title: Critical load: a novel approach to determining a sustainable intensity during resistance exercise.
abstract: BACKGROUND
  A hyperbolic function as well as a linear relationship between power output and time to exhaustion (Tlim) has been consistently observed during dynamic non-resistive exercises. However, little is known about its concept to resistance exercises (RE), which could be defined as critical load (CL). This study aimed to verify the existence of CL during dynamic RE and to verify the number of workbouts necessary to determine the optimal modeling to achieve it.
  
  
  METHODS
  Fifteen healthy men (23±2.5 yrs) completed 1 repetition maximum test (1RM) on a leg press and 3 (60%, 75% and 90% of 1RM) or 4 (+ 30% of 1RM) workbouts protocols to obtain the CL by hyperbolic and linear regression models between Tlim and load performed. Blood lactate and leg fatigue were also measured.
  
  
  RESULTS
  CL was obtained during RE and 3 workbouts protocol estimate it at 53% while 4 tests at 38% of 1 RM. However, based on coefficients of determination, 3 protocols provided a better fit than the 4-parameter model, respectively (R2>0.95 vs. >0.77). Moreover, all intensities increased blood lactate and leg fatigue, however, when corrected by Tlim, were significantly lower at CL.
  
  
  CONCLUSIONS
  It was possible to determinate CL during dynamic lower limbs RE and that 3 exhaustive workbouts can be used to better estimate the CL, constituting a new concept of determining this threshold during dynamic RE and reducing the physically demanding nature of the protocol. These findings may have important applications for functional performance evaluation and prescription of RE programs.
authors: Cardiopulmonary Physiotherapy Laboratory, Department of Physiotherapy, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.|University of São Paulo, Sao Carlos, Brazil.
authors: Vivian M
authors: VM
authors: Arakelian
authors: Cardiopulmonary Physiotherapy Laboratory, Department of Physiotherapy, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Renata G
authors: RG
authors: Mendes
authors: Cardiopulmonary Physiotherapy Laboratory, Department of Physiotherapy, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Renata
authors: R
authors: Trimer
authors: Cardiopulmonary Physiotherapy Laboratory, Department of Physiotherapy, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Flavia C
authors: FC
authors: Rossi Caruso
authors: Laboratory of Exercise Physiology, Department of Physiological Science, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Nuno M
authors: NM
authors: de Sousa
authors: Laboratory of Exercise Physiology, Department of Physiological Science, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Vanessa C
authors: VC
authors: Borges
authors: Laboratory of Exercise Physiology, Department of Physiological Science, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Camila
authors: C
authors: do Valle Gomes Gatto
authors: Laboratory of Exercise Physiology, Department of Physiological Science, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil.
authors: Vilmar
authors: V
authors: Baldissera
authors: Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois, Chicago, IL, USA.
authors: Ross
authors: R
authors: Arena
authors: Cardiopulmonary Physiotherapy Laboratory, Department of Physiotherapy, Federal University of Sao Carlos, UFSCar, Sao Carlos, Brazil - audrey@ufscar.br.|University of São Paulo, Sao Carlos, Brazil.
authors: Audrey
authors: A
authors: Borghi-Silva
mesh_terms: D000222:Adaptation, Physiological; D015308:Anaerobic Threshold / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000502:physiology; D055070:Resistance Training / Q000379:methods*; D055815:Young Adult