Dain LaRoche Assistant Professor, Department of Kinesiology CHHS travels to Brazil

Professor LaRoche traveled to Brazil in January 2012 for research on neuromuscular performance and mobility in older adults at the Universidade Estadual Paulista – Rio Claro

Initial neuromuscular performance in older women influences response to explosive resistance training

The purpose of the study was to identify both demographic and neuromuscular traits that characterize successful or unsuccessful adaptation to resistance training in older women. Twelve, older women underwent electrically evoked muscle twitches for the knee extensors; and performed maximal, voluntary, isometric knee extensions, followed by eight weeks of resistance training. Prior to training nonresponders had 67% higher twitch peak torque than responders (0.29 ± 0.05 vs. 0.18 ± 0.06 Nm·kg−1 respectively), 64% higher twitch rate of torque development (RTD) (3.96 ± 0.47 vs. 2.42 ± 0.62 Nm·s−1·kg−1), 51% higher voluntary peak torque (1.86 ± 0.40 vs. 1.23 ± 0.33 Nm·kg−1), 101% greater RTD (9.43 ± 1.52 vs. 4.70 ± 2.40 Nm·s−1·kg−1), 86% greater impulse (0.13 ± 0.01 vs. 0.07 ± 0.03 Nm·s·kg−1) and 27% faster motor time (80 ± 13 vs. 109 ± 34 ms), (all P \u3c 0.05). Following training, responders showed an 11% increase in twitch peak torque over baseline (0.18 ± 0.06 to 0.20 ± 0.05 Nm·kg−1), 15% increase in voluntary peak torque (1.23 ± 0.33 to 1.41 ± 0.36 Nm·kg−1), 47% increase in RTD (4.70 ± 2.40 to 6.93 ± 2.02 Nm·s−1·kg−1), 43% increase in impulse (0.07 ± 0.03 to 0.10 ± 0.04 Nm·s·kg−1), and 26% increase in rate of EMG rise (886 ± 214 to 1116 ± 102 % pEMG·s−1) (all P \u3c 0.05). Initially higher muscle mass and contractility, coupled with greater neural drive, likely explains why older women with good muscle performance seem to have a lower capacity for improvement than women with low initial levels of performance

Strength asymmetry increases gait asymmetry and variability in older women.

Purpose—The aim of the research was to determine how knee extensor strength asymmetry influences gait asymmetry and variability since these gait parameters have been related to mobility and falls in older adults. Methods—Strength of the knee extensors was measured in 24 older women (65 – 80 yr). Subjects were separated into symmetrical strength (SS, n = 13) and asymmetrical strength (SA, n = 11) groups using an asymmetry cutoff of 20%. Subjects walked at a standard speed of 0.8 m s−1 and at maximal speed on an instrumented treadmill while kinetic and spatiotemporal gait variables were measured. Gait and strength asymmetry were calculated as the percent difference between legs and gait variability as the coefficient of variation over twenty sequential steps. Results—SA had greater strength asymmetry (27.4 ± 5.5%) than SS (11.7 ± 5.4%, P \u3c 0.001). Averaged across speeds, SA had greater single (7.1% vs. 2.5%) and double-limb support time asymmetry (7.0 vs. 4.3%) than SS and greater single-limb support time variability (9.7% vs. 6.6%, all P \u3c 0.05). Group × speed interactions occurred for weight acceptance force variability (P = 0.02) and weight acceptance force asymmetry (P = 0.017) with greater variability at the maximal speed in SA (5.0 ± 2.4% vs. 3.7 ± 1.2%) and greater asymmetry at the maximal speed in SA (6.4 ± 5.3% vs. 2.5 ± 2.3%). Conclusion—Gait variability and asymmetry are greater in older women with strength asymmetry and increase when they walk near their maximal capacities. The maintenance of strength symmetry, or development of symmetry through unilateral exercise, may be beneficial in reducing gait asymmetry, gait variability, and fall risk in older adults

Low strength is related to diminished ground reaction forces and walking performance in older women

