Forearm muscle quality as a better indicator of physical performance than handgrip strength in older male ground golf players aged 70 to 89.

OBJECTIVES: To examine the associations between absolute and relative handgrip strength (HGS) and physical performance. METHODS: A total of 135 old men aged 70-89 years had muscle thickness (MT) measured by ultrasound at anterior forearm (MT-ulna). Maximum voluntary HGS was measured for the dominant hand. Relative HGS was calculated as ratios of HGS to MT-ulna (HGS/MT-ulna, kg/cm), HGS to forearm girth (HGS/forearm-girth, kg/cm), and HGS to body mass (HGS/body mass, kg/kg). Physical performance was also assessed using the short physical performance battery (SPPB). RESULTS: Age was significantly correlated with absolute and relative HGS (r=-0.479 and r=-0.315 to -0.427, respectively all p<0.001) and physical performance (walking speed, r=-0.218, p=0.011; chair stand, r=0.348, p<0.001), but not with SPPB score (r=-0.083). Absolute HGS was positively correlated with usual-walking speed (r=0.354, p<0.001) and was inversely correlated with chair-stand time (r=-0.386, p<0.001). The strongest correlations were seen between HGS/MT-ulna and usual-walking speed (r=0.426, p<0.001) or chair-stand (r=-0.461, p<0.001). Stepwise regression analysis revealed that HGS/MT-ulna was a significant predictor for U-walk speed (R2=0.205) and chair-stand time (R2=0.241) while absolute HGS was not a significant predictor of either one. CONCLUSION: Thus, we suggest that forearm muscle quality (HGS/MT-ulna) may be a stronger predictor of physical performance than absolute HGS in active old men.

The WATCH (Weight Activity and Time Contributes to Health) paradigm and quality of life: the impact of overweight/obesity duration on the association between physical activity and health-related quality of life.

PURPOSE: Physical activity has been shown to reduce various health risks associated with obesity; however, it is less known how the duration of overweight/obesity impacts these associations. The purpose of this study was to determine how overweight/obesity status and overweight/obesity duration effects the association between physical activity and health-related quality of life (HRQOL). DESIGN: Cross-sectional and retrospective. SETTING: NHANES 2003-2006. SUBJECTS: One thousand five hundred and seventy-eight adults were included in this study. MEASURES: Moderate to vigorous physical activity was defined as ≥ 2020 activity counts in a given minute for ≥ 150 min/week; HRQOL assessed from the CDC HRQOL-4 survey; present BMI was objectively measured and 10 year prior BMI was calculated using self-reported body mass. Six groups were created: (i) physically active, normal weight now and 10 years ago; (ii) physically inactive, normal weight now and 10 years ago; (iii) physically active, overweight/obese now but not 10 years ago; (iv) physically active, overweight/obese now and 10 years ago; (v) physically inactive, overweight/obese now but not 10 years ago and (vi) physically inactive, overweight/obese now and 10 years ago. ANALYSIS: Multivariable ordinal regression. RESULTS: In comparison to active individuals who were normal weight at the examination and 10 years prior, only those who were inactive and overweight at the examination and 10 years prior had a worse HRQOL; ß = 0.91 (95% CI: 0.20-1.63; p = 0.01). CONCLUSIONS: Among individuals who have been overweight/obese for longer durations, physical activity may help to improve HRQOL.

Does blood flow restriction result in skeletal muscle damage? A critical review of available evidence.

Blood flow restriction (BFR) alone or in combination with exercise has been shown to result in muscle hypertrophy and strength gain across a variety of populations. Although there are numerous studies in the literature showing beneficial muscular effects following the application of BFR, questions have been raised over whether BFR may lead to or even increase the incidence of muscle damage. The purpose of this review is to examine the proposed mechanisms behind muscle damage and critically review the available BFR literature. The available evidence does not support the hypothesis that BFR in combination with low-intensity exercise increases the incidence of muscle damage. Instead, the available literature suggests that minimal to no muscle damage is occurring with this type of exercise. This conclusion is drawn from the following observations: (a) no prolonged decrements in muscle function; (b) no prolonged muscle swelling; (c) muscle soreness ratings similar to a submaximal low load control; and (d) no elevation in blood biomarkers of muscle damage.

