Common Muscular Weaknesses

Hey all,

Check out this article from exrx.net regarding common muscular weaknesses. Whether you purchase programming from us or write your own, it will and always will be important to be able to diagnose and prescribe corrections to weaknesses in your athletes.

Abdominal Weakness
Increased risk of lower back injury can occur during hip flexion, extension, stabilization and back extensionactivities. Erector Spinae muscles can hyperextend lower back more than usual if abdominal muscles are weak. The abdominal muscles tilt the pelvis forward, improving the mechanical positioning of the Erector Spinae, specifically when the lumbar spine becomes straight. When abdominal strength/endurance is not adequate to counter the pull of the antagonist Erector Spinae under load, these low back muscles are put at a mechanical disadvantage (active insufficiency) further placing additional stresses on these very same lower back muscles. Iliopsoas can pull on the spine during hip flexor activities if the abdominal muscles are weak. Risk is compounded when abdominal weakness is combined with hip flexor inflexibility.

Examples of affected exercises:
Squat
Deadlifts
Military Press (standing)
Lying Leg Raise (full extension): hands may be placed under lower portion of glutes to decrease tilt of pelvis and subsequent hyperextension of spine.

Example preventative / corrective exercise:
Crunch
Hamstrings Weakness
Increased risk of knee injury (instability) occurs during knee extensionactivities, specifically when knees are flexed more than 90°. When hip and knee are simultaneously extending during a compound movement, hamstrings counter the anteriorly directed forces of Quadriceps. Also see Knee Stability and Angle of Pull for force vector explanation. Hamstrings / Quadriceps strength ratios should be greater than 56% to 80%, depending on the population tested.
Examples of affected exercises:
Squat
Leg Press
Example preventative / corrective exercises:
Leg Curls
Straight Leg Deadlift

Supraspinatus Weakness
Increased risk of shoulder injury during shoulder flexionand abduction activities, specifically when the elbow travels below the shoulder during shoulder abduction. Risk is compounded with a winged scapula condition. Paradoxically, avoiding full range of motion (i.e. not initiating deltoid exercises from a fully adducted position) may not allow the Supraspinatus to be fully strengthened, since it is more fully activated at these initial degrees of shoulder abduction/flexion. Once an injury has occurred, however, range of motion is typically restricted on the shoulder press. See shoulder abduction force vector diagram.
Examples of affected exercises:
Shoulder Press
Upright Row
Lateral Raise

Example preventative / corrective exercises:
Front Lateral Raise
Lying Lateral Raise

Serratus Anterior Weakness
A weak or fatigued Serratus Anterior may not allow for adequate Scapulohumeral Rhythm compromising proper shoulder mechanics. Weak or fatigued serratus anterior can fail to adequately protract and upwardly rotate the scapula which may not allow for adequate subacromial space for the biceps tendon and rotator cuff and maintaining ideal spacing between the humeral head and the glenoid fossa (Tovin 2006).
Also see Swimming Injuries (shoulder / overuse and fatigue / example).
A Winged Scapula condition is indicative of a serratus anterior weakness.

Example preventative / corrective exercise:
Incline Shoulder Raise

Infraspinatus Weakness
Increased risk of shoulder injury occurs during throwing andshoulder transverse flexion and transverse adductionactivities, particularly when the elbow travels behind shoulder. Risk is compounded with a protracted shoulder girdle. The strong stabilizing and dislocating forces of the Pectoralis Major (Sternal and Clavical) is counteracted by theInfraspinatus, Teres Minor, and to a lesser extent, the rear deltoid and long head of the triceps brachii.

This counter force is most crucial during:
initiation of a transverse adduction/flexion
elbows behind shoulders
stabilizing force
during the end of a throwing movement
high deceleration dislocating forces required of the posterior cuff can cause breakdown in their tendons near their humeral attachment.
External rotation-muscular endurance / internal rotation-muscular endurance should be greater than 70%.

Examples of affected exercises with suggestions for high risk individuals:
Bench Press: Bring bar lower on chest, keeping elbows closer to sides.
Chest Press: Elevate seat so elbows are closer to sides
Range of motion may need to be limited, so elbows do not go behind shoulders

Example preventative / corrective exercises:
Lying External Rotation
Rows

Erector Spinae Weakness
Increased risk of lower back injury occurs during lumbar spine extension or stabilization activities. Back extension exercises involving complete lumbar spine range of motion have demonstrated primarily excellent or good results for those with chronic lower back pain. Excellent or good results by diagnosis: 76% Mechanical / Strain, 72% Degenerative, 78% Disc Syndrome, 75% Spondylo. In contrast, McGill condemns the use of isolated lumbar spine exercise apparatuses and argues erector spinae endurance is more important than strength. SeeLow Back Debate.

Examples of affected exercises:
Straight Leg Deadlift
Squat
Deadlift

Example preventative / corrective exercises:
Back Extension (novice)
Cable Row (with spinal articulation) (novice to intermediate)
Stiff Leg Deadlift (advanced)

Vastus Medialis Weakness
Increased risk of knee injury (chondromalacia) occurs duringknee extension activities. The patella becomes laterally displaced with the pull of the vastus lateralis. This patella tracking problem can produce wear on the inferior patellar surface. Greater pain is usually experienced during leg extension activities in which the knee is a greater than a 20 to 30 degree angle. Avoiding full range of motion (i.e. not locking out) during Quadricep exercise may not allow the Vastus Medialis to be fully strengthened since it is more fully activated at these final degrees of knee extension.

Examples of affected exercises:
Leg Press
Squat
Leg Extension

Example preventative / corrective exercises:
Single Leg Extensions (last 20 degrees of extension)
Leg Press (last 20 degrees of extension)

Hip Abductor Weakness
One hip can sag when weight is shifted to one leg. Possible increase risk of Iliotibial band friction syndrome(ITBFS) when combined with Gluteus Maximus and/or Tensor Fascia Latea Inflexibility (Fredericson, et. al. 2000).

Examples of affected exercises:
Lunges | Step-Ups
Running | Stair Climber | Gauntlet | Elliptical

Example preventative / corrective exercises:
Lever Seated Hip Abduction
Eventually reintroduce affected exercises in a progressive manner

(Reference: Common Muscular Weaknesses. (2007, January 2). Retrieved March 5, 2015, from http://www.exrx.net/Kinesiology/Weaknesses.html)

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