# AI-Enhanced Prediction of Peak Rate of Torque Development from Accelerometer Signals
## 1 Introduction  
Rate of Torque Development (RTD) is a crucial metric that assesses an individual's ability to rapidly generate strength--also known as explosive strength [1; 2; 3]. RTD has been categorized as early (\(\leq\)100 ms) or late (\(\geq\)200 ms) [4; 5]. The former is mainly affected by mechanisms involving neural activation transmitted by motor neurons to muscles [1; 2; 5; 6; 7], and the latter is strongly linked to maximal strength and is influenced by similar underlying mechanisms [4; 8; 9]. Consequently, a higher RTD indicates a faster and more efficient neuromuscular response, determined by motor unit activation rate (i.e., higher neural drive increases the explosive capacity) and muscle morphology (i.e., muscle thickness and muscle architecture) [10; 11; 12]. RTD extends our capacity to evaluate the maximal force-generating capacity and plays a pivotal role in activities requiring quick muscle contractions and short-duration execution, such as jumping, sprinting, or weightlifting [13; 14; 15; 16], as it reflects the muscles' capability to swiftly generate force during the very initial phase of muscle contraction [1; 2]. Also, RTD is often associated with enhanced athletic performance, injury prevention, and return to sport readiness [18; 19; 20; 21; 22; 23; 24; 25; 26; 27]. Thus, by incorporating a time-restricted framework for strength generation, RTD enhances our understanding of muscle force production by examining how someone can respond appropriately to external stimuli and adjust their motor responses during specific events. A quick motor adaptation could be a key factor not only in enhancing performance but also in preventing injuries by theoretically improving dynamic joint stabilization and reducing the risk of orthopedic injuries, such as anterior cruciate ligament tears. Furthermore, measuring RTD in general clinical populations can provide insights into the rehabilitationprogress and functional capabilities of patients recovering from musculoskeletal injuries or neurological disorders. Therefore, monitoring RTD can serve as a valuable diagnostic and prognostic tool in both, sports medicine, and physical therapy [28,29]. Measuring RTD typically demands specialized equipment such as an isokinetic dynamometer or load cells [2,30,31]. It is a fact that relying on an isokinetic dynamometer is a costly and laboratory-based choice. However, while this option may suit major sports institutions, scheduling an evaluation session remains a logistical challenge to balance with training sessions. Although load cells are relatively less costly and can be used in the field, they still face technical struggles regarding signal processing--including onset detection--and data extraction. In fact, to the best of our knowledge, there is currently no commercially available tool for generating RTD indexes in real-time [31], and the torque x time signal requires post-processing by a digital signal processing expert, limiting its accessibility to sports practitioners. Those factors are barriers to the widespread use of RTD for sports and the general population. Thus, our work looks at creating the opportunity to investigate viable alternatives for measuring explosive strength capacity. Inertial sensors, particularly accelerometers, are capable of measuring acceleration or vibrations and are widely accessible nowadays [32,33]. Accelerometers are specifically designed sensors to measure linear acceleration (ACC). These sensors are commonly found in devices such as smartphones and fitness trackers [34,35]. In human performance sciences, accelerometers are utilized to monitor and analyze human movement patterns, providing valuable insights into activities like walking, running, jumping, and other physical activities [33,36]. They can measure acceleration in multiple axes--typically the x, y, and z axes--allowing for a comprehensive analysis of motion dynamics. An accelerometer placed on the segment moved by a muscle can provide information about muscle contraction, including initial force production.