Physical activity enhances metabolic fitness independently of cardiorespiratory fitness in marathon runners

Foot and Ankle Bone Marrow Edema Assessment in Long Distance Runners

BACKGROUND

The clinical significance of foot and ankle bone marrow edema (BME) is poorly understood.

METHODS

Magnetic resonance imaging (MRI) and the visual analog scale (VAS) pain scores were collected for 17 runners who participated in the Twin Cities Marathon, immediately postmarathon and at a 6-week follow-up. Bone marrow edema lesions were classified using lesion frequency, anatomical location, and grading scale change to calculate a BME score for each affected bone. Spearman rank correlation coefficient test was used to identify a possible correlation between VAS and postmarathon BME. A paired Student t test was used to detect differences between total mileage ran 6 weeks postmarathon in participants with or without BME.

RESULTS

After completing the marathon, 8 BME lesions were identified in 5 participants (29.4%; 5/17), 3 were men, and 2 were women, with a mean age of 33.8 years (range: 24-52), and BMI of 22.9 ± 4. All lesions were resolved on 6-week follow-up imaging. VAS pain scores did not correlate with postmarathon BME. A significant difference in total miles logged over 6 weeks postmarathon could not be found among participants with and without BME.

CONCLUSION

Foot and ankle BME changes identified by MRI were not correlated to clinical symptoms and may resolve with self-directed activity in less time than other areas of the lower extremity.

LEVEL OF EVIDENCE

Level II, Prospective Cohort Study.

Health status of recreational runners over 10-km up to ultra-marathon distance based on data of the NURMI Study Step 2

Endurance running is well-documented to affect health beneficially. However, data are still conflicting in terms of which race distance is associated with the maximum health effects to be obtained. Therefore, the aim of this study was to compare the health status of endurance runners over different race distances. A total of 245 recreational runners (141 females, 104 males) completed an online survey. Health status was assessed by measuring eight dimensions in two clusters of health-related indicators (e.g., body weight, mental health, chronic diseases and hypersensitivity reactions, medication intake) and health-related behaviors (e.g., smoking habits, supplement intake, food choice, healthcare utilization). Each dimension consisted of analytical parameters derived to a general domain score between 0 and 1. Data analysis was performed by using non-parametric ANOVA and MANOVA. There were 89 half-marathon (HM), 65 marathon/ultra-marathon (M/UM), and 91 10-km runners. 10-km runners were leaner than both the HM and M/UM runners (p ≤ 0.05). HM runners had higher health scores for six dimensions (body weight, mental health, chronic diseases and hypersensitivity reactions, medication intake, smoking habits, and health care utilization), which contributed to an average score of 77.1% (score range 62–88%) for their overall state of health. Whereas 10-km and M/UM runners had lesser but similar average scores in the overall state of health (71.7% and 72%, respectively). Race distance had a significant association with the dimension “chronic diseases and hypersensitivity reactions” (p ≤ 0.05). Despite the null significant associations between race distance and seven (out of eight) multi-item health dimensions, a tendency towards better health status (assessed by domain scores of health) among HM runners was found compared to other distance runners. However, the optimal state of health across all race distances supported the notion that endurance running contributed to overall health and well-being.

Trial registration number: ISRCTN73074080. Retrospectively registered 12th June 2015.

Exercise and health: historical perspectives and new insights

Since ancient times, the health benefits of regular physical activity/exercise have been recognized and the classic studies of Morris and Paffenbarger provided the epidemiological evidence in support of such an association. Cardiorespiratory fitness, often measured by maximal oxygen uptake, and habitual physical activity levels are inversely related to mortality. Thus, studies exploring the biological bases of the health benefits of exercise have largely focused on the cardiovascular system and skeletal muscle (mass and metabolism), although there is increasing evidence that multiple tissues and organ systems are influenced by regular exercise. Communication between contracting skeletal muscle and multiple organs has been implicated in exercise benefits, as indeed has other interorgan "cross-talk." The application of molecular biology techniques and "omics" approaches to questions in exercise biology has opened new lines of investigation to better understand the beneficial effects of exercise and, in so doing, inform the optimization of exercise regimens and the identification of novel therapeutic strategies to enhance health and well-being.

