Quantifying muscle strength, size, and neuromuscular activation in adolescent and young adult survivors of musculoskeletal sarcoma: Identifying correlates and responses to functional strengthening.

BACKGROUND: Medical and surgical treatment for musculoskeletal sarcoma (MSS) place survivors at risk for impairments in muscle properties including muscle strength, muscle size, and neuromuscular activation. The purpose of this study was to explore muscle properties, gross motor performance, and quality of life (QoL) and the changes in response to a 6-week functional strengthening intervention (PT-STRONG) in MSS survivors of childhood cancer (CCS). METHODS: Eight lower extremity MSS CCS (13-23 years old) performed baseline testing and three completed PT-STRONG. Participants completed measurements of knee extension strength using handheld dynamometry, vastus lateralis (VL) and rectus femoris (RF) muscle thickness using ultrasonography at rest, and neuromuscular activation using electromyography during strength testing and a step-up task. Participants also completed gross motor and QoL assessments. RESULTS: Compared with the non-surgical limb, MSS CCS had lower surgical limb knee extension strength, VL muscle thickness, and RF step-up muscle rate of activation (RoA). Compared with normative values, MSS CCS had decreased bilateral knee extension strength, gross motor performance, and physical QoL. Positive correlations among muscle strength, muscle thickness, and gross motor performance were identified. After PT-STRONG, MSS CCS had improvements in VL muscle thickness, VL and RF RoA duing step-up, gross motor performance, and physical QoL. CONCLUSIONS: Positive association between larger muscle thickness with greater knee extension strength, and higher knee extension strength with better gross motor performance indicate that comprehensive physical therapy assessment and interventions that identify and target impairments in muscle properties to guide clinical decision making should be considered for MSS CCS into survivorship.

The Efficacy of Targeted Exercise on Gross Motor and Neuromuscular Performance in Survivors of Childhood Leukemia: A Pilot Study.

Objectives: This quasi-experimental study examined the efficacy of targeted exercise training on gross motor performance and neuromuscular impairments in survivors of childhood acute lymphoblastic leukemia (ALL CCS). Materials and Methods: Ten ALL CCS (median age: 10 years; range: 6-14 years) performed a 6-week training program three times per week (five in-person sessions), including a warm-up, total body stretching, progressive jump rope training, and a cool down. Gross motor performance (test of gross motor proficiency) and lower extremity rate of muscle activation (electromyography), joint torques (motion capture and force plate), and jump height (motion capture) were measured during a countermovement jump at baseline and post-training. Results: Post-training, ALL CCS demonstrated improvements in body coordination, strength and agilty, bilateral coordination, running speed and agility, and strength gross motor performance (mean change: 1.6-8.1; p < 0.05), the rate of muscle activation of the tibialis anterior and vastus lateralis muscles (mean change: 0.58-0.75; p < 0.05), hip and ankle joint torques (mean change: 0.07; p < 0.05), and jump height (mean change: 0.05; p < 0.05). Conclusion: This study demonstrated that targeted exercise training can improve gross motor performance and neuromuscular impairments in ALL CCS post-medical treatment.

Electrophysiological effects of anthracyclines in adult survivors of pediatric malignancy.

BACKGROUND: Anthracycline use is limited by cardiotoxicity, including arrhythmias and left ventricular (LV) dysfunction. We aim to characterize the association between electrophysiological changes and LV dysfunction. METHODS: A retrospective chart review was conducted, including all 147 pediatric cancer survivors at our institution over 18 years of age and treated with an anthracycline. One hundred thirty-four patients who had at least one electrocardiogram (ECG) and echocardiogram were analyzed. The association between dysfunction and baseline characteristics, treatment history, and electrocardigraphic parameters were analyzed using multivariable logistic regression. Additionally, a longitudinal generalized estimating equation (GEE) model was used to examine the temporal association between repeated measure corrected QT (QTc) intervals and subsequent LV function. RESULTS: In our population, 24% of patients had LV dysfunction. The initial posttreatment QTc interval was longer in patients with LV dysfunction (438 ± 35 vs. 420 ± 20 msec, P = 0.002). In logistic regression analysis, QTc interval (P < 0.001) and cumulative radiation dose (P = 0.027) were associated with LV dysfunction. On ECGs performed prior to evidence of LV dysfunction, the QTc was longer than on ECGs preceding a normal echocardiogram (451 ± 32 msec vs. 423 ± 25 msec, P < 0.001). Mean time from QTc ≥ 450 msec to evidence of LV dysfunction was 1.8 ± 2.9 years. In the longitudinal GEE model, QTc prolongation was associated with subsequent decreased fractional shortening. CONCLUSIONS: Among adult survivors of pediatric cancer treated with anthracyclines, prolongation of the QTc interval was associated with subsequent LV dysfunction.