PURPOSE: The importance of training to failure, especially when using low-loads (i.e., 30% 1RM) is well established. However, it remains unknown if lifting 15% 1RM can disrupt muscular blood flow enough to induce failure and stimulate adaptation. This study was designed to compare muscular adaptations between training with 15% 1RM and 70% 1RM, to determine if blood flow restriction (BFR) could augment the response to 15% 1RM, and if the effect of BFR is pressure dependent [40% versus 80% arterial occlusion pressure (AOP)]. METHODS: 40 untrained participants performed 4 sets of unilateral knee extension 2x/week for 8 weeks, with two conditions, one per leg. Conditions (label) were: 15% 1RM 0% AOP (15/0), 15% 1RM 40% AOP (15/40), 15% 1RM 80% AOP (15/80), 70% 1RM 0% AOP (70/0). Sets were stopped at 90 repetitions or volitional failure, as determined by an inability to maintain metronome cadence (2 s/contraction) or full repetitions. Inter-set rest was 30 s for 15/0, 15/40, 15/80 and 90 s for 70/0. A 10 cm wide nylon cuff was used for BFR. RESULTS: Data presented as [mean change (95% CI)]. There were condition x time interactions for 1RM (p<.001) and endurance (p=.028). 70/0 increased 1RM [3.15 (2.04, 4.25) kg]; 15/0 [-0.06 (-1.13, 1.01), 15/40 [0.066 (-1.06, 1.20), and 15/80 [0.68 (-0.41, 1.79) did not. Increased endurance was greatest for 15/80 [6.2 (4.3, 8.0)] compared to 15/0 [4.2 (2.4, 6.0)], 15/40 [4.7 (2.8, 6.5)], and 70/0 [4.0 (2.2, 5.9)]. There were main effects of time for isometric MVC [10.51 (3.87, 17.16) Nm, p=.002] and isokinetic MVC at 180°/s [change = 8.61 (5.54, 11.68) Nm, p<.001]. Isokinetic MVC at 60°/s did not change [2.45 (-1.84, 6.74) Nm, p=.261]. There were no condition x time interactions for muscle thickness sites (all p≥.313), which increased over time (all p<.001). There were main effects of condition for each site (70/0 was greater, all p<.001) except 30% lateral (p=.059). CONCLUSION: Most muscle strength and size changes appear similar despite large discrepancies in training load and restriction pressure. While the change in 1RM with high-load may be due to motor learning or practicing, the greater endurance adaptation favoring high restriction pressures should be explored further regarding underlying mechanisms. These results are relevant to mechanistic exploration, therapeutic purposes, and program design.
Abstract Low‐load exercise performed to or near task failure appears to result in similar skeletal muscle adaptations as low‐load exercise with the addition of blood flow restriction (BFR). However, there may be a point where the training load becomes too low to stimulate an anabolic response without BFR. This study examined skeletal muscle adaptions to very low‐load resistance exercise with and without BFR. Changes in muscle thickness (MTH), strength, and endurance were examined following 8‐weeks of training with a traditional high‐load [70% 1RM,(7000)], low‐load [15% 1RM,(1500)], low‐load with moderate BFR [15%1RM + 40%BFR(1540)], or low‐load with greater BFR [15% 1RM + 80%BFR(1580)]. 1RM strength changes were greater in the 7000 condition [2.09 (95% CI = 1.35–2.83) kg] compared to all low‐load conditions. For isometric and isokinetic strength, there were no changes. For endurance, there was a main effect for time [mean pre to post change = 7.9 (4.3–11.6) repetitions]. At the 50% site, the mean change in MTH in the 7000 condition [0.16 (0.10–0.22) cm] was greater than all low‐load conditions. For the 60% site, the mean change in MTH [0.15 (0.08–0.22)] was greater than all low‐load conditions. For the 70% site there was a main effect for time [mean pre to post change = 0.09 (0.05–0.14 cm]. All groups increased muscle size; however, this response was less in all very low training conditions compared to high‐load training. 1RM strength increased in the 7000 condition only, with no other changes in strength observed.
Although often used as a surrogate, comparisons between traditional blood pressure measurements and limb occlusion assessed via hand-held Doppler have yet to be completed. Using limb occlusion pressure as a method of assessing systolic pressure is of interest to those studying the acute effects of blood flow restriction, where the removal of the cuff may alter the physiological response.
