The TAP® Incline Board Technical White Paper: Rationale and Evidence

Evidence tiers used in this paper

• Tier 1: peer-reviewed journal research.
• Tier 2: graduate theses, dissertations, and conference proceedings.
• Tier 3: practitioner observation, field use, and news reports.

These tiers identify source type and review status, not certainty of effect. Directness to the board, study design, sample size, controls, and how outcomes were measured determine how much weight a finding receives. A single-case journal study is not stronger than a well-designed thesis simply because of its tier.

1. Purpose and Scope

Oates Specialties works where field practice often runs ahead of laboratory study, a gap described in the Oates Education Hub article “The Lag.” Practitioners frequently find useful training methods years before research measures them. The TAP® Incline Board is offered on that basis: designed from research on mounds, sloped surfaces, landing mechanics, and practice design, and used in the field by practitioners, ahead of controlled study of the device itself. The Lag cuts both ways: some field practices are later confirmed, while others prove ineffective, task-specific, or suited only to some athletes. During that interval, Oates explains the rationale and its limits, and coaches evaluate individual responses within the product’s operating conditions. Related research gives a reason to explore the idea, not an assurance of the result.

This paper serves readers who want to examine that reasoning in detail: sports scientists, clinicians, coaches, program directors, and knowledgeable athletes. It separates what has been measured, what has been reported by practitioners, and what remains a hypothesis. It is written so that the hypothesis can be evaluated by coaches with individual athletes and by independent researchers and, if the evidence warrants, rejected.

2. Device Geometry and Physics

2.1 Dimensions

• Measured geometry used for these calculations: 10 inches at the highest point, a 30-inch sloped surface, and a slope of approximately 15.7 degrees. The low edge sits above the ground, so the surface angle is less than a simple 10-over-30 right triangle would suggest. Confirm production measurements, low-edge contact, and support height at the chosen mark before using the table as a placement reference.
• Surface: bonded rubber sheet.
• Width: approximately 20 inches. The low edge sits about 1.7 inches above the ground; that offset is included in the heights above and must be included when establishing a mark.
• Weight: approximately 30 pounds; folds via a hinged joint with locking supports; designed for turf.

2.2 Height at any point

Height above the ground at any point = the low-edge height (about 1.7 inches) plus the distance along the surface multiplied by sin 15.7 degrees (about 0.27). The surface climbs about 1 inch for every 3¾ inches along it. Measured marks: 6.75 inches along the surface stands 3.5 inches off the ground; 10.5 inches stands 4.5 inches; 14.25 inches stands 5.5 inches; 18 inches stands 6.5 inches.

2.3 Matching a regulation mound’s drop

On a regulation mound, the slope begins 6 inches in front of the pitching rubber and falls about 1 inch per foot. The drop from the mound’s top to the landing point is therefore approximately (stride in feet minus 0.5) inches.

Stride is measured from the ball of the drive foot to the ball of the landing foot. The match is geometric: it equates height change, not surface conditions, and it does not by itself produce a mound-like movement response. Positions are the board’s measured drive-foot marks. The low edge sits above the ground, so the surface climbs about 1 inch for every 3¾ inches along it. In the sideways stance the shoe’s length runs across the board’s 20-inch width. A conservative program range for the drive foot is about 9 to 24 inches along the surface (about 4 to 8 inches of drop). Positions are approximate; the exact match depends on measured stride, foot placement relative to the rubber, and the actual profile of the athlete’s mound.

Average fall across the stride is arctangent(drop divided by stride). A regulation mound is level for 6 inches in front of the rubber and then falls about 1 inch per foot (about 4.8 degrees), so its average fall across 4-, 5-, and 6-foot strides is about 4.2, 4.3, and 4.4 degrees. At a mound-matched position the board produces the same average, because the drop and the stride are the same. From the top edge of the board with a 5-foot stride, the average is about 9.5 degrees.

2.4 Grip and downhill pull

• Minimum friction coefficient to stand still without sliding: tan 15.7 degrees = 0.28.
• Force along the surface at rest: sin 15.7 degrees = 0.27 times body weight, about 54 pounds for a 200-pound athlete.
• For comparison, Chang and colleagues distinguish friction required during level walking from friction available at the shoe–floor interface and examine slip probabilities (Tier 2). These task- and measurement-dependent values are not safety thresholds for board use.

These are idealized static calculations for a body supported on the inclined surface. They are not measurements of shoe-to-board friction, and they do not describe a pitcher whose weight shifts between two contacts during a dynamic push. Grip during the push depends on the rubber sheet, footwear, sole wear, surface contamination, and movement speed, and has not been measured on the board (Section 8.4).

