Prefrontal activation when suppressing an automatic balance recovery step.

BACKGROUND: The present study investigated neural mechanisms for suppressing a highly automatic balance recovery step. Response inhibition has typically been researched using focal hand reaction tasks performed by seated participants, and this has revealed a neural stopping network including the Inferior Frontal Gyrus (IFG). It is unclear if the same neural networks contribute to suppressing an unwanted balance reaction. RESEARCH QUESTION: Is there greater IFG activation when suppressing an automatic balance recovery step? METHODS: Functional near-infrared spectroscopy (fNIRS) was used to measure brain activity in 21 young adults as they performed a balance recovery task that demanded rapid step suppression following postural perturbation. The hypothesis was that the IFG would show heightened activity when suppressing an automatic balance recovery step. A lean and-release system was used to impose temporally unpredictable forward perturbations by releasing participants from a supported forward lean. For most trials (80%), participants were told to recover balance by quickly stepping forward (STEP). However, on 20% of trials at random, a high-pitch tone was played immediately after postural perturbation signaling participants to suppress a step and fully relax into a catch harness (STOP). This allowed us to target the ability to cancel an already initiated step in a balance recovery context. Average oxygenated hemoglobin changes were contrasted between STEP and STOP trials, 1-6 s post perturbation. RESULTS: The results showed a greater bilateral prefrontal response during STOP trials, supporting the idea that executive brain networks are active when suppressing a balance recovery step. SIGNIFICANCE: Our study demonstrates one way in which higher brain processes may help us prevent falls in complex environments where behavioral flexibility is necessary. This study also presents a novel method for assessing response inhibition in an upright postural context where rapid stepping reactions are required.

Suppressing a Blocked Balance Recovery Step: A Novel Method to Assess an Inhibitory Postural Response.

Stepping to recover balance is an important way we avoid falling. However, when faced with obstacles in the step path, we must adapt such reactions. Physical obstructions are typically detected through vision, which then cues step modification. The present study describes a novel method to assess visually prompted step inhibition in a reactive balance context. In our task, participants recovered balance by quickly stepping after being released from a supported forward lean. On rare trials, however, an obstacle blocked the stepping path. The timing of vision relative to postural perturbation was controlled using occlusion goggles to regulate task difficulty. Furthermore, we explored step suppression in our balance task related to inhibitory capacity measured at the hand using a clinically feasible handheld device (ReacStick). Our results showed that ReacStick and step outcomes were significantly correlated in terms of successful inhibition (r = 0.57) and overall reaction accuracy (r = 0.76). This study presents a novel method for assessing rapid inhibition in a dynamic postural context, a capacity that appears to be a necessary prerequisite to a subsequent adaptive strategy. Moreover, this capacity is significantly related to ReacStick performance, suggesting a potential clinical translation.

Step edge highlighters and illuminance changes influence stair descent in a real-world setting.

Studies investigating the effect of tread edge highlighters on descent speed differ, but collectively report the potential benefit of reduced fall risk. Here we examine the impact of adding high-contrast black vinyl striping to the front edge of each step's tread and its impact on descending gait speed (intervention), while controlling for illumination. Descending gait speed was estimated from 5,824 video observations using the stairway length and entry and exit times. A second stairway was unaltered (control) to compare to the intervention. Stair users were primarily 18-30 years old with a small percentage being middle-aged and older adults. Descending gait speed was significantly slower on the intervention stairway (Linear mixed effects model: standardised coefficient = -0.07, 95% CI = [-0.12, -0.02], p = .010) compared to the control and may be impacted by illuminance. We propose that the slowed gait speed could be due to changes in gait kinematics (e.g. foot clearance) and may reduce fall-risk. Practitioner summary: Tread-edge contrast enhancement could be a low-cost means to reduce fall-risk on stairways, but its impact on gait kinematics is not well understood. We found that contrast enhancement reduced descending gait speed, but descending gait speed's impact on fall risk reduction ultimately requires further investigation.

Interaction between age and fatigue on antagonist muscle coactivation during an acute post-fatigue recovery phase.

