Musculation des quadriceps

Est ce un échec en cascade ou un échec complet qui induit l’échec au squat?

29/10/2015 | Musculation des quadriceps et Etudes Musculation

 

Pour une fois, une étude très intéressante

The limiting joint during a failed squat: A biomechanics case series.
Flanagan, SP   J Strength Cond Res 29(11): 3134–3142, 2015

This investigation examined the characteristics of a failed back squat. Subjects were instructed to perform 3 repetitions of a barbell squat with a 3 repetition maximum load while instrumented for biomechanical analyses and standing atop force platforms. Inverse dynamics calculations were used to determine the net joint moment (NJM) power, work, and energy of the hip, knee, and ankle. Five subjects failed to complete all 3 repetitions, allowing for comparisons between a successful and the failed repetition. Although the NJM power and work were lower at all 3 joints during the failed attempt, the only statistically significant differences were at the hip. These findings suggest that the energy generated by the hip joint NJM limited performance of the task. However, examination of the NJM energy generation over time on an individual basis uncovered some features that were masked by the aggregated group mean data. For some subjects, the knee NJM limited the movement. Additionally, negligible to modest compensations occurred between the hip and knee NJM: a decreased energy generated by one NJM was often accompanied by an increase in energy generated at the other. A limiting joint, or “weak link,” may explain the failure to complete a lift. Interventions should address the limiting joint on an individual-specific basis and incorporate assistive exercises that target these deficiencies.

Signature génétique d’un champion de sprint

17/06/2015 | Musculation des quadriceps et Etudes Musculation

 

Skeletal muscle signature of a champion sprint runner
Scott Trappe   Journal of Applied Physiology Published 15 June 2015 Vol. 118 no.  12,  1460-1466

We had the unique opportunity to study the skeletal muscle characteristics, at the single fiber level, of a world champion sprint runner who is the current indoor world record holder in the 60-m hurdles (7.30 s) and former world record holder in 110-m hurdles (12.91 s). Muscle biopsies were obtained from the vastus lateralis at rest and 4 h after a high-intensity exercise challenge (4 × 7 repetitions of resistance exercise). Single muscle fiber analyses were conducted for fiber type distribution (myosin heavy chain, MHC), fiber size, contractile function (strength, speed, and power) and mRNA expression (before and after the exercise bout).

The world-class sprinter’s leg muscle had a high abundance (24%) of the pure MHC IIx muscle fibers with a total fast-twitch fiber population of 71%.

Power output of the MHC IIx fibers (35.1 ± 1.4 W/l) was 2-fold higher than MHC IIa fibers (17.1 ± 0.5 W/l) and 14-fold greater than MHC I fibers (2.5 ± 0.1 W/l).

Additionally, the MHC IIx fibers were highly responsive to intense exercise at the transcriptional level for genes involved with muscle growth and remodeling (Fn14 and myostatin). To our knowledge, the abundance of pure MHC IIx muscle fibers is the highest observed in an elite sprinter. Further, the power output of the MHC IIa and MHC IIx muscle fibers was greater than any human values reported to date. These data provide a myocellular basis for the high level of sprinting success achieved by this individual.

Le psoas-iliaque: Combien de tendons?

14/04/2014 | Musculation des abdominaux et Musculation des quadriceps et Echauffement et blessures

 

Anatomic Variance of the Iliopsoas Tendon
Am J Sports Med April 2014 vol. 42 no. 4 807-811   Marc J. Philippon


Background: The iliopsoas tendon has been implicated as a generator of hip pain and a cause of labral injury due to impingement. Arthroscopic release of the iliopsoas tendon has become a preferred treatment for internal snapping hips. Traditionally, the iliopsoas tendon has been considered the conjoint tendon of the psoas major and iliacus muscles, although anatomic variance has been reported.


Hypothesis: The iliopsoas tendon consists of 2 discrete tendons in the majority of cases, arising from both the psoas major and iliacus muscles.


Study Design: Descriptive laboratory study.


Methods: Fifty-three nonmatched, fresh-frozen, cadaveric hemipelvis specimens (average age, 62 years; range, 47-70 years; 29 male and 24 female) were used in this study. The iliopsoas muscle was exposed via a Smith-Petersen approach. A transverse incision across the entire iliopsoas musculotendinous unit was made at the level of the hip joint. Each distinctly identifiable tendon was recorded, and the distance from the lesser trochanter was recorded.


Results: The prevalence of a single-, double-, and triple-banded iliopsoas tendon was 28.3%, 64.2%, and 7.5%, respectively. The psoas major tendon was consistently the most medial tendinous structure, and the primary iliacus tendon was found immediately lateral to the psoas major tendon within the belly of the iliacus muscle. When present, an accessory iliacus tendon was located adjacent to the primary iliacus tendon, lateral to the primary iliacus tendon.


