**1. Introduction**

The warm-up is widely understood as a preparation practice to perform before any physical exercise. It is usually used by athletes, coaches, and general physical activity participants, to obtain an optimal physical and psychological state and to get kinetic and coordinative preparation in the prevention of injuries during the practice [1–4].

Based on previous studies, the main benefits of the warm-up were increased body temperature, decreased muscle and joint stiffness, [5] increased efficiency in the transmission of nerve impulses, [6] and, simultaneously, the increase in metabolic reactions, leading to the improvement of muscle power [7]. It may also lead to an increase in the dissociation of oxygen, hemoglobin, and myoglobin, causing vasodilation and, consequently, an increase in muscle blood flow [8].

These changes could be promoted by two basic types of warm-up, specifically, the active and passive warm-up [3, 9]. Hot water bags, short waves, hot baths, sauna, are some of the means used to complete a passive warm-up [3, 9]. This type of warm-up provides an increase in muscle and central temperature without energy expenditure, with the use of external heating [3, 9]. On the other hand, the active warm-up can be performed through the use of physical activity, for instance, walking, running, swimming, cycling, or any other specific exercises [3, 9, 10]. One of the main advantages of the active warm-up is its specificity, as it prepares the muscles that will be used during the activity and could benefit from the movement itself [3, 9].

Despite the positive influence of warm-up on sports performance, [9] there is still a lack of specific investigations about the variables that compose it, the optimal warm-up design as well as its effects on the force production and strength training performance [11, 12]. Any movement performed during physical activity requires the use of specific muscles to produce movement. The movement depends on muscle performance and therefore force production, either in maximal or submaximal efforts so that the exercise could be carried out successfully. The role of muscle strength performance is widely recognized in the scientific and sports context [9, 13]. Maximizing the strength and optimizing force production should be a priority to any person participating or willing to participate in sports performance or physical exercise. For this performance improvement, in physical activity and sport context, resistance training (strength training exercises where muscles exert a force against an external load) assumes an important role to develop individual capacities. Moreover, to improve the efficiency of resistance training and force production, the warm-up could be essential. It is important to understand the way that warm-ups can influence strength training and performance, to analyze the effects, and then to provide a useful strategy to apply in the real context. With this knowledge, professionals are able to design a warm-up that will optimize resistance training and thus, maximizing strength gains, force production, and resulting in improvements in physical exercise performance.

It is then important to understand the effect of warm-up in strength performance and this may be through the assessment of maximum dynamic strength (load at 1 repetition maximum: 1RM), isometric strength, or even through the rate of production of muscle strength [3, 10–12, 14]. Previous findings suggested that the warm-up procedure (for example, aerobic exercise, specific activity, and stretching) seems to influence the results of the 1RM assessment, as well as to improve the strength produced during the assessments [3, 12, 15]. Generally, it is recommended that the warm-up routine prior to a 1RM test includes general (aerobic) and specific (imitating target activity) exercises [16–18]. The general warm-up is usually completed using an aerobic activity of low to moderate intensity with the main purpose to increase the muscle temperature, which can be performed with different types of aerobic activity (for example, running or cycling) [3, 10, 12]. Stretching exercises can also be performed as part of a typical warm-up routine. Regarding the specific warm-up, it is recommended to perform it by including exercises that use the same or similar movements as the main activity at progressively higher intensities in an attempt to increase neuromuscular activation [2, 12]. In fact, there is suitable scientific evidence in the literature to support the implementation of only specific warm-ups before exercise, [19, 20] however, the effects of general warm-up on strength measurements are not clear yet.

In order to design an effective warm-up, several parameters and variables are associated with it, which seems to be extremely difficult to select an ideal type of warm-up for all sports. Then, it is necessary to understand what type of warm-up *Warming-Up for Resistance Training and Muscular Performance: A Narrative Review DOI: http://dx.doi.org/10.5772/intechopen.96075*

is more appropriate to the variable that influences performance in all exercises, i.e. force production. Thus, our narrative review aimed to analyze and discuss the main results of the literature on the effects of warm-up on force production and strength, by analyzing responses during resistance training and assessments of maximum strength. The results determined in this study, aimed to elucidate sport-related professionals about the effects of warm-up and help them to design their training.
