Comparable Acute Metabolic Responses when Walking with Blood Flow Restriction and Walking with Load Carriage: Implication for Tactical Professionals.

The current study aimed to investigate exercise with blood flow restriction (BFR) as a low-intensity conditioning strategy in tactical professionals with load carriage. During the low-intensity exercise, researchers examined the acute metabolic responses from low-intensity BFR walking, walking with load carriage, and walking with BFR and load carriage. Twelve healthy adult males (age = 21.8 ± 1.5 yrs, height = 181.3 ± 7.2 cm, body mass = 84.4 ± 11.1 kg and BMI = 25.6 ± 2.6 kg·m2) completed five bouts of 3-min treadmill walking at 4.8 km·h-1 with 1-min rest interval under three different conditions: 1) blood flow restriction (BFR), 2) loaded with 15% of body mass (LOAD) and 3) loaded with 15% of body mass with blood flow restriction (BFR-LOAD). Oxygen consumption (V̇O2), heart rate, and local muscle oxygen saturation was measured during the exercise bouts. V̇O2 increased by 7% during the BFR- LOAD (p = 0.001) compared with BFR or LOAD alone. There were no differences in V̇O2 between BFR and LOAD (p = 0.202). BFR-LOAD showed significantly lower (-9%) muscle oxygen saturation (p = 0.044) and deoxygenated hemoglobin (p = 0.047) compared to LOAD. Low-intensity walking with the addition of BFR shares acute metabolic characteristics similar to walking with a load. These characteristics suggest there is potential for the use of BFR to increase exercise intensity for individuals training with load carriage.

The Effect of Direct and Remote Postexercise Ischemic Conditioning on Muscle Soreness and Strength 24 Hours After Eccentric Drop Jumps.

ABSTRACT: Lillquist, T, Mahoney, SJ, Kotarsky, C, McGrath, R, Jarajapu, Y, Scholten, SD, and Hackney, KJ. The effect of direct and remote postexercise ischemic conditioning on muscle soreness and strength 24 hours after eccentric drop jumps. J Strength Cond Res 37(9): 1870-1876, 2023-Strategic limb occlusion applied after exercise may facilitate recovery, not only in directly targeted tissue but also in remote areas of the body. The purpose of this study was to determine if postexercise ischemic conditioning (PEIC) applied directly to one leg facilitated recovery in the targeted leg and the contralateral leg that did not receive direct PEIC. Twenty active men participated in a single-blind, randomized, crossover design. Subjects completed 2 paired testing sessions (PEIC and control-SHAM) that included pre-assessments and 24-hour postassessments. Each paired testing session included an eccentric drop jump task, which has been shown to increase lower-body muscle soreness and decrease strength. After each drop jump task, occlusion cuffs were immediately applied. In the PEIC session, ∼198 mm Hg was applied directly to one leg (PEIC-Direct), whereas the contralateral leg received a nonphysiological stimuli of 20 mm Hg (PEIC-Remote). In the control-SHAM session, both legs directly and remotely received the 20 mm Hg pressure. Unilateral pre-assessments and 24-hour postassessments included muscle soreness using a visual analog scale and strength via peak torque assessment across the force-velocity spectrum (flexion/extension 60/60, 120/120, 180/180, 240/240, 300/300 °·s -1 ), and a maximal eccentric extension (30/30 °·s -1 ). Muscle soreness was significantly increased ( p < 0.05) at 24 hours compared with pretreatment except for PEIC-Direct (1.19 ± 0.78 vs. 2.32 ± 1.48, p = 0.096). Across the force-velocity spectrum, there were no significant differences observed between any associated pretest and posttest ( p > 0.05). PEIC applied directly to target leg after eccentric drop jumps attenuated perceived quadriceps muscle soreness 24 hours post; however, there was no effect on muscle strength.

Evenness of Dietary Protein Intake Is Positively Associated with Lean Mass and Strength in Healthy Women.