The purpose of this study was to determine how lower-limb strength in older women affected gait speed, supportive forces, spatial, and temporal aspects of walking gait. Twenty-four women between 65 – 80 yr performed maximal voluntary isometric contractions for the knee extensors (KE), knee flexors (KF), ankle plantarflexors (PF) and ankle dorsiflexors (DF) and were separated into low strength and normal strength groups using a KE torque threshold of 1.5 Nm kg−1 . They walked at both a standard speed of 0.8 m s−1 and at a self-selected maximal speed on an instrumented treadmill that recorded vertical ground reaction forces (vGRF) and spatiotemporal gait measures. Older women with low strength had 30% lower KE maximal torque, 36% lower PF maximal torque, 34% lower KE rate of torque development (RTD) and 30% lower KF RTD. Low strength women demonstrated slower maximal walking speeds (1.26 ± 0.20 vs. 1.56 ± 0.20 m s−1 ), lower vGRF during weight acceptance (1.15 ± 0.10 vs. 1.27 ± 0.13 BW), lower weight acceptance rates (11.3 ± 0.5 vs. 17.0 ± 5.5 BW s−1 ), slower stride rates, shorter stride lengths, and longer footground and double-limb support times (all P \u3c 0.05). Maximal gait speed was strongly correlated to peak vGRF and rate (r = 0.60 – 0.85, P \u3c 0.01) and moderately related to lower-limb strength (r = 0.42 – 0.60, P \u3c 0.05). In older women with low strength, diminished peak vGRFs were associated with slower walking speeds putting them at risk for mobility limitation, disability, poor health, and loss of independence

Fat mass limits lower-extremity relative strength and maximal walking performance in older women

The purpose of this study was to determine if excess fat negatively affects relative strength and walking gait performance in overweight, older women. Twenty five older women (65 – 80 yr) were separated into normal weight (BMI \u3c 25 kg m−2 , n=11) and overweight groups (BMI ≥ 25 kg m−2 , n=14). Strength and rate of torque development (RTD) of the knee extensors and flexors, ankle plantarflexors and dorsiflexors were measured. Participants walked at standard and maximal speeds during which muscle activation, spatiotemporal and kinetic gait variables were measured. Relative to mass, overweight older women had 24% lower maximal torque and 38% lower RTD than normal weight women. Maximal walking speed was slower in overweight (1.25 ± 0.22 m s−1 vs. 1.54 ± 0.25 m s−1 , P = 0.004) and was correlated to strength (r = 0.53, P \u3c 0.01) and fat mass (r = −0.65, P = 0.001). At maximal speed, overweight had 11% lower vertical ground reaction force relative to mass, 8% slower stride rate, 12% shorter strides, 13% longer foot-ground contact times, 21% longer double-limb support times, 65% greater knee extensor and 78% greater plantarflexor activation (P \u3c 0.05). Overweight, older women demonstrated altered gait and reduced walking performance related to poor relative strength and rate of torque development of lower-extremity muscles

Excess Body Weight and Gait Influence Energy Cost of Walking in Older Adults

Purpose: To study how excess body weight influences the energy cost of walking (Cw) and determine if overweight and obese older adults self-select stride frequency to minimize Cw. Methods: Using body mass index (BMI) men and women between the ages of 65–80 yr were separated into normal weight (NW, BMI ≤ 24.9 kg m−2, n = 13) and overweight-obese groups (OWOB, BMI ≥25.0 kg m−2, n = 13). Subjects walked at 0.83 m s−1 on an instrumented treadmill that recorded gait parameters, and completed three, six-minute walking trials; at preferred stride frequency (PSF), at +10% PSF, and at −10% PSF. Cw was determined by indirect calorimetry. Repeated measures analysis of variance was used to compare groups, and associations were tested with Pearson correlations, α = 0.05. Results: OWOB had 62% greater absolute Cw (301 ± 108 vs. 186 ± 104 J m−1, P \u3c 0.001) and 20% greater relative Cwkg (3.48 ± 0.95 vs. 2.91 ± 0.94 J kg−1 m−1, P = 0.046) than NW. Although PSF was not different between OWOB and NW (P = 0.626), Cw was 8% greater in OWOB at +10% PSF (P \u3c 0.001). At PSF OWOB spent less time in single-limb support (33.1 ± 1.5 vs. 34.9 ± 1.6 %GC, P = 0.021) and more time in double-limb support (17.5 ± 1.6 vs. 15.4 ± 1.4 %GC, P = 0.026) than NW. In OWOB, at PSF, Cw was correlated to impulse (r = −0.57, P = 0.027) and stride frequency (r = 0.51, P = 0.046). Conclusions: Excess body weight is associated with greater Cw in older adults, possibly contributing to reduced mobility in overweight and obese older persons

