title: Low-level laser therapy associated with high intensity resistance training on cardiac autonomic control of heart rate and skeletal muscle remodeling in wistar rats.
abstract: OBJECTIVE
  Phototherapy plus dynamic exercise can enhance physical performance and improve health. The aim of our study was to evaluate the effect of low-level laser therapy (LLLT) associated with high intensity resistance training (HIT) on cardiac autonomic and muscle metabolic responses in rats.
  
  
  METHODS
  Forty Wistar rats were randomized into 4 groups: sedentary control (CG), HIT, LLLT and HIT + LLLT. HIT was performed 3 times/week for 8 weeks with loads attached to the tail of the animal. The load was gradually increased by 10% of body mass until reaching a maximal overload. For LLLT, irradiation parameters applied to the tibialis anterior (TA) muscle were as follows: infrared laser (780 nm), power of 15 mW for 10 seconds, leading to an irradiance of 37.5 mW/cm(2), energy of 0.15 J per point and fluency of 3.8 J/cm(2). Blood lactate (BL), matrix metalloproteinase gelatinase A (MMP(-2)) gene expression and heart rate variability (HRV) indices were performed.
  
  
  RESULTS
  BL significantly increased after 8-weeks for HIT, LLLT and HIT + LLLT groups. However, peak lactate when normalized by maximal load was significantly reduced for both HIT and HIT + LLLT groups (P<0.05). MMP-2 in the active form was significantly increased after HIT, LLLT and HIT + LLLT compared tom the CG (P<0.05). There was a significant reduction in low frequency [LF (ms(2))] and increase in high frequency [HF (un)] and HF (ms(2))] for the HIT, LLLT and HIT + LLLT groups compared with the CG (P < 0.05). However, the LF/HF ratio was further reduced in the LLLT and HIT + LLLT groups compared to the CG and HIT group (P < 0.05).
  
  
  CONCLUSIONS
  These results provide evidence for the positive benefits of LLLT and HIT with respect to enhanced muscle metabolic and cardiac autonomic function in Wistar rats.
authors.affiliation: Optics Group from Physics Institute of São Carlos (IFSC), University of São Paulo (USP), Brazil.
authors.forename: Fernanda Rossi
authors.initials: FR
authors.lastname: Paolillo
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.forename: Daniela Bassi
authors.initials: DB
authors.lastname: Dutra
authors.forename: Rita
authors.initials: R
authors.lastname: de Cassia Marqueti Durigan
authors.forename: Heloisa Selistre
authors.initials: HS
authors.lastname: de Araujo
authors.forename: Hugo Celso Dutra
authors.initials: HC
authors.lastname: de Souza
authors.forename: Nivaldo Antonio
authors.initials: NA
authors.lastname: Parizotto
authors.forename: Gerson
authors.initials: G
authors.lastname: Cipriano
authors.forename: Gaspar
authors.initials: G
authors.lastname: Chiappa
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
mesh_terms: D000818:Animals; D015992:Body Mass Index; D006339:Heart Rate / Q000502:physiology / Q000528:radiation effects*; D019344:Lactic Acid / Q000097:blood; D028022:Low-Level Light Therapy; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism; D053580:Muscle Strength / Q000502:physiology / Q000528:radiation effects; D018482:Muscle, Skeletal / Q000201:enzymology / Q000503:physiopathology / Q000528:radiation effects*; D051381:Rats; D017208:Rats, Wistar; D055070:Resistance Training
chemical_list: D019344:Lactic Acid; D020778:Matrix Metalloproteinase 2
keywords: HRV; LLLT; MMP−2; lactate; resistance training