Brendan J. O'Brien

Genome-wide sperm DNA methylation changes after 3 months of exercise training in humans

AIM DNA methylation programs gene expression and is involved in numerous biological processes. Accumulating evidence supports transgenerational inheritance of DNA methylation changes in mammals via germ cells. Our aim was to determine the effect of exercise on sperm DNA methylation. MATERIALS & METHODS Twenty-four men were recruited and assigned to an exercise intervention or control group. Clinical parameters were measured and sperm samples were donated by subjects before and after the 3-month time-period. Mature sperm global and genome-wide DNA methylation was assessed using an ELISA assay and the 450K BeadChip (Illumina). RESULTS Global and genome-wide sperm DNA methylation was altered after 3 months of exercise training. DNA methylation changes occurred in genes related to numerous diseases such as schizophrenia and Parkinsons disease. CONCLUSIONS Our study provides the first evidence showing exercise training reprograms the sperm methylome. Whether these DNA methylation changes are inherited to future generations warrants attention.

Six minute walk distance is greater when performed in a group than alone

Objective: To investigate whether the distance covered in the six minute walk test was affected by walking with a group of others in comparison with performing the test alone. Methods: Eight healthy men (mean (SD) age 21.0 (0.9) years) and eight healthy women (mean (SD) age 20.8 (2.0) years) performed in random order two six minute walk tests either alone or in a group of four on two separate occasions one week apart. Results: Distance covered increased significantly from a mean of 653 (61) m in the individual male tests to 735 (79) m in the male group tests (p<0.05), and 616 (75) m in the individual female tests to 701 (54) m in the female group tests (p<0.01). The men increased the distance walked in six minutes by 12.5% and the women by 13.7% when they performed the test as a group. Conclusion: Performing the six minute walk test in a group facilitates its execution.

Increased expression of telomere-regulating genes in endurance athletes with long leukocyte telomeres

Leukocyte telomeres shorten with age, and excessive shortening is associated with age-related cardiometabolic diseases. Exercise training may prevent disease through telomere length maintenance although the optimal amount of exercise that attenuates telomere attrition is unknown. Furthermore, the underlying molecular mechanisms responsible for the enhanced telomere maintenance observed in endurance athletes is poorly understood. We quantified the leukocyte telomere length and analyzed the expression of telomere-regulating genes in endurance athletes and healthy controls (both n = 61), using quantitative PCR. We found endurance athletes have significantly longer (7.1%, 208-416 nt) leukocyte telomeres and upregulated TERT (2.0-fold) and TPP1 (1.3-fold) mRNA expression compared with controls in age-adjusted analysis. The telomere length and telomere-regulating gene expression differences were no longer statistically significant after adjustment for resting heart rate and relative V̇O(2 max) (all P > 0.05). Resting heart rate emerged as an independent predictor of leukocyte telomere length and TERT and TPP1 mRNA expression in stepwise regression models. To gauge whether volume of exercise was associated with leukocyte telomere length, we divided subjects into running and cycling tertiles (distance covered per week) and found individuals in the middle and highest tertiles had longer telomeres than individuals in the lowest tertile. These data emphasize the importance of cardiorespiratory fitness and exercise training in the prevention of biological aging. They also support the concept that moderate amounts of exercise training protects against biological aging, while higher amounts may not elicit additional benefits.

Assessment of decision-making performance and in-game physical exertion of Australian football umpires.

Abstract The aim of this study is to investigate the effects of in-game physical exertion on decision-making performance of Australian football umpires. Fifteen Australian football umpires (Mage = 36, s = 13.5 years; Mgames umpired = 235.2, s = 151.3) volunteered to participate in the study. During five competitive Australian football pre-season games, measures of in-game physical exertion (blood lactate levels, global positioning system [GPS]) and decision-making performance (video-based test) were obtained. There were no significant correlations between physical exertion in a particular quarter and decision-making performance in either the same quarter or any other quarter. Video-based decision-making performance was effected by time in game χ2(3) = 24.24, P = 0.001, with Quarter 4 performance significantly better than both Quarter 2 and Quarter 3. In-game physical exertion (blood lactate) significantly decreased over the course of the game χ2(3) = 11.58, P = 0.009. Results indicate no definable link between in-game physical exertion and decision-making performance. It is, however, presumed that decision-making performance may be affected by the time or context of the game. Future research is warranted to explore the relationship between physical exertion and decision-making performance to potentially inform Australian football umpire training programmes that replicate in-game physical and decision-making demands.