Muscular adaptations after two different volumes of blood flow-restricted training.

This study aimed to gain an insight into the adaptations of muscle strength and skeletal muscle thickness after two different volumes of blood flow restriction training (BFRT), and compare them with high-intensity training. The sample was divided into four groups: low-volume, low-intensity BFRT (BFRT LV); high-volume, low-intensity BFRT (BFRT HV); traditional high-intensity resistance training (HIT); and a control group, which maintained their routine activities (CON). Leg extension one repetition maximum (1RM), isokinetic peak knee extension, and flexion torques at 60°/s and 180°/s as well as muscle thickness of the rectus femoris (RF) and vastus lateralis (VL) were assessed at baseline and after 5 weeks of training BFRT LV (7.03%, P < 0.05), BFRT HV (6.24%, P < 0.05) and HIT (18.86%, P < 0.001) groups increased 1RM performance, while no changes were observed in the CON group. Muscle thickness of the RF and VL was increased irrespective of the training group (7.5%, P < 0.001; and 9.9%, P < 0.001, respectively). We conclude that doubling the exercise volume with BFRT causes no further benefit with muscular size or strength. Although similar increases in muscle thickness were observed between training groups, HIT increased 1RM performance to a greater extent compared to either volume of BFRT.

Relationship between lifting performance and skeletal muscle mass in elite powerlifters.

AIM: Aim of the study was to examine the relationship between whole body skeletal muscle mass (SMM) and powerlifting performance in elite powerlifters. METHODS: Twenty elite male powerlifters, including 4 world champions, volunteered. Muscle thickness (MTH) and subcutaneous fat thickness (FTH) were measured by ultrasound at 9 sites on the anterior and posterior aspects of the body. FTH was used to estimate body fat and fat-free mass and SMM was estimated from ultrasound-derived prediction equations. Best lifting performance in the squat (SQ), bench press (BP), and dead lift (DL) was recorded from competition performance. RESULTS: Significant strong correlations (P<0.01) were observed between absolute and relative (divided by height) SMM and performance of the SQ (r=0.93 and r=0.94, respectively), BP (r=0.88 and r=0.87), and DL (r=0.84 and r=0.85). Relative lifting performance to SMM for squat (SQ/SMM ratio) and bench press (BP/SMM ratio) were constant throughout a wide range of weight classes (56kg-145kg) and there were no significant correlation between the SMM and those performances (r=0.21 for SQ and r=0.12 for BP). However, the DL/SMM ratio was negatively correlated to DL performance (r=-0.47, P<0.05). CONCLUSION: SMM is a good predictor of powerlifting performance throughout all weight classes.

ß2 Adrenoceptor signaling-induced muscle hypertrophy from blood flow restriction: is there evidence?

Skeletal muscle hypertrophy and increases in muscular function have been observed following low intensity/load exercise with blood flow restriction (BFR). The mechanisms behind these effects are largely unknown, but have been hypothesized to include a metabolic accumulation induced increase in muscle activation, elevations in growth hormone, and improvements in muscle protein balance. However, many of the aforementioned mechanisms are not present with BFR in the absence of exercise. In these situations, signaling through the ß2 adrenoceptor has been hypothesized to possibly contribute to the positive muscle adaptions, possibly in concert with muscle cell swelling. Signaling through the ß2 adrenoceptor has been shown to stimulate both muscle protein synthesis and an inhibition of protein degradation through increasing cyclic adenosine monophosphate (cAMP) or signaling via the Gßγ subunit, especially in situations where the basal rates of protein synthesis are already reduced. Every study that has investigated the catecholamine response to BFR in the absence of exercise or in combination with exercise has shown a significant increase above resting conditions. However, from the available evidence, it is unlikely that the norepinephrine response from BFR, particularly with exercise, is playing a prominent role with muscle adaptation in skeletal muscle that is not immobilized by a cast or joint injury.

Acute and chronic testosterone response to blood flow restricted exercise.

