Cross-education: effects of age on rapid and maximal voluntary contractile characteristics in males

The purpose of this study was to determine the effect of age on the cross-education of rapid and maximal contractile properties for the knee extensors.

Young (n = 10; age = 21.1 ± 1.7 years) and older (n = 10; age = 65.3 ± 8.3 years) males performed unilateral isokinetic resistance training (RT) of the knee extensors for 4 weeks. Maximal voluntary isokinetic (45° s^-1 and 300° s^-1) and isometric testing was conducted for the trained and untrained leg before and after RT. Peak torque (PT) and acceleration were obtained from isokinetic testing as well as torque at 30 ms (TQ₃₀) and 100 ms (TQ₁₀₀) from the 45° s^-1 contraction. PT and rate of torque development were recorded from the isometric contractions.

Independent of age, isometric PT (10.1%; p = 0.006) as well as PT and acceleration at 300° s^-1 (6.7%; p = 0.008 and 4.0%; p = 0.016, respectively) increased in the untrained leg. At 45° s^-1, acceleration was increased (3.6%; p = 0.021), but PT remained unchanged (p = 0.227). TQ₁₀₀ increased similarly between groups (4.5%; p = 0.014), but TQ₃₀ increased only in the older group (9.5%; p = 0.022).

Cross-education of rapid and maximal contractile parameters can be achieved early during unilateral RT independent of age. These findings indicate the potential for particular unilateral RT protocols to be used for older adults in rehabilitative settings to offset disuse-related reductions in contractile function, which are most dramatic in this population.