This study investigated the age-related changes in antagonist muscle coactivation of the biceps femoris (BF) during an acute recovery period following a leg extensor fatiguing protocol. Twenty-three young (mean ± SD: age = 25.1 ± 3.0 years) and twenty-three old men (age = 71.5 ± 3.9 years) participated. Surface electromyography (sEMG) was recorded from the BF muscles for antagonist muscle coactivation. Testing involved participants performing leg extension isometric maximal voluntary contractions (MVCs) and isokinetic MVCs at 240°·s-1 at baseline (Pre) and again after the fatigue protocol at 0 (Post0), 7 (Post7), 15 (Post15), and 30 (Post30) minutes post fatigue. Root mean square (RMS) values were computed from the BF sEMG and were calculated as the first 200 ms from onset for the isometric (IsomCoact200ms) and dynamic isokinetic 240°·s-1 (DynCoact200ms) MVCs, and for the final 10° of the leg extension (DynCoact10°) on the isokinetic 240°·s-1 MVCs. Two-way ANOVAs [age group (young vs. old) × time (Pre vs. Post0 vs. Post7 vs. Post15 vs. Post30)] showed that DynCoact200ms had an effect for time (p = 0.018), with greater antagonist coactivation in Pre than Post0 (p = 0.009) and recovering by Post7 (p = 0.011) with no group differences. DynCoact10° had no age × time interaction (p = 0.070), but had a main effect for time (p = 0.020) with the Post0 being lower than the Pre. However, for this variable the young group showed a more severe Pre to Post0 fatigue decline (-45.9%) than the old group (-6.7%) indicating this may be a more sensitive variable for capturing age-related antagonist coactivation post-fatigue responses. Leg extensor fatigue affects some BF coactivation sEMG variables more than others, and any altered post-fatigue coactivation response recovers rapidly (<7 min) from baseline levels.

Safe stairway negotiation: Role of distractions and handrail use.

INTRODUCTION: This study sought to examine stairway safety by identifying associations between fall-related events on stairways, distractions, gait speed, drifting, as well as handrail use and proximity. METHOD: Video recordings captured 11,137 observations of stair users in two public stairways and recorded distractions (e.g., looking at a mobile device, talking on a mobile device, using earbuds or headphones, holding a mobile device, or talking with a peer), gait speed (m/s), drifting (change of direction), as well as handrail use and proximity to a handrail. RESULTS: In our sample, consisting of primarily young adults (observed 18-40 years old), we found that when a distraction was present, gait speed was reduced (p <.001), drifting increased (p <.001), and handrail use negatively impacted (p <.001) compared to stair users who were not distracted. CONCLUSIONS: These results indicate that distractions, such as mobile devices, used during stair negotiation can reduce handrail use and increase behaviors associated with fall-related events. PRACTICAL APPLICATIONS: Mobile device use during stairway negotiation increases the likelihood of distraction-induced events. Stair users should be encouraged to limit or avoid mobile device use in public stairway environments. Mobile manufacturers and mobile app developers could aim to develop strategies or mobile app alerts to reduce the impact of distractions (e.g., mobile device use) during stair negotiation to lessen the health and financial burden associated with fall-related events on stairways.

State of Knowledge on Molecular Adaptations to Exercise in Humans: Historical Perspectives and Future Directions.

For centuries, regular exercise has been acknowledged as a potent stimulus to promote, maintain, and restore healthy functioning of nearly every physiological system of the human body. With advancing understanding of the complexity of human physiology, continually evolving methodological possibilities, and an increasingly dire public health situation, the study of exercise as a preventative or therapeutic treatment has never been more interdisciplinary, or more impactful. During the early stages of the NIH Common Fund Molecular Transducers of Physical Activity Consortium (MoTrPAC) Initiative, the field is well-positioned to build substantially upon the existing understanding of the mechanisms underlying benefits associated with exercise. Thus, we present a comprehensive body of the knowledge detailing the current literature basis surrounding the molecular adaptations to exercise in humans to provide a view of the state of the field at this critical juncture, as well as a resource for scientists bringing external expertise to the field of exercise physiology. In reviewing current literature related to molecular and cellular processes underlying exercise-induced benefits and adaptations, we also draw attention to existing knowledge gaps warranting continued research effort. © 2021 American Physiological Society. Compr Physiol 12:3193-3279, 2022.

A method to assess response inhibition during a balance recovery step.

