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Christopher Kuenze, Jay Hertel and Joseph M. Hart

Purpose:

Persistent quadriceps weakness due to arthrogenic muscle inhibition (AMI) has been reported after anterior cruciate ligament (ACL) reconstruction. Fatiguing exercise has been shown to alter lower extremity muscle function and gait mechanics, which may be related to injury risk. The effects of exercise on lower extremity function in the presence of AMI are not currently understood. The purpose of this study was to compare the effect of 30 min of exercise on quadriceps muscle function and soleus motoneuron-pool excitability in ACL-reconstructed participants and healthy controls.

Methods:

Twenty-six (13 women, 13 men) healthy and 26 (13 women, 13 men) ACL-reconstructed recreationally active volunteers were recruited for a case-control laboratory study. All participants completed 30 min of continuous exercise including alternating cycles of inclined-treadmill walking and bouts of squats and step-ups. Knee-extension torque, quadriceps central activation ratio (CAR), soleus H:M ratio, and soleus V:M ratio were measured before and after 30 min of exercise.

Results:

There was a significant group × time interaction for knee-extension torque (P = .002), quadriceps CAR (P = .03), and soleus V:M ratio (P = .03). The effect of exercise was smaller for the ACL-R group than for matched controls for knee-extension torque (ACL-R: %Δ = −4.2 [−8.7, 0.3]; healthy: %Δ = −14.2 [−18.2, −10.2]), quadriceps CAR (ACL-R: %Δ = −5.1 [−8.0, −2.1]; healthy: %Δ = −10.0 [−13.3, −6.7]), and soleus V:M ratio (ACL-R: %Δ = 37.6 [2.1, 73.0]; healthy: %Δ = −24.9 [−38.6, −11.3]).

Conclusion:

Declines in quadriceps and soleus volitional muscle function were of lower magnitude in ACL-R subjects than in healthy matched controls. This response suggests an adaptation experienced by patients with quadriceps AMI that may act to maintain lower extremity function during prolonged exercise.

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Marcos Echegaray, Lawrence E. Armstrong, Carl M. Maresh, Deborah Riebe, Robert W. Kenefick, John W. Castellani, Stavros Kavouras and Douglas Casa

This study assessed the plasma glucose (PG) and hormonal responses to carbohydrate ingestion, prior to exercise in the heat, in a hypohydrated state versus partial rehydration with intravenous solutions. On separate days, 8 subjects (21.0 ± 1.8 years; 57.3 ± 3.7 ml · kg−1 · min−1) exercised at 50% V̇O2maxin a 33 °C environment until a 4% body weight loss was achieved. Following this, subjects were rehydrated (25 ml · kg−1) with either: 0.45% IV saline (45IV), 0.9% IV saline (9IV), or no fluid (NF). Subjects then ingested 1 g · kg−1 of carbohydrate and underwent an exercise test (treadmill walking, 50% V̇O2max, 36 °C) for up to 90 min. Compared to pre-exercise level (294 mg · dl−1), PG increased significantly (>124 mg · dl−1) at 15 min of the exercise test in all trials and remained significantly elevated for 75 min in NF, 30 min more than in the 2 rehydration trials. Although serum Insulin increased significantly at 15 min of exercise in the 45IV trial (7.2 ± 1.2 vs. 23.7 ± 4.7 μIU · ml−1) no significant differences between trials were observed. Peak plasma norepinephrine was significantly higher in NF (640 ± 66 pg · ml−1) compared to the 45IV and 9IV trials (472 ± 55 and 474 ± 52 pg · ml−1, respectively). In conclusion, ingestion of a small solid carbohydrate load prior to exercise in the 4% hypohydration level resulted in prolonged high PG concentration compared to partial IV rehydration.

