Effects of therapeutic ultrasound on the mechanical properties of skeletal muscles after contusion

CONTEXTUALIZAÇÃO: O ultra-som terapêutico (UST) é um recurso comumente aplicado na aceleração do reparo tecidual de lesões musculares. A absorção das ondas ultra-sônicas é determinada pela freqüência e pela intensidade, sendo que, em uma mesma intensidade, a profundidade atingida por 1MHz é maior quando comparada a 3MHz. OBJETIVO: Analisar o comportamento das propriedades mecânicas de músculos submetidos à lesão aguda por impacto e tratados com UST, utilizando as freqüências de 1 e 3MHz. MATERIAIS E MÉTODOS: Foram utilizadas 40 ratas Wistar (200,1±17,8g), divididas em quatro grupos: (1) controle; (2) lesão muscular sem tratamento; (3) lesão muscular tratada com UST de freqüência 1MHz (0,5W/cm²) e (4) lesão muscular tratada com UST de freqüência 3MHz (0,5W/cm²). A lesão foi provocada no músculo gastrocnêmio por mecanismo de impacto. O tratamento foi de cinco minutos diários durante seis dias consecutivos. Os músculos foram submetidos a ensaios mecânicos de tração em uma máquina universal de ensaios. RESULTADOS: As médias e desvios-padrão das propriedades mecânicas dos grupos lesionados e tratados com UST foram significativamente maiores quando comparadas ao grupo lesionado sem tratamento (p<0,05). Em destaque, a propriedade de rigidez que, com a aplicação do UST, teve acréscimo de aproximadamente 38%. CONCLUSÕES: A intervenção, por meio do UST, promoveu aumento das propriedades mecânicas nos músculos lesionados aproximando-as do grupo controle. Entretanto, não foi observada diferença significativa entre as propriedades mecânicas dos grupos tratados com ultra-som de freqüências 1MHz e 3MHz.BACKGROUND: Therapeutic ultrasound is a resource commonly applied to speed up tissue repair in muscle injuries. The absorption of the ultrasound waves is determined by their frequency and intensity. For a given intensity, the depth reached by 1MHz is greater than the depth reached by 3MHz. OBJECTIVE: To analyze the mechanical properties of muscles subjected to acute impact injury treated with therapeutic ultrasound at the frequencies of 1 and 3MHz. METHODS: Forty female Wistar rats (200.1±17.8g) were used, divided into four groups: (1) control; (2) muscle injury without treatment; (3) muscle injury treated with therapeutic ultrasound at the frequency of 1MHz (0.5W/cm²); and (4) muscle injury treated with therapeutic ultrasound at the frequency of 3MHz (0.5W/cm²). The injury was produced in the gastrocnemius muscle by means of an impact mechanism. The treatment consisted of a single five-minute session per day, for six consecutive days. The muscles were subjected to mechanical traction tests in a universal test machine. RESULTS: Means and standard deviations for the mechanical properties of the injured groups that received therapeutic ultrasound were significantly greater than those of the injured group without treatment (p<0.05). The property of stiffness should be highlighted: the application of therapeutic ultrasound increased muscle stiffness by approximately 38%. CONCLUSIONS: Therapeutic ultrasound increased the mechanical properties of the injured muscles, and brought them to a level close to the control group. However, no significant difference in mechanical properties was observed between the groups treated with ultrasound at the frequencies of 1MHz and 3MHz

Cardiopulmonary exercise testing in post-COVID-19 patients: Where does exercise intolerance come from?

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq). Background Post-COVID-19 persistent symptoms and exercise intolerance are poorly understood. Cardiopulmonary exercise testing (CPET) assessment is important to address the sources of the underlying symptoms and limitations. Purpose To evaluate the source and magnitude of exercise intolerance in post-COVID-19 subjects via CPET. Methods This cohort study assessed subjects with different SARS-CoV-2 illness severities. The propensity score matching method was used to select the control group. Patients with available CPET prior to SARS-CoV-2 infection were compared before and after COVID-19. Results 288 subjects (144 post-COVID-19 and 144 matched-controls) were assessed. The median age was 43.0 years, and 57% were male, with different illness severity (60.4% mild, 20.8% moderate, 18.8% severe). Residual symptoms were reported in 41% of the sample. CPET was performed 14.4±9.4 weeks after disease onset, with exercise limitations being attributed to the peripheral muscle (91.7%), pulmonary (6.3%), and cardiovascular (2.1%) systems. Lower median percent-predicted peak oxygen consumption was observed in the severe subgroup (72.2%) compared to both mild (98.5%) and control subgroups (91.6%). Peak oxygen consumption (peakVO2), VO2 at the ventilatory thresholds (VO2 at VT), and heart rate differed among illnesses, severities, and controls. Conversely, ventilatory equivalents, oxygen uptake efficiency slope, and peak oxygen pulse were similar (Figure 1). Additional subgroup analysis of 42 subjects with prior CPET revealed changes only on peak treadmill speed in the mild subgroup and additional reductions on peakVO2 and VO2 at VT in the moderate/severe subgroup (Figure 2), while ventilatory equivalents, oxygen uptake efficiency slope, and peak oxygen pulse remained unchanged. Conclusions Peripheral muscle fatigue was the most common etiology of exercise limitation in post-COVID-19 patients regardless of the SARS-CoV-2 illness severity. Our data suggest that treatment should emphasize comprehensive rehabilitation programs, including aerobic and muscle strengthening components