*3.2. Intensity*

The "I" within the FITT principle stands for "intensity". Within the context of PA, intensity refers to the energy expended during a given time period [63]. In the context of

FMS session design, however, another interpretation of intensity might also be considered as the number of skill executions within a given time period. Children's practice of FMS, whether in the context of a PE lesson or a coaching session, will ideally achieve the dual objectives of reaching moderate-to-vigorous levels of PA for immediate health benefits while also promoting quality skill development [62]. With appropriate activity design and monitoring of intensity, both of these objectives can be met within the same session.

For children and adolescents between the ages of 5 and 17 years old, the World Health Organisation (WHO) recommend 60 min of moderate-to-vigorous physical activity (MVPA) daily [64]. There are five categories of well-established PA-related exercise intensities, beginning with *sedentary*, which typically refers to sitting or other stationary activities, requiring minimal energy and low levels of movement [65]. *Light*-*intensity* activity refers to activities that can be easily sustained for 60 min without incurring a noticeable change in breathing rate, and often, these activities require less than three times the resting energy expenditure [65]. *Moderate intensity* refers to using between 3 and 6 times more energy than a resting state, while *vigorous intensity* refers to using 6 to 9 times more energy when compared to a resting state [65]. *High-intensity* activity, however, refers to expending energy in excess of 9 times the amount used at rest.

Monitoring PA intensity is a critical component for evaluating cardiorespiratory fitness, and consistent participation at higher-intensity PA has the potential to positively impact other health markers, such as blood glucose and blood lipid levels [66]. The consistent associations found between FMS and PA indicate that a high level of motor competence can contribute to long-term PA engagement [67]. Minimal research, however, exists pertaining to the intensity of activity accrued during the performance of FMS activities [68] or the associated quality of skill execution.

Recent studies with populations of children and adolescents have examined energy expenditure during the performance of object-control skills (kick, throw, strike) [68,69]. The Sacko et al. (2019) study (*n* = 42; 22 males; mean age = 8.1 ± 0.8 years) reported that the practice of kicking, throwing, and striking at a rate of two maximal-effort attempts per minute appears to meet the threshold for moderate-intensity PA as it surpasses the 4.0 metabolic equivalent (METs) [69]. Further research among children (*n* = 30; 16 males; (9.4 ± 1.4 years) has suggested a slow cadence (i.e., kicking a football in a passing motion every 6 s but not at maximal effort), results in a light intensity of activity between 1.5 and 2.9 METs [70]. Notably, these studies differ in the effort applied from participants; the Sacko et al. (2019) study sought maximal effort from participants, whereas the Duncan et al. (2020) study referred to a short passing motion with a football at a slow tempo [69,71]. Such tempo and light-energy expenditure may be common within physical education or coaching during isolated task practices [69,71]. To achieve a *vigorous PA intensity* threshold, 10 attempts per minute at a maximal effort for FMS-related practices were deemed to be needed [69], whereas 20 attempts of short-range kicking were required to reach moderate intensity [71]. Thus, depending upon the effort required and rate of attempts, the practice of individual FMS may produce light, moderate, or vigorous levels of PA.

In contrast to the aforementioned studies on energy expenditure when performing individual FMS [69,71], FMS practice sessions will often include activities in which multiple FMS are performed within the context of a game [72]. According to the compendium of physical activities for children and adolescents, various forms of game play commonly result in levels of vigorous intensity being attained [73]. Several examples of organised games (i.e., basketball, soccer, tennis), in addition to less formal playground and active locomotor play (i.e., hopscotch, freeze tag, sharks and minnows) typically allow children and adolescents to meet the vigorous-intensity threshold across 4 identified age ranges (6 to 9 years old, 10 to 12 years old, 13 to 15 years old, and 16 to 18 years old) [73]. Thus, provided that games are appropriately designed (i.e., number of participants, size of playing area, etc.), it appears that such activities are a viable means of meeting the PA objective of FMS sessions [59].

In relation to skill development, extensive research has shown that practicing FMS in isolation, coupled with appropriate instruction and feedback, can develop children's skill levels [33,40,74,75]. While the overall time spent in activities is typically reported in these studies, the number of skill executions within that time period is not. Interventions with a larger emphasis on the use of games to enhance FMS have also proved successful [59,71,76,77]. As with interventions based upon practicing skills in isolation, specific information on the rate of skill executions within these games is typically not provided either. Additional information on the rate of skill executions per unit time would prove valuable for practitioners in their design of practice sessions, and potentially to researchers seeking to understand the mechanisms underpinning effective interventions.

Skill development is an individual process that demands a tailored approach due to varying environmental constraints and the interactions between the task and the individual themselves [5]. Game-based approaches, such as Teaching Games for Understanding [78,79], propose that the teacher or coach draw upon both game forms and more isolated activities as required to meet their individual learners' needs. Practitioners need to understand how their choice of activity (isolated task or game form; maximum or submaximal effort; etc.) will influence both PA levels and skill development. As such, a singular definitive recommendation regarding which intensity to utilise in a physically active setting to develop FMS is not advisable from the current evidence presented. Instead, Physical Education teachers, sport pedagogues, coaches, and researchers should acknowledge and justify their selections of individual activities and combinations of activities within a session/lesson plan so as to meet learners' PA and skill development needs [68,69].