Predictors of postprandial glycaemia, insulinaemia and insulin resistance in adolescents

Postprandial glycaemia and insulinaemia are important risk factors for type 2 diabetes. The prevalence of insulin resistance in adolescents is increasing, but it is unknown how adolescent participant characteristics such as BMI, waist circumference, fitness and maturity offset may explain responses to a standard meal. The aim of the present study was to examine how such participant characteristics affect the postprandial glycaemic and insulinaemic responses to an ecologically valid mixed meal. Data from the control trials of three separate randomised, crossover experiments were pooled, resulting in a total of 108 participants (fifty-two boys, fifty-six girls; aged 12·5 (SD 0·6) years; BMI 19·05 (SD 2·66) kg/m2). A fasting blood sample was taken for the calculation of fasting insulin resistance, using the homoeostatic model assessment of insulin resistance (HOMA-IR). Further capillary blood samples were taken before and 30, 60 and 120 min after a standardised lunch, providing 1·5 g/kg body mass of carbohydrate, for the quantification of blood glucose and plasma insulin total AUC (tAUC). Hierarchical multiple linear regression demonstrated significant predictors for plasma insulin tAUC were waist circumference, physical fitness and HOMA-IR (F(3,98) = 36·78, P < 0·001, adjusted R2 = 0·515). The variance in blood glucose tAUC was not significantly explained by the predictors used (F(7,94) = 1·44, P = 0·198). Significant predictors for HOMA-IR were BMI and maturity offset (F(2,102) = 14·06, P < 0·001, adjusted R2 = 0·021). In summary, the key findings of the study are that waist circumference, followed by physical fitness, best explained the insulinaemic response to an ecologically valid standardised meal in adolescents. This has important behavioural consequences because these variables can be modified.

Running and Swimming Differently Adapt the BDNF/TrkB Pathway to a Slow Molecular Pattern at the NMJ

Physical exercise improves motor control and related cognitive abilities and reinforces neuroprotective mechanisms in the nervous system. As peripheral nerves interact with skeletal muscles at the neuromuscular junction, modifications of this bidirectional communication by physical activity are positive to preserve this synapse as it increases quantal content and resistance to fatigue, acetylcholine receptors expansion, and myocytes' fast-to-slow functional transition. Here, we provide the intermediate step between physical activity and functional and morphological changes by analyzing the molecular adaptations in the skeletal muscle of the full BDNF/TrkB downstream signaling pathway, directly involved in acetylcholine release and synapse maintenance. After 45 days of training at different intensities, the BDNF/TrkB molecular phenotype of trained muscles from male B6SJLF1/J mice undergo a fast-to-slow transition without affecting motor neuron size. We provide further knowledge to understand how exercise induces muscle molecular adaptations towards a slower phenotype, resistant to prolonged trains of stimulation or activity that can be useful as therapeutic tools.

Factors Influencing Running Velocity at Lactate Threshold in Male and Female Runners at Different Levels of Performance

BACKGROUND

The primary aim was to examine the relationship between lactate threshold (LT) expressed as percentage of maximal oxygen uptake (VO2max) and running velocity at LT (LTV). A secondary aim was to investigate to what extent VO2max, oxygen cost of running (CR), and maximal aerobic speed (MAS) determined LTV. A third aim was to investigate potential differences in LT and LTV between elite, national and recreational runners, as well as possible gender differences regarding VO2max, CR, LT, and LTV.

METHODS

Seventy-five competitive runners (37 males and 38 females) with an average VO2max of 63.0 ± 9.3 mL⋅kg-1⋅min-1, and an average LTV of 13.6 ± 2.3 km⋅h-1 were tested for VO2max, LT, LTV, MAS, and CR.

RESULTS

Lactate threshold did not correlate with LTV. With an r - value of 0.95 (p < 0.001) and a standard error of estimate of 4.0%, the product of MAS and individual LT determined 90% of LTV, outside a range of ±0.27 km⋅h-1. LTV increased with higher performance level. However, LT did not differ between elite, national and recreational runners. Female runners had 2.5% higher LT, 8% lower LTV, and 21% lower VO2max, but 9% better CR than male runners.

CONCLUSION

Lactate threshold did not correlate with LTV. The product of MAS and LT correlated strongly with LTV. There were no differences between elite, national and recreational runners regarding LT, but female runners had higher LT than the male runners. Female runners at the same relative performance level had lower LTV and VO2max, but better CR than male runners.

Vascular improvements in individuals with type 2 diabetes following a 1 year randomised controlled exercise intervention, irrespective of changes in cardiorespiratory fitness

AIMS/HYPOTHESIS

Vascular changes in individuals with type 2 diabetes mellitus majorly contribute to the development of cardiovascular disease. Increased cardiorespiratory fitness (CRF) has been associated with improvements in vascular health. Although CRF tends to improve with exercise training, there remains a portion of participants with little or no improvement. Given the importance of vascular function in individuals with type 2 diabetes, we assessed whether individuals who failed to improve CRF following a 1 year exercise intervention also failed to improve arterial stiffness and structural indices.