The American College of Sports Medicine recommends lifting a weight of at least 70% 1RM to achieve muscular hypertrophy as it is believed that anything below this intensity rarely produces substantial muscle growth. At least part of this recommendation is related to elevated systemic hormones following heavy resistance training being associated with skeletal muscle hypertrophy. Despite benefits of high intensity resistance training, many individuals are unable to withstand the high mechanical stresses placed upon the joints during heavy resistance training. Blood flow restricted exercise offers a novel mode of exercise allowing skeletal muscle hypertrophy at low intensities, however the testosterone response to this exercise has yet to be discussed. The acute and chronic testosterone response to blood flow restricted exercise appears to be minimal when examining the current literature. Despite this lack of response, notable increases in both size and strength are observed with this type of exercise, which seems to support that systemic increases of endogenous testosterone are not necessary for muscular hypertrophy to occur. However, definitive conclusions cannot be made without a more thorough analysis of responses of androgen receptor density following blood flow restricted exercise. It may also be that there are differing mechanisms underlying hypertrophy induced by high intensity resistance training and via blood flow restricted exercise.

Potential safety issues with blood flow restriction training.

The focal point of previous literature was establishing the efficacy of blood flow restriction training with respect to muscular strength, muscular hypertrophy, and muscular endurance. After mounting evidence supporting the efficacy of low-intensity blood flow restriction training, research has shifted to the overall safety of this training modality. The aim of this review was to summarize the research on the overall safety of blood flow restriction training, focusing on the cardiovascular system (central and peripheral), muscle damage, oxidative stress, and nerve conduction velocity responses compared with those observed with regular exercise. Although still sparse, the blood flow restriction training research thus far is promising with respect to safety outcomes. Individuals respond similarly to blood flow restriction training and to regular exercise; however, longer term studies are required to better understand the chronic effects of low-intensity blood flow restriction training and possible safety issues.

The perceptual responses to occluded exercise.

The purpose was to determine repetitions to failure and perceptual responses to exercise with and without occlusion. 15 subjects participated in a randomized crossover study of 3 trials. The first determined one repetition maximum (1RM) on the leg extension. Subjects were then assigned to an occlusion (OCC) or control (CON) group. After trial 2, subjects crossed over to the opposite trial. Knee wraps (KW) were placed around the upper thigh of each leg during OCC. Subjects completed 2 sets of leg extensions to failure at 30% 1RM, with 30 s rest between sets. Ratings of perceived exertion (RPE) and pain (P) were taken following each set. Data were analyzed using paired sample t-tests with an alpha level of 0.01. OCC repetitions were lower for the first and second set compared to CON (p=0.001). Total work completed was significantly lower with OCC compared to CON (p=0.001). OCC RPE were higher for both the first (p=0.01) and second set (p=0.003) compared to CON. P was not different following one set but was higher with OCC over CON following the second (p=0.009). In conclusion, KW provide an OCC stimulus allowing failure to occur sooner. However, the higher perceptual responses with OCC may limit its application to the highly motivated.

A mechanistic approach to blood flow occlusion.

Low-Intensity occlusion training provides a unique beneficial training mode for promoting muscle hypertrophy. Training at intensities as low as 20% 1RM with moderate vascular occlusion results in muscle hypertrophy in as little as three weeks. The primary mechanisms by which occlusion training is thought to stimulate growth include, metabolic accumulation, which stimulates a subsequent increase in anabolic growth factors, fast-twitch fiber recruitment (FT), and increased protein synthesis through the mammalian target of rapamycin (mTOR) pathway. Heat shock proteins, Nitric oxide synthase-1 (NOS-1) and Myostatin have also been shown to be affected by an occlusion stimulus. In conclusion, low-intensity occlusion training appears to work through a variety of mechanisms. The research behind these mechanisms is incomplete thus far, and requires further examination, primarily to identify the actual metabolite responsible for the increase in GH with occlusion, and determine which mechanisms are associated to a greater degree with the hypertrophic/anti-catabolic changes seen with blood flow restriction.

Accelerometer-Determined Intensity and Duration of Habitual Physical Activity and Walking Performance in Well-Functioning Middle-Aged and Older Women: A Cross-Sectional Study.

