Abstract
effects of occlusal splints on sport performance have already been studied, although their biomechanical impacts are often overlooked. We investigated the kinematical changes during running until exhaustion at severe intensity while wearing a mandibular advancement occlusal splint. Twelve trained runners completed (i) an incremental protocol on a track to determine their velocity corresponding to maximal oxygen uptake and (ii) two trials of square wave transition exercises at their velocity corresponding to maximal oxygen until exhaustion, wearing two occlusal splints (without and with mandibular advancement). Running kinematics were compared within laps performed during the square wave transition exercises and between splint conditions. The mandibular advancement occlusal splint increased the running distance covered (~1663±402 vs. 1540±397 m,p= 0.03), along with a noticeable lap effect in decreasing
transition exercises at their velocity corresponding to maximal oxygen until exhaustion, wearing two occlusal splints (without and with mandibular advancement). Running kinematics were compared within laps performed during the square wave transition exercises and between splint conditions. The mandibular advancement occlusal splint increased the running distance covered (~1663±402 vs. 1540±397 m,p= 0.03), along with a noticeable lap effect in decreasing stride frequency (p= 0.04) and increasing stride length (p= 0.03) and duty factor (p <0.001). No spatiotemporal differences were observed between splints, except for improved balance foot contact times in the mandibular advancement condition. An increased knee flexion angle at initial contact (p= 0.017) was noted along laps in the non-advancement condition, despite the fact that no differences between splints were found. Running patterns mainly shifted within laps rather than between conditions, indicating that a mandibular advancement occlusal splint had a trivial kinematical effect. Keywords:occlusal splints; mandibular repositioning; velocity at maximal oxygen uptake; running biomechanics; linear kinematics; angular kinematics; time to exhaustion; running economy 1. Introduction Biomechanical changes often occur as runners progress over time [1–3], with fatigue being one of the primary factors contributing to the substantial running modifications on lower limb mechanics [4–6]. Therefore, runners adopt different and individual strategies in trying to compensate for exhaustion, thereby making them effective in maintaining the same force output as they approach exhaustion [5,7,8]. Since fatigue can play a major role in modifying running patterns, the kinematic adjustments may be even more impactful when running at a severe exercise intensity, where exhaustion is reached within a short time period, typically between 3 and 10 min [9–11]. Mandibular advancement occlusal splints are extensively recognized as an alternative treatment for obstructive sleep apnea syndrome given their positive effects in increasing the upper airway size and enhancing airflow [12]. Based on these ventilatory effects, some Sensors2024,24, 6032.
Sensors2024,24, 6032 2 of 11 studies have also investigated their use regarding potential benefits during exercise [13–15]. Through necessary design and manufacturing modifications, mandibular advancement devices have demonstrated positive physiological effects and sport performance improve- ments, particularly increased ventilation and prolonged exercise time to exhaustion [13,15]. If mandibular advancement positively influences time to exhaustion, runners could eventu- ally sustain exercise for extended periods with fewer or more minor kinematical changes. However, it remains unclear whether the kinematic changes observed with the use of a spe- cific occlusal splint are a consequence of the improved physiological variables, or whether they are due to a mechanism that affects gait patterns as a direct result of manipulated mandibular position. Although research on the impact of mandibular advancement occlusal splints on sport performance is limited, the effects on gas exchange have garnered significant attention due to their direct influence on the upper airway. Furthermore, small adjustments in mandibular position have also been linked to changes in gait and running patterns [16–18], prompting inquiry into whether these devices may also affect exercise biomechanics. While indirect evidence indicates that changes in mandibular position might affect body posture [17,19], the extent to which such alterations influence gait patterns, particularly during exercise activities with a broader range of motion than standing or walking, remains uncertain. This study aimed to analyze the kinematical effects of a mandibular advancement occlusal splint during running at severe intensity, hypothesizing that runners (i) would alter their running technique as they approach exhaustion and (ii) would extend the distance covered, and, eventually, influence running patterns during a running until exhaustion at severe intensity. 2. Materials and Methods 2.1. Participants Twelve trained male runners (26.3±4.4 years old, 176.0±6.3 cm of height, 65.5±7.2 kg of body mass, 13±5 years of running experience, and 12±4 h of weekly training) volunteered to participate in the current study. All included subjects were (i) over 18 years of age; (ii) without severe dental and/or periodontal disease, and/or temporo- mandibular joint disorders; (iii) not currently under orthodontic treatment; and (iv) not suffering from any restricting injury within the three months prior
