Analyze The Joint Movements, Muscle Actions, And Agonist Mus ✓ Solved

Analyze the joint movements, muscle actions, and agonist mus

Analyze the joint movements, muscle actions, and agonist muscles for four pictures (Phase 1 Bottom, Phase 2 Top, Phase 1 Right, Phase 2 Left). For each phase, list the joints, the movement(s), the muscle action type (concentric, eccentric, isometric), and the agonist(s). Then write a 1000-word paper explaining the biomechanics, muscle function, and clinical relevance of these movements, with in-text citations and at least 10 credible references.

Paper For Above Instructions

Overview

This paper analyzes four described phases (Phase 1 Bottom, Phase 2 Top, Phase 1 Right, Phase 2 Left) by listing the primary joints, movement(s), muscle action types (concentric, eccentric, isometric), and agonist muscles, then discusses biomechanical function and clinical relevance. Abbreviations used: AF = acetabulofemoral (hip), TF = tibiofemoral (knee), TC = talocrural (ankle), ST = subtalar, GH = glenohumeral (shoulder), SCAP = scapulothoracic, C‑SP = cervical spine, HU = humeroulnar, RU = radioulnar, RC = radiocarpal, MCP/IP = finger joints, CMC‑1 = first carpometacarpal (thumb).

Phase 1 (Bottom Picture) — Joint/Muscle Summary

AF (hip): Extension — concentric agonists: gluteus maximus, semitendinosus, semimembranosus, biceps femoris, posterior adductor magnus. AF abduction — concentric agonist: gluteus medius. TF (knee): Extension — concentric agonists: rectus femoris, vastus medialis, vastus intermedius, vastus lateralis. TC (ankle/talocrural): Dorsiflexion — isometric: tibialis anterior, extensor digitorum longus, peroneus tertius. ST, MTP, IP: anatomical-position isometric stabilization.

Phase 2 (Top Picture) — Joint/Muscle Summary

AF (hip): Flexion — eccentric control by hip flexors (psoas major, iliacus, pectineus, sartorius, rectus femoris, TFL, portions of adductor longus/magnus); AF adduction — concentric agonists: gracilis, pectineus, adductor longus, adductor magnus, adductor brevis. TF (knee): Flexion — eccentric agonists: biceps femoris, semitendinosus, semimembranosus, sartorius. TC dorsiflexion, ST, MTP, IP: largely isometric stabilization in this phase.

Phase 1 (Right Picture — Upper Body) — Joint/Muscle Summary

Spine and C‑SP: anatomical‑position isometric stabilization. GH (shoulder): Flexion — concentric agonists: pectoralis major (clavicular fibers), anterior deltoid; Horizontal adduction — concentric agonists: pectoralis major, anterior deltoid. SCAP (scapulothoracic): Elevation, abduction, upward rotation — concentric agonists: upper trapezius, levator scapulae, serratus anterior (upward rotation with trapezius), with pectoralis minor and serratus anterior implicated in scapular positioning. HU, RU, RC, MCP, IP, CMC‑1: primarily isometric for hand/forearm posture.

Phase 2 (Left Picture — Upper Body) — Joint/Muscle Summary

Spine and C‑SP: anatomical‑position isometric. GH: Extension and horizontal abduction — eccentric control by pectoralis major (sternal), posterior deltoid, latissimus dorsi, teres major; concentric/horizontal abduction by posterior/middle deltoid, infraspinatus, teres minor. SCAP: Depression, adduction, downward rotation — eccentric or concentric roles for pectoralis minor, serratus anterior, middle trapezius, rhomboids, and levator scapulae depending on movement phase. Distal joints again show primarily isometric stabilization for grip and wrist posture.

Biomechanical Discussion

Identifying agonist muscles and action types clarifies how segments are accelerated, decelerated, or stabilized during functional tasks. Concentric actions (shortening under tension) produce joint motion—e.g., hip extension via gluteus maximus accelerates the thigh posteriorly and contributes to propulsion in gait and rising from sitting (Neumann, 2017). Eccentric actions (lengthening while active) control or decelerate motion; for example, hip flexors acting eccentrically restrain rapid hip extension or control the lowering of the limb (Kendall et al., 2005). Isometric actions stabilize joints against external forces—e.g., tibialis anterior isometrically stabilizing the ankle to maintain foot posture during stance.

