The respiratory muscles may fatigue during prolonged exercises and thereby become a factor that limits extreme physical activity. The aim of the current study was to determine whether respiratory muscle fatigue imposes a limitation on extreme physical activity of well-trained young men. Electromyography (EMG) signals of respiratory (external intercostal and sternomastoid) and calf muscles (gastrocnemius) were measured (N = 8) during 1 hr of treadmill marching at a speed of 8 km/hr with and without a 15 kg backpack. The root mean square (RMS) and the mean power frequency of the EMG signals were evaluated for calculating fatigue indices. The EMG RMS revealed that the respiratory and calf muscles did not fatigue during the marching without a backpack load. The study did show, however, a significant rise in the EMG values when a backpack was carried with respect to the no-load condition (p < .05), which suggests that respiratory muscles should be trained in military recruits who are required to carry loaded backpacks while marching.
Yaara Nadiv, Ricki Vachbroit, Amit Gefen, David Elad, Uri Zaretsky, Dani Moran, Pinchas Halpern and Anat Ratnovsky
Jean-Thomas Aubert and Christian Ribreau
Blood flows toward the heart through collapsible vessels, the veins. The equations of flow in collapsible tubes in motion show a strong dependence on body forces resulting from gravity and acceleration. This paper analyzes the contribution of body forces to venous blood flow during walking on level ground. It combines the biomechanics of gait and theory of collapsible tubes to point out that body forces due to gravity and limb acceleration cannot be overlooked when considering the determinants of venous blood flow during locomotion. The study involved the development of a kinematic model of the limb as a multi-pendulum arrangement in which the limb segments undergo angular displacements. Angular velocities and accelerations were determined and the body forces were calculated during various phases of the gait cycle. A vascular model of the leg's major venous system was also constructed, and the accelerations due to body and gravity forces were calculated in specific venous segments, using the data from the kinematic model. The results showed there were large, fast variations in the axial component (Gx–Mx) of the body forces in veins between the hip and the ankle. Acceleration peaks down to –2G were obtained at normal locomotion. At fast locomotion, a distal vein in the shank displayed values of (Gx–Mx)/G equal to –3.2. Given the down-to-up orientation of the x-axis, the axial component Mx was usually positive in the axial veins, and Mx could shift from positive to negative during the gait cycle in the popliteal vein and the dorsal venous arch.
Stephanie Chester, Audrey Zucker-Levin, Daniel A. Melcher, Shelby A. Peel, Richard J. Bloomer and Max R. Paquette
The purpose of this study was to compare knee and hip joint kinematics previously associated with anterior knee pain and metabolic cost among conditions including treadmill running (TR), standard elliptical (SE), and lateral elliptical (LE) in healthy runners. Joint kinematics and metabolic parameters of 16 runners were collected during all 3 modalities using motion capture and a metabolic system, respectively. Sagittal knee range of motion (ROM) was greater in LE (P < .001) and SE (P < .001) compared with TR. Frontal and transverse plane hip ROM were greater in LE compared with SE (P < .001) and TR (P < .001). Contralateral pelvic drop ROM was smaller in SE compared with TR (P = .002) and LE (P = .005). Similar oxygen consumption was found during LE and TR (P = .39), but LE (P < .001) and TR (P < .001) required greater oxygen consumption than SE. Although LE yields similar metabolic cost to TR and produces hip kinematics that may help strengthen hip abductors, greater knee flexion and abduction during LE may increase symptoms in runners with anterior knee pain. The findings suggest that research on the implications of elliptical exercise for injured runners is needed.
Mansour Eslami, Mohsen Damavandi and Reed Ferber
There is evidence to suggest that navicular drop measures are associated with specific lower-extremity gait biomechanical parameters. The aim of this study was to examine the relationship between navicular drop and a) rearfoot eversion excursion, b) tibial internal rotation excursion, c) peak ankle inversion moment, and d) peak knee adduction moment during the stance phase of running. Sixteen able-bodied men having an average age of 28.1 (SD = 5.30) years, weight of 81.5 (SD = 10.40) kg, height of 179.1 (SD = 5.42) cm volunteered and ran barefoot at 170 steps/minute over a force plate. Navicular drop measures were negatively correlated with tibial internal rotation excursion (r = −0.53, P = .01) but not with rearfoot eversion excursion (r = −0.19; P = .23). Significant positive correlations were found between navicular drop and peak knee adduction moment (r = .62, P < .01) and peak ankle inversion moment (r = .60, P < .01). These findings suggest that a low navicular drop measure could be associated with increasing tibial rotation excursion while high navicular drop measure could be associated with increased peak ankle and knee joint moments. These findings indicate that measures of navicular drop explained between 28% and 38% of the variability for measures of tibial internal rotation excursion, peak knee adduction moment and peak ankle inversion moments.
Bruce Elliott, J. Robert Grove and Barry Gibson
Eight international baseball pitchers were filmed in a laboratory while throwing from a pitching rubber attached to a Kistler force platform. Following a warm-up, all subjects threw fastballs (FB) until two strike pitches were assessed by an umpire positioned behind the catcher for both wind-up and set pitching techniques. Subjects then followed the same procedures for curveball pitches (CB). Both vertical (Z) and horizontal (Y) ground reaction force (GRF) data were recorded. A shutter correlation pulse was encoded so the temporal data from the film could be synchronized with the kinetic data from the force platform. Analysis of variance was used to analyze differences in force data at selected points in both pitching actions for both techniques. Vertical and horizontal GRFs increased from the first balance position to maximum levels at the cocked position for both techniques. Nonsignificant changes in GRF then occurred between the cocked position and front-foot landing. The Z GRFs were similar throughout the pitching action but higher in magnitude for the CB compared to the FB. Mean resultant forces were similar for the three fastest FB pitchers when compared to the three slowest pitchers. However, the slower group produced their peak resultant force earlier in the action, thus reducing the ability to drive over a stabilized front leg.