Effects of a Seven Day Overload-Period of High-Intensity Training on Performance and Physiology of Competitive Cyclists

Objectives Competitive endurance athletes commonly undertake periods of overload training in the weeks prior to major competitions. This investigation examined the effects of two seven-day high-intensity overload training regimes (HIT) on performance and physiological characteristics of competitive cyclists. Design The study was a matched groups, controlled trial. Methods Twenty-eight male cyclists (mean ± SD, Age: 33±10 years, Mass 74±7 kg, VO2 peak 4.7±0.5 L·min−1) were assigned to a control group or one of two training groups for seven consecutive days of HIT. Before and after training cyclists completed an ergometer based incremental exercise test and a 20-km time-trial. The HIT sessions were ∼120 minutes in duration and consisted of matched volumes of 5, 10 and 20 second (short) or 15, 30 and 45 second (long) maximal intensity efforts. Results Both the short and long HIT regimes led to significant (p<0.05) gains in time trial performance compared to the control group. Relative to the control group, the mean changes (±90% confidence limits) in time-trial power were 8.2%±3.8% and 10.4%±4.3% for the short and long HIT regimes respectively; corresponding increases in peak power in the incremental test were 5.5%±2.7% and 9.5%±2.5%. Both HIT (short vs long) interventions led to non-significant (p>0.05) increases (mean ± SD) in VO2 peak (2.3%±4.7% vs 3.5%±6.2%), lactate threshold power (3.6%±3.5% vs 2.9%±5.3%) and gross efficiency (3.2%±2.4% vs 5.1%±3.9%) with only small differences between HIT regimes. Conclusions Seven days of overload HIT induces substantial enhancements in time-trial performance despite non-significant increases in physiological measures with competitive cyclists.

Telomeres, exercise and cardiovascular disease: finding the means to justify the ends

Telomeres are repetitive tandem DNA sequences (TTAGGG) located at chromosomal ends where they protect genomic DNA from enzymatic degradation. Telomeres are scaffolded upon six regulatory proteins, collectively known as the shelterin complex. A state of replicative senescence is triggered when telomeres reach a critically shortened threshold. This article is protected by copyright. All rights reserved.

Oxygen Uptake in Maximal Effort Constant Rate and Interval Running

This study investigated differences in average V˙O2 of maximal effort interval running to maximal effort constant rate running at lactate threshold matched for time. The average V˙O2 and distance covered of 10 recreational male runners (V˙O2 max: 4158 ± 390 mL·min−1) were compared between a maximal effort constant-rate run at lactate threshold (CRLT), a maximal effort interval run (INT) consisting of 2 min at V˙O2 max speed with 2 minutes at 50% of V˙O2 repeated 5 times, and a run at the average speed sustained during the interval run (CR submax). Data are presented as mean and 95% confidence intervals. The average V˙O2 for INT, 3451 (3269–3633) mL·min−1, 83% V˙O2 max, was not significantly different to CRLT, 3464 (3285–3643) mL·min−1, 84% V˙O2 max, but both were significantly higher than CR sub-max, 3464 (3285–3643) mL·min−1, 76% V˙O2 max. The distance covered was significantly greater in CLRT, 4431 (4202–3731) metres, compared to INT and CR sub-max, 4070 (3831–4309) metres. The novel finding was that a 20-minute maximal effort constant rate run uses similar amounts of oxygen as a 20-minute maximal effort interval run despite the greater distance covered in the maximal effort constant-rate run.

Exercise induced plasma volume expansion is accompanied by a decrease in intracellular fluid volume

The mechanism of the expanded plasma volume observed after exercise was investigated. Nine subjects cycled for 60 rain on four consecutive days at 65% of VO 2 max in a hot ambient environment (35°C, 50% Relative humidity). Prior to, and 24 hr after completing the exercise training, plasma oncotic pressure, total body water, extracellular, intracellular, blood, plasma and interstitial volume were measured. 24 hr upon completion of the exercise training, plasma volume increased from 2.94+0.1 to 3.09-+0.1 litres (p<0.05). Total body water remained unchanged after four days of exercise (48.7_+1.5 to 48.1_+2 litres; n=6). The extracellular volume increased from 15.1_+1. t to 17.69_+1.1 litres (p<0.05); and the interstitial volume from 12.2_+1 to 14.6+_1 litres (p<0.05; n=6}. Intraceltular volume decreased from 34.2_+1.9 to 32.2_+2.3 litres; p<0.05, n=6). Oncotic pressure fell from 31.2_+0.6 to 29.7_+0.5 mm Hg (p<0.05). Urinary sodium output did not significantly differ from pre-exercise levels during the training. In conclusion, the plasma volume expansion that occurs after exercise is at the expense of the intracellular volume. As the oncotic pressure decreased after training, an increase in intravascutar protein concentration is not the drixdng force initiating the hypervolemia. This results suggests that an alteration in the hydrostatic pressure gradient across the capillary walt is the primary mechanism for exercise induced hypervolemia.