**1. Introduction**

Recent advances in technological developments have enabled the mass production of small, unobtrusive wearable inertial sensors [1]. These sensors can be used to directly monitor an athlete's biomechanics as well as to instrument the equipment an athlete interacts with in a laboratory, training, or competitive setting. Previous studies using wearable inertial sensors for athlete performance analysis show the hindrance of normal movement to be minimal [2]. The miniaturisation of inertial sensors is attributable to microelectromechanical systems (MEMS). MEMS are chip-level devices based on movement of silicon-based arms acting as a mass and spring. The acceleration and rotation can be logged and transmitted [3–5]. MEMS accelerometer technologies include those based on capacitive, piezoelectric, and piezoresistive effects [3]. When inertial sensors are used in rowing, the device must be waterproof. Moreover, if an athlete is being monitored on-water training, then other technologies such as global positioning system (GPS) and on-board video are recommended so that the inertial sensor data can be synchronised.

This review outlines the published literature to assess the applications of inertial sensors in rowing. From this, athletes and coaches have a guide for inertial sensors applications and design method for implementations.

A systematic review evaluating the integration of wearable inertial sensors into a sporting environment for performance monitoring was published in March 2018 [6]. The review captured 286 records and of these 10/286 (3.50%) included on-boat water sports such as rowing and kayaking. These relatively few records either show that there is a gap in using MEMS in performance monitoring in rowing or this is an under researched area. Due to the physically demanding and technical nature of rowing, it is hypothesized that performance monitoring tools would be of grea<sup>t</sup> benefit.

Reviews of scientific literature pertinent to rowing have been published; however, to the best of our knowledge, none have focused on the use of technology. Previous literature reviews in rowing have focused on the biomechanical and metabolic factors imperative for a successful rower and the likely injures to rowers. Baudouin and Hawkins [7] looked to bridge the gap between physiological, biomechanics and physical aspects involved in rowing by understanding the interrelationship between the biological and mechanical systems. They propose that the blade force is the only propulsive force counter-acting the drag forces (air drag and hydrodynamic drag acting on the rowing system. It was found that the impact of vertical oscillations of the shell are minimal. The link between blade force and the rower is the oar and this force is transmitted via the oarlock. They sugges<sup>t</sup> that sustainable power is maximized through matching the rigging setup and blade design to the rower's joint torque–velocity characteristics. They concluded that a more comprehensive understanding of force-time profiles are needed so that deficiencies in a rower's biomechanics can be optimised to achieve greater force generation.

Michael et al. [8] reviewed literature surrounding the metabolic demands of kayaking. The scientific literature highlights the high levels of both aerobic power and anaerobic capacity across kayak athletes. They suggested that velocity of the kayak as well as force, power, technique and aerobic fitness are valuable metrics for athlete performance monitoring. Understanding the physiological demands of kayaking is a useful tool for coaches as it helps them make informed decisions about an athlete's suitability for race distances. It also helps to optimise training regimes to improve the performance of specific athletes.

Thornton et al. [9] evaluated published material focused on injuries in rowing. This review was updated in 2016 as rowing specific injury research has increased over the last decade. Key points found from the review were that the largest risk factor for rowing injury were rapid increases in training frequency, intensity and/or volume, appropriate loading in the boat and on a rowing ergometer can reduce the likeliness of overuse injuries, and, finally, there is still a significant demand for well-designed prospective studies focused on rowing injuries. It is evident that an athlete's rowing performance and likelihood of injury can possibly be quantified by metrics obtained via inertial sensors.

The previous literature reviews on rowing do not address the technology and methodologies used in rowing research. Without a framework, ad hoc methodologies concerning the selection and implementation of wearable technologies could reduce the accuracy and validity of rowing sport performance measures [3,10].

### **2. Materials and Methods**

A systematic review of literature was conducted (current as of 24 April 2019) using a methodology based on PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) recommendations for completing and reporting the findings of systematic reviews [11]. An electronic database search was completed in total of six relevant scholarly databases (Google Scholar, Web of

Science (core collection), ProQuest, Scopus, Sage Journals and Science Direct) using the keywords identified in Table 1. Exclusion criteria meant manuscripts were only included in the final review if they satisfied the following: It must be a methods-based research article from a scholarly journal (available in English), which contains the use of inertial sensors and have a relevance to human performance monitoring in a rowing setting.


**Table 1.** Searched databases and associated search terms used, IMU (Inertial Measurement Unit).

The included papers were reviewed on the following: (i) the geographical location of where the study was conducted; (ii) properties of the inertial sensor used in the study; (iii) the placement of the inertial sensor in the study; (iv) what algorithms were used for data processing; (v) what performance features were analysed; (vi) study design, and (vii) whether other validated technologies/procedures were implemented to ensure accuracy and validity of the investigation. The record screening process is shown in Figure 1.

**Figure 1.** Flow diagram of study selection.
