Factors Related to Average Concentric Velocity of Four Barbell Exercises at Various Loads.

Fahs, CA, Blumkaitis, JC, and Rossow, LM. Factors related to average concentric velocity of four barbell exercises at various loads. J Strength Cond Res 33(3): 597-605, 2019-The resistance exercise load is the primarily determinant of the average concentric velocity (ACV) during a repetition. It is unknown whether individual factors such as training experience or anthropometrics also influence the ACV. Previous research has shown the ACV during the 1 repetition maximum (1RM) varies between exercises, but it is not clear whether ACV is different between exercises at various percentages of the 1RM. This information could provide practical guidelines for trainees using ACV to select training loads. Therefore, the purpose of this study was to determine whether training age, current training frequency, limb length, height, and relative strength are related to ACV at loads between 35 and 100% of the 1RM for the squat, bench press, deadlift, and overhead press. A secondary purpose was to compare the ACV values between the 4 lifts at each relative load. Fifty-one (18 women and 33 men) completed 2 testing sessions in which the squat, bench press, deadlift, and overhead press ACV were measured during a modified 1RM protocol. Average concentric velocity values were significantly different among the 4 lifts (p < 0.05) at all relative loads between 35 and 100% 1RM except for 55% 1RM (p = 0.112). Generally, compared at the same relative loads, the overhead press exhibited the greatest ACV followed by the squat, bench press, and deadlift (in order). In addition, relative strength level was inversely related to ACV at maximal loads (≥95% 1RM) for the squat, bench press, and deadlift while height was positively related to ACV at moderate loads (55% 1RM) for all lifts (p < 0.05). These results suggest that the load-velocity profile is unique for each of these exercises, and that velocity ranges used for exercise prescription should be specific to the exercise. A trainee's relative strength and height may be a primary influence on the ACV.

Analysis of Factors Related to Back Squat Concentric Velocity.

Fahs, CA, Rossow, LM, and Zourdos, MC. Aanalysis of factors related to back squat concentric velocity. J Strength Cond Res 32(9): 2435-2441, 2018-Measuring bar velocity during barbell exercises can be a useful metric for prescribing resistance training loads and for predicting the 1 repetition maximum (1RM). However, it is not clear whether either anthropometric factors (e.g., limb length) or training experience influences bar velocity. The purpose of this study was to determine the relationships between 1RM back squat bar velocity and femur length, training experience, strength, and 36.6-m sprint time in college athletes. Thirteen college football (22 ± 1 years) and 8 college softball players (20 ± 1 years) performed the 36.6-m sprint followed by a 1RM back squat protocol while average concentric velocity and peak concentric velocity were measured. Height (m), body mass (kg), squat training experience (years), squat frequency (d·wk), and femur length (m) were also measured. Pearson product moment correlations were used to determine the relationship between variables. Average concentric velocity was not related to training age (r = 0.150, p = 0.515), squat frequency (r = 0.254, p = 0.266), femur length (r = 0.002, p = 0.992), or relative strength (r = -0.090, p = 0.699). Peak concentric velocity was related to 36.6-m sprint time (r = -0.612, p = 0.003), relative squat average (r = 0.489, p = 0.029), and relative peak (r = 0.901, p < 0.001) power. These results suggest that college athletes using velocity to regulate squat training may not necessarily need to modify velocity ranges based on limb length or training age. In addition, peak velocity during a 1RM back squat may be a useful indicator of an athlete's relative power output ability and speed. Coaches may consider measuring velocity during strength testing as a surrogate measure for speed and power.

Relationships between central arterial stiffness, lean body mass, and absolute and relative strength in young and older men and women.

