Exercise Training Attenuates the Muscle Mitochondria Genomic Response to Bed Rest.

PURPOSE: Exercise training during the National Aeronautics and Space Administration 70-d bed rest study effectively counteracted the decline in aerobic capacity, muscle mass, strength, and endurance. We aimed to characterize the genomic response of the participants' vastus lateralis on day 64 of bed rest with and without exercise countermeasures. METHODS: Twenty-two healthy young males were randomized into three groups: 1) bed rest only ( n = 7), 2) bed rest + aerobic (6 d·wk -1 ) and resistance training (3 d·wk -1 ) on standard equipment ( n = 7), and 3) bed rest + aerobic and resistance training using a flywheel device ( n = 8). The vastus lateralis gene and microRNA microarrays were analyzed using GeneSpring GX 14.9.1 (Agilent Technologies, Palo Alto, CA). RESULTS: Bed rest significantly altered the expression of 2113 annotated genes in at least one out of the three study groups (fold change (FC) > 1.2; P < 0.05). Interaction analysis revealed that exercise attenuated the bed rest effect of 511 annotated genes (FC = 1.2, P < 0.05). In the bed rest only group, a predominant downregulation of genes was observed, whereas in the two exercise groups, there was a notable attenuation or reversal of this effect, with no significant differences between the two exercise modalities. Enrichment analysis identified functional categories and gene pathways, many of them related to the mitochondria. In addition, bed rest significantly altered the expression of 35 microRNAs (FC > 1.2, P < 0.05) with no difference between the three groups. Twelve are known to regulate some of the mitochondrial-related genes that were altered following bed rest. CONCLUSIONS: Mitochondrial gene expression was a significant component of the molecular response to long-term bed rest. Although exercise attenuated the FC in the downregulation of many genes, it did not completely counteract all the molecular consequences.

Effects of exercise countermeasures on multisystem function in long duration spaceflight astronauts.

Exercise training is a key countermeasure used to offset spaceflight-induced multisystem deconditioning. Here, we evaluated the effects of exercise countermeasures on multisystem function in a large cohort (N = 46) of astronauts on long-duration spaceflight missions. We found that during 178 ± 48 d of spaceflight, ~600 min/wk of aerobic and resistance exercise did not fully protect against multisystem deconditioning. However, substantial inter-individual heterogeneity in multisystem response was apparent with changes from pre to postflight ranging from -30% to +5%. We estimated that up to 17% of astronauts would experience performance-limiting deconditioning if current exercise countermeasures were used on future spaceflight missions. These findings support the need for refinement of current countermeasures, adjunct interventions, or enhanced requirements for preflight physiologic and functional capacity for the protection of astronaut health and performance during exploration missions to the moon and beyond.

Aerobic exercise deconditioning and countermeasures during bed rest.

Bed rest is a well-accepted model for spaceflight in which the physiologic adaptations, particularly in the cardiovascular system, are studied and potential countermeasures can be tested. Bed rest without countermeasures results in reduced aerobic capacity and altered submaximal exercise responses. Aerobic endurance and factors which may impact prolonged exercise, however, have not been well studied. The initial loss of aerobic capacity is rapid, occurring in parallel with the loss of plasma volume. Thereafter, the reduction in maximal aerobic capacity proceeds more slowly and is influenced by central and peripheral adaptation. Exercise capacity can be maintained during bed rest and may be improved during recovery with appropriate countermeasures. Plasma volume restoration, resistive exercise, orthostatic stress, aerobic exercise, and aerobic exercise plus orthostatic stress all have been tested with varying levels of success. However, the optimal combination of elements-exercise modality, intensity, duration, muscle groups exercised and frequency of aerobic exercise, orthostatic stress, and supplementary resistive or anaerobic exercise training-has not been systematically evaluated. Currently, frequent (at least 3 days per week) bouts of intense exercise (interval-style and near maximal) with orthostatic stress appears to be the most efficacious method to protect aerobic capacity during bed rest. Further refinement of protocols and countermeasure hardware may be necessary to insure the success of countermeasures in the unique environment of space.