Background: Evenness of protein intake is associated with increased lean mass, but its relationship with muscle strength and performance is uncertain. Objectives: We determined the association of evenness of protein intake with lean mass, muscle strength and endurance, and functional ability. Design: This was a cross-sectional study. Setting: Data were collected at a research university in the upper midwestern United States. Participants: One hundred ninety-two healthy women, aged 18 to 79 years, mean ± SEM 41.9 ± 1.3, completed the study. Measurements: Dietary intake was assessed using 3-day food diaries verified with food frequency questionnaires. To assess evenness of protein intake, the day was divided into 3 periods: waking to 11:30, 11:31 to 16:30, and after 16:30. Lean mass was measured with dual energy X-ray absorptiometry. Lower-body muscle strength and endurance were determined using isokinetic dynamometry. Upper-body muscle strength was maximal handgrip strength. Functional ability was assessed using 6-m gait speed and 30-second chair stand tests. Accelerometry measured physical activity. Results: Intakes of 25 g or more of protein at 1 or more of the 3 periods was positively associated with lean mass (ß ± S.E.; 1.067 ± 0.273 kg, P < .001) and upper-body (3.274 ± 0.737 kg, P < .001) and lower-body strength (22.858 ± 7.918 Nm, P = .004) when controlling for age, body mass index, physical activity, and energy and protein intakes. Consuming at least 0.24 g/kg/period for those under 60 years and 0.4 g/kg/period for those 60 years and older was related to lean mass (0.754 ± 0.244 kg, P = .002), upper-body strength (2.451 ± 0.658 kg, P < .001), and lower-body endurance (184.852 ± 77.185 J, P = .018), controlling for the same variables. Conclusions: Evenness of protein intake is related to lean mass, muscle strength, and muscular endurance in women. Spreading protein intake throughout the day maximizes the anabolic response to dietary protein, benefiting muscle mass and performance.

Handgrip Strength Asymmetry Is Associated With Limitations in Individual Basic Self-Care Tasks.

This investigation sought to determine the associations between handgrip strength (HGS) asymmetries and limitations in individual activities of daily living (ADL). The analytic sample included 18,468 participants from the 2006 to 2016 waves of the Health and Retirement Study. Those with HGS >10% stronger on either hand had any HGS asymmetry. Individuals with HGS >10% stronger on their dominant or non-dominant hand had dominant or non-dominant HGS asymmetry, respectively. ADL abilities were self-reported. Those with any HGS asymmetry had 1.21 (95% confidence interval [CI] = [1.01-1.46]) greater odds for a toileting limitation and 1.25 (CI = [1.03-1.52]) greater odds for a transferring limitation. Individuals with dominant HGS asymmetry had 1.24 (CI = [1.01-1.53]) greater odds for a transferring limitation. Those with non-dominant HGS asymmetry had 1.39 (CI = [1.01-1.93]) and 1.44 (CI = [1.05-1.96]) greater odds for a bathing and toileting limitation, respectively. HGS asymmetries could help to identify future limitations in specific ADLs.

Differences in Muscle Activity and Kinetics Between the Goblet Squat and Landmine Squat in Men and Women.

ABSTRACT: Collins, KS, Klawitter, LA, Waldera, RW, Mahoney, SJ, and Christensen, BK. Differences in muscle activity and kinetics between the goblet squat and landmine squat in men and women. J Strength Cond Res 35(10): 2661-2668, 2021-Squat exercise variations are widely used and extensively researched. However, little information exists on the goblet squat (GBS) and landmine squat (LMS) and differences between men and women. This study investigated the differences in muscle activity and kinetics between the GBS and the LMS in 16 men and 16 women. Five repetitions of each squat type were performed loaded at 30% of their body mass. Vertical and anteroposterior ground reaction forces for the eccentric and concentric phases and peak vertical force were recorded with a force plate. Electromyographic (EMG) signals were recorded for the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and biceps femoris (BF). Normalized mean EMG values and ground reaction forces were analyzed with repeated measures analysis of variance (p < 0.05). Significant main effects for squat condition and sex were found. The LMS reduced activity in the quadriceps (VM and VL) muscles and vertical forces, while increasing posterior horizontal forces. In the LMS, men showed decreased ST activity, whereas women had decreased BF activity. Women exhibited greater quadriceps activity in both the GBS and LMS and greater ST in the LMS. Women also produced greater eccentric vertical force in both the GBS and LMS and less posterior horizontal forces in the LMS. The LMS may be useful to balance hamstring to quadriceps activity, increase horizontal loading, and reduce vertical loading. Conversely, the GBS can better target quadriceps activity and increase vertical loading. Sex differences should be considered for training programs that include the GBS and LMS.