Relationships between muscular strength and arterial stiffness as well as between muscle mass and arterial stiffness have been observed suggesting a link between the neuromuscular system and vascular health. However, the relationship between central arterial stiffness and absolute and relative strength along with muscle mass has not been investigated in both sexes across a broad age range. The purpose of this study was to examine the relationship between central arterial stiffness and absolute and relative strength as well as between central arterial stiffness and lean body mass (LBM) in men and women across a broad age range. LBM, central arterial stiffness and strength were measured on 36 men and 35 women between the ages of 18 and 75 years. Strength was measured on five machine resistance exercises and summed as one measure of overall strength (absolute strength). Relative strength was calculated as total strength divided by LBM (relative strength). Central arterial stiffness was inversely related to both absolute (r = -0·230; P = 0·029) and relative strength (r = -0·484; P < 0·001) but not LBM (r = 0·097; P = 0·213). The relationship between central arterial stiffness and relative strength was attenuated but still present when controlling for either age, per cent body fat, LBM or mean arterial pressure. These results suggest that, across a wide age range, the expression of relative muscular strength has a stronger relationship with central arterial stiffness compared to either LBM or absolute strength. This suggests that muscle function more than muscle mass may be coupled with vascular health.

Let's talk about sex: where are the young females in blood flow restriction research?

Low-load resistance exercise with the blood flow restriction (BFR) has been shown to increase muscle size similar to that of traditional high-load resistance training. Throughout the BFR literature, there is a vast difference between the quantity of young females included in the literature compared to young males, older males and older females. Therefore, the purpose of this minireview is to discuss the underrepresentation of young females in the BFR literature and review the potential physiologic reasons as to why they may have been excluded. In conclusion, the female menstrual cycle, a normal physiological occurrence, is presumably the reason as to why majority of young females are excluded from participation in BFR studies. Instead of excluding females, we recommend that BFR studies should include both sexes and plot the results separately to determine whether a sex difference exists.

Time-course of muscle growth, and its relationship with muscle strength in both young and older women.

AIM: The time-course for changes in muscle size and strength is not well understood, particularly in women. In addition, contributions of muscle size to strength are commonly assessed utilizing a pre-post change score; however, a more appropriate within-subject correlational analysis has never been used. METHODS: To determine the time-course for thigh muscle size and strength in young (aged 18-25 years) and older (aged 50-65 years) women, and determine the relationship between size and strength after 8 weeks of training carried our three times per week. RESULTS: Anterior muscle thickness at the 50% site increased after 1 week of training, and exceeded the measurement error after 2 weeks (mean difference 0.23 cm, 95% CI 0.12-0.34 cm). Anterior muscle thickness at the 70% site increased and exceeded the measurement error after 2 weeks (mean difference 0.30 cm, 95% CI 0.15-0.45 cm). Posterior muscle thickness at the 50% site increased after 1 week of training, and exceeded the measurement error after 2 weeks (mean difference 0.24 cm, 95% CI 0.03-0.44 cm). Posterior muscle thickness at the 70% site increased after 1 week, and exceeded the measurement error after 3 weeks (mean difference 0.21 cm, 95% CI 0.07-0.35 cm). Muscle strength, assessed through one-repetition maximum, increased by 2 weeks in most measurements, and the within-subject variance explained by changes in muscle size ranged between 9% and 35%. CONCLUSIONS: Muscle growth appeared to occur early into a training program in both young and older women. Furthermore, although a large portion remains unexplained, the variance in muscle strength explained by muscle size is greater than previous studies not utilizing within-subject correlations. Geriatr Gerontol Int 2017; 17: 2000-2007.

Appendicular lean mass and site-specific muscle loss in the extremities correlate with dynamic strength.