Pengaruh lama penyimpanan bubuk beluntas (Pluchea indica Less.) dalam tea bag terhadap perubahan sifat fisikokimia air seduhan

Daun beluntas merupakan tanaman perdu yang sering digunakan sebagai obat tradisional. Pemanfaatan daun beluntas sebagai minuman seduhan teh beluntas menjadi salah satu inovasi. Pengolahan beluntas yang dikemas dalam tea bag akan lebih efisien dan juga lebih praktis. Produk bubuk sangat sensitif dan mudah mengalami perubahan selama penyimpanan. Berdasarkan hal tersebut maka lama penyimpanan bubuk beluntas dalam tea bag diduga berpengaruh pada sifat fisikokimia seperti kekeruhan, total asam dan pH dari minuman seduhan teh beluntas. Tujuan penelitian yang dilakukan adalah untuk mengetahui pengaruh lama penyimpanan bubuk daun beluntas dalam tea bag terhadap perubahan sifat fisikokimia meliputi kekeruhan, pH, dan total asam pada air seduhan teh beluntas. Rancangan penelitian yang digunakan yaitu rancangan acak kelompok (RAK) dengan satu faktor yaitu lama penyimpanan bubuk beluntas dalam tea bag yang terdiri dari 9 taraf perlakuan yaitu P1 (0 minggu), P2 (2 minggu), P3 (4 minggu), P4 (6 minggu), P5 (10 minggu), P6 (14 minggu), P7 (18 minggu), P8 (22 minggu) dan P9 (26 minggu) dengan ulangan sebanyak tiga kali. Parameter utama yang diuji yaitu sifat fisikokimia meliputi kadar air, pH, kekeruhan dan total asam. Data yang diperoleh dilakukan analisa varian (ANOVA) pada α=5% dan dilanjutkan analisa regresi linear untuk menentukan model trendline dan melihat kecenderungan kurva. Hasil penelitian menunjukkan bahwa lama penyimpanan bubuk daun beluntas berpengaruh terhadap sifat fisikokimia air seduhan. Kadar air, kekeruhan, derajat keasaman (pH) dan total asam masing-masing sebesar 8,88%-8,37% (db), 5,68-15,90 NTU; 6,85-8,10 dan 0,43-0,95 mg asam klorogenat/100g bahan. Kinetika degradasi kadar air mengikuti orde 0 dengan perkiraan umur simpan 148 hari

Plantarflexor passive-elastic properties related to BMI and walking performance in older women