In the lower‑limb phases described, coordinated hip and knee muscle activity is essential. Hip extension requires strong gluteal and hamstring concentric force while the quadriceps may act isometrically or eccentrically depending on knee demand (Perry & Burnfield, 2010). Conversely, hip flexion under eccentric control (Phase 2 top) reflects a controlled lengthening of hip flexors, common in lowering tasks and deceleration phases of gait and kicking (Neumann, 2017).

The scapulothoracic‑glenohumeral system illustrates proximate stability enabling distal mobility. Upward rotation and elevation of the scapula by serratus anterior and trapezius optimize the glenoid orientation for shoulder flexion and horizontal adduction (Moore et al., 2013). In the opposite phase, eccentric activity of pectoralis major and latissimus dorsi controls shoulder extension/horizontal abduction, protecting tendons and labrum by smoothing deceleration (Kibler et al., 2013).

Clinical Relevance and Application

Understanding which muscles are agonists and whether they act concentrically, eccentrically, or isometrically guides assessment and rehabilitation. Weak hip extensors (gluteus maximus) or poor eccentric control of hip flexors can alter gait mechanics and increase knee loading, contributing to patellofemoral pain or iliotibial band syndrome (Powers, 2010). Rehabilitation often emphasizes eccentric strengthening to improve deceleration capacity and tissue tolerance (LaStayo et al., 2014).

Scapular dyskinesis—altered scapular motion—can result from imbalance between trapezius and serratus anterior; targeted concentric and eccentric training of these muscles improves shoulder kinematics and reduces shoulder pain (Kibler & Sciascia, 2016). Similarly, ankle dorsiflexor isometric stabilization is crucial after ankle sprain to prevent excessive plantarflexion moments that can compromise balance (Hertel, 2002).

Functional exercise selection should reflect action types: concentric drills for power (sprinting hip extension), eccentric training for controlled deceleration (downhill running, eccentric squats), and isometric holds for postural endurance and joint stability (planks, single‑leg balance) (Sahrmann, 2002; Neumann, 2017).

Conclusion

Mapping joints to movement types and agonist muscles clarifies the mechanical roles of muscle groups in the four described phases. Hip and knee muscles alternate concentric and eccentric roles according to task demands, while scapular and shoulder muscles coordinate to position the limb for effective force transfer. Clinicians and trainers should assess the quality of concentric, eccentric, and isometric control across these joints to prescribe targeted interventions that restore efficient and safe movement patterns (Tortora & Derrickson, 2017).

References

  1. Neumann, D. A. (2017). Kinesiology of the Musculoskeletal System: Foundations for Rehabilitation (3rd ed.). Elsevier.
  2. Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2013). Clinically Oriented Anatomy (7th ed.). Wolters Kluwer/Lippincott Williams & Wilkins.
  3. Tortora, G. J., & Derrickson, B. H. (2017). Principles of Anatomy and Physiology (15th ed.). Wiley.
  4. Kendall, F. P., McCreary, E. K., Provance, P. G., Rodgers, M. M., & Romani, W. A. (2005). Muscles: Testing and Function with Posture and Pain (5th ed.). Lippincott Williams & Wilkins.
  5. Gray, H., & Standring, S. (2008). Gray's Anatomy: The Anatomical Basis of Clinical Practice (40th ed.). Elsevier.
  6. Powers, C. M. (2010). The influence of altered lower‑extremity kinematics on patellofemoral joint dysfunction: a theoretical perspective. Journal of Orthopaedic & Sports Physical Therapy, 40(7), 42–51.
  7. Kibler, W. B., Sciascia, A., & Wilkes, T. (2013). Scapular dyskinesis and its relation to shoulder injury. Journal of the American Academy of Orthopaedic Surgeons, 21(6), 363–372.
  8. LaStayo, P. C., Woolf, J. M., Lewek, M. D., Snyder‑Mackler, L., & Lindstedt, S. L. (2014). The positive effects of negative work: increased muscle strength and decreased fall risk in a frail elderly population. Journal of Gerontology: Medical Sciences, 59(5), 567–574.
  9. Hertel, J. (2002). Functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability. Journal of Athletic Training, 37(4), 364–375.
  10. Sahrmann, S. A. (2002). Diagnosis and Treatment of Movement Impairment Syndromes. Elsevier Health Sciences.

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