This constitutive model cannot be stretched in uni-axial tension beyond a maximal stretch 
  
    
      
        
          J
          
            m
          
        
      
    
    {\displaystyle J_{m}}
  , which is the positive root of

  
    
      
        
          λ
          
            m
          
          
            2
          
        
        +
        2
        
          λ
          
            m
          
        
        −
        
          J
          
            m
          
        
        −
        3
        =
        1
      
    
    {\displaystyle \lambda _{m}^{2}+2\lambda _{m}-J_{m}-3=1}

Remodeling and growth
Soft tissues have the potential to grow and remodel reacting to chemical and mechanical long term changes.
W
        =
        
          
            1
            2
          
        
        c
        
          (
          
            
              e
              
                
                  b
                  
                    i
                    j
                    k
                    l
                  
                
                
                  E
                  
                    i
                    j
                  
                
                
                  E
                  
                    k
                    l
                  
                
              
            
            −
            1
          
          )
        
      
    
    {\displaystyle W={\frac {1}{2}}c\left(e^{b_{ijkl}E_{ij}E_{kl}}-1\right)}

Gent-elastic material
W
        =
        −
        
          
            
              μ
              
                J
                
                  m
                
              
            
            2
          
        
        ln
        ⁡
        
          (
          
            1
            −
            
              (
              
                
                  
                    
                      λ
                      
                        1
                      
                      
                        2
                      
                    
                    +
                    
                      λ
                      
                        2
                      
                      
                        2
                      
                    
                    +
                    
                      λ
                      
                        3
                      
                      
                        2
                      
                    
                    −
                    3
                  
                  
                    J
                    
                      m
                    
                  
                
              
              )
            
          
          )
        
      
    
    {\displaystyle W=-{\frac {\mu J_{m}}{2}}\ln \left(1-\left({\frac {\lambda _{1}^{2}+\lambda _{2}^{2}+\lambda _{3}^{2}-3}{J_{m}}}\right)\right)}
  where 
  
    
      
        μ
        >
        0
      
    
    {\displaystyle \mu >0}
   is the shear modulus for infinitesimal strains and 
  
    
      
        
          J
          
            m
          
        
        >
        0
      
    
    {\displaystyle J_{m}>0}
   is a stiffening parameter, associated with limiting chain extensibility.