7.1 Resistance Training Guidelines, Hemodynamics & Sternal Precautions

7.1 Resistance Training Guidelines, Hemodynamics & Sternal Precautions

Progressive resistance training is an essential pillar of secondary cardiovascular prevention. Contemporary AACVPR and ACSM guidelines confirm that structured resistance training is safe, well-tolerated, and effective for restoring functional capacity in cardiac rehabilitation.

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Physiological Adaptations & Clinical Benefits

Resistance training stimulates peripheral adaptations that complement aerobic conditioning:

• Reversal of Sarcopenia: Cardiovascular disease, bed rest, and aging accelerate muscle wasting. Progressive loading stimulates myofibrillar protein synthesis, motor unit recruitment, and restores lean mass.
• Enhanced Functional Independence: Activities of daily living (ADLs)—carrying groceries, stair climbing, and chair transfers—depend on muscular strength. Expanding strength reduces the relative effort (% MVC) needed for daily tasks, delaying fatigue.
• Bone Mineral Density Preservation: Mechanical strain delivered via tendon insertions stimulates osteoblasts via Wolff's law, counteracting osteoporosis in postmenopausal women and corticosteroid-treated patients.
• Metabolic Regulation: Muscular contraction stimulates GLUT-4 transporter translocation independently of insulin, enhancing insulin sensitivity, improving glycemic control in type 2 diabetes, and reducing visceral adiposity.
• Attenuation of Rate Pressure Product (RPP): Resistance training lowers the double product ($\text{RPP} = \text{HR} \times \text{SBP}$) during submaximal lifting. Greater muscular strength dampens the reflex sympathetic pressor response, lowering myocardial oxygen demand ($MVO_2$) and raising the ischemic threshold.

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Clinical Initiation Criteria & Timing

Initiating resistance training requires confirmed clinical stability and adequate tissue healing:

• Post-PCI: Initiate 2 to 3 weeks post-procedure following at least 2 weeks of uneventful supervised aerobic conditioning, ensuring vascular access sites are healed without hematoma.
• Post-MI: Initiate 2 to 3 weeks post-infarction (4 to 5 weeks in extensive necrosis or LV dysfunction) following $\ge 2$ weeks of stable aerobic exercise.
• Post-CABG & Sternal Surgery: Upper-body resistance training must be deferred for 5 to 8 weeks postoperatively (traditionally 6 to 8 weeks) to permit bony consolidation of the sternum. Lower-body resistance exercise using light loads can begin at 3 to 4 weeks post-CABG provided handrails are not gripped forcefully.
• Clearance Benchmarks: Resting blood pressure $<160/100\text{ mmHg}$, absence of unstable symptoms or uncompensated heart failure, and functional capacity $\ge 5\text{ METs}$ without exercise-induced ischemia or complex arrhythmias.

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Resistance Training Prescription: The FITT Framework

The resistance exercise prescription must be individualized, progressive, and conservative:

• Frequency: 2 to 3 non-consecutive days per week, with $\ge 48$ hours of recovery between sessions targeting the same muscle groups.
• Intensity: Prescribed relative to One-Repetition Maximum (1-RM) or perceived exertion:
  • Upper Body Initiation: 30% to 40% 1-RM (or 12 to 15 comfortable repetitions).
  • Lower Body Initiation: 40% to 50% 1-RM.
  • Progression: Advance to 60% to 70% 1-RM in stable patients once initial loads are tolerated.
  • RPE: Maintain exertion at RPE 11 to 14 (Borg 6–20 scale). Avoid RPE $>15$ during early rehabilitation.
• Volume: 1 to 3 sets of 10 to 15 repetitions per exercise. Single-set protocols achieve 70% to 80% of strength gains and maximize compliance in early rehabilitation.
• Type: 8 to 10 distinct exercises targeting major muscle groups (chest press, seated row, shoulder press, biceps curl, triceps extension, leg press, leg curl, calf raise). Machine weights are preferred initially because guided tracks prevent balance loss. Elastic bands and light cuff weights provide safe alternatives.
• Cadence: Controlled movement—2 seconds concentric (lifting) and 3 seconds eccentric (lowering). Avoid ballistic movements.

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Resistance Training Protocol Comparison

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Hemodynamics, Pressor Reflex & Avoiding Valsalva

Isometric contractions compress local vessels, triggering the exercise pressor reflex. This evokes sympathetic discharge, increasing systemic vascular resistance (SVR) and driving steep blood pressure surges.

Straining against heavy loads induces the Valsalva maneuver (forced expiration against a closed glottis). Intrathoracic pressure surges ($+50\text{ to }+100\text{ mmHg}$), collapsing the vena cavae and impeding venous return. Upon release, blood rushes into cardiac chambers against constricted peripheral arteries, producing a blood pressure overshoot that sharply increases left ventricular wall stress and myocardial oxygen demand, predisposing to ischemia or arrhythmias.

Breathing Mechanics: Staff must coach patients to exhale during the concentric phase (lifting) and inhale during the eccentric phase (lowering). Instruct patients to count repetitions aloud to ensure an open glottis, and avoid tight gripping of handles to minimize reflex sympathetic vasoconstriction.

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Post-Sternotomy Precautions & "Move in the Tube"

Median sternotomy divides the sternum longitudinally. Sternal non-union or infection carries a 15% to 25% mortality rate.

• Traditional Precautions: For 6 to 8 weeks post-surgery, restrict lifting to <5 to 10 pounds. Avoid unilateral arm pushing/pulling and bilateral shoulder horizontal abduction/extension.
• "Move in the Tube" (MITT): Rigid immobility causes frozen shoulder and deconditioning. The MITT paradigm recognizes that sternal distraction forces depend on lever arm length. By keeping upper arms close to the torso within an imaginary cylinder (short lever arms), patients can safely perform functional tasks (such as rising from a chair with tucked elbows) with minimal sternal shear.
• Sternal Assessment: Before clearing upper-body resistance exercise, palpate the sternum during deep breathing and coughing to confirm absence of pain, clicking, or crepitus. Instability requires immediate suspension of arm training and surgical consultation.

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Clinical Application: Post-CABG Resistance Progression

Clinical Scenario: A 66-year-old male is 7 weeks post-CABG x 3 with 12 uneventful aerobic sessions completed. Sternal examination reveals a well-healed incision with no tenderness, clicking, or crepitus. Resting BP is 126/78 mmHg.

Program Design:

• Clearance: At 7 weeks post-sternotomy with verified sternal stability and aerobic tolerance, he qualifies for upper-body resistance training.
• Prescription: 2 days/week; 8 exercises; 1 set of 10 to 12 reps. Upper body at 30% to 40% 1-RM (RPE 11–12); lower body at 40% to 50% 1-RM (RPE 12–13).
• Execution: Coach the patient on "Move in the Tube" mechanics, keeping elbows close to the torso during chest presses and rows. Enforce exhalation on exertion and prompt reporting of any chest wall clicking or discomfort.