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.

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.

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%.

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.

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.

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.

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.

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 prevalence of sarcopenia before and after correction for DXA-derived fat-free adipose tissue.

The literature suggests that the estimate of lean mass may be overestimated in the obese using dual-energy X-ray absorptiometry (DXA), as ~15% of adipose tissue is composed of fat-free tissue. The purpose of this study was to investigate how the DXA-derived fat-free adipose influences appendicular lean mass and prevalence of sarcopenia across a range of body fat % in both men and women using a national sample (n=1946). The appendicular lean mass/m2 went from 7.0 kg/m2 (confidence interval (CI): 6.9, 7.2) to 5.9 kg/m2 (CI: 5.8, 6.1) following correction in those with ⩾35% body fat, whereas it only went from 7.5 kg/m2 (CI: 7.2, 7.8) to 7.1 kg/m2 (CI: 6.8, 7.4) following correction in those with <25% body fat. Fat-free adipose tissue may need to be accounted for when estimating appendicular lean mass and failure to account for fat-free adipose tissue may underestimate the prevalence of sarcopenia.

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.

Site-specific associations of muscle thickness with bone mineral density in middle-aged and older men and women.

It is unknown whether age-related site-specific muscle loss is associated with areal bone mineral density (aBMD) in older adults. To examine the relationships between aBMD and whole-body muscle thickness distribution, 97 healthy adults (46 women and 51 men) aged 50-78 years volunteered. Total and appendicular lean soft tissue mass, aBMD of the lumbar spine (LS-aBMD) and femoral neck (FN-aBMD) were determined using dual-energy X-ray absorptiometry. Muscle thickness (MT) was measured by ultrasound at nine sites of the body (forearm, upper arm, trunk, upper leg, and lower leg). Relationships of each co-variate with aBMD were tested partialling out the effect of age. aBMD was not correlated with either MT of the trunk or anterior lower leg in either sex. In men, significant and relatively strong correlations were observed between anterior and posterior upper arms, posterior lower leg, and anterior upper leg MT and LS-aBMD or FN-aBMD. In women, significant correlations were observed between anterior and posterior upper legs, posterior lower leg, and anterior upper arm MT and FN-aBMD. LS-aBMD was only correlated with forearm and posterior upper leg MT in women. In conclusion, the site-specific association of MT and aBMD differs between sexes and may be associated with the participants' daily physical activity profile.

The acute muscular effects of cycling with and without different degrees of blood flow restriction.

The aim was to compare the acute effects of work matched high intensity (75% peak aerobic capacity) aerobic exercise to low intensity (40% peak aerobic capacity) aerobic exercise with different degrees of blood flow restriction (BFR) [40% estimated arterial occlusion (40 BFR) and 60% estimated arterial occlusion (60 BFR)] on variables previously hypothesized to be important for muscle adaptation. There were no meaningful changes in torque. Anterior thigh muscle thickness was increased from baseline with high intensity cycling and 40 BFR (~2 mm increase, p ≤ 0.008). A significant increase in lactate occurred in all exercise conditions but was greatest with high intensity cycling (~5.4 mmol/L increase). Muscle activation was significantly higher with high intensity cycling compared to low intensity cycling with BFR, regardless of pressure (~25% vs. ~12% MVC). Mean power frequency was not different between conditions but did increase from the first 5 minutes of exercise to the last 5 minutes (93% vs. 101%, p < 0.001). Ratings of perceived exertion (RPE) were higher with high intensity cycling but discomfort was similar between conditions. We wish to suggest that high intensity cycling produces greater muscular stress than that observed with work matched low intensity cycling in combination with BFR.

Cycle training induces muscle hypertrophy and strength gain: strategies and mechanisms.

Cycle training is widely performed as a major part of any exercise program seeking to improve aerobic capacity and cardiovascular health. However, the effect of cycle training on muscle size and strength gain still requires further insight, even though it is known that professional cyclists display larger muscle size compared to controls. Therefore, the purpose of this review is to discuss the effects of cycle training on muscle size and strength of the lower extremity and the possible mechanisms for increasing muscle size with cycle training. It is plausible that cycle training requires a longer period to significantly increase muscle size compared to typical resistance training due to a much slower hypertrophy rate. Cycle training induces muscle hypertrophy similarly between young and older age groups, while strength gain seems to favor older adults, which suggests that the probability for improving in muscle quality appears to be higher in older adults compared to young adults. For young adults, higher-intensity intermittent cycling may be required to achieve strength gains. It also appears that muscle hypertrophy induced by cycle training results from the positive changes in muscle protein net balance.