BACKGROUND: Correlations between falls and individual differences in inhibitory control, suggest the ability to suppress automatic, but unwanted, action is important in fall prevention. Response inhibition has been a topic of considerable interest in the cognitive neuroscience community for many decades, bringing a wealth of techniques that could potentially inform assessment of reactive balance. For example, the stop signal task is a popular method to quantify inhibitory control ability. RESEARCH QUESTION: Can we apply the stop signal task to measure response inhibition in a balance recovery task? METHODS: Twenty healthy, young adults completed a novel reactive balance test that required occasional suppression of a balance recovery step. Participants were released from a supported lean ('Go' cue) requiring them to quickly step forward to regain balance. On some trials, a tone ('Stop' cue) instructed participants to suppress a step and relax into a harness. Step trials were more frequent (80%) than stop trials (20%) to bias a rapid stepping response. The stop tone was presented at various delays following cable release, to manipulate task difficulty (i.e., longer delays make step suppression difficult). Individual differences in inhibitory control were determined using lift off times from force plates, and by contrasting muscle activation in failed compared to successful stop trials. RESULTS: Most participants were able to successfully suppress a balance recovery step on occasion, allowing for accurate estimation of individual differences in inhibitory control. The successful suppression of a balance recovery step was more likely in the group (n = 10) where shorter stop signal delays were used (i.e., the task was easier). SIGNIFICANCE: While balance assessments often stress reflexive action, there is a need for methods that evaluate response inhibition. The present study leveraged a well-established cognitive test of inhibitory control to develop a method to quantify stopping ability in a reactive balance context.

Potential Benefits of a Minimal Dose Eccentric Resistance Training Paradigm to Combat Sarcopenia and Age-Related Muscle and Physical Function Deficits in Older Adults.

The ability of older adults to perform activities of daily living is often limited by the ability to generate high mechanical outputs. Therefore, assessing and developing maximal neuromuscular capacity is essential for determining age-related risk for functional decline as well as the effectiveness of therapeutic interventions. Interventions designed to enhance neuromuscular capacities underpinning maximal mechanical outputs could positively impact functional performance in daily life. Unfortunately, < 10% of older adults meet the current resistance training guidelines. It has recently been proposed that a more "minimal dose" RT model may help engage a greater proportion of older adults, so that they may realize the benefits of RT. Eccentric exercise offers some promising qualities for such an approach due to its efficiency in overloading contractions that can induce substantial neuromuscular adaptations. When used in a minimal dose RT paradigm, eccentric-based RT may be a particularly promising approach for older adults that can efficiently improve muscle mass, strength, and functional performance. One approach that may lead to improved neuromuscular function capacities and overall health is through heightened exercise tolerance which would favor greater exercise participation in older adult populations. Therefore, our perspective article will discuss the implications of using a minimal dose, submaximal (i.e., low intensity) multi-joint eccentric resistance training paradigm as a potentially effective, and yet currently underutilized, means to efficiently improve neuromuscular capacities and function for older adults.

Design of an eccentric recumbent ergometer to elicit delayed onset muscle soreness.

INTRODUCTION: Our objective was to design an eccentric bicycle design to elicit delayed onset muscle soreness (DOMS). METHODS: To assess the bicycle designs' ability to elicit DOMS, fourteen, recreationally active, males performed five-minutes of eccentric bicycling at 50% of their individualized power determined from a modified six-second Wingate test. Outcome measures to assess DOMS included the Likert pain scale, creatine kinase, lactate blood concentration, and pressure algometry detection evaluated at four time points (baseline (before the eccentric bicycling), immediate post, 24 hours post, and 48 hours post). RESULTS: The Likert pain scale was different (F = 75.88, p < 0.001) at baseline (0.14 ± 0.36) and immediate post (0.21 ± 0.43), compared to 24 hours post (3.07 ± 0.83), and 48 hours post (2.93 ± 1.07). No changes were reported for creatine kinase (F = 0.7167, p = 0.475), lactate blood concentration (F = 2.313, p = 0.107), or pressure algometry detection. CONCLUSIONS: To understand mechanisms of DOMS, there is a need for a consistent, reliable method for producing DOMS. Our eccentric bicycle design and protocol offers an alternative approach to previous eccentric ergometer designs - demonstrating the potential to elicit DOMS in one, five-minute session.

Promoting Generalized Learning in Balance Recovery Interventions.