BACKGROUND: Previous studies have reported the non-homogenous loss of muscle mass (site-specific muscle loss) with ageing, but this relationship to the loss of strength is not totally understood. PURPOSE: To investigate the relationship between maximal dynamic strength and site-specific muscle mass of the thigh and upper arm. METHODS: Thirty-five recreationally active men were separated into young-aged (YG, 20-39 years, n = 12), middle-aged (MG, 40-59 years, n = 13) and old-aged groups (OG, 60-75 years, n = 10). One-repetition maximum strength (1-RM; leg press, chest press, knee flexion, lat pull-down, and knee extension), muscle thickness (MTH, anterior and posterior thigh and upper arm) and appendicular lean mass (aLM) index were obtained from participants. Site-specific thigh MTH ratio was determined by dividing anterior thigh MTH (50% of thigh length) by posterior thigh MTH (50% of thigh length). RESULTS: aLM index was not significantly different between age groups, but a significantly smaller site-specific MTH thigh ratio was found in the OG. Collapsed across age groups both site-specific thigh MTH ratio and aLM index were significantly correlated with leg press, knee extension and knee flexion1-RM strength (r = 0·390-0·699), but not with knee extension: knee flexion (KE:KF) 1-RM strength ratios (r = 0·037-0·081). Separated by age groups only aLM index was correlated with KE:KF 1-RM ratio for the OG (r = 0·780). CONCLUSIONS: Site-specific thigh MTH ratio may be an important assessment tool in older individuals as it is different among age groups and is significantly related to dynamic maximal strength. However, maximal dynamic strength ratios appear to be less sensitive to differences in site-specific MTH ratios.

Comparative Effects of Vigorous-Intensity and Low-Intensity Blood Flow Restricted Cycle Training and Detraining on Muscle Mass, Strength, and Aerobic Capacity.

Traditional high-intensity aerobic training has been shown to improve muscle protein synthesis and aerobic capacity; however, recent research indicates that low-intensity aerobic training with blood flow restriction (BFR) may have similar effects. The purpose of this study was to compare the effects of vigorous-intensity (VI) cycling vs. low-intensity cycling with BFR (LI-BFR) on muscle mass, strength, and aerobic capacity after training and subsequent detraining. Thirty-one physically active subjects were assigned to one of 3 groups: VI (n = 10, 60-70% heart rate reserve [HRR]), LI-BFR (n = 11, 30% HRR with BFR at 160-180 mm Hg), and no exercise control (n = 10, no exercise). Subjects in VI and LI-BFR cycled 3 times per week for 6 weeks (total 18 sessions). Body composition, muscle mass, strength, and aerobic capacity were measured pre, post, and after 3 weeks of detraining. A group × time interaction (p = 0.019) effect for both knee flexion and leg lean mass was found. For both VI and LI-BFR groups, knee flexion strength was significantly increased between pre and post (p = 0.024, p = 0.01) and between pre and 3 week-post (p = 0.039, p = 0.003), respectively. For the LI-BFR group, leg lean mass was significantly increased between pre and 3 week-post (p = 0.024) and between post and 3 week-post (p = 0.013). However, there were no significant differences between groups for any variables. The LI-BFR elicits an increase in the knee flexion muscle strength over time similar to the VI. An increase in the leg lean mass over time was seen in the LI-BFR, but not in VI and CON.

Effects of age on arterial stiffness and central blood pressure after an acute bout of resistance exercise.

PURPOSE: To investigate the influence of age on arterial stiffness and blood pressure after performing a resistance exercise bout. METHODS: Recreationally active men were separated into young (YG, n = 12, 26.5 ± 3.3 years), middle (MG, n = 14, 49.4 ± 5.7 years), and old (OG, n = 10, 67.4 ± 6.3 years)-aged groups. In a randomized cross-over design, participants performed control and exercise conditions with at least 3 days separating conditions. The exercise condition consisted of leg press, chest press, knee flexion, lat pulldown and knee extension at ~65% one-repetition maximum for three sets of 10 repetitions. Brachial and central blood pressures, augmented pressure, augmentation index, central and peripheral pulse wave velocities were measured prior to each condition and starting at 5 min post-exercise. RESULTS: Brachial systolic blood pressure (SBP) significantly increased similarly after exercise for all age groups (YG, 8 ± 8 mmHg; MG, 5 ± 5 mmHg; OG, 5 ± 6 mmHg; p < 0.05). However, central SBP did not significantly increase for any age group after exercise. Augmentation index significantly increased after exercise only in the YG (11 ± 8%, p < 0.05). Central pulse wave velocity did not significantly increase in any age group after exercise when compared to the control condition. CONCLUSIONS: When performing a whole body moderate resistance exercise bout, acute changes in arterial stiffness and blood pressure appear to be minimally affected by age.