2.5 Drive-foot tilt and foot angle

In the standard orientation, the slope runs across the drive foot, inside edge lower. When the foot is turned by an angle φ from the board’s edge:

Side-to-side tilt = arcsin(0.27 × cos φ)

Toe-to-heel tilt = arcsin(0.27 × sin φ)

Here 0.27 is the sine of 15.7 degrees.

Field demonstrations show the drive foot set at a natural angle rather than strictly parallel to the edge (Tier 3).

2.6 Energy from the drop

As an illustration, the gravitational energy change of a mass descending through a vertical distance h is m × g × h. For a 200-pound (90.7 kg) mass:

These calculations illustrate the energy change of a mass falling through the stated distance. In pitching, the relevant displacement is that of the body’s center of mass, which has not been measured on this board and can differ from the support-height difference in either direction. The values are not estimates of added pitching energy, ball speed, or landing absorption.

2.7 Starting height and timing

Changing the starting height changes the geometry of the task. Its effect on the timing of front-foot contact is unknown, because the athlete can change movement speed, foot path, knee action, and stride. Free-fall calculations for an object dropped from rest do not describe an actively moving, supported athlete, so timing should be measured rather than predicted.

3. The Working Hypothesis

Short, mixed blocks of throws from the TAP® Incline Board, set to a mound-matched drop and chosen for a named coaching problem, will produce changes in drive-leg push, pelvis timing, or landing mechanics that carry over to subsequent mound throws in some athletes, and those changes can be retained when the board is faded.

The hypothesis rests on four linked premises

1. A change to the support surface under the drive leg was followed by less pelvic or hip opening in pitching and batting, and by greater drive-leg force in the pitching case, on test throws after practice (Section 4.1).
2. Mound and flat-ground pitching differ most at front-foot contact. Because a mound’s drop and downhill landing occur together, these studies do not isolate the drop’s contribution (Section 4.2).
3. Preserving relevant task information and including mound throws gives a reason to test transfer and a way to observe it. The cited studies do not show that this board-and-mound arrangement transfers better than matched mound-only practice (Section 4.4).
4. Training on angled surfaces can transfer to flat performance surfaces (Section 4.5).

Related evidence informs these premises at different levels of directness. Neither the combined intervention nor its advantage over matched mound-only practice has been established on this device.

4. Evidence

4.1 Inclined-platform studies in baseball

Kageyama, Suzuki, Fujii, and Maeda (2015). Sports Performance Research 7:42-54. Tier 1, single case. Read in full.

• Participant: one pitcher, age 11.7, height 156.1 cm, mass 40.5 kg, identified as opening the body early with limited trunk rotation after stride-foot contact.
• Equipment: 12-camera motion capture at 500 fps with 37 markers; two Kistler force plates at 2000 Hz; radar gun; soft baseball thrown at a net 10 m away.
• Fixed sequence: Pre (5 maximal throws); verbal coaching to delay hip opening (10 throws) then Post I (5 throws); practice on a platform of about 10 degrees under the pivot leg, with the instruction not to lunge forward (10 throws), then Post II (5 throws).
• Ball speed, maximum / mean (km/h): Pre 88.0 / 86.0; Post I 88.0 / 86.0; Post II 89.0 / 88.0.
• Lower-trunk (pelvis) angle at stride-foot contact (degrees): 22.3 / 20.6 / 16.4, indicating less opening after platform practice.
• Pivot-leg force toward the target, peak (N/kg): 6.9 / 7.0 / 7.4, about 7% higher after platform practice.
• Stride-leg peak braking force (N/kg): -9.8 / -9.5 / -9.7, essentially unchanged; the authors describe more force only from maximum external rotation to release.
• Measurement: motion and force were recorded on the Pre, Post I, and Post II test throws. The platform practice throws themselves were not recorded, so the study does not show the athlete’s mechanics or forces while on the platform.
• Instruction: platform practice was paired with the verbal instruction not to lunge forward, so the result cannot be attributed to the platform alone.
• Not reported: the platform’s slope direction relative to the throwing line, or its dimensions.
• Limitations acknowledged or evident: one athlete, no statistics, fixed order so a warm-up or practice effect cannot be excluded, immediate effects only, very small velocity changes measured over 5 throws.
• Interpretation note: the pre-test pelvis angle shows the pelvis was already partly rotated at foot contact, as is normal. The target in this study, and on the board, is rotation that comes sooner than is useful for the athlete, not any rotation before contact. Park (2024) shows that pelvis orientation at contact varies widely among effective pitchers.
• Relevance: the closest published analog to the board. The direction of change, a more closed pelvis at foot contact and more drive-leg push toward the target, matches the board’s intended uses.

Itoh, Suda, Yamada, Ogawara, Ohgimi, and Miyazaki (2018). Tokai Journal of Sports Medicine Science 30:39-44. Tier 2. Read in full.