BACKGROUND: The association of physical activity (PA) intensities and duration spent in those activities with different walking tasks remains unclear. OBJECTIVES: To examine the association between the duration of PA intensities and three walking speeds (usual walking speed, maximal walking speed and zig-zag walking speed). DESIGN: Multiple linear regression analysis was used to estimate the association of age, BMI, maximum knee extension strength, light PA, moderate PA and vigorous PA with walking speeds. SETTING: University lab. PARTICIPANTS: Eighty-six older women (67 ± 7 years). MEASUREMENTS: PA was measured for 30 consecutive days using the Lifecorder-EX accelerometer. Exercise intensity was categorized as light (levels 1-3), moderate (levels 4-6) and vigorous (levels 7-9) based on the manufacturer algorithms. Usual straight walking speed (20 m), maximal straight walking speed (20 m) and zig-zag walking speed tests (10 m) were performed by each participant. RESULTS: For the usual straight walking speed model (R2 = 0.296, SEE = 0.15 m/s), the significant predictors were BMI, knee extension strength, light PA and vigorous PA. For the maximal straight walking speed model (R2 = 0.326, SEE = 0.20 m/s), only age was a significant predictor. For the zig-zag walking speed model (R2=0.417, SEE = 0.14 m/s), age and maximum knee strength were significant predictors in the model. CONCLUSIONS: Overall, the results of this study suggest that vigorous PA and maximal knee extension strength are two important factors that are associated with different walking speeds in older women.

Impact of Fat-Free Adipose Tissue on the Prevalence of Low Muscle Mass Estimated Using Calf Circumference in Middle-Aged and Older Adults.

Previous studies proposed calf circumference cutoff values for predicting dual-energy X-ray absorptiometry (DXA)-derived low muscle mass. However, DXA-derived appendicular lean mass (aLM) includes non-skeletal muscle components such as the appendicular fat-free component of adipose tissue fat cells (aFFAT). The purpose of this study was to compare the calf circumference method of classification before (Model #1) and after (Model #2) eliminating the influence of FFAT in healthy Japanese adults (50 to 79 years; mean age 70 (SD 7) years). Model 1, and Model 2 for classifying low muscle mass had a sensitivity of 78% and 64%, specificity of 76% and 75%, positive predictive value of 31% and 28%, and negative predictive value of 96% and 93%, respectively. Appendicular fat-free component of adipose tissue has the potential to influence the ability of calf circumference to accurately classify individuals with low muscle mass. Consideration should be made when using this as a screening tool for low muscle mass.

An Ultrasound Prediction Equation to Estimate DXA-Derived Body Fatness for Middle-Aged and Older Caucasian Adults.

BACKGROUND AND OBJECTIVES: Currently, only one study has used dual-energy X-ray absorptiometry (DXA)-derived percent body fat (BF%) as the criterion measure to develop ultrasound prediction equations to estimate BF% in adults between the ages of 50 and 80 years. The aim of this study was to examine the relationship between BF% estimated from subcutaneous fat thickness using a previously published Japanese-based prediction equation and DXA-derived BF% in Caucasian middle-aged and older adults. A secondary aim was to develop a new prediction equation for Caucasian adults if the previously published equation did not predict BF% well in Caucasians. DESIGN: Cross-sectional study. PARTICIPANTS AND MEASUREMENTS: One-hundred and two Caucasian adults aged 50-76 years (59 men and 43 women) had ultrasound fat thickness and DXA values measured. A new BF% prediction model was developed using ordinary least squares multiple linear regression. RESULTS: There was a strong correlation between ultrasound predicted and DXA-derived BF% (r = 0.882, p<0.001). Bland-Altman analysis did not indicate a bias in the prediction of BF% for Caucasian adults (r = -0.092, p>0.05). However, the predicted BF% was significantly higher compared to DXA-derived BF% (approximately 4%). A newly developed nonlinear prediction model used to estimate BF% was significant [F(17,84) = 33.44, p<0.001] with an R2 of 0.871 and an adjusted R2 of 0.845. When examining the stability of the model, bootstrapping (n=1000) resulted in an optimism value of 0.1135 so that the corrected R2 was 0.758. After removing an outlier, the model was significant [F(17,83) = 34.82, p<0.001] and it's R2 was 0.877 and adjusted R2 was 0.852. CONCLUSION: The developed equation was stable with a high degree of variance compared to results from previous studies. The results of this study also suggest that ethnicity should be considered when choosing which prediction equations should be used to estimate BF%.

Blood flow restriction augments the skeletal muscle response during very low-load resistance exercise to volitional failure.