Lower limb position during treadmill jogging and fast running in microgravity.

INTRODUCTION: The second-generation ISS treadmill has a faster maximum operating speed than the current ISS treadmill. In normal gravity (1 G), bone loading benefits and cardiorespiratory stress are directly related to locomotion speed. A kinematic comparison of locomotion between 1 G and microgravity will provide information to evaluate the potential efficacy of fast running as an in-flight exercise countermeasure. METHODS: Subjects exercised on a treadmill at 3.13 m x s(-1) (8.5 min x mi(-1)) (JOG; N = 6) and 5.36 m x s(-1) (5 min x mi(-1)) (RUN; N = 5) in microgravity during parabolic flight and in 1 G. During microgravity trials, subjects performed locomotion using a subject loading system (in a configuration identical to ISS) with approximately 80% bodyweight loading. Kinematic analyses of joint position at heel strike were performed using video software. RESULTS: During the JOG trials, differences were found in thigh angle (microgravity = 54.09 degrees +/- 4.87; 1 G = 64.04 degrees +/- 3.12, mean +/- SD) and knee angle (microgravity = 33.17 degrees +/- 8.68; 1 G = 21.28 degrees +/- 5.22), indicating a more squatted position at heel strike in microgravity. No kinematic differences were found during the RUN condition. DISCUSSION: The subject loading system and decreased external load throughout the stride in microgravity may account for the observed kinematic differences during JOG. The kinematic compensations for microgravity during JOG may result in in-flight adaptations that are different from expected based on 1-G studies. However, similar kinematics between gravity conditions during RUN suggest in-flight training may provide benefits similar to 1 G.

Moderate protein intake improves total and regional body composition and insulin sensitivity in overweight adults.

A high protein intake (approximately 40% of energy intake) combined with aerobic and resistance exercise training is more closely associated with improved body composition and cardiovascular risk profile than a traditional protein intake (approximately 15% of intake) combined with moderate-intensity aerobic exercise. However, there is concern that such high-protein diets may adversely affect health. We therefore tested the hypothesis that moderate protein intake (approximately 25% of energy intake) would elicit similar benefits on body composition and metabolic profile as high protein intake. Twenty-four overweight/obese men and women (body mass index [BMI] = 32.2 +/- 3.4, percentage of body fat [%BF] = 37.3 +/- 8.0) were matched for BMI and %BF and randomly assigned to one of 3 groups for a 3-month nutrition/exercise training intervention: (1) high-protein diet (approximately 40% of energy intake) and combined high-intensity resistance and cardiovascular training (HPEx, n = 8, 5 female and 3 male), (2) moderate-protein diet (approximately 25% of energy intake) and combined high-intensity resistance and cardiovascular training (MPEx, n = 8, 5 female and 3 male), or (3) high-protein diet only (HPNx, n = 8, 5 female and 3 male). Total and regional body composition (dual-energy x-ray absorptiometry), insulin sensitivity (insulin sensitivity index to the oral glucose tolerance test), insulin-like growth factor-1 (IGF-1), IGF binding protein-1 (IGFBP-1), IGF binding protein-3 (IGFBP-3), and blood lipids were measured at baseline and after the intervention. All groups experienced significant (P < .05) and similar losses of body weight, BMI, and total and abdominal %BF, and similar improvements in insulin sensitivity (HPEx, 6.3 +/- 1.2 vs 9.5 +/- 0.98; MPEx, 6.2 +/- 1.4 vs 8.4 +/- 1.6; HPNx, 3.7 +/- 1.1 vs 7.0 +/- 1.1; insulin sensitivity index to the oral glucose tolerance test; P < .05) and leptin levels. Furthermore, the HPEx group demonstrated decreases in total cholesterol (TC) and triglycerides, and increases in IGF-1 and IGFBP-1. The MPEx group experienced decreases in TC, whereas the HPNx group had increases in high-density lipoprotein cholesterol, TC to high-density lipoprotein, IGF-1, and IGFBP-1. In conclusion, moderate protein intake elicits similar benefits in body composition and insulin sensitivity as a high-protein diet. These findings may have practical implications for individuals interested in diets containing elevated dietary protein.

