, Charles Boyle, 5:40.82
W50-59 4x400 Meter: Mary Lowe Mayhugh, Ida Draim, Betty Blank, Hannah Phillips, 6:04.24
M80-89 4x400 Meter: Darrell Dempster, Robert Gurtler, Lawrence Dickerson, Ino Cantu, 8:52.60
M90-99 4x200 Meter: Orville Rogers, Charles Ross, Dixon Hemphill, Roy Englert, 12:54.81
W50-59 4x800 Meter: Mary Lowe Mayhugh, Ida Draim, Liza Recto, Elizabeth Row, 14:20.54
M30-39 4x800 Meter: Muraji Nakazawa, Mike Cannon, Terence McLaughlin, Miles Aitken, 11:49.52
M50-59 4x800 Meter: Mario Zuniga, Duane WIlliamson, Ted Poulos, Steven Anderson, 10:38.21
M80-89 4x800 Meter: Darrell Dempster, Robert Gurtler, Lawrence Dickerson, Ino Cantu, 20:36.33
M90-99 4x800 Meter: Orville Rogers, Charles Ross, Roy Englert, Dixon Hemphill, 29:47.68
W75-79 High Jump: Tami Graf, 0.85 meters
M55-59 High Jump: Bruce McBarnette, 1.80m
W45-49 Long Jump: Tracey Battle, 4.48m
W75-79 Long Jump: Tami Graf, 1.99m
W45-49 Triple Jump: Tracey Battle, 9.44m
W40-44 Shot Put: Jennifer Stephens, 9.03m
M35-39 Shot Put: Ibrahim Babiker (international athlete), 13.57m
W40-44 Weight Throw: Jennifer Stephens, 10.08m
W40-44 Super Weight Throw: Jennifer Stephens, 5.81m
M85-89 Super Weight Throw: Darrell Dempster, 5.41m
M60-64 3000 Meter Race Walk: Peter Blank, 19:52.61
While the ability to run at high top speed has been clearly related to the ability to generate high amounts of [ground reaction force] in the vertical direction3,4, much less is known about the determinants of the acceleration phase of a sprint. Coaching practice has long considered the capability of force production as an inherent feature of acceleration and sprint capability. It is a common belief that how much force and impulse one athlete is able to produce and how hard they can ‘push the ground’ and ‘push with a forward incline’ during the entire acceleration phase are key variables.
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It was found that the [decrement in ratio of force] was significantly and highly correlated to the two main 100 m performance parameters: mean and maximal 100 m velocity, as was the mean value of HF over the entire acceleration9. In contrast, neither vertical nor [ratio of the contact-averaged HF to the corresponding resultant GRF="TOTF"] averaged over the acceleration phase were significantly correlated to these performance parameters. Further, subjects’ TOTF was not significantly correlated to DRF. It was concluded that the force application technique, as opposed to the amount of total force subjects are able to apply onto the ground, is a key determinant of field 100 m sprint performance. However, one limitation of this study was that the results were obtained in low-level sprinters and in non-specialists.
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[They did an experiment with very-good-to-elite sprinters]
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Overall, the main and very novel results of these two studies show that the way sprinters apply force onto the ground (technical ability) seems to be more important to field sprint performance than the amount of total force they are able to produce (physical capability). In addition, these two mechanical features of the acceleration kinetics were not correlated, which means they represent two distinct skills.