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.

Predicting METs from the heart rate index in persons with Down syndrome.

Persons with Down syndrome (DS) have altered heart rate modulation and very low aerobic fitness. These attributes may impact the relationship between metabolic equivalent units (METs) and the heart rate index (HRindex-the ratio between heart rate during activity and resting heart rate), thereby altering the HRindex thresholds for moderate- and vigorous-intensity physical activity. This study examined whether the relationship between METs and HRindex differs between persons with and without DS and attempted to develop thresholds for activity intensity based on the HRindex for persons with DS. METs were measured with portable spirometry and heart rate with a monitor in 18 persons with DS (25 ± 7 years; 10 women) and 18 persons without DS (26 ± 5 years; 10 women) during 6 over-ground walking trials, each lasting 6min, at the preferred walking speed and at 0.5, 0.75, 1.0, 1.25, and 1.5m/s. The relationship between METs and HRindex in the two groups was analyzed with multi-level modeling with random intercepts and slopes. Group, HRindex, and the square of HRindex were significant predictors of METs (p<0.001; R(2)=0.65). Absolute percent error did not differ significantly between groups across speeds (DS: 19.6 ± 14.4%; non-DS: 21.0 ± 14.5%). Bland-Altman plots demonstrated somewhat greater variability in the difference between actual and predicted METs in participants with than without DS. The HRindex threshold for moderate-intensity activity was 1.32 and 1.20 for persons with and without DS, respectively. The HRindex threshold for vigorous-intensity activity was 1.80 and 1.65 for persons with and without DS, respectively. Persons with DS have an altered relationship between METs and HRindex and higher HRindex thresholds for moderate- and vigorous-intensity physical activity.

Arterial stiffness and blood flow adaptations following eight weeks of resistance exercise training in young and older women.

Resistance training is recommended for all adults of both sexes. The arterial stiffness and limb blood flow responses to resistance training in young and older women have not been well-studied. The purpose of this study was to examine arterial stiffness and blood flow adaptations to high-intensity resistance exercise training in young and older women. Young (aged 18-25) and older (aged 50-64) women performed full-body high-intensity resistance exercise three times per week for eight weeks. The following measurements were performed twice prior to training and once following training: carotid to femoral and femoral to tibialis posterior pulse wave velocity (PWV), blood pressure, heart rate, resting forearm blood flow and forearm reactive hyperemia. Data was analyzed by ANOVAs with alpha set at 0.05. Correlations were also examined between changes in arterial stiffness and baseline arterial stiffness values. Older subjects had higher carotid-femoral PWV than younger subjects. No significant effects were found for femoral-tibialis posterior PWV or for resting forearm blood flow. Changes in carotid-femoral and femoral-tibialis posterior PWV correlated significantly with their respective baseline values. Older subjects increased peak forearm blood flow while young subjects showed no change. Total hyperemia increased significantly in both groups. In conclusion, in both young and older women, eight weeks of high-intensity resistance training appeared to improve microvascular forearm function while not changing carotid-femoral or femoral-tibialis posterior arterial stiffness. However, a large degree of individual variation was found and arterial stiffness adaptations appeared positively related to the initial stiffness values.

Obesity and overweight associated with increased carotid diameter and decreased arterial function in young otherwise healthy men.

