MPT Therapeutic Exercise and Functional Rehabilitation 1 — Questions and Answers

Question 1: The SAID principle (Specific Adaptation to Imposed Demands) states that:

Exercises must be performed daily to maintain gains
The body adapts specifically to the type, intensity, and mode of training imposed (Correct answer)
Muscles can only strengthen in the plane they are trained
Aerobic conditioning automatically improves strength

Correct answer: The body adapts specifically to the type, intensity, and mode of training imposed

The SAID principle states that the body makes specific physiological adaptations in response to the specific demands placed on it. Training adaptations are specific to the movement pattern, speed, load, and energy system used.

SAID (Specific Adaptation to Imposed Demands) is a foundational exercise science principle. Strength training produces neural and hypertrophic adaptations specific to the movement, velocity, and joint angle trained. Endurance training improves mitochondrial density, capillary density, and oxidative enzyme activity in the specific muscles used. This principle justifies sport-specific and task-specific training in PT rehabilitation. PTs design rehabilitation programs that progress to mirror the demands of the patient's target activities.

Question 2: According to the ACSM, the recommended intensity for aerobic exercise to improve cardiovascular fitness is:

20-40% of VO2 reserve
40-85% of VO2 reserve or heart rate reserve (Correct answer)
90-100% of maximum heart rate
Below 30% of maximum heart rate

Correct answer: 40-85% of VO2 reserve or heart rate reserve

ACSM recommends 40-85% of VO2 reserve (or HRR) for cardiovascular fitness improvement, with beginners starting at the lower end (40-60%) and progressing to moderate-to-vigorous intensities.

ACSM exercise prescription for cardiorespiratory fitness uses the FITT-VP principle. For intensity, 40-85% VO2R or HRR covers moderate (40-60%) to vigorous (60-85%) intensity. Sedentary or deconditioned individuals begin at 40-50%, while conditioned individuals can exercise at 60-85%. PTs use this framework to prescribe cardiac rehabilitation programs, calculate target heart rate ranges using the Karvonen formula, and monitor exercise tolerance in patients with cardiovascular disease.

Question 3: Open kinetic chain (OKC) knee extension exercises are contraindicated during early ACL reconstruction rehabilitation primarily because:

They are too easy and do not load the graft
Terminal knee extension creates anterior shear forces at the tibia, placing high stress on the healing ACL graft (Correct answer)
They cannot be performed with a brace
They cause excessive patellar compression

Correct answer: Terminal knee extension creates anterior shear forces at the tibia, placing high stress on the healing ACL graft

During terminal OKC knee extension (from approximately 40 degrees to full extension), the quadriceps pull anteriorly on the tibia via the patellar tendon, placing anterior tibial shear forces that stress an ACL graft.

Biomechanical studies show that OKC knee extension from 40 degrees to 0 degrees generates significant anterior tibial shear forces from the quadriceps, directly loading the ACL or ACL graft. Early post-reconstruction (0-8 weeks), this can elongate or re-rupture the graft before ligamentization. OKC extension from 90-40 degrees generates less anterior shear and is generally permitted earlier. Closed kinetic chain exercises (squats, leg press, step-ups) are preferred early because co-contraction of hamstrings neutralizes anterior tibial shear.

Question 4: What is the primary metabolic pathway used during high-intensity exercise lasting 30 seconds to 2 minutes?

Alactic anaerobic (ATP-PC) system
Glycolytic (lactic acid) system (Correct answer)
Oxidative (aerobic) system
Beta-oxidation of free fatty acids

Correct answer: Glycolytic (lactic acid) system

The glycolytic (lactic acid) system is the primary energy source for high-intensity exercise lasting approximately 30 seconds to 2 minutes, producing ATP through anaerobic glycolysis with lactate as a byproduct.

The three energy systems: (1) ATP-PC (alactic): 0-10 seconds, very high intensity, no lactate. (2) Glycolytic (lactic): 30 seconds to 2 minutes, high intensity, produces pyruvate and lactate. (3) Oxidative: greater than 2-3 minutes, moderate intensity, requires oxygen. These systems overlap substantially. Interval training at 30-120 seconds targets the glycolytic system, improving lactate threshold and buffer capacity. PTs designing conditioning programs use these principles to progressively overload appropriate energy systems.

Question 5: Proprioceptive neuromuscular facilitation (PNF) techniques rely on which neurophysiological mechanism for inhibiting a tight muscle?

Reciprocal inhibition (antagonist contraction inhibits agonist)
Autogenic inhibition via Golgi tendon organs during muscle contraction
Both reciprocal inhibition and autogenic inhibition (Correct answer)
Direct reflex arc inhibition of the motor cortex

Correct answer: Both reciprocal inhibition and autogenic inhibition

PNF stretching uses both autogenic inhibition (GTO activation during contract-relax reduces agonist tension) and reciprocal inhibition (antagonist contraction inhibits agonist) to achieve greater ROM.

PNF stretching techniques: (1) Contract-relax (CR): isometric contraction of the tight muscle activates GTOs, leading to autogenic inhibition, the muscle relaxes, allowing greater stretch. (2) Agonist-contract (AC): contraction of the antagonist produces reciprocal inhibition of the tight muscle. (3) Contract-relax agonist-contract (CRAC): combines both mechanisms. PNF stretching has been shown to be superior to static stretching for acute ROM gains. PTs apply PNF to increase ROM in post-surgical contractures, spasticity management, and flexibility training.

Question 6: The overload principle in resistance training states that muscle adaptations occur only when:

Exercise is performed at the same load for extended periods
Training load exceeds what the body is currently accustomed to, progressively challenging the neuromuscular system (Correct answer)
Exercise is performed to failure on every set
The same exercise is performed every day without variation

Correct answer: Training load exceeds what the body is currently accustomed to, progressively challenging the neuromuscular system

The overload principle requires that training stimulus progressively exceeds current capacity — muscles adapt to loads greater than habitual, so training intensity, volume, or complexity must be progressively increased.

Progressive overload is fundamental to strength and conditioning. Adaptation requires a training stimulus that exceeds the body's current capacity. Methods of progressive overload include: increasing load (most common), increasing volume (sets times reps), increasing frequency, decreasing rest intervals, or increasing movement complexity. Insufficient overload leads to plateaus; excessive overload leads to overtraining and injury. PTs apply this principle systematically in post-surgical rehabilitation, using measurable progression markers to guide safe and effective resistance training progressions.

MPT Therapeutic Exercise and Functional Rehabilitation 1

The SAID principle (Specific Adaptation to Imposed Demands) states that: