Related Experiment Video
Updated: Dec 27, 2025
14:55
Methods to Quantify Pharmacologically Induced Alterations in Motor Function in Human Incomplete SCI
Published on: April 18, 2011
14.1K
Voluntary Activation and Reflex Responses after Hamstring Strain Injury
Robert Buhmann, Gabriel S Trajano1, Graham Kerr1
1School of Exercise and Nutrition Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, AUSTRALIA.
Medicine and Science in Sports and Exercise
|February 27, 2020
Summary
Prior moderate to severe hamstring injuries lead to lasting deficits in eccentric knee flexor strength and voluntary activation. These injuries also impair stretch and tendon reflexes, impacting muscle function long-term.
Area of Science:
- Sports Medicine
- Neuromuscular Physiology
- Rehabilitation Science
Background:
- Definitive evidence for voluntary activation deficits post-hamstring injury is lacking.
- The role of spinal mechanisms in suspected deficits remains unclear.
Purpose of the Study:
- To investigate the long-term effects of hamstring strain injury on knee flexor function.
- To assess differences in strength, voluntary activation, and reflex responses between injured and uninjured limbs.
Main Methods:
- Recruited 25 participants (12 with prior hamstring strain injury).
- Measured knee flexor strength, voluntary activation, and surface electromyography (sEMG) during maximal eccentric and concentric contractions.
- Recorded stretch and tendon reflexes at rest.
Main Results:
- Previously injured limbs showed significantly lower voluntary activation, strength, and normalized sEMG during eccentric contractions.
- No significant differences were observed during concentric contractions.
- Stretch and tendon reflex amplitudes were reduced in previously injured limbs.
Conclusions:
- Moderate to severe hamstring strain injury is linked to persistent deficits in voluntary activation during eccentric contractions.
- A history of hamstring injury is associated with diminished stretch and tendon reflex amplitudes, suggesting long-term neuromuscular alterations.
More Related Videos
Related Concept Videos
01:22Somatic Spinal Reflexes
4.5K
Somatic spinal reflexes are rapid, involuntary muscular responses to external stimuli that involve the somatic musculature and the spinal cord.
One of the most well-known somatic spinal reflexes is the stretch reflex, which is activated by the sudden stretching of a muscle. This reflex involves the activation of specialized sensory receptors called muscle spindles, which are located in the muscle tissue and detect changes in the length and speed of muscle contractions. When a muscle is suddenly...
One of the most well-known somatic spinal reflexes is the stretch reflex, which is activated by the sudden stretching of a muscle. This reflex involves the activation of specialized sensory receptors called muscle spindles, which are located in the muscle tissue and detect changes in the length and speed of muscle contractions. When a muscle is suddenly...
4.5K
01:08Reflex Activity
2.8K
A reflex activity is an automatic, involuntary response to specific stimuli. It is a part of our survival mechanism, designed to protect us from potential harm. For example, when a bright light suddenly shines into our eyes, we instinctively close them or look away. This is a simple reflex activity orchestrated by the nervous system without conscious thought or effort.
A reflex exam is a diagnostic procedure performed by a healthcare professional to evaluate the functionality of a patient's...
A reflex exam is a diagnostic procedure performed by a healthcare professional to evaluate the functionality of a patient's...
2.8K
01:23Muscles that Move the Leg
4.8K
The movement of the legs is facilitated by numerous muscles located within the anterior, medial, and posterior compartments of the thigh.
Anterior Compartment
The quadriceps femoris, the most visible muscle of the anterior compartment, is integral for leg extension and thigh flexion. It is formed by merging four distinct muscles — the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris. The quadriceps tendon, a shared tendon of the four quadriceps muscles, is affixed...
Anterior Compartment
The quadriceps femoris, the most visible muscle of the anterior compartment, is integral for leg extension and thigh flexion. It is formed by merging four distinct muscles — the vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris. The quadriceps tendon, a shared tendon of the four quadriceps muscles, is affixed...
4.8K
01:15Muscle Contraction
95.5K
95.5K
01:10Muscle Contraction
8.6K
In skeletal muscles, acetylcholine is released by nerve terminals at the motor endplate—the point of synaptic communication between motor neurons and muscle fibers. The binding of acetylcholine to its receptors on the sarcolemma allows entry of sodium ions into the cell and triggers an action potential in the muscle cell. Thus, electrical signals from the brain are transmitted to the muscle. Subsequently, the enzyme acetylcholinesterase breaks down acetylcholine to prevent excessive...
8.6K
01:16Vascular Spasm
3.1K
The vascular phase, also known as vasospasm, is the initial stage of hemostasis, crucial for preventing excessive bleeding when a blood vessel is injured. After a vessel is cut, nerves in the damaged area trigger pain and other sensory impulses. Simultaneously, the smooth muscles in the vessel wall contract, resulting in a vascular spasm. This contraction reduces the vessel's diameter at the injury site, slowing or stopping blood loss through the vessel wall. Vascular spasms typically last...
3.1K