BACKGROUND: Obesity is linked to cardiovascular disease, stroke, increased mortality and vascular remodeling. Although increased arterial diameter is associated with multiple cardiovascular risk factors and obesity, it is unknown whether lumen enlargement is accompanied by unfavorable vascular changes in young and otherwise healthy obese individuals. The purpose of this study was to compare carotid and brachial artery diameter, blood pressure, arterial stiffness, and endothelial function in young, apparently healthy, normal-weight, overweight, and obese male subjects. METHODS: One hundred sixty-five male subjects (27.39±0.59 years) were divided into 3 groups (normal weight, overweight, and obese) according to body mass index. Subjects underwent cardiovascular measurements to determine arterial diameter, function, and stiffness. RESULTS: After adjusting for age, the obese group had significantly greater brachial, carotid, and aortic pressures, brachial pulse wave velocity, carotid intima media thickness, and carotid arterial diameter compared with both the overweight and normal-weight groups. CONCLUSIONS: Obesity is associated with a much worse arterial profile, as an increased carotid lumen size was accompanied by higher blood pressure, greater arterial stiffness, and greater carotid intima media thickness in obese compared with overweight or normal-weight individuals. These data suggest that although obesity may be a factor in arterial remodeling, such remodeling is also accompanied by other hemodynamic and arterial changes consistent with reduced arterial function and increased cardiovascular risk.

Effect of lower limb preference on local muscular and vascular function.

Unilateral physical training can enhance muscular size and function as well as vascular function in the trained limb. In non-athletes, the preferred arm for use during unilateral tasks may exhibit greater muscular strength compared to the non-preferred arm. It is unclear if lower limb preference affects lower limb vascular function or muscular endurance and power in recreationally active adults. To examine the effect of lower limb preference on quadriceps muscle size and function and on lower limb vascular function in middle-aged adults. Twenty (13 men, 7 women) recreationally-active middle-aged (55 ± 7 yrs) adults underwent measurements of quadriceps muscle thickness, strength, mean power, endurance, and arterial stiffness, calf venous compliance, and calf blood flow in the preferred and non-preferred lower limb. The preferred limb exhibited greater calf vascular conductance (31.6 ± 15.5 versus 25.8 ± 13.0 units flow/mmHg; p = 0.011) compared to the non-preferred limb. The interlimb difference in calf vascular conductance was negatively related to weekly aerobic activity (hrs/week) (r = -0.521; p = 0.019). Lower limb preference affects calf blood flow but not quadriceps muscle size or function. Studies involving unilateral lower limb testing procedures in middle-aged individuals should consider standardizing the testing to either the preferred or non-preferred limb rather than the right or left limb.

Hypertension risk: exercise is medicine* for most but not all.

Hypertension is a risk factor for heart disease, and chronic exercise is recognized as a method for reducing resting blood pressure. Recent studies report that while exercise may benefit the majority of the population, the blood pressure adaptation is not always uniform; some individuals have an adverse blood pressure response to chronic aerobic exercise programmes. The purpose of this study was to examine the individual changes in resting blood pressure in response to exercise training regimens aimed at increasing muscle mass and strength. We have also included exercise (resistance and aerobic) in combination with blood flow restriction (BFR). Of 74 individuals, 11% had an increased risk, 16% had a decreased risk and 73% had no change in risk classification following exercise. The statistical analysis found that the group that decreased risk with exercise tended to have higher baseline levels of blood pressure. However, there were little baseline differences between the group that increased risk or the group that had no change in risk, suggesting that starting values may not necessarily determine who will see a beneficial response. In conclusion, the blood pressure adaptation to resistance training and exercise with BFR is not homogeneous with some participants increasing, decreasing or staying in the same risk category following an exercise intervention. These are important findings as they would not have been noted or discussed when looking only at the group means. Future research may identify molecular predictors so that individuals at risk for adverse events can be identified prior to exercise.

Vascular adaptations to low-load resistance training with and without blood flow restriction.

