Variable valve actuation (VVA) plays a promising role in supporting advanced combustion methods to meet increasingly stringent fuel efficiency and emission standards in modern vehicles. Much research has been done on VVA to exploit its potential for increasing the overall engine performance. Consequently, the use of VVA in internal combustion engines (ICE) has become more prevalent in recent past. Different flexible VVA technologies have been designed and manufactured to make it possible to control valve events and valve timing over the entire operating range of an engine. Therefore, it is of high interest to comprehensively understand the benefits of numerous VVA mechanisms that can be used to ensure the flexibility of the valve train system. Variable valve timing (VVT) technologies include early or late opening or closing time of the intake or exhaust valves. VVA combine any method of valve timing with variable lift, phase, and duration. This paper presents the assessment of the effects of the above-mentioned VVA strategies and their combinations on the intake and exhaust gas flow dynamics. A computational analysis is performed on a single-cylinder four-stroke engine using GT-POWER simulation software. A comparative study of the effects of various VVA mechanisms on the pressure-volume (PV) diagrams and the volumetric efficiency (VE) is carried out for different engine operating conditions. Simulation results are discussed and examined in contrast with the most relevant data available in literature. The outcome of this study strongly indicates that the use of a properly designed VVA mechanism facilitates the reduction of pumping losses and thus improves volumetric efficiency.