• Tier note: the paper is presented as an original article in a university-published journal. It is placed in Tier 2 because the journal’s peer-review process has not been confirmed.
• Six middle school players (about 13.5 years), single session of tee batting: 3 flat trials, 10 trials on a 20-degree platform under the pivot leg, 3 flat trials.
• Methodological limits: the abstract reports age 13.5 ± 0.5 years, while the methods report 13.6 ± 0.74 years; height and mass also differ between those sections. The authors analyzed the last pre-intervention trial and the first post-intervention trial, rather than averaging all three trials. They selected the first posttrial to capture the immediate residual feel. This limits the assessment of repeatability and does not establish retention. Source check: these details are present in the original PDF, pages 39–41.
• Lower-body (hip) rotation at impact was significantly reduced after platform practice (p < 0.05). Upper-body rotation, trunk twist, and center-of-mass speed toward the pitcher did not change significantly; bat speed was not measured.
• Angle rationale: in pilot testing, 30 degrees made loading the pivot leg difficult, and the 10 degrees used in earlier work did not make adolescent players aware of pivot-leg loading. The authors chose 20 degrees.
• No safety outcomes, platform material, footwear, or slope direction were reported. The study had university ethics approval with guardian consent; ethics approval is not evidence of product safety.
• Relevance: the closest published precedent for the board’s angle under the back leg (20 degrees versus about 15.7), in adolescent players, though in batting rather than pitching. It does not establish an optimal pitching angle or the safety of a cross-foot pitching surface.

Kageyama, Nakashima, Suzuki, and Maeda (2017). Sports Performance Research 9:94-110. Tier 1, single case.

• One university hitter, four weeks of practice with an inclined step on the stride-leg side, five days per week.
• Forward center-of-mass travel fell about 42% (takeback) and 56% (stride); swing speed did not change; game batting average rose from .200 (1 for 5) to .364 (4 for 11).
• Relevance: an inclined support used deliberately to alter weight shift over several weeks. The movement findings carry more weight than the very small batting sample.

Miura (2015). Master’s thesis, Naruto University of Education. Tier 2.

• Five batters on flat, 5-degree downhill, and 5-degree uphill surfaces.
• A group tendency for the downhill surface to limit center-of-gravity movement, but no consistent individual pattern; the author concluded the effect was not established.
• Relevance: a mixed result, a reminder that not every slope produces a reliable change.

Summary of 4.1: these are related studies, not replications of one setup. Two used a pivot-leg incline: Kageyama (2015), a youth pitching case with immediate post-practice measurements; and Itoh (2018), six adolescent batters with less lower-body rotation at impact. Kageyama (2017) used a stride-side incline over four weeks and reported phase-specific reductions in forward drift. Miura (2015) reported no consistent effect. The positive studies are small single-session or single-case investigations without randomized concurrent control groups or delayed retention testing. Pre/post comparisons do not isolate the incline from instruction, order, or additional practice.

4.2 Pitching experiments on surface and slope

Fleisig, Diffendaffer, Ivey, and Oi (2018). Am J Sports Med. Tier 1.

• 21 youth pitchers (12 to 13 years) on flat ground, a 6-inch mound, and a 10-inch mound.
• 10 of 25 kinematic measures differed by surface, 8 of them at front-foot contact (stride length, lead-foot position and angle, lead-knee flexion, pelvis rotation, trunk lateral tilt, shoulder external rotation, elbow flexion). On flat ground, pitchers used shorter strides and more lead-knee flexion. The 6- and 10-inch mounds did not differ from each other. Ball velocity and shoulder and elbow kinetics did not differ.

Kageyama, Suzuki, Fujii, Nakamoto, Wada, and Maeda (2016). Japan J Phys Educ Health Sport Sci 61(2):517-535. Tier 1.

• 12 high school and college pitchers. The mound produced higher maximum and mean velocity, greater stride-leg ground reaction force, greater hip and knee motion on both legs, and greater pelvis and trunk angular velocity than flat ground.

Diffendaffer, Slowik, Lo, Drogosz, and Fleisig (2019). J Sci Med Sport 22(7):858-861. Tier 1.

• 20 college pitchers on 6-, 8-, 10-, and 12-inch mounds. Most joint-angle differences were under 2 degrees; fastball elbow varus torque about 90 to 91 N·m; no differences in velocity or break.

Chen, Huang, Lin, and Ko (2014). ISBS Proceedings. Tier 2.

• 8 adolescent pitchers; the mound condition used a landing plate tilted 4 degrees. The mound raised trailing-leg propulsive force to about 120% and lead-leg braking to about 108% of flat-ground values; ball velocity did not differ.

Dowling, McElheny, Camp, Ling, and Dines (2020). Orthop J Sports Med 8(12). Tier 1.

