Jeremy T. Barnes

Blood flow restriction reduces time to muscular failure

Abstract Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low-intensity exercise likely requires more repetitions and individuals with injuries may be incapable of sustaining the mechanical stress to reach failure. The aim of this study was to determine if knee wraps provide a stimulus to decrease time to failure. Twenty healthy individuals participated in a randomized crossover study consisting of three trials. The first trial was used to determine one-repetition maximum (1-RM) on leg extension. Participants were then assigned to a blood flow restriction or control group. After trial 2, participants crossed over to the opposite trial. Knee wraps were placed around the upper thigh of each leg during blood flow restriction. Leg extensions were completed at 30% 1-RM until failure. A rating of perceived exertion was taken after exercise and whole blood samples were taken before, after, and 3 min after exercise for the determination of lactate. Repetitions until failure and total work were significantly lower with practical blood flow restriction compared with the control trial. Metabolic stress as measured by whole blood lactate was higher immediately after muscular failure in the control compared with the blood flow restriction trial, but not so 3 min after exercise. There were no differences in ratings of perceived exertion. In conclusion, knee wraps provide a stimulus for blood flow restriction allowing failure to occur sooner with similar metabolic stress after reperfusion. However, similar perceptual responses despite the lower workload with blood flow restriction may limit its application to the highly motivated.

Blood flow-restricted walking does not result in an accumulation of metabolites.

The American College of Sports Medicine recommends lifting a weight of at least 70% of one’s concentric one repetition maximum to achieve muscular hypertrophy as it is believed that anything below this intensity does not produce significant muscle growth. Recent studies have found muscle hypertrophy to occur with low‐intensity ‘aerobic–like’ exercise with the application of blood flow restriction (BFR) to the limbs. Previous research with low load resistance training has shown that elastic knee wraps provide a practical means to induce elevations in whole blood lactate (WBL), which has been hypothesized to result in many of the adaptations observed with this type of exercise. However, this has yet to be investigated with low‐intensity walking. Thus, the purpose of this paper was to determine the degree to which WBL increases with practical BFR walking. Exercise consisted of five 2‐min bouts of walking at 75 m per min on a motor‐driven treadmill with a 1‐min rest period following each exercise bout. Participants completed the walking with (BFR) and without [control (CON)] restriction to the upper thigh in a randomized order. Practical BFR with elastic knee wraps did statistically increase WBL compared with CON; however, this was not considered a real change because the minimal difference between conditions was not exceeded. In conclusion, metabolic stress is not increased following practical BFR walking exercise. This study may provide an explanation for the lower hormone response observed with BFR walking and provide further evidence that mechanisms other than metabolic accumulation exist with BFR.

Time under tension decreased with blood flow–restricted exercise

Objectives: Exercise to failure results in similar muscle protein synthesis responses, independent of intensity. However, low‐intensity exercise likely requires more time under tension and those with injuries may be incapable of sustaining the mechanical stress to reach failure. Design: The purpose was to determine whether elastic knee wraps (KW) provide a stimulus to decrease time under tension and overall volume of work while maintaining a similar level of metabolic stress. Methods: Thirteen healthy subjects participated in a randomized crossover study consisting of three trials. The first determined 1 repetition maximum (1RM) on the bilateral leg extension. Subjects were then assigned to a blood flow restriction (BFR) or control (CON) group. After trial 2, subjects crossed over to the opposite trial. KW were placed around the thigh of each leg during BFR. Leg extensions were completed at 30% 1RM until failure. Whole blood lactate (WBL) was taken pre‐, post‐, and 3 and 5 min postexercise. Heart rate (HR) was measured before, following the first and second sets, and 3 and 5 min postexercise. Results: This study found KW provide a BFR stimulus allowing failure to occur sooner with similar metabolic stress postreperfusion. There were no differences in HR at any time point. Conclusions: These results may benefit populations that cannot sustain the mechanical stress of high‐intensity exercise or low‐intensity exercise that requires a longer sustained time under tension.

Validity and reliability of an ultrasound system for estimating adipose tissue

When health professionals measure the fitness levels of clients, body composition is usually estimated. In field settings, body composition is commonly estimated with skinfolds or bioelectrical impedance analysis. Recently, a portable ultrasound device has been manufactured to estimate what percentage of body mass is composed of adipose tissue (AT%). A reported advantage of using ultrasound is that inter‐ and intrarater variations may be minimized when compared with the skinfold technique. Therefore, the purpose of this pilot study was twofold; 1) to determine the validity of a portable ultrasound device compared with skinfolds and 2) determine the reliability of the portable ultrasound device. Participants had their measurements taken in the following order: urine specific gravity, body mass, height, skinfolds and ultrasound determined. Participants had their urine specific gravity and ultrasound determined AT% estimates measured again 48 h later. The current pilot study found that the ultrasound was not a valid estimate of AT% when compared with the skinfold estimate (TE > 4%). In addition, the 1‐site estimate from the ultrasound was more reliable than the 3‐site estimate of AT%. These data are of importance to practitioners because it demonstrates that while the ultrasound is not a valid estimate compared with skinfolds, the 1‐site estimate may be able to track changes in AT% over time, making the ultrasound an option for assessing changes in body composition.

Reliability of field methods for estimating body fat.

