Lindy M. Rossow

The anabolic benefits of venous blood flow restriction training may be induced by muscle cell swelling

Venous blood flow restriction (VBFR) combined with low intensity resistance exercise (20-30% concentric 1-RM) has been observed to result in skeletal muscle hypertrophy, increased strength, and increased endurance. Knowledge of the mechanisms behind the benefits seen with VBFR is incomplete, but the benefits have traditionally been thought to occur from the decreased oxygen and accumulation of metabolites. Although many of the proposed mechanisms appear valid and are likely true with VBFR combined with resistance exercise, there are certain situations in which benefits are observed without a large accumulation of metabolites and/or large increases in fast twitch fiber type recruitment. Cell swelling appears to be a likely mechanism that appears to be present throughout all studies. VBFR may be able to induce cell swelling through a combination of blood pooling, accumulation of metabolites, and reactive hyperemia following the removal of VBFR which may contribute to skeletal muscle adaptations that occur with VBFR. We hypothesize that cell swelling is important for muscle growth and strength adaptation but when coupled with higher metabolic accumulation, this adaptation is even greater.

Impact of Excess Body Weight on Arterial Structure, Function, and Blood Pressure in Firefighters

Cardiovascular disease is the leading cause of death among firefighters. The purpose of the present study was to examine the effect of excess body weight on arterial structure and function and blood pressure (BP) in relatively young, apparently healthy, firefighters. The body mass index, brachial BP, carotid BP, aortic BP, radial augmentation index, central pulse wave velocity, forearm blood flow, forearm vasodilatory capacity, carotid arterial compliance, carotid intima-media thickness, and brachial flow-mediated dilation were assessed in 110 firefighters (aged 29.7 +/- 8.0 years). The group was divided into equal tertiles according to the body mass index (<25.9, 25.9 to 29.4, and >or=29.5 kg/m(2)). Group differences in hemodynamics, anthropometrics, microvascular function, and macrovascular structure and function were tested using multivariate analysis of variance. The obese group was older, heavier, and had a larger waist circumference compared to the lean and overweight groups (p <0.05). The overweight group was also older, heavier, and had a larger waist circumference than the lean group (p <0.05). Compared to the lean group, the overweight and obese groups had a greater systolic BP (p <0.05). The obese group also had a significantly greater mean arterial BP and carotid systolic BP than the lean group (p <0.05). The obese group had greater beta stiffness and elastic modulus compared to the lean and overweight groups (p <0.05), but no group differences were found in endothelial function. In conclusion, in a population of relatively young firefighters, an increased body mass index was associated with elevated peripheral BP and arterial stiffness, with no apparent decrements in endothelial function.

Exercise intensity and muscle hypertrophy in blood flow–restricted limbs and non‐restricted muscles: a brief review

Although evidence for high‐intensity resistance training–induced muscle hypertrophy has accumulated over the last several decades, the basic concept of the training can be traced back to ancient Greece: Milo of Croton lifted a bull‐calf daily until it was fully grown, which would be known today as progressive overload. Now, in the 21st century, different types of training are being tested and studied, such as low‐intensity exercise combined with arterial as well as venous blood flow restriction (BFR) to/from the working muscles. Because BFR training requires the use of a cuff that is placed at the proximal ends of the arms and/or legs, the BFR is only applicable to limb muscles. Consequently, most previous BFR training studies have focused on the physiological adaptations of BFR limb muscles. Muscle adaptations in non‐BFR muscles of the hip and trunk are lesser known. Recent studies that have reported both limb and trunk muscle adaptations following BFR exercise training suggest that low‐intensity (20–30% of 1RM) resistance training combined with BFR elicits muscle hypertrophy in both BFR limb and non‐BFR muscles. However, the combination of leg muscle BFR with walk training elicits muscle hypertrophy only in the BFR leg muscles. In contrast to resistance exercise with BFR, the exercise intensity may be too low during BFR walk training to cause muscle hypertrophy in the non‐BFR gluteus maximus and other trunk muscles. Other mechanisms including hypoxia, local and systemic growth factors and muscle cell swelling may also potentially affect the hypertrophic response of non‐BFR muscles to BFR resistance exercise.

Cardiovascular and perceptual responses to blood‐flow‐restricted resistance exercise with differing restrictive cuffs

The purpose of this study was to determine (i) the cardiovascular responses to acute blood‐flow‐restricted (BFR) resistance exercise and (ii) the influence of applied BFR cuff type on the cardiovascular and perceptual responses.

The effect of acute fish-oil supplementation on endothelial function and arterial stiffness following a high-fat meal

This study examined whether a commercially available fish-oil supplement offers protection from the acute effects of a high-fat meal (HFM) on endothelial function and arterial stiffness. An HFM causes acute impairments in endothelial function, whereas the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have a variety of cardioprotective effects. However, little is known about the efficacy of moderate fish-oil supplementation on the endothelial dysfunction induced by an HFM. Endothelial function (brachial artery flow-mediated dilation (FMD)), forearm blood flow (FBF), total hyperemia, central and peripheral blood pressure, and central artery stiffness were assessed in 20 healthy men (n = 10) and women (n = 10) at rest and 4 h after an HFM supplemented with either placebo or approximately 1 g EPA and DHA. Brachial artery FMD normalized for shear rate was significantly impaired (p = 0.033) following the HFM with placebo but remained unchanged compared with baseline following the HFM with the fish-oil supplement (p = 0.039; condition x time interaction). Resting FBF (p = 0.020) and total hyperemia (p = 0.014) were elevated following the HFM. All other vascular and hemodynamic measurements were unchanged in both trials. Commercially available fish-oil supplements taken with an HFM appear to preserve endothelial function following an HFM.