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J. Luke Pryor, Brittany Christensen, Catherine G. R. Jackson and Stephanie Moore-Reed

Background: Yoga is a popular alternative to walking, but the tempo at which asanas must be performed to elicit comparable metabolic and cardiorespiratory demands is unknown. Therefore, the authors aim to compare the metabolic demands of moderate-intensity walking to Surya Namaskar yoga performed at varying tempos. Methods: Inactive obese adults with limited prior yoga experience (n = 10) completed 10 minutes of treadmill walking at a self-selected pace (rating of perceived exertion = 12–13) and three, 10-minute bouts of yoga at a low (6 s/pose; LSUN), medium (4 s/pose; MSUN), and high (3 s/pose; HSUN) tempo with 10-minutes rest between exercise bouts. Results: Mean metabolic equivalents observed in MSUN (3.64 [0.607]), HSUN (4.22 [0.459]), and treadmill (5.29 [1.147]) were greater than 3.0 (P ≤ .01), but not LSUN (3.28 [0.529], P = .13). Treadmill elicited greater caloric and kilocaloric expenditure (1.36 [0.23] L·min−1; 64 [11] kcal) than LSUN (0.87 [0.24] L·min−1; 39 [11] kcal) and MSUN (1.00 [0.29] L·min−1; 45 [13] kcal) (P ≤ .01). Absolute V˙O2 between yoga tempos were not different, but relative V˙O2 was higher in HSUN (14.89 [1.74] mL·min−1·kg) versus LSUN (11.39 [1.83] mL·min−1·kg) (P = .02). Conclusions: Yoga can meet (LSUN) or exceed (MSUN and HSUN) moderate-intensity exercise recommendations. For unfit or obese populations, varying tempos of yoga practice may serve as a lower-impact option for beginning an exercise program.

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Anson B. Rosenfeldt, Amanda L. Penko, Andrew S. Bazyk, Matthew C. Streicher, Tanujit Dey and Jay L. Alberts

individuals, self-paced treadmill walking is comparable to overground walking given a proper acclimation period ( Plotnik et al., 2015 ). It is not known how a self-paced treadmill would compare to overground walking in individuals with PD. The primary aim of this project was to evaluate the potential of the

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Salman Nazary-Moghadam, Mahyar Salavati, Ali Esteki, Behnam Akhbari, Sohrab Keyhani and Afsaneh Zeinalzadeh

during movement with inherent periodicity, and it is primarily effective for the gait analysis. 7 The LyE has been examined in treadmill walking with and without cognitive loads. 5 LyE measures gait stability or the sensitivity of a dynamic system to exceedingly small perturbations. To the best

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Adam M. Fullenkamp, Danilo V. Tolusso, C. Matthew Laurent, Brian M. Campbell and Andrea E. Cripps

belt speed data . Gait Posture . 2015 ; 41 ( 1 ): 141 – 145 . PubMed ID: 25311386 doi:10.1016/j.gaitpost.2014.09.017 25311386 10.1016/j.gaitpost.2014.09.017 6. Lee SJ , Hidler J . Biomechanics of overground vs. treadmill walking in healthy individuals . J Appl Physiol . 2008 ; 104 ( 3 ): 747

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Merrill D. Funk, Cindy L. Salazar, Miriam Martinez, Jesus Gonzalez, Perla Leyva, David Bassett Jr. and Murat Karabulut

accelerometer during various daily activities in a laboratory setting (treadmill walking/jogging, indoor cycling, sweeping, watching television, etc.) and during seven days of performing normal daily activities in a free-living setting. GPS-enabled smartphones have also been examined for accuracy at measuring

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Whitney A. Welch, Scott J. Strath, Michael Brondino, Renee Walker and Ann M. Swartz

20% (36 min), 40% (72 min), and 60% (108 min) LPA routine consisting of treadmill walking and household, occupational, and leisure-time activities at the beginning of the visit followed by sitting for the remainder of the visit (Table  1 ). Activity conditions were designed to elicit a dose

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Greg Petrucci Jr., Patty Freedson, Brittany Masteller, Melanna Cox, John Staudenmayer and John Sirard

. Another Misfit model has shown reliability in estimating steps during repeated treadmill walking bouts at 3.2 km·h −1 , 4.82 km·h −1 , and 6.42 km·h −1 ( Fokkema, Kooiman, Krijnen, Van Der Schans, & Groot, 2017 ). However, before widespread adoption of the MS in research, as an intervention tool or as a

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Alexander H.K. Montoye, John Vusich, John Mitrzyk and Matt Wiersma

lasting for five minutes. The activities are shown in Table  2 and were performed in descending order, with 1–3 min breaks between activities so the participant could rest and so that activity-specific kcals and steps could be recorded from the activity monitors. For the treadmill walking and jogging