Age-related site-specific muscle loss in the thigh and zigzag walking performance in older men and women.

To investigate the relationships between site-specific muscle loss in the thigh, muscle quality and zigzag walking performance, 40 men and 41 women aged 65-79 years had muscle thickness (MTH) measured by ultrasound at nine sites on the anterior and posterior aspects of the body. Skeletal muscle mass (SM) was estimated from an ultrasound-derived prediction equation. Site-specific thigh sarcopenia was calculated using ultrasound-measured MTH at the anterior/posterior aspects of the thigh (AP-MTH ratio). Zigzag walking time (ZWT) and maximum isometric knee extension (KE) and flexion (KF) torques were measured. Muscle quality (torque/thigh SM) and knee joint strength index (torque/body mass) were calculated. There were no significant correlations between SM index and ZWT. However, AP-MTH ratio was inversely correlated (P < 0.05) to ZWT in men (r = -0.335) and women (r = -0.309). ZWT was also inversely correlated (P < 0.05) to KE-strength index in both sexes (men, r = -0.328; women, r = -0.372). Similarly, ZWT was correlated to KF-strength index (r = -0.497) and muscle quality (r = -0.322) in women, but not in men. After adjusting for age, height and body mass, AP-MTH ratio was inversely correlated to ZWT in men (r = -0.325) and tended to be correlated to ZWT in women (r = -0.263). Zigzag walking performance may be associated with site-specific thigh sarcopenia in older men and women.

Muscle damage after low-intensity eccentric contractions with blood flow restriction.

Discrepancies exist whether blood flow restriction (BFR) exacerbates exercise-induced muscle damage (EIMD). This study compared low-intensity eccentric contractions of the elbow flexors with and without BFR for changes in indirect markers of muscle damage. Nine untrained young men (18-26 y) performed low-intensity (30% 1RM) eccentric contractions (2-s) of the elbow flexors with one arm assigned to BFR and the other arm without BFR. EIMD markers of maximum voluntary isometric contraction (MVC) torque, range of motion (ROM), upper arm circumference, muscle thickness and muscle soreness were measured before, immediately after, 1, 2, 3, and 4 days after exercise. Electromyography (EMG) amplitude of the biceps brachii and brachioradialis were recorded during exercise. EMG amplitude was not significantly different between arms and did not significantly change from set 1 to set 4 for the biceps brachii but increased for the brachioradialis (p ≤ 0.05, 12.0% to 14.5%) when the conditions were combined. No significant differences in the changes in any variables were found between arms. MVC torque decreased 7% immediately post-exercise (p ≤ 0.05), but no significant changes in ROM, circumference, muscle thickness and muscle soreness were found. These results show that BFR does not affect EIMD by low-intensity eccentric contractions.

Blood flow restriction: effects of cuff type on fatigue and perceptual responses to resistance exercise.

Blood flow restriction (BFR) combined with low load resistance training has been shown to result in muscle hypertrophy similar to that observed with higher loads. However, not all studies have found BFR efficacious, possibly due to methodological differences. It is presently unclear whether there are differences between cuffs of similar size (5 cm) but different material (nylon vs. elastic). The purpose was to determine if there are differences in repetitions to fatigue and perceptual ratings of exertion (RPE) and discomfort between narrow elastic and narrow nylon cuffs. Sixteen males and females completed three sets of BFR knee extension exercise in a randomized cross-over design using either elastic or nylon restrictive cuffs applied at the proximal thigh. There were no differences in repetitions to fatigue (marker of blood flow) or perceptual ratings between narrow elastic and narrow nylon cuffs. This data suggests that either elastic or nylon cuffs of the same width should cause similar degrees of BFR at the same pressure during resistance exercise.

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.