ORIGINAL ARTICLE Light-emitting diode therapy (LEDT) improves functional capacity in rats with heart failure Lucas Capalonga 1,2 & Marlus Karsten 1,2 & Vítor Scotta Hentschke 1,3 & Douglas Dalcin Rossato 4 & Maurício Pinto Dornelles 1 & Anelise Sonza 1,2 & Vanderlei Salvador Bagnato 5 & Cleber Ferraresi 5,6,7 & Nivaldo Antonio Parizotto 6 & Pedro Dal Lago 1,2,3,8 Received: 24 June 2015 /Accepted: 8 March 2016 # Springer-Verlag London 2016 Abstract The syndrome of heart failure (HF) promotes central and peripheral dysfunctions that result in functional capacity de- crease, leading to fatigue, dyspnea, and exercise intolerance. The use of light-emitting diode therapy (LEDT) has shown good re- sults reducing fatigue and exercise intolerance, when applied on skeletal muscles before or after exercises. Thereby, the aim of this study was to compare the effects of LEDT on functional capacity, aerobic power, and hemodynamic function in HF rats. Male Wistar rats (230–260 g) were randomly allocated into three ex- perimental groups: Sham ( n = 6), Control-HF (n = 4), and LEDT- HF (n = 6). The animals were subjected to an exercise perfor- mance test (ET) with gas analysis coupled in a metabolic chamber for rats performed two times (6 and 14 weeks after myocardial infarction). On the day after the baseline aerobic capacity test, the animals were submitted during 8 weeks to the phototherapy pro- tocol, five times/week, 60 s of irradiation, 6 J delivered per muscle group. Statistical analysis was performed by one- and two-way ANOVAs with repeated measures and Student-Newman-Keuls post hoc tests (p ≤ 0.05). Comparing the percentage difference (Δ) between baseline and the final ET, there was no significant difference for the VO 2max variable considering all groups. However, Sham and LEDT-HF groups showed higher relative values than the Control-HF group, respectively, for distance cov- ered (27.7 and 32.5 %), time of exercise test (17.7 and 20.5 %), and speed (13.6 and 12.2 %). In conclusion, LEDT was able to increase the functional capacity evaluated by distance covered, time, and speed of exercise in rats with HF. Keywords Phototherapy . Maximal oxygen uptake . Exercise test . Hemodynamic function Introduction Heart failure (HF) is characterized by severe exercise intoler- ance associated with early fatigue and dyspnea on exertion [1]. The responsible mechanisms for exercise capacity impair- ment are multifactorial and are related with an increase of the sympathetic and renin-angiotensin-aldosterone system activi- ties, together with an augment in vasopressin and natriuretic * Pedro Dal Lago pdallago@ufcspa.edu.br 1 Laboratory of Experimental Physiology, Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Porto Alegre, Rio Grande do Sul, Brazil 2 Post-Graduation Program in Rehabilitation Sciences, UFCSPA, Porto Alegre, Rio Grande do Sul, Brazil 3 Post-Graduation Program in Health Sciences, UFCSPA, Porto Alegre, Rio Grande do Sul, Brazil 4 Centro Universitário Franciscano, Santa Maria, Rio Grande do Sul, Brazil 5 Physics Institute of Sao Carlos, Universidade de São Paulo (USP), São Carlos, São Paulo, Brazil 6 Laboratory of Electrothermophototherapy, Department of Physical Therapy, Universidade Federal de São Carlos (UFSCar), São Carlos, São Paulo, Brazil 7 Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Harvard University, Boston, MA, USA 8 Programa de Pós-Graduação em Ciências da Reabilitação (PPG-CR), Universidade Federal de Ciências da Saúde de Porto Alegre (UFCSPA), Rua Sarmento Leite, 245, Porto Alegre, Rio Grande do Sul 90050-170, Brazil Lasers Med Sci DOI 10.1007/s10103-016-1922-y