Recent studies have shown balance recovery can be enhanced via task-specific training, referred to as perturbation-based balance training (PBT). These interventions rely on principles of motor learning where repeated exposure to task-relevant postural perturbations results in more effective compensatory balance responses. Evidence indicates that compensatory responses trained using PBT can be retained for many months and can lead to a reduction in falls in community-dwelling older adults. A notable shortcoming with PBT is that it does not transfer well to similar but contextually different scenarios (e.g., falling sideways versus a forward trip). Given that it is not feasible to train all conditions in which someone could fall, this limited transfer presents a conundrum; namely, how do we best use PBT to appropriately equip people to deal with the enormous variety of fall-inducing scenarios encountered in daily life? In this perspective article, we draw from fields of research that explore how general learning can be promoted. From this, we propose a series of methods, gleaned from parallel streams of research, to inform and hopefully optimize this emerging field where people receive training to specifically improve their balance reactions.

Resveratrol and exercise combined to treat functional limitations in late life: A pilot randomized controlled trial.

PURPOSE: To evaluate the safety and feasibility of combining exercise (EX) and resveratrol to treat older adults with physical function limitations. METHODS: Three-arm, two-site pilot randomized, controlled trial (RCT) for community-dwelling adults (N = 60), 71.8 ± 6.3 years of age with functional limitations. Participants were randomized to receive either 12 weeks of (1) EX + placebo [EX0], (2) EX + 500 mg/day resveratrol [EX500], or (3) EX + 1000 mg/day resveratrol [EX1000]. EX consisted of two sessions a week for 12 weeks of center-based walking and whole-body resistance training. Safety was assessed through adverse events and feasibility through exercise session and supplement (placebo, or resveratrol) protocol adherence. Outcome measures included a battery of indices of physical function as well as skeletal muscle mitchondrial function. Data were adjusted for age and gender using the Intent-To-Treat approach. RESULTS: Adverse event frequency and type were similar between groups (n = 8 EX0, n = 12 EX500, and n = 7 EX1000). Overall, 85% of participants met the supplement adherence via pill counts while 82% met the exercise session adherence. Adjusted within group mean differences (95% confidence interval) from week 0 to 12 for gait speed ranged from -0.04 (EX0: -0.1, 0.03) m/s to 0.04 (EX1000: -0.02, 0.11) and the six-minute walk test mean differences were 9.45 (EX0: -9.02, 27.7), 22.9 (EX500: 4.18, 41.6), and 33.1 (EX1000: 13.8, 52.4) meters. Unadjusted mean differences for citrate synthase were -0.80 (EX0: -15.45, 13.84), -1.38 (EX500: -12.16, 9.39), and 7.75 (EX1000: -4.68, 20.18) mU/mg. COX activity mean within group changes ranged from -0.05 (EX0) to 0.06 (EX500) k/s/mg. Additional outcomes are detailed in the text. CONCLUSION: The pilot RCT indicated that combined EX + resveratrol was safe and feasible for older adults with functional limitations and may improve skeletal muscle mitochondrial function and mobility-related indices of physical function. A larger trial appears warranted and is needed to formally test these hypotheses.

Single leg aerobic capacity and strength in individuals with surgically repaired anterior cruciate ligaments.

OBJECTIVES: Compare single-leg aerobic capacity and strength differences between the surgically repaired ACL leg (injured) and the uninjured leg. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: Eight participants (5 female, 3 male, age = 23 ± 3.5 y, mass = 72.3 ± 17.3 kg, height = 169.7 ± 9.4 cm) that returned to play from ACL surgery between six and 18 months. MAIN OUTCOME MEASURES: Participants performed an aerobically-based, single-leg cycling protocol to determine maximum oxygen consumption, ventilatory threshold, heart rate, rating of perceived exertion, and maximal watts cycled. Participants also performed isokinetic knee flexion and extension on a dynamometer to assess peak torque, total work, work fatigue, and power. RESULTS: There were no statistical differences in single-leg aerobic capacity or strength outcomes between the injured and uninjured legs. CONCLUSIONS: Individuals who have had an ACL surgically repaired six to 18 months after return to play do not appear to have aerobic capacity or strength deficits between the injured leg and uninjured leg.

Wearable Technology To Reduce Sedentary Behavior And CVD Risk In Older Adults: A Pilot Randomized Clinical Trial.

