## 1 Introduction  
Performing landings and jumps successfully is an essential element in many sports such as basketball. An observational analysis [1] reported that basketball players performed 70 landings in a typical game, wherein players landed from low jumps as frequently as from high jumps, depending on their positions. During landing, the peak vertical ground reaction forces (vGRF) experienced by players are several times that of body weight, and the forces increase with drop heights [2]. In terms of kinematics, there are mixed findings as to whether lower body joint ranges of motion (ROM) increased [3] or remained consistent [4] with increasing drop heights. Regarding the neuromuscular response at the lower extremity, higher drop heights induce higher muscle activation prior to landing as a preparation strategy [5; 6]. An epidemiology study on US high school basketball injuries reported an injury rate of 1.94 per 1000 athlete exposure, with ankle/foot (30.5%) and knee (18.6%) being the most commonly injured [7]. Appropriate footwear design is one possible way to aid protecting basketball players from injuries [8; 9; 10]. A recent review on basketball footwear concluded that softer midsoles are related to better impact attenuation in unanticipated test scenarios [10]. In step-off landings, shoes with a soft midsole (40 Shore C) were able to better attenuate impacts compared with a regular (55 Shore C) and a hard (70 Shore C) midsole from different drop heights [11]. Another study comparing shoes with soft (38 Shore C), medium (42 Shore C), and hard (57 Shore C) midsole hardness found that a soft midsole reduced vGRF in shot block landing but not in drop landing or lay-up landing [12]. It should be noted that many previous studies used widely disparate midsole properties [6; 11; 12; 13] that often exceeded the typical range of commercially offered basketball footwear. While using such wider ranges of footwear properties may facilitate statistical comparisons for research studies and thereby provide insight in general concepts of locomotion and movement adaptation, it is of practical and industrial interest to examine how athletes respond to subtle differences in midsole characteristics that are within commercially relevant ranges [14; 15]. There are currently no studies that comprehensively examine how subtle differences in midsole hardness affect the kinetics, kinematics, and muscle activation of vertical drop jumps from different heights. Examining the perceptual response together with biomechanical variables in footwear studies offers insights into the interplay between subjective and objective measures [12; 13; 15; 16]. In general, players preferred soft shoes over hard shoes when executing basketball-related tasks [12; 15]. When executing a lay-up task, basketball players could not perceive any difference in mediolateral stability between shoes with softer (50 Shore C) and harder (60 Shore C) midsoles, but despite this, the subtle difference in midsole hardness was objectively quantified by center of pressure path variation [15]. During landings, the ability to accurately perceive and appropriately respond to impact stimuli is important for developing safe landing strategies. Currently, it is not known whether athletes can accurately perceive the intensity of landing impact jointly altered by drop heights and footwear features [6; 17]. Such knowledge is of importance because athletes do not have easy access to force measurements and therefore tend to rely on subjective perception of their landing intensity. The primary aim of this study was to examine how subtle differences in midsole hardness of basketball footwear affect lower extremity biomechanics during drop jumps from various heights. The secondary aim was to examine the relationship between the perceived landing impact and objective impact loading measures.