Changes in muscle thickness (MT), isometric torque, and arterial occlusion pressure (AOP) were examined following four sets of twenty unilateral elbow flexion exercise. Participants performed four sets of maximal voluntary contractions with no external load throughout a full range of motion of a bicep curl with and without the application of blood flow restriction (BFR). For torque there was an interaction (p = 0.012). The BFR condition had lower torque following exercise (56.07 ± 17.78 Nm) compared to the control condition (58.67 ± 19.06 Nm). For MT, there was a main effect for time (p < 0.001). MT increased from pre (3.52 ± .78cm) to post (3.68 ± 81cm) exercise and remained increased above baseline 15 min post-exercise. For AOP, there was an interaction (p = 0.027). The change in AOP was greater in the BFR condition (16.6 ± 13.42mmHg) compared to the control (11.1 ± 11.84 mmHg). NO LOAD exercise with BFR let to greater reductions in torque and an exaggerated cardiovascular response compared to exercise alone. There were no differences in swelling. These results suggest that the application of BFR to NO LOAD exercise may result in greater fatigue.
Blood flow restriction (BFR) in combination with exercise has been well studied, however, little is known about the actual blood flow response to this type of exercise. The range of applied pressures in the research is wide, and previous studies have only examined the blood flow response using the same pressure for every individual independent of limb size, and have only done so at rest, after inflation of the cuff, and following exercise. No investigations have examined this response using relative applied pressures as a percentage of arterial occlusion pressure (AOP) nor have they investigated this within an exercise bout. PURPOSE: To measure blood flow before, during, and after low-load elbow flexion exercise combined with no restriction (NOBFR), 40% of AOP (40BFR), and 80% of AOP (80BFR). METHODS: 140 participants (women=75, men=65) were randomized into one of three conditions. After AOP and one-repetition maximum (1RM) measurement, ultrasound measures of standing blood flow at rest in the right brachial artery were taken. Participants performed four sets comprising 75 total goal repetitions of elbow flexion at 30% 1RM. Blood flow was measured between sets and at one and five minutes post-exercise. RESULTS: Blood flow decreased following inflation, with no difference between BFR conditions (40BFR: 38.1 ml·min−1 vs. 80BFR: 36.3 ml·min−1, p=0.85). Men had greater blood flow than women in all conditions at all time points (411.6 vs. 214.0 ml·min−1, respectively, p<0.001). Maximum blood flow was decreased during exercise with pressure (NOBFR=406.7 ml·min−1, 40BFR=311.1 ml·min−1, 80BFR=188.5 ml·min−1, p<0.001). Blood flow tended to increase across sets regardless of condition. One minute following cuff deflation, blood flow was higher in 80BFR than in 40BFR for women only (372.2 vs. 253.1 ml·min−1, p=0.005). One minute following cuff deflation, there was no group difference in blood flow for men (NOBFR=675.2 ml·min−1, 40BFR=715.4 ml·min−1, 80BFR=666.3 ml·min−1, p=0.75). CONCLUSIONS: The reduction in exercise-induced blood flow during BFR is pressure-dependent, with higher pressures eliciting a decrease in the magnitude of the hyperemic response. Blood flow increased above baseline during all BFR conditions; the use of relative applied pressures ensures that full occlusion does not occur during exercise.
To investigate the skeletal muscle mass to fat-free mass (SM-FFM) ratio in female and male athletes, as well as to examine the relationship between ultrasound predicted SM and magnetic resonance imaging (MRI)-measured SM.Seven female track and field athletes (female), 8 male collegiate swimmers (male-G1) and 8 male collegiate Olympic weightlifters (male-G2) volunteered. Whole-body SM volume was measured using MRI images obtained from the first cervical vertebra to the ankle joints. The volume of SM tissue was calculated and the SM volume was converted into mass units by an assumed skeletal muscle density. Muscle thickness was measured using ultrasound at nine sites and SM was estimated using an ultrasound-derived prediction equation.Percent body fat was similar among the groups. FFM, MRI-measured SM and SM-FFM ratio were greater in Males-G2 compared to the other two groups and those variables of Male-G1 were higher than the Female group. There was an excellent correlation (r=0.976) between MRI-measured and ultrasound-predicted SM (total error=1.52 kg). No significant difference was observed between MRI-measured and ultrasound-predicted SM in the overall sample or within each group. The SM-FFM ratio was positively correlated (r=0.708) with FFM in female and male athletes.We provide evidence for how the MRI-measured SM-FFM ratio changes with increasing levels of FFM and provide data that the ultrasound may be useful in estimating SM in athletes. Given the size limitations with MRI, both of these findings may be useful for future research investigating large sized athletes.