The purpose of this study was to compare the acute muscular response with resistance exercise between the following conditions [labeled (% one-repetition maximum/% arterial occlusion pressure)]: high-load (70/0), very low-load (15/0), very low-load with moderate (15/40), and high (15/80) blood flow restriction pressures. Twenty-three participants completed four sets of unilateral knee extension to failure (up to 90 repetitions) with each condition, one condition per leg, each day. Muscle thickness and maximal voluntary contraction (MVC) were measured before (Pre), immediately after (Post-0), and 15 min after (Post-15) exercise and electromyography (EMG) amplitude during exercise. Pre to Post-0 muscle thickness changes in cm [95% CI] were greater with 15/40 [0.57 (0.41, 0.73)] and 15/80 [0.49 (0.35, 0.62)] compared to 70/0 [0.33 (0.25, 0.40)]. Pre to Post-0 MVC changes in Nm [95% CI] were higher with 15/40 [-127.0 (-162.1, -91.9)] and 15/80 [-133.6 (-162.8, -104.4)] compared to 70/0 [-48.4 (-70.1, -26.6)] and 15/0 [-98.4 (-121.9, -74.9)], which were also different. Over the first three repetitions, EMG increased across sets, whereas in the last three repetitions it did not. EMG was also different between conditions and was generally greater during 70/0. Repetitions decreased across sets reaching the lowest for 70/0, and for very low loads decreased with increased pressure. In trained participants exercising to failure, lower load and the application of restriction pressure augment changes in muscle thickness and torque. The EMG amplitude was augmented by load. Training studies should compare these conditions, as the results herein suggest some muscular adaptations may differ.

DXA-Rectified Appendicular Lean Mass: Development of Ultrasound Prediction Models in Older Adults.

OBJECTIVE: Dual-energy X-ray absorptiometry (DXA)-derived appendicular lean soft tissue mass (aLM) is used to diagnose sarcopenia. However, DXA-derived aLM includes non-skeletal muscle components, such as fat-free component of adipose tissue fat cell. These components, if not accounted for, could falsely inflate the aLM in individuals with a high amount of adipose tissue mass. B-mode ultrasound accurately measures muscle size in older adults. We sought to develop regression-based prediction equations for estimating DXA-rectified appendicular lean tissue mass (i.e. DXA-derived aLM minus appendicular fat-free adipose tissue (aFFAT); abbreviated as aLM minus aFFAT) using B-mode ultrasound. DESIGN: Cross-sectional study. MEASUREMENTS: Three hundred and eighty-nine Japanese older adults (aged 60 to 79 years) volunteered in the study. aLM was measured using a DXA, and muscle thickness (MT) was measured using ultrasound at nine sites. An ordinary least-squares multiple linear regression model was used to predict aLM minus aFFAT from sex, age and varying muscle thicknesses multiplied by height. Based on previous studies, we chose to use 4 MT sites at the upper and lower extremities (4-site MT model) and a single site (1-site MT model) at the upper extremity to develop prediction models. RESULTS: The linear prediction models (4 site MT model; R2 = 0.902, adjusted R2 = 0.899, and 1-site MT model; R2 = 0.868, adjusted R2 = 0.866) were found to be stable and accurate for estimating aLM minus aFFAT. Bootstrapping (n=1000) resulted in optimism values of 0.0062 (4-site MT model) and 0.0036 (1-site MT model). CONCLUSION: The results indicated that ultrasound MT combined with height, age and sex can be used to accurately estimate aLM minus aFFAT in older Japanese adults. Newly developed ultrasound prediction equations to estimate aLM minus aFFAT may be a valuable tool in population-based studies to assess age-related rectified lean tissue mass loss.

The affective and behavioral responses to repeated "strength snacks".

Background A training program consisting of only one-repetition maximum (1RM) training results in similar strength adaptations as traditional resistance exercise. However, little is known regarding the affective or behavioral responses to this type of training. Aim To examine the affective and behavioral response to either a traditional resistance exercise program or a biweekly 1RM-training program. Methods Participants were trained for 8 weeks (2× per week). The HYPER group completed four sets of 8-12 repetitions; the 1RM group (TEST) worked up to a single maximal repetition. Results The TEST group felt more revitalized and had an increase in positive engagement during their first visit, whereas the HYPER group showed an increase in feelings of physical exhaustion during their first and last visits. There were no pre to post differences for the change in behavior or self-efficacy between groups. Conclusion 1RM training appears to elicit a more favorable affective response, compared with HYPER training, which may ultimately improve adherence to resistance-type exercise.

