The physiological demands of holding a small object when running.

It is the norm for humans to swing their contralateral arm and leg during the gait cycle to reduce angular momentum and balance rotational momentum Collins et al. (2009). This is also due to activation of the posterior oblique sling between the Gluteus Maximus and contralateral Latissimus Dorsi, connected via the thoracolumbar fascia Shin et al. (2013). The role of lower limb kinematics on running performance and economy has been widely researched; however, there remains a gulf in the literature (MacAdam et al. 2018; Moore 2016) regarding the role of the arms on overall running performance, economy, and their subsequent link to injury
reduction. In their paper ‘How Biomechanical Improvements in Running Economy Could Break the 2-hour Marathon Barrierʼ, Hoogkamer et al. (2017) do not acknowledge the potential role of the arms. Historically the function of the arms during running has been thought to assist with balance (Bunn 1972; Hay 1978). Sayers (2000) concurred, however also suggested that the
arms have a role in increasing step-frequency. Miller et al. (2009) report how restraining the arms during running has an impact on lower limb kinematics such as peak hip and knee flexion angles during stance phase. Runners training for a marathon will no doubt encounter mixed advice regarding hydration levels. Leggett et al. (2018) reported that there is a lack of understanding of adequate hydration amongst recreational runners. It is suggested, however, that overhydration, rather than dehydration, poses the greater risk to runners due to potential exercise-associated hyponatraemia EAH. 58.7% of the authorʼs cohort of London Marathon 2014 runners planned to ‘drink to thirstʼ during the event, as supported by Noakes (2010), of which the median planned volume was 1 L (±0.6). In contrast, 5.8% planned on purposefully drinking >3.5 L. The latter of the two options posing the greatest risk of EAH; however, both options would require a runner to take fluid with them during their long training runs, ultimately resulting in the need to carry a bottle when running. Another item recreational runners are commonly observed to carrying is their Smartphone, for reasons such as listening to music to aid motivation Hutchinson et al. (2015), to set cadence Bood et al. (2013), as a method of emergency contact, or to track and share their run via GPS (Runnerʼs World, 2017). Aral and Nicolaides (2017) analysed ‘millionsʼ of
runners GPS data and concluded that when runners share their activities on a social network, they run farther, faster, and longer. Whilst the alternative less cumbersome option of GPS watches are also frequently used (as well as various straps for Smartphones) it is not uncommon to observe runners carrying their Smartphone in their hand. A recent study by Vincent et al. (2018), suggested that although the counteractions of holding a water bottle or phone during running may be small with each step, it is possible that this may significantly affect the physiological response and energy expenditure over long distance events such as an ultralong marathon.