The objective of this study was to examine the influence of BMI on the passive-elastic properties of the ankle plantarflexors in older women. Twenty-three women, 65–80 yr, were separated into normal weight (NW, BMI \u3c 25.0 kg m−2, n = 11) and overweight-obese (OW, BMI ≥ 25.0 kg m−2, n = 12) groups. Resistive torque of the ankle plantarflexors was recorded on an isokinetic dynamometer by passively moving the ankle into dorsiflexion. Stiffness, work absorption, and hysteresis were calculated across an ankle dorsiflexion angle of 10–15°. Maximal plantarflexor strength was assessed, then participants walked at maximal speed on an instrumented gait analysis treadmill while muscle activation (EMG) was recorded. Plantarflexor stiffness was 34% lower in OW (26.4 ± 12.7 Nm rad−1) than NW (40.0 ± 15.7 Nm rad−1, p = 0.032). Neither work absorption nor hysteresis were different between OW and NW. Stiffness per kg was positively correlated to strength (r = 0.66, p \u3c 0.001), peak vertical ground reaction force during walking (r = 0.72, p \u3c 0.001), weight acceptance rate of force (r = 0.51, p = 0.007), push-off rate of force (r = 0.41, p = 0.026), maximal speed (r = 0.61, p = 0.001), and inversely correlated to BMI (r = −0.61, p = 0.001), and peak plantarflexor EMG (r = −0.40, p = 0.046). Older women who are OW have low plantarflexor stiffness, which may limit propulsive forces during walking and necessitate greater muscle activation for active force generation

Effects of Stretching on Passive Muscle Tension and Response to Eccentric Exercise

Background: Stretching is used in an attempt to improve performance and reduce the risk of muscle injury, with little evidence to support its effectiveness. Hypothesis: Four weeks of static or ballistic stretching can attenuate the increased soreness and decreased flexibility seen after eccentric exercise. Study Design: Controlled laboratory study. Methods: Twenty-nine male subjects were randomly assigned to a static stretching, ballistic stretching, or control group. On each of 4 consecutive days, they completed 4 maximal range of motion stretches using a Cybex isokinetic dynamometer to passively stretch the hamstrings at 0.087 rad · s–1 (5 deg · s–1). Stiffness from 0.87 to 1.48 rad (50°-85°), peak range of motion, work absorption, peak resistive torque, and soreness were measured. Participants then completed 4 weeks of either static or ballistic stretching for a total stretching duration of 3600 seconds. After training, the 4 days of testing were repeated with an eccentric exercise task added after day 1. Results: Stretching groups had an increase in range of motion and stretch tolerance after 4 weeks of stretching, with no change in muscle stiffness, work absorption, or delayed onset muscle soreness. After eccentric exercise, they also had greater range of motion and stretch tolerance than did controls. Conclusion: Both static stretching and ballistic stretching increase range of motion, most likely as a result of enhanced stretch tolerance rather than changes in muscle elasticity. Four weeks of stretching maintain range of motion and stretch tolerance in the days after eccentric exercise

Grade Influences Blood Lactate Kinetics During Cross-Country Skiing

The purpose of this study was to examine the effects of level vs. graded skate skiing on capillary blood lactate (BLa), heart rate (HR), oxygen consumption (V_ O2), and training intensity prescriptions. Eleven Nordic skiers completed 2 submaximal skate roller skiing treadmill protocols during which intensity was increased either by grade (Ginc) or by speed (Sinc). The protocols were compared for prethreshold BLa, HR, and V_ O2 at lactate threshold (LT) and the HR/V_ O2 relationship. Additionally, double-pole (primarily upper body) and skating (arms and legs combined) protocols were used to measure peak V_ O2 and peak HR. Heart rate and V_ O2 at LT were lower during Ginc compared with Sinc (154.9 6 6.8 b min21 vs. 162.0 6 9.1 b min21 and 46.3 6 2.8 ml kg21 min21 vs. 49.1 6 1.6 ml kg21 min21 , respectively, both p , 0.01). Prethreshold BLa and the HR/V_ O2 relationship were not different between the submaximal protocols. V_ O2peak and HRpeak were higher in skating compared with double poling (64.6 6 1.8 ml kg21 min21 vs. 60.3 6 2.8 ml kg21 min21 , 192.6 6 5.8 b min21 vs. 187.8 6 6.7 b min21 , respectively, both p , 0.01). Greater reliance on upper-body musculature during graded skiing and its associated lower aerobic capacity increases BLa when compared with level skiing. The leftward shift in the BLa vs. intensity curve during uphill skiing should be recognized to properly prescribe training intensity as well as interpret laboratory results