Postexercise Hypotension in an Endurance-Trained Population of Men and Women Following High-Intensity Interval and Steady-State Cycling

BACKGROUND The acute effect of high-intensity interval exercise (HI) on blood pressure (BP) is unknown although this type of exercise has similar or greater cardiovascular benefits compared to steady-state aerobic exercise (SS). This study examined postexercise hypotension (PEH) and potential mechanisms of this response in endurance-trained subjects following acute SS and HI. Sex differences were also evaluated. METHODS A total of 25 endurance-trained men (n = 15) and women (n = 10) performed a bout of HI and a bout of SS cycling in randomized order on separate days. Before exercise, 30 min postexercise, and 60 min postexercise, we measured brachial and aortic BP. Cardiac output (CO), stroke volume (SV), end diastolic volume (EDV), end systolic volume (ESV), and left ventricular wall-velocities were measured using ultrasonography with tissue Doppler capabilities. Ejection fraction and fractional shortening (FS), total peripheral resistance (TPR), and calf vascular resistance were calculated from the above variables and measures of leg blood flow. RESULTS BP, ejection fraction, and FS decreased by a similar magnitude following both bouts but changes in CO, heart rate (HR), TPR, and calf vascular resistance were greater in magnitude following HI than following SS. Men and women responded similarly to HI. Although men and women exhibited a similar PEH following SS, they showed differential changes in SV, EDV, and TPR. CONCLUSIONS HI acutely reduces BP similarly to SS. The mechanistic response to HI appears to differ from that of SS, and endurance-trained men and women may exhibit differential mechanisms for PEH following SS but not HI.

Muscular adaptations to fatiguing exercise with and without blood flow restriction.

The purpose of this study was to determine the muscular adaptations to low‐load resistance training performed to fatigue with and without blood flow restriction (BFR). Middle‐aged (42–62 years) men (n = 12) and women (n = 6) completed 18 sessions of unilateral knee extensor resistance training to volitional fatigue over 6 weeks. One limb trained under BFR, and the contralateral limb trained without BFR [free flow (FF)]. Before and after the training, measures of anterior and lateral quadriceps muscle thickness (MTh), strength, power and endurance were assessed on each limb. The total exercise training volume was significantly greater for the FF limb compared with the BFR limb (P<0·001). Anterior quadriceps thickness and muscle function increased following the training in each limb with no differences between limbs. Lateral quadriceps MTh increased significantly more (P<0·05) in the limb trained under BFR (BFR: 3·50 ± 0·61 to 3·67 ± 0·62 cm; FF: 3·49 ± 0·73 to 3·56 ± 0·70 cm). Low‐load resistance training to volitional fatigue both with and without BFR is viable options for improving muscle function in middle‐aged individuals. However, BFR enhanced the hypertrophic effect of low‐load training and reduced the volume of exercise needed to elicit increases in muscle function.

Acute effects of firefighting on arterial stiffness and blood flow.

Sudden cardiac events are responsible for 40—50% of line-of-duty firefighter fatalities, yet the exact cause of these events is unknown. Likely, combinations of thermal, physical, and mental factors impair cardiovascular function and trigger such events. Therefore, the purpose of this study was to examine the impact of firefighting activities on vascular function. Sixty-nine young (28 ± 1 years) male firefighters underwent 3 hours of firefighting activities. Carotid, aortic, and brachial blood pressures (BP), heart rate (HR), augmentation index (AIx), wave reflection timing (TR), aortic pulse wave velocity (PWV), forearm blood flow (FBF), and forearm reactive hyperemia (RH) were measured before and after firefighting activities. Paired samples t-tests revealed significant (p < 0.05) increases in aortic diastolic BP, HR, AIx, PWV, RH, and FBF, and significant decreases in brachial and aortic pulse pressure and TR following firefighting activities. In conclusion, these results suggest that 3 hours of firefighting activities increase both arterial stiffness and vasodilation.

Blood flow restriction pressure recommendations: a tale of two cuffs.

Blood flow restriction (BFR) alone or in combination with exercise has been shown to result in favorable effects on skeletal muscle function and morphology (Loenneke et al., 2012a). BFR is a stimulus commonly applied with specialized pressure cuffs placed at the top of a limb which are inflated to a set pressure throughout exercise. The pressure applied should be high enough to occlude venous return from the muscle but low enough to maintain arterial inflow into the muscle. Throughout the literature several different methods are applied with respect to setting the BFR pressure, however, many of these appear methodologically flawed. The purpose of the current manuscript is to discuss the importance of setting BFR cuff pressure based on appropriate factors. This manuscript will focus on applying pressures to the lower limbs because the majority of the data has been collected on the lower body.

The effect of acute blood-flow-restricted resistance exercise on postexercise blood pressure

Introduction:  Blood‐flow‐restricted (BFR) exercise is an emerging type of exercise that may be particularly beneficial to elderly or special populations. These populations may also benefit from reductions in blood pressure (BP). The effect of BFR exercise on postexercise BP has not been examined; this should first be examined in a young, healthy population as a preliminary investigation.