Asymmetry is the norm, not the other way around.
"For many years, mainly to simplify data analysis, scientists assumed that during a gait, the lower limbs moved symmetrically. However, even a cursory survey of the more recent literature reveals that the human walk is symmetrical only in some aspects."http://www.ncbi.nlm.nih.gov/pubmed/23486255
"H:q ratios and bilateral leg strength in college field and court sports players" found significant bilateral differences according to type of sport and leg dominance.http://www.ncbi.nlm.nih.gov/pubmed/23487043
"...the findings of the current study suggest an association between knee strength imbalances and the joint angle, as well as the torque produced in single-leg jumps, although no relationship between knee strength and jump height was observed."http://www.ncbi.nlm.nih.gov/pubmed/23462444
" Statistically significant differences were recorded between the most and less efficient leg in strength and power performances for both genders." http://www.ncbi.nlm.nih.gov/pubmed/22233795
" EMG variability was asymmetric and appears to be strongly influenced by exercise intensity for cyclists and non-cyclists, especially during sub-maximal intensity."http://www.ncbi.nlm.nih.gov/pubmed/21120741
"During cycling, bilateral differences are frequently found and vary with the competitive situation, pedaling cadence, exercise intensity and exercise duration. Regardless of the variability of asymmetry index between subjects, few suggestions are available to overcome lateral differences. Most of the research suggests that bilateral pedaling asymmetries decrease as the workload increases, however the relationship to injury risk was not clearly addressed."http://www.ncbi.nlm.nih.gov/pubmed/21055708
There are lots more. Do a pubmed search.