Distinguishing juvenile homicide from violent juvenile offending.

Juvenile homicide is a social problem that has remained a central focus within juvenile justice research in recent years. The term juvenile murderer describes a legal category, but it is purported to have significant scientific meaning. Research has attempted to conceptualize adolescent murderers as a clinical category that can be reliably distinguished from their nonhomicidal counterparts. This study examined 33 adolescents adjudicated delinquent or awaiting trial for murder and 38 adolescents who committed violent, nonhomicidal offenses to determine whether the two groups differed significantly on family history, early development, delinquency history, mental health, and weapon possession variables. The nonhomicide group proved more problematic on many of these measures. Two key factors did distinguish the homicide group: These adolescents endorsed the greater availability of guns and substance abuse at the time of their commitment offenses. The significance of this finding is discussed, and the implications for risk management and policy are reviewed.

Blood flow-restricted exercise in space.

Prolonged exposure to microgravity results in chronic physiological adaptations including skeletal muscle atrophy, cardiovascular deconditioning, and bone demineralization. To attenuate the negative consequences of weightlessness during spaceflight missions, crewmembers perform moderate- to high-load resistance exercise in conjunction with aerobic (cycle and treadmill) exercise. Recent evidence from ground-based studies suggests that low-load blood flow-restricted (BFR) resistance exercise training can increase skeletal muscle size, strength, and endurance when performed in a variety of ambulatory populations. This training methodology couples a remarkably low exercise training load (approximately 20%-50% one repetition maximum (1RM)) with an inflated external cuff (width, ranging between approximately 30-90 mm; pressure, ranging between approximately 100-250 mmHg) that is placed around the exercising limb. BFR aerobic (walking and cycling) exercise training methods have also recently emerged in an attempt to enhance cardiovascular endurance and functional task performance while incorporating minimal exercise intensity. Although both forms of BFR exercise training have direct implications for individuals with sarcopenia and dynapenia, the application of BFR exercise training during exposure to microgravity to prevent deconditioning remains controversial. The aim of this review is to present an overview of BFR exercise training and discuss the potential usefulness of this method as an adjunct exercise countermeasure during prolonged spaceflight. The work will specifically emphasize ambulatory BFR exercise training adaptations, mechanisms, and safety and will provide directions for future research.

Increased dietary protein and combined high intensity aerobic and resistance exercise improves body fat distribution and cardiovascular risk factors.

We investigated the effectiveness of two lifestyle modification programs of exercise training and nutritional intake (ad libitum) on improving body composition and disease risk in overweight/obese men and women. Sixty-three subjects were weight matched and assigned to one of three groups for a 12 wk intervention: (1) high-intensity resistance and cardiovascular training and a balanced diet (RC+BD, 40% CHO: 40% PRO; n=27, 16 female/11 male, age = 42 +/- 9 y); (2) moderate-intensity cardiovascular training and a traditional food guide pyramid diet (C+TD, CHO 50 to 55%; PRO 15 to 20%; FAT < 30%; n=19, 10 female/9 male, age = 43 +/- 10 y); and (3) an inactive control group (C, n=17, 5 female/12 male, age 43 +/- 11 y). RC+BD resulted in more favorable changes (P < 0.01) in percent body fat (-15.8% vs. -6.9%) and abdominal fat (-15.6% vs. -7.5%) compared to C+TD and C. Total cholesterol (-13.8%), LDL-cholesterol (-20.8%), and systolic blood pressure (-5.7%) declined (P > 0.05) in RC+BD, whereas C+TD and C remained unchanged. Our results suggest that RC+BD may be more effective than C+TD and C in enhancing body composition and lowering cardiovascular risk in obese individuals.