Blood flow restriction allows individuals to exercise with low loads while producing similar increases in muscle size as high load resistance training. It has been suggested that the pressure should be made relative to the individual (as a percentage of their arterial occlusion pressure), but it remains unknown if a given pressure results in a similar reduction in blood flow, and further, whether this differs based on the width of the cuff being applied. PURPOSE: To examine hemodynamic responses to various relative pressures in the supine position using two commonly used cuffs (10 cm and 12 cm). METHODS: Participants (men=17, women=14) came to the laboratory for two visits. One cuff (10 cm or 12 cm) was randomly applied to the right proximal thigh for each visit and arterial occlusion pressure was measured. Ultrasound measures of blood flow, mean blood velocity, peak blood velocity, and artery diameter were taken from the posterior tibial artery at rest and during the application of 10% increments of the arterial occlusion pressure. A repeated measures ANOVA was used to examine differences across conditions. RESULTS: There was no significant interaction or overall difference between the 10 cm and 12 cm cuff relating to blood flow [-0.501 (7.9) ml•min-1, p = 0.728], mean blood velocity [-0.168 (1.7) cm•sec-1, p = 0.590], peak blood velocity [0.586 (11.7) cm•sec-1, p = 0.783], or artery diameter [0.003 (0.02) cm, p = 0.476]. There was a main effect of pressure for blood flow (p < 0.05), mean blood velocity (p < 0.05), peak blood velocity (p < 0.05), and artery diameter (p < 0.05), with each decreasing with increasing pressures. Peak blood velocity increased until 60% of arterial occlusion pressure before decreasing with increased pressure. The 80% and 90% arterial occlusion pressures reduced blood flow by 69.4% and 79.3% respectively when collapsed across the 10 cm and 12 cm cuffs. No other pressures differed significantly between the relative applied pressure and amount of blood flow restricted. CONCLUSIONS: Provided relative pressures are applied, cuff width appears to have little to no effect on the blood flow response at rest. Importantly, relative pressures may not indicate the magnitude of blood flow being reduced (e.g. 80% arterial occlusion may not reduce 80% of blood flow), particularly at higher arterial occlusion pressures.
Dear Editor-in-Chief, Regarding periodization, three arguments are often put forward: 1) everything is periodization, 2) periodization has not been well studied in the literature (i.e., programming ≠ periodization) (1), or 3) periodization has never been appropriately studied. If the first is true, then there is no need to discuss or research the topic. If the second or third is true, then it would be useful to scale the convictions to the available evidence. The goal of our article was to provide some context for that discussion (2). A recent position stand for training older adults recommended that those looking to improve muscle mass, strength, and functional ability should follow a periodized approach to optimize adaptations (3). This, to the point of our article, is quite a strong recommendation to make for something that many believe has not been well studied (1). HYPERTROPHY AND STRENGTH GAINS Our position on the role of muscle growth and strength gain is based on the lack of experimental data that one contributes to the other (4). Despite this, we do see the logical connection between the two and make the suggestion that "it may be the preference of the strength coach to still include hypertrophy work" (2). In addition, we go on to suggest that "if coaches scale its focus to the weight of the evidence, much less time can be spent on hypertrophy, and more time can be dedicated to specific sport practice or rest" (2). TRAINING VARIATION Stone et al. (5) suggests that variation is important because it is difficult to lift heavy for extended periods of time. The citation is one where the purpose was to induce overtraining, and we discussed in our article why this has little relevance to the current discussion in the "Periodization and overtraining" section. Their second claim is grounded in the general adaptation syndrome being relevant to human exercise (1), which may not be well founded, also noted in our article. TRAINING TO FAILURE We agree that failure is unnecessary. We suggested that "there are likely strategies or techniques more likely to "optimize" adaptation (i.e., training to or near failure for muscle growth with a load that can largely be determined by preference …" Recent work corroborates that activation of type 2 muscle fibers is similar between low and high loads when exercise is performed to task failure (6). Muscle growth does not appear load dependent (7). MISREPRESENTATION OF THE LITERATURE It is clear that Morehouse and Miller were skeptical on the relationship between changes in muscle size and strength (8). Although their thoughts are not pivotal to a discussion for the evidence of periodization, they are interesting from a historical perspective. We echo Stone et al. (5) and encourage readers to examine the entire chapter on Muscular Performance (chapter 5). The section titled "Rationale for Strength Increase During Training" begins with the following: "Since hypertrophy is a questionable explanation for increased strength in trained muscle, other reasons must be examined." Skepticism and caution should be practiced when data are scarce. Samuel L. Buckner USF Muscle Laboratory Exercise Science Program University of South Florida Tampa, FL Matthew B. Jessee Department of Health Exercise Science and Recreation Management University of Mississippi University, MS Scott J. Dankel Exercise Physiology Laboratory Department of Health and Exercise Science Rowan University Glassboro, NJ Kevin T. Mattocks Exercise Science Lindenwood University Belleville, IL Zachary W. Bell Takashi Abe Jeremy P. Loenneke Kevser Ermin Applied Physiology Laboratory Department of Health, Exercise Science and Recreation Management University of Mississippi University, MS