METHODS

Individuals with type 2 diabetes with no major micro- and macrovascular complications and aged between 30 and 75 years old (n = 63) participated in a three-arm, 1 year, randomised controlled exercise intervention in Lisbon, Portugal. The study involved a non-exercise control group, a moderate continuous training combined with resistance training (RT) group and a high-intensity interval training with RT group. Allocation of participants into the intervention and control groups was done using a computer-generated list of random numbers. An improvement in CRF was defined as a change in [Formula: see text] ≥5%. Vascular stiffness and structural indices were measured using ultrasound imaging and applanation tonometry. Generalised estimating equations were used to compare changes in vascular measures across individuals in the control group (n = 22) and those in the exercise groups who either had improved CRF (CRF responders; n = 14) or whose CRF did not improve (CRF non-responders; n = 27) following 1 year of exercise training.

RESULTS

Compared with the control group, exercisers, with and without improvements in CRF, had decreased carotid intima-media thickness (IMT) (CRF responders: β = -2.84 [95% CI -5.63, -0.04]; CRF non-responders: β = -5.89 [95% CI -9.38, -2.40]) and lower-limb pulse wave velocity (PWV) (CRF responders: β = -0.14 [95% CI -0.25, -0.03]; CRF non-responders: β = -0.14 [95% CI -0.25, -0.03]), the latter being an indicator of peripheral arterial stiffness. Only CRF responders had decreased PWV of the upper limb compared with control participants (β = -0.12 [95% CI -0.23, -0.01]). As for central stiffness, CRF non-responders had increased aortic PWV compared with CRF responders (β = 0.19 [95% CI 0.07, 0.31]), whereas only the CRF non-responders had altered carotid distensibility coefficient compared with the control group (β = 0.00 [95% CI 3.01 × 10^-5, 0.00]). No interaction effects between the CRF responders and non-responders vs control group were found for the remaining stiffness or haemodynamic indices (p>0.05).

CONCLUSIONS/INTERPRETATION

Regardless of improvements in CRF, individuals with type 2 diabetes had significant improvements in carotid IMT and lower-limb arterial stiffness following a 1 year exercise intervention. Thus, a lack of improvement in CRF following exercise in people with type 2 diabetes does not necessarily entail a lack of improvement in vascular health.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03144505 FUNDING: This work was supported by fellowships from the Portuguese Foundation for Science and Technology. This work is also financed by a national grant through the Fundação para a Ciência e Tecnologia (FCT), within the unit I&D 472.

Sex differences in the relationship between cardiorespiratory fitness and brain function in older adulthood

We investigated sex differences in the association between a measure of physical health, cardiorespiratory fitness (CRF), and brain function using resting-state functional connectivity fMRI. We examined these sex differences in the default, frontoparietal control, and cingulo-opercular networks, assemblies of functionally connected brain regions known to be impacted by both age and fitness level. Healthy older adults ( n = 49; 29 women) were scanned to obtain measures of intrinsic connectivity within and across these 3 networks. We calculated global efficiency (a measure of network integration) and local efficiency (a measure of network specialization) using graph theoretical methods. Across all three networks combined, local efficiency was positively associated with CRF, and this was more robust in male versus female older adults. Furthermore, global efficiency was negatively associated with CRF, but only in males. Our findings suggest that in older adults, associations between brain network integrity and physical health are sex-dependent. These results underscore the importance of considering sex differences when examining associations between fitness and brain function in older adulthood. NEW & NOTEWORTHY We examined the association between cardiorespiratory fitness and resting state functional connectivity in several brain networks known to be impacted by age and fitness level. We found significant associations between fitness and measures of network integration and network specialization, but in a sex-dependent manner, highlighting the interplay between sex differences, fitness, and aging brain health. Our findings underscore the importance of considering sex differences when examining associations between fitness and brain function in older adulthood.