mass, 13±5 years of running experience, and 12±4 h of weekly training) volunteered to participate in the current study. All included subjects were (i) over 18 years of age; (ii) without severe dental and/or periodontal disease, and/or temporo- mandibular joint disorders; (iii) not currently under orthodontic treatment; and (iv) not suffering from any restricting injury within the three months prior to the data collection. All participants provided written informed consent upon receiving detailed information on the study’s aims and procedures and could withdraw from the study at any time. The study was conducted in accordance with the Declaration of Helsinki on human experimentation and was approved by the local ethics board. 2.2. Experimental Procedures Each participant completed three experimental sessions on a 400 m outdoor track field, with a 48 h interval between each session. To minimize circadian variations, subjects were tested at the same time of the day (±2 h), with wind conditions maintained below 2 m·s −1 (assessed by a digital handheld anemometer, Mastech ® MS6252A, Charlotte, NC, USA). All participants were advised to avoid strenuous exercise the day before the experiments and to maintain usual training routines. During the first session, participants completed a running intermittent incremental protocol of 800 m steps (with increments of 1 km·h −1 per step and 30 s intervals in between) until volitional exhaustion, to assess the maximal oxygen uptake ( . V O2max) and associated velocity (v . V O2max) [20,21]. Afterwards, the participants performed, in a randomized and counterbalanced order, two trials of square wave transition exercises at the predetermined v . V O2maxuntil exhaustion [21,22] wearing an intraoral occlusal splint without and with mandibular advancement (Figure). The intraoral occlusal splints were custom manufactured beforehand for each participant by a specialized dentist following specific fabrication procedures [14]. The splints without mandibular advancement were designed so as not to alter mandibular position and were carefully trimmed on the occlusal surfaces to avoid any interference with the runners’ dental occlusion or occlusal vertical dimension.
specialized dentist following specific fabrication procedures [14]. The splints without mandibular advancement were designed so as not to alter mandibular position and were carefully trimmed on the occlusal surfaces to avoid any interference with the runners’ dental occlusion or occlusal vertical dimension.
Sensors2024,24, 6032 3 of 11Sensors 2024, 24, x FOR PEER REVIEW 3 of 11 mandibular advancement were designed so as not to alter mandibular position and were carefully trimmed on the occlusal surfaces to avoid any interference with the runners’ dental occlusion or occlusal vertical dimension. During the incremental protocol and square wave transition exercises, V ˙ O2max was continuously measured using a portable telemetric gas analysis system (K4b2, Cosmed, Rome, Italy) fixed to the runner’s back, and capillary blood samples were collected from the fingertip (5 µL, Lactate Pro2; Arkay, Inc., Kyoto, Japan) for posterior lactate concentration analysis [19]. Blood lactate concentrations were measured at rest, during each 30 s interval, immediately at the end of the exercise, and at the 3rd min post-exercise cessation [14]. Capillary blood collection was always performed by applying controlled pressure to the finger to minimize volume variations and ensure consistent results, and all initial blood samples were discarded to eliminate contaminants and guarantee measurement accuracy. For the square wave transition exercise trials, subjects were marked manually with black skin landmarks on the greater trochanter, lateral femoral epicondyle, and lateral malleolus (Figure 2) [22]. The time sustained at v V ˙ O2max was obtained using a stopwatch (Seiko, Tokyo, Japan) and biomechanical assessment was conducted using two high-definition cameras (GoPro HERO6 Black, San Mateo, CA, USA), operating at 120 Hz and strategically positioned 3 m from the middle of the 200– 300 m running track section and 3 m from the 1st lane (Figure 2) [14]. Figure 1. Implemented setup for the three experimental sessions. Figure 1.Implemented setup for the three experimental sessions. During the incremental protocol and square wave transition exercises, . V O2maxwas continuously measured using a portable telemetric gas analysis system (K4b2, Cosmed, Rome, Italy) fixed to the runner ′ s back, and capillary blood samples were collected from the fingertip (5µL, Lactate Pro2; Arkay, Inc., Kyoto, Japan) for posterior lactate concentration analysis [19]. Blood lactate concentrations were measured at rest, during each 30 s interval, immediately at the end of the exercise, and at the 3rd min post-exercise cessation [14].