Leisure time sedentary behavior, physical activity and frequency of protein consumption on lower extremity strength and lean mass.

BACKGROUND/OBJECTIVES: The purpose of this study was to evaluate the independent and combined associations of moderate-to-vigorous physical activity (MVPA), leisure time sedentary behavior and daily protein consumption on lower extremity muscular strength and lean mass. SUBJECTS/METHODS: Data from the 1999-2002 NHANES were utilized (N=1080 adults 50-85 y). Leg lean mass was estimated from dual-energy x-ray absorptiometry scans. Knee extensor strength was assessed objectively using the Kin Com MP dynamometer. MVPA and leisure time sedentary behavior were assessed via questionnaire, with the number of meals per day of ⩾30 g of protein per meal assessed via a 'multiple pass' 24-h dietary interview. RESULTS: Meeting MVPA guidelines (ß=16.3, P=0.02) and consuming at least two meals per day of ⩾30 g of protein per meal (ß=28.8, P=0.02) were independently associated with greater lower extremity strength, whereas sedentary behavior was not (ß=11.6, P=0.23). Finally, there was no evidence of a three-way interaction of these behaviors on lower extremity strength (ß=-8.7; P=0.70) or lower extremity lean mass (ß=144.5; P=0.75). CONCLUSIONS: Although MVPA and frequency of protein consumption of ⩾30 g of protein per meal were independently associated with lower extremity lean mass and strength, the results of the present study do not provide evidence to suggest that there is a three-way interplay between MVPA, sedentary behavior and frequency of protein consumption ⩾30 g of protein per meal on lower extremity lean mass and strength.

Are higher blood flow restriction pressures more beneficial when lower loads are used?

The application of blood flow restriction during low-load resistance exercise has been shown to induce muscle growth with high or low restriction pressures, however, loads lower than 20% one-repetition maximum (1RM) remain unexplored. Fourteen trained individuals completed six elbow flexion protocols involving three different loads (10%, 15%, and 20% 1RM) each of which was performed with either a low (40% arterial occlusion) or high (80% arterial occlusion) pressure. Pre- and post-measurements of surface electromyography (sEMG), isometric torque, and muscle thickness were analyzed. An interaction was present for torque (p < 0.001) and muscle thickness (p < 0.001) illustrating that all increases in pressure and/or load resulted in a greater fatigue and muscle thickness. There was no interaction for sEMG (p = 0.832); however, there were main effects of condition (p = 0.002) and time (p = 0.019) illustrating greater sEMG in the 20% 1RM conditions. Higher blood flow restriction pressures may be more beneficial for muscle growth when very low loads are used.

The acute muscular response to two distinct blood flow restriction protocols.

The purpose of this study was to determine acute physiological and perceptual responses to two commonly implemented blood flow restriction protocols. Using a within-subject design, 15 participants (age ∼25) performed four sets of unilateral elbow flexion with each arm. One arm exercised using a 3-cm elastic cuff inflated to 160 mmHg, whereas the other arm exercised using a 5-cm nylon cuff inflated to 40% of the individual's arterial occlusion pressure. While both protocols elicited increases in acute muscle thickness [pre: 4.5 (0.2) cm, post: 5.0 (0.2) cm; p < 0.001] and electromyography amplitude [first 3 reps: 55 ( 5 ) %MVC; last 3 reps: 87 ( 10 ) %MVC], there were no differences between conditions. Both protocols produced decreases in post-exercise strength (pre: 70 Nm, post: 51 Nm; p < 0.001) with no difference between conditions. The nylon protocol resulted in more repetitions during sets 2 [13 ( 2 ) vs. 9 ( 4 ); p = 0.001] and 3 [10 ( 2 ) vs. 7 ( 4 ); p = 0.05], while producing lower levels of discomfort following each set (average 3 vs. 4; p < 0.05). In conclusion, both protocols produced similar acute responses thought to be important for promoting muscle growth. However, the use of arbitrary pressures may place some individuals under complete arterial occlusion which may increase the potential risk of an adverse event.