Exercise effects on physiological function during aging

The decrease in cognitive/motor functions and physical abilities severely affects the aging population in carrying out daily activities. These disabilities become a burden on individuals, families and society in general. It is known that aging conditions are ameliorated with regular exercise, which attenuates the age-associated decline in maximal oxygen uptake (VO2max), production of reactive oxygen species (ROS), decreases in oxidative damage to molecules, and functional impairment in various organs. While benefits of physical exercise are well-documented, the molecular mechanisms responsible for functional improvement and increases in health span are not well understood. Recent findings imply that exercise training attenuates the age-related deterioration in the cellular housekeeping system, which includes the proteasome, Lon protease, autophagy, mitophagy, and DNA repair systems, which beneficially impacts multiple organ functions. Accumulating evidence suggests that exercise lessens the deleterious effects of aging. However, it seems unlikely that systemic effects are mediated through a specific biomarker. Rather, complex multifactorial mechanisms are involved to maintain homeostatic functions that tend to decline with age.

Utilization of lactic acid in human myotubes and interplay with glucose and fatty acid metabolism

Once assumed only to be a waste product of anaerobe glycolytic activity, lactate is now recognized as an energy source in skeletal muscles. While lactate metabolism has been extensively studied in vivo, underlying cellular processes are poorly described. This study aimed to examine lactate metabolism in cultured human myotubes and to investigate effects of lactate exposure on metabolism of oleic acid and glucose. Lactic acid, fatty acid and glucose metabolism were studied in myotubes using [¹⁴C(U)]lactic acid, [¹⁴C]oleic acid and [¹⁴C(U)]glucose, respectively. Myotubes expressed both the MCT1, MCT2, MCT3 and MCT4 lactate transporters, and lactic acid was found to be a substrate for both glycogen synthesis and lipid storage. Pyruvate and palmitic acid inhibited lactic acid oxidation, whilst glucose and α-cyano-4-hydroxycinnamic acid inhibited lactic acid uptake. Acute addition of lactic acid inhibited glucose and oleic acid oxidation, whereas oleic acid uptake was increased. Pretreatment with lactic acid for 24 h did not affect glucose or oleic acid metabolism. By replacing glucose with lactic acid during the whole culturing period, glucose uptake and oxidation were increased by 2.8-fold and 3-fold, respectively, and oleic acid oxidation was increased 1.4-fold. Thus, lactic acid has an important role in energy metabolism of human myotubes.

Nitration of MnSOD in the Carotid Body and Adrenal Gland Induced by Chronic Intermittent Hypoxia

Chronic intermittent hypoxia (CIH), main feature of obstructive sleep apnea, produces nitro-oxidative stress, which contributes to potentiate carotid body (CB) chemosensory discharges and sympathetic-adrenal-axis activity, leading to hypertension. The MnSOD enzymatic activity, a key enzyme on oxidative stress control, is reduced by superoxide-induced nitration. However, the effects of CIH-induced nitration on MnSOD enzymatic activity in the CB and adrenal gland are not known. We studied the effects of CIH on MnSOD protein and immunoreactive (MnSOD-ir) levels in the CB, adrenal gland and superior cervical ganglion (SCG), and on 3-nitrotyrosine (3-NT-ir), CuZnSOD (CuZnSOD-ir), MnSOD nitration, and its enzymatic activity in the CB and adrenal gland from male Sprague-Dawley rats exposed to CIH for 7 days. CIH increased 3-NT-ir in CB and adrenal gland, whereas MnSOD-ir increased in the CB and in adrenal cortex, but not in the whole adrenal medulla or SCG. CIH nitrated MnSOD in the CB and adrenal medulla, but its activity decreased in the adrenal gland. CuZnSOD-ir remained unchanged in both tissues. All changes observed were prevented by ascorbic acid treatment. Present results show that CIH for 7 days produced MnSOD nitration, but failed to reduce its activity in the CB, because of the increased protein level.

Improved Exercise-Related Skeletal Muscle Oxygen Consumption Following Uptake of Endurance Training Measured Using Near-Infrared Spectroscopy