Time-restricted eating and concurrent exercise training reduces fat mass and increases lean mass in overweight and obese adults.

The purpose of this study was to determine whether time-restricted eating (TRE), also known as time-restricted feeding, was an effective dietary strategy for reducing fat mass and preserving fat-free mass while evaluating changes in cardiometabolic biomarkers, hormones, muscle performance, energy intake, and macronutrient intake after aerobic and resistance exercise training in physically inactive and overweight or obese adults. This study was a randomized, controlled trial. Overweight and obese adults (mean ± SD; age: 44 ± 7 years; body mass index [BMI]: 29.6 ± 2.6 kg/m2 ; female: 85.7%) were randomly assigned to a TRE or normal eating (NE) dietary strategy group. The TRE participants consumed all calories between 12:00 p.m. and 8:00 p.m., whereas NE participants maintained their dietary habits. Both groups completed 8 weeks of aerobic exercise and supervised resistance training. Body composition, muscle performance, energy intake, macronutrient intake, physical activity, and physiological variables were assessed. A total of 21 participants completed the study (NE: n = 10; TRE: n = 11). A mild energy restriction was observed for TRE (~300 kcal/day, 14.5%) and NE (~250 kcal/day, 11.4%). Losses of total body mass were significantly greater for TRE (3.3%) relative to NE (0.2%) pre- to post-intervention, of which TRE had significantly greater losses of fat mass (9.0%) compared to NE (3.3%). Lean mass increased during the intervention for both TRE (0.6%) and NE (1.9%), with no group differences. These data support the use of TRE and concurrent exercise training as a short-term dietary strategy for reducing fat mass and increasing lean mass in overweight and obese adults.

Increased velocity at VO2max and load carriage performance in army ROTC cadets: prescription using the critical velocity concept.

The purpose of this study was to evaluate the effects of using the critical velocity (CV) concept to prescribe two separate high-intensity interval training (HIT) exercise programs aimed at enhancing CV and load carriage performance. 20 young adult participants (male = 15, female = 5) underwent a 4-week training period where they exercised 2 d wk-1. Participants were randomly assigned into two groups: (1) HIT or (2) Load Carriage-HIT (LCHIT). Pre- and post-training assessments included running 3-minute All-Out Test (3MT) to determine critical velocity (CV) and distance prime (D') and two load carriage tasks (400 and 3200 m). There were significant increases in CV (p = 0.005) and velocity at V˙ O2max (vV˙ O2max) (p = 0.037) among the sample but not between training groups. Improvements were observed in 3200 m load carriage performance time (p < 0.001) with a 9.8 and 5.4% decrease in the LCHIT and HIT groups, respectively. Practitioner summary: Critical velocity has shown efficacy as a marker for performance in tactical populations. With the addition of load carriage, there is a reduction in the individual's CV. The CV-concept-prescribed exercises (HIT and LCHIT) 2 days per week for 4 weeks showed improvements in CV, vV˙ O2max and load carriage performance. The use of the CV concept provides a method to prescribe HIT to increase running and load carriage performances in tactical populations.

Limb occlusion pressure for blood flow restricted exercise: Variability and relations with participant characteristics.