Gabriel Andrade Paz, Jason DeFreitas, Marianna de Freitas Maia, Jurandir Silva, Vicente Lima and Humberto Miranda
Excessive valgus and varus force which affected the knee joint during dynamic tasks has been often associated to lower extremity injuries. Strategies to increase the resistance against these asymmetries (eg, the use of a physioball between the knees or elastic bands around the knees) are often applied in rehabilitation and conditioning programs.
The purpose of this study was to investigate the effect of performing leg press (LP) 45° using a physioball and elastic band over multiple sets with submaximal loads on electromyographic (EMG) amplitude and fatigue indices.
18 trained females volunteered (age: 24.4 ± 2.1 y; height: 168.1 ± 4 cm; body mass: 65.1 ± 4.4 kg) participated in this study. The 10 repetition maximum (RM) loads were determined for the LP. Then, 3 experimental protocols were followed in a randomized crossover design over 3 nonconsecutive days: control protocol—the participants performed 4 LP sets; physioball between knees—4 LP sets were performed with the physioball between the knees; elastic band—4 LP sets were performed with the elastic band involving the knees. Ten repetitions were performed during each set with 70% of 10-RM loads; EMG spectral indices (CRMS and Cf5) was collected from the biceps femoris (BF), vastus lateralis (VL), vastus medialis obliquus (VMO), and rectus femoris (RF) muscles.
Higher levels of CRMS and Cf5 were noted for RF, VL, and VM muscles using the physioball and elastic band when compared with control protocol, respectively. CRMS index of BF muscle was significantly higher using physioball and elastic band protocol versus control condition, respectively.
Therefore, both physioball and elastic band can be adopted during LP with the goal to reduce excessive varus and valgus forces, respectively, even performing consecutive sets with submaximal loads. Furthermore, this may be an interesting alternative to increasing quadriceps activation and improving the knee joint stabilization.
Mati Pääsuke, Jaan Ereline, Helena Gapeyeva, Kadri Joost, Karin Mõttus and Pille Taba
The lower extremity performance in elderly female patients with mild to moderate Parkinson’s disease (PD; n = 12) and controls (n = 16) was compared. Isometric dynamometry and force-plate measurements were used. PD patients had lower (p < .05) bilateral (BL) maximal isometric leg-extension force (MF), BL isometric MF relative to body mass, and maximal rate of isometric force development than control participants. BL strength deficit was greater (p < .05) in PD patients than in controls. A significantly longer chair-rise time and lower maximal rate of vertical-ground-reaction-force development while rising from a chair was found in PD patients than in controls. These findings suggest that elderly women with PD have lowered voluntary isometric force-generation capacity of the leg-extensor muscles. Reduced BL leg-extension strength might contribute to the difficulty of individuals with PD to rise from a chair.
Marcos de Noronha, Eleisha K. Lay, Madelyn R. Mcphee, George Mnatzaganian and Guilherme S. Nunes
Context: Ankle sprains are common injuries in sports, but it is unclear whether they are more likely to occur in a specific period of a sporting game. Objective: To systematically review the literature investigating when in a match ankle sprains most likely occurred. Evidence Acquisition: The databases CINAHL, EMBASE, MEDLINE, and SPORTDiscus were searched up to August 2016, with no restriction of date or language. The search targeted studies that presented data on the time of occurrence of ankle sprains during sports matches. Data from included studies were analyzed as a percentage of ankle sprain occurrence by halftime and by quarters. Meta-analyses were run using a random effects model. The quality assessment tool for quantitative studies was used to assess the article’s quality. Evidence Synthesis: The searches identified 1142 studies, and 8 were included in this review. A total of 500 ankle sprains were reported during follow-up time, which ranged from 1 to 15 years, in 5 different sports (soccer, rugby, futsal, American football, and Gaelic football). The meta-analyses, including all 8 studies, showed that the proportion of ankle sprains during the first half (0.44; 95% confidence interval [CI], 0.38–0.50) was smaller than the second half (0.56; 95% CI, 0.50–0.62). For the analyses by quarters, the proportion of ankle sprains in the first quarter (0.14; 95% CI, 0.09–0.19) was considerably smaller than the second (0.28; 95% CI, 0.24–0.32), third (0.25; 95% CI, 0.17–0.34), and fourth (0.29; 95% CI, 0.22–0.36) quarters. Conclusion: The results of this review indicate that ankle sprains are more likely to occur later in the game during the second half or during the latter minutes of the first half.
Montassar Tabben, Daniele Conte, Monoem Haddad and Karim Chamari
, Kizami-Zuki, Gyaku-zuki, Oi-zuki, etc). Lower limb actions represent any kicking techniques (eg, Mae-geri, Uko-geri , Mawashi-geri , etc). Throwing is defined as any grappling techniques that involve off-balancing an opponent, and throwing him/her to the ground regardless of the fact that it leads to punch
Ryan S. Garten, Matthew C. Scott, Tiffany M. Zúñiga, Austin C. Hogwood, R. Carson Fralin and Jennifer Weggen
more sitting and sedentary time further exacerbates this problem. 4 Prolonged sitting interventions have emerged as a useful tool to better understand the impact of sitting, a common sedentary activity, on the development of vascular dysfunction and atherosclerosis in the lower limbs. 5 , 6 Indeed