Conclusion: Once considered a rare anatomic variant, the finding of ≥2 distinct tendinous components to the iliacus and psoas major muscle groups is an important discovery. It is essential to be cognizant of the possibility that more than 1 tendon may exist to ensure complete release during endoscopy.


Clinical Significance: Arthroscopic release of the iliopsoas tendon is a well-accepted surgical treatment for iliopsoas impingement. The most widely used site for tendon release is at the level of the anterior hip joint. The findings of this novel cadaveric anatomy study suggest that surgeons should be mindful that more than 1 tendon may be present and require release for curative treatment.

Michael Gundill montre l’amplitude compléte sur un mouvement de cuisses

29/01/2014 | Musculation des fessiers et Musculation des quadriceps et Musculation des ischio-jambiers et Machines de musculation

 

 

 

Michael Gundill fait de la Hammer Strength H squat (part 2)

29/08/2013 | Musculation des fessiers et Musculation des quadriceps et Musculation des ischio-jambiers et Machines de musculation

 

Michael Gundill fait les cuisses sur une Hammer Strength H squat

01/08/2013 | Musculation des fessiers et Musculation des quadriceps et Musculation des ischio-jambiers et Machines de musculation

 

Différences de recrutement musculaire entre le front squat et le back squat

18/06/2013 | Musculation des fessiers et Musculation des quadriceps et Musculation des ischio-jambiers et Etudes Musculation

 

ACTIVATION OF LOWER-EXTREMITY MUSCULATURE DURING VARRIED SQUAT CONFIGURATIONS: COMPARING FRONT AND BACK SQUATS
B. CAMPBELL   Journal of Strength and Conditioning Research       VOLUME 27 | SUPPLEMENT 4 | APRIL 2013 | S73

There is limited information available comparing changes in
muscle activity among these two squat configurations. This is
especially true when both variations of the back squat (high-bar
and low-bar) are compared with the front squat. Purpose: To
evaluate the muscle activation levels in select lower extremity
muscles during a high-bar back squat, a low-bar back squat,
and a front squat.

Methods: Eleven recreationally trained individuals
(8 males and 3 females) between the ages of 19 and 25
yrs participated. Eligibility was dependent upon the following
criteria: being able to squat to parallel, squat 75% of one’s bodyweight,
and have participated in squat exercises regularly within
the past year. One session was used to collect all of the EMG
data. The muscles examined were the rectus femoris, biceps
femoris, gluteus medius, and vastus medialis. Parallel squat
depth was controlled by electronic beepers placed on the thigh
of each participant. The participants performed five bodyweight
squats for a baseline measurment while EMG data was being
sampled. Each participant then performed one set of five repetitions
of each squat variation (HBS – high bar back squat, LBS –
low bar back squat and FS – Front Squat) with 75% of their
bodyweight loaded on a standard Olympic barbell. Two minutes
of rest was provided between squat variations and the order of
squat variations was randomized. The EMG data for all participants
was processed and smoothed using a 50 ms moving
window RMS. The mean EMG value for the middle three repetitions
of each squat condition was evaluated and normalized to
the body weight squat condition yielding a percent change from
the body weight condition (i.e. normalized mean EMG activity).

Results: The front squat (FS) elicited the greatest normalized
mean EMG activity for the biceps femoris and gluteus medius
(202.8% and 201.7%, respectively). The low-bar squat (LBS)
elicited the greatest normalized mean EMG activity for the rectus
femoris and the vastus medialis (176% and 185.6%, respectively).

Conclusions: Our preliminary findings demonstrate that
the FS elicited greater normalized mean EMG activity for the
biceps femoris while the LBS elicited greater normalized mean
EMG activity for the rectus femoris and vastus medialis. While it
was not directly measured in this study, a plausible explanation
for this initial finding is that the placement of the barbell during
the LBS shifted the COM posteriorly thereby eliciting more anterior
thigh (RF and VM) muscle activity, whereas the FS shifted the
COM anteriorly causing the posterior thigh (BF) musculature to
become more active to control the increased hip flexion moment.
Additionally, it may be appropriate to evaluate frontal plane knee
and hip kinematics during these squat variations in future studies
as it appears that the increase in gluteus medius activity during
the FS trials could be linked to an increased demand in hip
adduction and or knee valgus control.

Practical Applications:
Given these results it may be possible to use specific squatting
techniques to focus on specific lower extremity musculature. For
example, an athlete that suffers from a hamstring injury may
want to perform the LBS which seems to increase the amount
of quadriceps muscle activity and may reduce the hamstring
demand. Conversely, a person with weak or injured quadriceps
may want to perform FS which seems to increase hamstring
demand.

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