BACKGROUND: Physical exercise is associated with decreased cardiovascular disease (CVD) risk, but recent large-scale trials suggest that exercise alone is insufficient to reduce CVD events in high-risk older adults. PURPOSE: This pilot randomized clinical trial aimed to collect critical data on feasibility, safety, and protocol integrity necessary to design a fully powered randomized controlled trial (RCT) and evaluate the impact of combining structured exercise with an intervention designed to enhance non-exercise physical activity (EX+NEPA) compared to EX alone. METHODS: Forty participants aged ≥60 years with moderate-to-high risk of coronary heart disease events were randomly assigned to either the EX+NEPA or EX groups and followed for 20 weeks. Both groups underwent a twice-weekly, 8-week center-based exercise intervention with aerobic and resistance exercises. EX+NEPA group also received a wearable activity tracking device along with behavioral monitoring and feedback throughout the study. Study outcomes were evaluated at 8 and 20 weeks. RESULTS: Data are presented as adjusted mean change of the differences over time with 95% confidence intervals at 20 weeks. Relative to EX, the change in steps/day at 20 weeks was 1994 (-40.27, 4028) higher for EX+NEPA. For sedentary time at close-out, the EX+NEPA group was -6.8 (-45.2, 31.6) min/day relative to EX. The between-group differences for systolic and diastolic blood pressure were -9.9 (-19.6, -0.3) and -1.8 (-6.9, 3.3) mmHg, respectively. CONCLUSION: The addition of wearable technology intervention appeared to positively influence daily activity patterns and changes in blood pressure - potentially improving risk factors for CVD. A fully powered randomized trial is needed to ultimately test this hypothesis.

Non-Motor Symptoms after One Week of High Cadence Cycling in Parkinson's Disease.

The objective was to investigate if high cadence cycling altered non-motor cognition and depression symptoms in individuals with Parkinson's disease (PD) and whether exercise responses were influenced by brain-derived neurotrophic factor (BDNF) Val66Met polymorphism. Individuals with idiopathic PD who were ≥50 years old and free of surgical procedures for PD were recruited. Participants were assigned to either a cycling (n = 20) or control (n = 15) group. The cycling group completed three sessions of high cadence cycling on a custom motorized stationary ergometer. The primary outcome was cognition (attention, executive function, and emotion recognition were assessed via WebNeuro® and global cognition via Montreal Cognitive Assessment). Depression symptoms were assessed via Beck Depression Inventory-II. There was a main effect of time for emotional recognition (p = 0.048), but there were no other changes in cognition or depression symptoms. Regardless of intervention or Val66Met polymorphism, high cadence cycling does not alter cognition or depression symptoms after three sessions in one week.

Exercise is Medicine as a Vital Sign: Challenges and Opportunities.

Exercise is widely recognized as a critical component of a healthy lifestyle by multiple scientific and regulatory bodies. Yet only 35% of adults in the United States even report engaging in regular physical activity. In response to this challenge, the Exercise is Medicine (EIM) initiative encourages clinicians in all settings to regularly assess and counsel patients on physical activity in an attempt to reduce levels of inactivity. The purpose of this article is to highlight key challenges to the implementation of the EIM initiative to promote physical activity and to identify potential opportunities to overcome these challenges. EIM is a global health initiative that endorses "exercise" to be a "vital sign" in all clinical settings. Specifically to assess and compare the patient's physical activity level to national guidelines for physical activity and then promote discussions or referrals based on results. Since its 2007 launch, advocates of the EIM initiative have increased global awareness to promote the EIM mission of integrating and implementing physical activity into healthcare systems, local communities, and individuals' daily lives. Physical activity is fundamental to the overall health of all people across all geographic locations and throughout the lifespan. Promoting physical activity as a healthy lifestyle change has specific challenges but necessary to decrease health disparities related to inactivity.

Multimodal Intervention to Improve Functional Status in Hypertensive Older Adults: A Pilot Randomized Controlled Trial.

This pilot randomized controlled trial (RCT) was designed to provide the preliminary data necessary to conduct a full-scale trial to compare the efficacy of differing first-line antihypertensive medications in improving functional status in older adults, when combined with exercise. The primary objectives were to assess study feasibility, safety, and protocol integrity. Dependent outcomes included gait speed, exercise capacity, body composition, and systemic cardiometabolic biomarkers. Thirty-one physically inactive older adults (70.6 ± 6.1 years) with hypertension and functional limitations were randomly assigned to 1) Perindopril (8 mg/day n = 10), 2) Losartan (100 mg/day; n = 13), or 3) Hydrochlorothiazide (HCTZ: 25 mg/day; n = 8). Participants were also assigned to a 24-week multimodal exercise intervention, separated into an aerobic and concurrent (aerobic + resistance) phase to evaluate potential mode effects. Retention was 84% (26/31), and compliance was >90% and >79% with medication and exercise, respectively. A total of 29 adverse events (Perindopril = 5; Losartan = 12; HCTZ = 11) and one unrelated serious adverse event were observed throughout the trial. Overall, this pilot RCT provided critical data and identified several challenges to ultimately designing and implementing a fully powered trial.

