Accumulation of which of the following molecules in the muscles occurs as a result of vigorous exercise ?

Solution :
\[\underset{\begin{smallmatrix} \text{stored in} \\ \text{the}\,\,\text{form of}\,\,\downarrow \\ \text{Glycogen} \end{smallmatrix}}{\mathop{\text{Glucose}}}\,\xrightarrow[\begin{align} & \text{(does not need } \\ & \text{oxygen;} \\ & \text{need only} \\ & \text{enzymes)} \\ \end{align}]{}\underset{\begin{smallmatrix} \,\,\,\,\,\,\,\,\,\downarrow \\ \text{Lactic acid} \end{smallmatrix}}{\mathop{\text{Pyruvic acid}}}\,\xrightarrow{{{O}_{2}}}C{{O}_{2}}+{{H}_{2}}O\]
During vigorous exercise sufficient oxygen is not available to meet the energy demand so, energy is derived through conversion of pyruvic acid to lactic acid.