PURPOSE: To examine the effects of low-load knee extensor training to fatigue with and without blood flow restriction (BFR) on calf vascular conductance, calf venous compliance, and peripheral arterial stiffness in middle-aged individuals. METHODS: Eleven men (55 ± 8 years) and five post-menopausal women (57 ± 5 years) completed 6 weeks of unilateral knee extensor training with one limb exercising with BFR (BFR limb) and the contralateral limb exercising without BFR (free flow, FF limb). Before and after the training, femoral pulse wave velocity (PWV), calf blood flow (normalized as conductance), and calf venous compliance were measured in each limb. RESULTS: PWV increased following training in both limbs (main effect of time, p = 0.036; BFR limb 8.9 ± 0.8 vs. 9.5 ± 0.9 m/s, FF limb 9.0 ± 1.2 vs. 9.0 ± 1.1; Pre vs. Post). Calf blood flow increased (p = 0.026) in the FF limb (25.0 ± 7.0 vs. 31.8 ± 12.0 flow/mmHg; Pre vs. Post) but did not change (p = 0.831) in the BFR limb (29.1 ± 11.3 vs. 28.7 ± 11.5 flow/mmHg; Pre vs. Post). Calf venous compliance did not change in either limb following training. CONCLUSIONS: These results suggest low-load BFR resistance training to fatigue elicits small increases in peripheral arterial stiffness without eliciting concomitant changes in venous compliance. In addition, unlike low-load knee extensor training without BFR, training with BFR did not enhance calf blood flow.

The effects of elastic band resistance training combined with blood flow restriction on strength, total bone-free lean body mass and muscle thickness in postmenopausal women.

INTRODUCTION: Elastic band (EB) training is a common form of resistance training used by the elderly, individuals with joint problems or those recovering from injury. EB training performed at low intensities by these populations may have little effect on muscle hypertrophy. However, when combined with blood flow restriction (BFR), low-intensity EB resistance training may result in muscle hypertrophy. METHODS: Postmenopausal women (61 ± 5 years) were assigned to a moderate-to-high-intensity EB group (MH, n = 8) or a low-intensity EB group combined with BFR (LI-BFR, n = 6). Each group performed seated chest press, seated row and seated shoulder press with EB three times a week for eight weeks. EB colours progressed in each group by having participants maintain a rating of 7-9 on the OMNI Resistance for active muscle (OMNI-RES AM) scale (0-10) throughout training. In the LI-BFR group, BFR pressure progressed during the first 4 weeks of training (80-120 mmHg), after which EB colours were progressed. RESULTS: 1-repetition maximum increased for chest press (P = 0.01), shoulder press (P = 0.02) and seated row (P = 0.01), but no differences were found between groups. Only pectoralis major muscle thickness in the upper body increased (P = 0.04). A trend was found for an increase in total bone-free lean body mass (P = 0.055). CONCLUSIONS: The main findings of this study were that moderate-to-high-intensity EB training and low-intensity EB training with BFR resulted in similar increases in strength, total bone-free lean body mass and muscle thickness.

Effect of cuff type on arterial occlusion.

Blood flow restriction (BFR) by itself or in combination with exercise has been shown to be beneficial for skeletal muscle. Despite most of the literature showing positive effects of BFR on skeletal muscle, not all studies show a benefit of BFR exercise compared with exercise without BFR. Some of the discrepancy can be explained by differences in methodology. For example, wide (13·5 cm) nylon cuffs result in arterial occlusion at a much lower pressure than narrow elastic (5 cm) cuffs. However, although it is evident that there are differences between elastic narrow (5 cm) cuffs and nylon wide (13·5 cm) cuffs, it is presently unclear whether or not there are differences between two cuffs of similar size (5 cm) but different material (nylon versus elastic). We hypothesized that although the cuffs are of similar size, there would be significant differences in arterial occlusion between two cuff materials. With the participants supine, in a randomized order, either the nylon (5 × 83 cm) or elastic (5 × 135 cm) cuffs were applied to the most proximal portion of each leg. Arterial blood flow was detected using a hand-held bidirectional Doppler probe placed on the posterior tibial artery. A paired sample t-test found no difference between cuff types for arterial occlusion pressure. In conclusion, arterial occlusion pressure is not different between two cuffs of a similar size but different material. This suggests that either elastic or nylon cuffs of the same width should restrict blood flow similarly at the same pressure during resting conditions.