Blood-Flow Restriction Resistance Exercise for Older Adults with Knee Osteoarthritis: A Pilot Randomized Clinical Trial.

In a pilot randomized clinical trial, participants aged ≥60 years (n = 35) with physical limitations and symptomatic knee osteoarthritis (OA) were randomized to 12 weeks of lower-body low-load resistance training with blood-flow restriction (BFR) or moderate-intensity resistance training (MIRT) to evaluate changes in muscle strength, pain, and physical function. Four exercises were performed three times per week to volitional fatigue using 20% and 60% of one repetition maximum (1RM). Study outcomes included knee extensor strength, gait speed, Short Physical Performance Battery (SPPB) performance, and pain via the Western Ontario and McMaster Universities OA Index (WOMAC). Per established guidance for pilot studies, primary analyses for the trial focused on safety, feasibility, and effect sizes/95% confidence intervals of dependent outcomes to inform a fully-powered trial. Across three speeds of movement, the pre- to post-training change in maximal isokinetic peak torque was 9.96 (5.76, 14.16) Nm while the mean difference between groups (BFR relative to MIRT) was -1.87 (-10.96, 7.23) Nm. Most other directionally favored MIRT, though more spontaneous reports of knee pain were observed (n = 14) compared to BFR (n = 3). BFR may have lower efficacy than MIRT in this context-though a fully-powered trial is needed to definitively address this hypothesis.

Angiotensin Converting Enzyme Inhibitors Combined with Exercise for Hypertensive Seniors (The ACES Trial): Study Protocol of a Randomized Controlled Trial.

Prior evidence suggests that the choice of antihypertensive medication may influence functional status among older adults with hypertension, particularly in conjunction with exercise. In particular, angiotensin converting enzyme (ACE) inhibitors have shown potential to positively influence function. However, randomized, controlled trials are needed to confirm this hypothesis. This paper outlines an RCT designed to determine if choice of first-line antihypertensive medication influences functional and cardiovascular risk factor responses to exercise among older adults with hypertension. Two hundred and thirteen inactive, community-dwelling adults ≥60 years of age with hypertension and functional limitations will be recruited to engage in a 32-week intervention study. Participants will be randomized to one of three first-line antihypertensive agents: (1) the ACE inhibitor perindopril, (2) the AT1 receptor antagonist losartan, or (3) the thiazide diuretic hydrochlorothiazide (HCTZ). Six weeks after randomization, participants will begin a 20-week structured aerobic exercise intervention. Participants will perform two 45-min center-based sessions coupled with 60 min of home-based walking per week. The primary aim is to determine if perindopril improves self-paced gait speed when compared with losartan and HCTZ. The secondary aim is to determine the relative effect of perindopril on secondary outcomes such as: (a) exercise capacity, (b) body mass and composition, and (c) circulating indices of cardiovascular risk. This RCT is expected to identify differential effects of first-line antihypertensive medications when combined with physical exercise thus have potential implications for antihypertensive prescription guidelines for older adults. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03295734.

Circadian Rhythms, Exercise, and Cardiovascular Health.

Human circadian rhythmicity is driven by a circadian clock comprised of two distinct components: the central clock, located in the suprachiasmatic nucleus (SCN) within the hypothalamus, and the peripheral clocks, located in almost all tissues and organ systems in the body. Entrainment, or alignment, of circadian rhythmicity is dependent upon time of day and can occur through environmental influences such as light cues and physical activity exerted on skeletal muscle. Entrainment of the circadian clock through exercise has been reported to improve health by reducing risk of conditions such as cardiovascular disease (CVD), but further research is still needed. The purpose of this review is to discuss the effects exercise has on the regulation of circadian rhythmicity, specifically with respect to CVD risk factors - including hormonal levels, sleep/wake cycles, blood pressure, and heart rate. Additionally, the impact of exercise-induced circadian entrainment is discussed relative to hormone regulation, nocturnal blood pressure dipping, post-exercise hypotension, and overall cardiovascular health.