Skeletal muscle metabolic function is known to respond positively to exercise interventions. Developing non-invasive techniques that quantify metabolic adaptations and identifying interventions that impart successful response are ongoing challenges for research. Healthy non-athletic adults (18–35 years old) were enrolled in a study investigating physiological adaptations to a minimum of 16 weeks endurance training prior to undertaking their first marathon. Before beginning training, participants underwent measurements of skeletal muscle oxygen consumption using near-infrared spectroscopy (NIRS) at rest (resting muscleV˙O₂) and immediately following a maximal exercise test (post-exercise muscleV˙O₂). Exercise-related increase in muscleV˙O₂ (ΔmV˙O₂) was derived from these measurements and cardio-pulmonary peakV˙O₂ measured by analysis of expired gases. All measurements were repeated within 3 weeks of participants completing following the marathon and marathon completion time recorded. MuscleV˙O₂ was positively correlated with cardio-pulmonary peakV˙O₂ (r = 0.63, p < 0.001). MuscleV˙O₂ increased at follow-up (48% increase; p = 0.004) despite no change in cardio-pulmonary peakV˙O₂ (0% change; p = 0.97). Faster marathon completion time correlated with higher cardio-pulmonary peakV˙O₂ (r_partial = −0.58, p = 0.002) but not muscleV˙O₂ (r_partial = 0.16, p = 0.44) after adjustment for age and sex [and adipose tissue thickness (ATT) for muscleV˙O₂ measurements]. Skeletal muscle metabolic adaptions occur following training and completion of a first-time marathon; these can be identified non-invasively using NIRS. Although the cardio-pulmonary system is limiting for running performance, skeletal muscle changes can be detected despite minimal improvement in cardio-pulmonary function.

Predictors of cardiorespiratory fitness in female and male adults with different body mass index: National Health and Nutrition Examination Survey 1999-2004 dataset

BACKGROUND

The aim of this study was to explore factors affecting cardiorespiratory fitness in males and females with different body mass index (BMI).

METHODS

The National Health and Nutrition Examination Survey 1999-2004 data were used for this retrospective study. Estimated maximal oxygen uptake (VO_2max) is surrogate for cardiorespiratory fitness (CRF). Univariate and multivariate linear regression analyses were performed to explore whether study variables were associated with estimated VO_2max stratified by gender and BMI categories.

RESULTS

A total of 3292 subjects 20-49 years of age were included in the analysis. CRF significantly decreased as BMI increased in both females and males. Ethnic difference was found in normal BMI in both genders and obese females; homocysteine was significantly negatively associated with estimated VO_2max, as was total cholesterol. Obese male subjects with diabetes had a lower estimated VO_2max than those without diabetes, and C-reactive protein (CRP) level and vitamin B12 level were significantly negatively associated with CRF. Female subjects with diabetes had higher estimated VO_2max than those without diabetes. Folate was significantly positively correlated with estimated VO_2max, whereas CRP was negatively correlated in obese female.

CONCLUSIONS

There are different predictors of CRF in males and females, and in individuals with different BMI. Key messages Different BMI classes are associated with different predictors of cardiorespiratory fitness. Indicators of cardiorespiratory fitness differ between sexes.

Fitness, but not physical activity, is related to functional integrity of brain networks associated with aging

Greater physical activity and cardiorespiratory fitness are associated with reduced age-related cognitive decline and lower risk for dementia. However, significant gaps remain in the understanding of how physical activity and fitness protect the brain from adverse effects of brain aging. The primary goal of the current study was to empirically evaluate the independent relationships between physical activity and fitness with functional brain health among healthy older adults, as measured by the functional connectivity of cognitively and clinically relevant resting state networks. To build context for fitness and physical activity associations in older adults, we first demonstrate that young adults have greater within-network functional connectivity across a broad range of cortical association networks. Based on these results and previous research, we predicted that individual differences in fitness and physical activity would be most strongly associated with functional integrity of the networks most sensitive to aging. Consistent with this prediction, and extending on previous research, we showed that cardiorespiratory fitness has a positive relationship with functional connectivity of several cortical networks associated with age-related decline, and effects were strongest in the default mode network (DMN). Furthermore, our results suggest that the positive association of fitness with brain function can occur independent of habitual physical activity. Overall, our findings provide further support that cardiorespiratory fitness is an important factor in moderating the adverse effects of aging on cognitively and clinically relevant functional brain networks.

Aging, Fitness, and Marathon Times in a 91 Year-old Man Who Competed in 627 Marathons

Aging is associated with a decline in maximal aerobic capacity (VO_2max) that may be attenuated by chronic endurance exercise. This case study chronicles the changes in marathon times in a 91 year old man who completed 627 marathons and 117 ultramarathons over 42 years. He began running marathons at age 48. His yearly best times remained fairly constant at ~240 minutes from age 50 – 64 years and then gradually rose to about 260 minutes in his early seventies followed by a curvilinear deterioration as he approached his ninth decade. His times plateaued at ~ 600 minutes in his late eighties. Between ages 68 and 89 his VO_2max declined from 43 to 20 ml/kg/min. His marathon times were highly correlated with his VO_2max (r²=0.87). The decline in marathons times and VO_2max may reflect the contributions of biological aging, changes in exercise training volume and intensity, injuries, and comorbid disease.