When health professionals measure the fitness levels of clients, body composition is usually estimated. In practice, the reliability of the measurement may be more important than the actual validity, as reliability determines how much change is needed to be considered meaningful. Therefore, the purpose of this study was to determine the reliability of two bioelectrical impedance analysis (BIA) devices (in athlete and non‐athlete mode) and compare that to 3‐site skinfold (SKF) readings. Twenty‐one college students attended the laboratory on two occasions and had their measurements taken in the following order: body mass, height, SKF, Tanita body fat‐350 (BF‐350) and Omron HBF‐306C. There were no significant pairwise differences between Visit 1 and Visit 2 for any of the estimates (P>0·05). The Pearson product correlations ranged from r = 0·933 for HBF‐350 in the athlete mode (A) to r = 0·994 for SKF. The ICCs ranged from 0·93 for HBF‐350(A) to 0·992 for SKF, and the MDs ranged from 1·8% for SKF to 5·1% for BF‐350(A). The current study found that SKF and HBF‐306C(A) were the most reliable (<2%) methods of estimating BF%, with the other methods (BF‐350, BF‐350(A), HBF‐306C) producing minimal differences greater than 2%. In conclusion, the SKF method presented with the best reliability because of its low minimal difference, suggesting this method may be the best field method to track changes over time if you have an experienced tester. However, if technical error is a concern, the practitioner may use the HBF‐306C(A) because it had a minimal difference value comparable to SKF.

Quality protein intake is inversely related with abdominal fat

Dietary protein intake and specifically the quality of the protein in the diet has become an area of recent interest. This study determined the relationship between the amount of quality protein, carbohydrate, and dietary fat consumed and the amount of times the ~10 g essential amino acid (EAA) threshold was reached at a meal, with percent central abdominal fat (CAF). Quality protein was defined as the ratio of EAA to total dietary protein. Quality protein consumed in a 24-hour period and the amount of times reaching the EAA threshold per day was inversely related to percent CAF, but not for carbohydrate or dietary fat. In conclusion, moderate to strong correlations between variables indicate that quality and distribution of protein may play an important role in regulating CAF, which is a strong independent marker for disease and mortality.

Accuracy of Field Methods in Assessing Body Fat in Collegiate Baseball Players

When assessing the fitness levels of athletes, body composition is usually estimated, as it may play a role in athletic performance. Therefore, the purpose of this study was to determine the validity of bioelectrical impedance analysis (BIA) and skinfold (SKF) methods compared with dual-energy X-ray absorptiometry (DXA) for estimating percent body fat (%BF) in Division 1 collegiate baseball players (n = 35). The results of this study indicate that the field methods investigated were not valid compared with DXA for estimating %BF. In conclusion, this study does not support the use of the TBF-350, HBF-306, HBF-500, or SKF thickness for estimating %BF in collegiate baseball players. The reliability of these BIA devices remains unknown; therefore, it is currently uncertain if they may be used to track changes over time.

Validity of the Current NCAA Minimum Weight Protocol: A Brief Review

Historically, collegiate wrestlers have been associated with utilizing rapid weight loss methods to reach a desired weight class. Following three deaths in 1997, the National Collegiate Athletic Association (NCAA) implemented a program which prevents wrestlers from wrestling below a minimum weight (MW) of 5% body fat. Although numerous studies have investigated adolescent wrestlers, few have investigated collegiate wrestlers using the methods outlined by the NCAA. The purpose of this review paper is to outline potential problems with the current NCAA protocol as well as critique studies investigating the validity of methods to assess MW.

Validity of a portable computer‐based ultrasound system for estimating adipose tissue in female gymnasts

The aim of this investigation was to determine the validity of a portable ultrasound instrument for estimating adipose tissue (AT%) compared to dual‐energy X‐ray absorptiometry (DXA) in female collegiate gymnasts. Participants had their measurements taken in the following order: urine‐specific gravity, body mass, height, ultrasound determined AT% (1‐site and 3‐site) and DXA determined AT%. The current pilot study found significant differences between estimates of AT% (P < 0·001). Pearsons correlations between DXA and 1‐site and 3‐site estimates were r = 0·786 and r = 0·753, respectively. The standard error of the estimate between DXA and 1‐site and 3‐site estimates was 3·6% and 3·9%, respectively. However, the average deviation of individual scores from the line of identity was 6·7% for the 1‐site and 4·9% for the 3‐site, when compared with the DXA estimate. The results of this preliminary study found that the portable ultrasound was not a valid estimate of AT% when compared with the DXA estimate in female collegiate gymnasts.

A WORKLOAD SELECTION PROCEDURE FOR THE ÅSTRAND-RYHMING TEST FOR WOMEN.

The Åstrand-Ryhming Submaximal Bicycle Test is an accurate and widely used test to estimate maximal oxygen consumption. This test requires a participant to maintain a workload over a 6-min. period. The issue facing many employing this protocol is the identification of an appropriate workload for the cycling regimen. The present study is designed to identify a method for determining an appropriate workload for female participants. A prior study designed a workload selection procedure specifically for men; however, the selection procedure designed for women in this study was better able to elicit a final heart rate (average of minutes five and six) between 165–170 bpm compared to the original Åstrand-Ryhming procedure.