(K4b2, Cosmed, Rome, Italy) fixed to the runner ′ s back, and capillary blood samples were collected from the fingertip (5µL, Lactate Pro2; Arkay, Inc., Kyoto, Japan) for posterior lactate concentration analysis [19]. Blood lactate concentrations were measured at rest, during each 30 s interval, immediately at the end of the exercise, and at the 3rd min post-exercise cessation [14]. Capillary blood collection was always performed by applying controlled pressure to the finger to minimize volume variations and ensure consistent results, and all initial blood samples were discarded to eliminate contaminants and guarantee measurement accuracy. For the square wave transition exercise trials, subjects were marked manually with black skin landmarks on the greater trochanter, lateral femoral epicondyle, and lateral malleolus (Figure) [ 22]. The time sustained at v . V O2maxwas obtained using a stopwatch (Seiko, Tokyo, Japan) and biomechanical assessment was conducted using two high-definition cameras (GoPro HERO6 Black, San Mateo, CA, USA), operating at 120 Hz and strategically positioned 3 m from the middle of the 200–300 m running track section and 3 m from the 1st lane (Figure) [14].
Sensors2024,24, 6032 4 of 11Sensors 2024, 24, x FOR PEER REVIEW 4 of 11 Figure 2. Landmarks and camera-specific positions adopted for the square wave transition exercise trials. 2.3. Data Analysis From the running incremental protocol, V ˙ O2max was considered when a V ˙ O2 plateau (<2.1 mL·kg −1 ·min −1 ) was observed despite an increase in running velocity, a respiratory exchange ratio >1.1, blood lactate concentrations >8 mm·L −1 , heart rate >90% of [220-age] and volitional exhaustion (controlled through visual inspection and individual case analysis), and v V ˙ O2max computed as the running velocity of the first incremental step that elicited V ˙ O2max [9,20]. All spatiotemporal and angular kinematic variables were assessed in Kinovea ® software (v. 0.9.5, Boston, MA, USA) from the first, penultimate, and ultimate laps (defined as lap 1, 2, and 3, respectively) performed during the square wave transition exercise trials. For each runner, three running cycles (strides) per lap were analyzed for the respective splint conditions. The total distance covered, stride frequency, stride length, and duty factor during running until exhaustion at severe intensity were calculated based on the following equations [23–25]: (i) total distance (m) = v V ˙ O2max (m·s −1 )· time sustained at vV ˙ O2max (s); (ii) stride frequency (Hz) = stride time (s) −1 ; and (iii) stride length (m) = vV ˙ O2max (m·s −1 ) · stride frequency (Hz) −1 and (iv) duty factor = contact time (s) · stride time (s) −1 , where stride time (s) is the duration to complete a running cycle, i.e., the time between successive initial contacts of the same foot and contact time is the time from initial contact to toe-off of the same foot (Figure 3, panel A). All angular kinematic analyses were conducted exclusively in the left sagittal plane, where (i) knee angle was measured at initial contact and toe-off moments; (ii) the minimum knee angle was assessed at maximum knee flexion during the running cycle; and (iii) the knee range of motion was calculated as the difference between the most extended and
(Figure 3, panel A). All angular kinematic analyses were conducted exclusively in the left sagittal plane, where (i) knee angle was measured at initial contact and toe-off moments; (ii) the minimum knee angle was assessed at maximum knee flexion during the running cycle; and (iii) the knee range of motion was calculated as the difference between the most extended and most flexed knee positions during the whole running cycle (Figure 3, panel B) [26–28]. All spatiotemporal and angular variables were analyzed and measured by the same operator. Figure 2.Landmarks and camera-specific positions adopted for the square wave transition exer- cise trials. 2.3. Data Analysis From the running incremental protocol, . V O2maxwas considered when a . V O2plateau (<2.1 mL·kg −1 · min −1 ) was observed despite an increase in running velocity, a respira- tory exchange ratio >1.1, blood lactate concentrations >8 mm·L −1 , heart rate >90% of and volitional exhaustion (controlled through visual inspection and individual case anal- ysis), and v . V O2maxcomputed as the running velocity of the first incremental step that elicited . V O2max[9,20]. All spatiotemporal and angular kinematic variables were assessed in Kinovea ® software (v. 0.9.5, Boston, MA, USA) from the first, penultimate, and ultimate laps (defined as lap 1, 2, and 3, respectively) performed during the square wave transition exercise trials. For each runner, three running cycles (strides) per lap were analyzed for the respective splint conditions. The total distance covered, stride frequency, stride length, and duty factor during running until exhaustion at severe intensity were calculated based on the following equations [23–25]: (i) total distance (m) = v . V O2max(m·s −1 )·time sustained at v . V O2max(s); (ii) stride frequency (Hz) = stride time (s) −1 ; and (iii) stride length (m) = v . V O2max(m·s −1 )·stride frequency (Hz) −1 and (iv) duty factor = contact time (s)·stride time (s) −1 , where stride time (s) is the duration to complete a running cycle, i.e., the time between successive initial contacts of the same foot and contact time is the time from initial contact to
and (iii) stride length (m) = v . V O2max(m·s −1 )·stride frequency (Hz) −1 and (iv) duty factor = contact time (s)·stride time (s) −1 , where stride time (s) is the duration to complete a running cycle, i.e., the time between successive initial contacts of the same foot and contact time is the time from initial contact to toe-off of the same foot (Figure All angular kinematic analyses were conducted exclusively in the left sagittal plane, where (i) knee angle was measured at initial contact and toe-off moments; (ii) the minimum knee angle was assessed at maximum knee flexion during the running cycle; and (iii) the knee range of motion was calculated as the difference between the most extended and most flexed knee positions during the whole running cycle (Figure 26–28]. All spatiotemporal and angular variables were analyzed and measured by the same operator.
