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.
Marcos Echegaray, Lawrence E. Armstrong, Carl M. Maresh, Deborah Riebe, Robert W. Kenefick, John W. Castellani, Stavros Kavouras and Douglas Casa
Billy Chun-Lung So, Calvin Hong-Nin Yuen, Ken Long-Hin Tung, Sheena Lam, Sammy Lan Cheng, Zina Wing-Lam Hung, Rainy Wai-Kwan Leung and Grace Pui-Yuk Szeto
Context: Deep water running (DWR) is an aquatic aerobic exercise which involves running in water without the feet touching the bottom of the pool, and it may involve different activation of trunk muscles compared with running or walking on land. This form of exercise is gradually being adopted as a form of therapeutic exercise for people with low back pain. It is proposed that different types of running or walking in water may be a more comfortable form of training for the trunk and abdominal muscles compared with exercising on dry land. Objectives: This study aimed to examine the trunk muscle activation in DWR in 2 different styles—high knee style and cross-country style, and these were compared with walking on land. Participants: Eleven healthy individuals (2 females and 9 males, mean age = 24 [4.6]) were recruited for this study. Outcome Measures: Surface electromyography was used to examine the activities of the right transversus abdominis, rectus abdominis, lumbar multifidus, and lumbar erector spinae muscles in 5 conditions: static standing on land and in water, running in deep water with high knee and cross-country styles, and finally walking on a treadmill. Results: The percentage of maximal voluntary contraction of the transversus abdominis was significantly higher for both running styles in DWR, compared with that of static standing in water. Comparing directly the 2 styles, muscle activity was higher with a high knee action compared to without. The activation of transversus abdominis during high-knee DWR was comparable with that during treadmill walking and this may have clinical implications. Conclusion: The results of this study confirmed that running in deep water with a high knee action activated trunk muscles differently compared with standing or walking on land.
Christopher Kuenze, Jay Hertel and Joseph M. Hart
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.
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.
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]).
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.
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  kcal) than LSUN (0.87 [0.24] L·min−1; 39  kcal) and MSUN (1.00 [0.29] L·min−1; 45  kcal) (P ≤ .01). Absolute
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
Christopher P. Connolly, Jordana Dahmen, Robert D. Catena, Nigel Campbell and Alexander H.K. Montoye
, Bassett, and Thompson ( 2011 ) examined the step-count accuracy of four commonly used activity monitors at various treadmill walking speeds, specifically finding two consumer-grade devices (Omron HJ-720 [OM] and New Lifestyles 2000 [NL]) to perform most accurately. While these two monitors were
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
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
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
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