OBJECTIVE: Assess lower-extremity blood flow restricted exercise (BFR) limb occlusion pressure (LOP) variability and identify related intrinsic characteristics using a portable Delphi BFR system. DESIGN: Repeated measures. SETTING: Laboratory. PARTICIPANTS: Forty-two healthy males (n = 25) and females (n = 17) (25.8 ± 5.2 y, 1.76 ±0 .09 m, 78.9 ± 14.9 kg) completed two visits. Brachial artery blood pressure, thigh circumferences (TC), and LOP were measured supine. MAIN OUTCOME MEASURES: Linear mixed-effects models (LMM) and generalizability theory were used to evaluate LOP between legs and days, determine intrinsic characteristic relations, and assess random variance components. RESULTS: LOP was not different between legs (p = .730) or days (p = .916; grand mean = 183.7 mmHg [178.4, 189.1]). LOP varied significantly between participants (p = .011, standard error = 47.3 mmHg). 47% of LOP variance was between participants, 18% and 6% was within participants between days and legs, respectively, and 28% was associated with random error. The relative error variance was 14.4 mmHg. Pulse pressure (PP) (p = .005) and TC (p = .040) were positively associated with LOP. A LMM including PP and TC predicted LOP with a mean absolute difference of 11.1 mmHg [9.7, 12.6] compared to measured LOP. CONCLUSIONS: The relative error variance suggests that clinicians should measure LOP consistently for each patient to ensure BFR safety and effectiveness.

Evaluating Additional Aspects of Muscle Function with a Digital Handgrip Dynamometer and Accelerometer for Cognitive Functioning in Older Adults: A Pilot Study.

Handgrip dynamometers are used to assess handgrip strength (HGS), and low HGS is linked to poor cognitive function. Although HGS is a reliable measure of muscle function, it is only measuring maximal grip force. Other aspects of muscle function such as force control, fatigability, and steadiness are unaccounted for in current HGS protocols. This pilot study sought to determine the role of maximal HGS, submaximal HGS force control, HGS fatigability, and HGS neuromuscular steadiness on cognitive function in older adults. Our findings indicate that these additional HGS measurements could factor into detecting poorer cognitive functioning, while also evolving HGS protocols.

Acute Cardiovascular, Metabolic, and Muscular Responses to Blood Flow Restricted Rowing Exercise.

INTRODUCTION: Microgravity leads to a progressive loss in muscular strength, endurance, and aerobic capacity (Vo2peak). Blood flow restricted (BFR) exercise has been shown to elicit rapid gains in muscular strength and Vo2peak. Rowing exercise combined with BFR could be a supplemental countermeasure to maintain preflight muscle function and Vo2peak, especially within future space vehicles with restricted physical volume.METHODS: There were 20 men who completed 19 min of rowing exercise during CON or BFR in a randomized order. Exercise intensity for all sets was 30% of peak work load achieved during a separate incremental maximal exercise test. Kaatsu training cuffs were inflated around each leg during BFR. Muscle oxygen saturation (Smo2) and heart rate (HR) were measured throughout exercise and rest. Rate of perceived exertion (RPE) and muscle activation, using surface electromyography (sEMG), were measured during the last 30 s of each exercise set. Blood pressure (BP) and whole blood lactate ([La-]b) were measured at rest and postexercise.RESULTS: Smo2 declined significantly in BFR during exercise and rest by 13% and 14%, respectively. HR and RPE showed significant increases during BFR (120.5 ± 5.53 vs. 128.9 ± 9.86 bts · min-1) (9.8 ± 1.85 vs. 11.8 ± 1.88 arbitrary units). No differences were observed for BP, [La-]b, and sEMG.DISCUSSION: Findings indicate exercise intensity and cuff pressure elicited acute muscular, cardiovascular, and perceptual responses. BFR rowing exercise could be advantageous as an adjunct for future exercise countermeasures where aerobic and anaerobic exercise may be performed on one device or in limited physical space.Mahoney SJ, Dicks ND, Lyman KJ, Christensen BK, Hackney KJ. Acute cardiovascular, metabolic, and muscular responses to blood flow restricted rowing exercise. Aerosp Med Hum Perform. 2019; 90(5):440-446.