Sensors2024,24, 6032 5 of 11Sensors 2024, 24, x FOR PEER REVIEW 5 of 11 Figure 3. Running temporal and knee angular variables (panels (A,B), respectively) analyzed in Ki- novea software while running until exhaustion at severe intensity. 2.4. Statistical Analysis Assuming biomechanical changes within laps with a moderate effect size (f = 0.25), an α = 0.05, a power of 0.8, and a correlation among repeated measures of 0.8, the sample size calculation resulted in the recruitment of 10 participants (G*Power, v. 3.1.9.7, Düssel- dorf, Germany). The effect of the lap and splint and the interaction effect of lap*splint on biomechanical variables were investigated using two-way repeated measures ANOVA. Sphericity was assessed using the Mauchly test and, if violated, the Greenhouse–Geisser correction was applied. In the event of a significant main effect, a Bonferroni post hoc Figure 3.Running temporal and knee angular variables (panels (A,B), respectively) analyzed in Kinovea software while running until exhaustion at severe intensity. 2.4. Statistical Analysis Assuming biomechanical changes within laps with a moderate effect size (f = 0.25), an α= 0.05, a power of 0.8, and a correlation among repeated measures of 0.8, the sample size calculation resulted in the recruitment of 10 participants (G*Power, v. 3.1.9.7, Düsseldorf, Germany). The effect of the lap and splint and the interaction effect of lap*splint on biomechanical variables were investigated using two-way repeated measures ANOVA. Sphericity was assessed using the Mauchly test and, if violated, the Greenhouse–Geisser correction was applied. In the event of a significant main effect, a Bonferroni post hoc multiple comparison was conducted. Comparisons between splints for the distance covered and differences between feet were undertaken using paired t-tests. For each ANOVA and
Sensors2024,24, 6032 6 of 11 paired t-test, partial eta-squared (η²) and Cohen’sd(d) were computed as a measure of effect size (respectively). All data were reported as mean±standard deviation and the statistical analyses were performed on SPSS (v. 29.0, IBM Corp., Armonk, NY, USA) with the significance level set atp≤0.05. 3. Results The distance covered by the runners ranged from 1200 to 2329 m and from 1223 to 2400 m for the occlusal splints without and with mandibular advancement (respectively), with the condition involving mandibular advancement resulting in runners covering ~8% more distance (~1663±402 vs. 1540±397 m,p= 0.03,d= 0.62). The spatiotemporal variables during running until exhaustion at severe intensity while wearing both occlusal splints are depicted in Figure. A significant main effect of lap was identified on stride frequency and stride length (p= 0.04 and 0.03;η 2= 0.32 and 0.35, respectively) in the mandibular advancement condition, with post hoc analysis showing a decreased stride frequency between the first and second laps, and between the first and third laps (p= 0.02 and 0.05, respectively), and an increased stride length between the first and second laps, and between the first and third laps (p= 0.01 and 0.03, respectively). Nevertheless, there were no main effects of splint nor interaction lap*splint on the same variables.Sensors 2024, 24, x FOR PEER REVIEW 6 of 11 multiple comparison was conducted. Comparisons between splints for the distance cov- ered and differences between feet were undertaken using paired t-tests. For each ANOVA and paired t-test, partial eta-squared (η²) and Cohen’s d (d) were computed as a measure of effect size (respectively). All data were reported as mean ± standard deviation and the statistical analyses were performed on SPSS (v. 29.0, IBM Corp., Armonk, NY, USA) with the significance level set at p ≤ 0.05. 3. Results The distance covered by the runners ranged from 1200 to 2329 m and from 1223 to 2400 m for the occlusal splints without and with mandibular advancement (respectively), with the condition involving mandibular advancement resulting in runners covering ~8% more distance (~1663 ± 402 vs. 1540 ± 397 m, p = 0.03, d
Description
This study investigates kinematical changes during running with a mandibular advancement occlusal splint.