• 21 high school pitchers. Mound pitches were faster than flat-ground pitches, without a significant increase in elbow varus torque.

Nissen and colleagues (2013), Sports Health; Cage and colleagues (2019), J Sports Med Allied Health Sci; Gdovin (2017), dissertation. Tiers 1 and 2.

• Each reported slightly higher shoulder or elbow loading from the mound than from flat ground in small samples.

Ryu (2017). PhD dissertation, Korea University. Tier 2. Findings from the author’s abstract.

• 7 university and high school pitchers on flat ground and on 5- and 10-degree mound slopes.
• Release angle was significantly higher on sloped surfaces than on flat ground and peaked at 5 degrees; velocity and several trunk and arm variables were highest at 5 degrees and lowest at 10 degrees; release height rose with slope; horizontal release distance was lower at 10 than at 5 degrees. The author recommended avoiding slopes over 10 degrees.
• Important distinction: Ryu changed the slope of the entire mound, including the landing. The board matches a mound’s drop and tilts only the drive-foot surface. The findings, available here only from the abstract, suggest that responses may differ across whole-mound slopes; they do not determine the board’s preferred height or angle. For the angle of the drive surface, Itoh (2018) is the closer precedent.

Baseball Development Group (2021). Tier 3.

• 8 athletes striding up onto a mound (uphill landing): slower throws at the same perceived effort, shorter strides, a more closed pelvis at foot plant, about 7 degrees more lead-knee flexion, and later lead-knee extension. No statistical tests.

Erickson and colleagues (2021). ISAKOS ePoster. Tier 2.

• 36 youth pitchers on a 15-week velocity program; gains did not differ whether tested on flat ground or the mound.

Raasch and colleagues (2008), reported in Pacific Standard. Tier 3.

• A news report of a mound-height study states that the front foot lands earlier in the delivery on flat ground than on a slope. No values were reported in the news account.

Summary of 4.2: mound pitching changes lower-body mechanics at front-foot contact compared with flat ground; because the drop and downhill landing change together, these studies do not isolate which feature is responsible; 6- and 10-inch mounds produced similar mechanics; velocity and arm-loading differences are small and inconsistent; a steeper whole-mound slope (10 degrees) performed worse than 5 degrees in the one study that tested it, reported here from its abstract.

4.3 Correlational pitching biomechanics

Park, Lee, Cho, Cho, and Kim (2024). Korean Journal of Sport Science 35(4):600-608. Tier 1. Read in full.

• 40 Korean professional pitchers grouped by normalized stride length (about 102% vs. 93% of height).
• The longer-stride group had greater drive-leg anterior impulse (22.67 vs. 20.37 N·s/BW), a more open pelvis and trunk at stride-foot contact, higher pelvic angular velocity, and later stride-foot contact, maximum external rotation, and release as percentages of the pitch cycle.
• Ball velocity did not differ (135.18 vs. 136.60 km/h, p = .374); lead-leg braking force and impulse did not differ.
• Relevance: more drive-leg push, a longer stride, or a particular pelvis angle is not automatically better. Stable velocity does not imply an unchanged delivery. Between-group design; it does not show what happens when one athlete changes stride.

Giordano, Nebel, Fava, and Oliver (2024). Am J Sports Med 52(12):3110-3117. Tier 1.

• In-game observations of 64 college pitchers linked greater vertical center-of-mass deviation in either direction during the stride with higher velocity, with no detected association with elbow valgus torque. The measure describes deviation from a straight-line center-of-mass path between peak knee height and foot contact, not simply total vertical descent. This association does not establish that instructing an athlete to rise or drop will increase velocity.

Dowling, Manzi, Raab, Coladonato, Dines, and Fleisig (2024; online 2022). Sports Biomechanics 23(12):2664-2674. Tier 1.

• Three-dimensional motion capture assessed 322 professional pitchers. The high-velocity group (99 pitchers) showed more lead-knee extension from contact to release than the low-velocity group (88 pitchers), approximately 17 versus 5 degrees, and higher elbow varus torque, approximately 91.1 versus 84.0 N·m. Across the full sample, lead-knee extension and extension velocity were statistical predictors of ball velocity, but not elbow varus torque. These associations do not show that prescribing additional extension increases velocity or reduces loading.

Plummer, Bordelon, Wasserberger, Opitz, Anz, and Oliver (2021). Int J Sports Phys Ther 16(5):1323-1329. Tier 1.

• 25 high school pitchers: greater drive-leg hip internal rotation was associated with less trunk rotation toward home at foot contact.

4.4 Practice design, constraints, and transfer

• Constraints-led approach. Movement emerges from individual, task, and environmental constraints; changing the environment can shape a movement solution without prescribing it (Gray and Sullivan, 2023; Tier 3 practitioner text).
• Representative learning design. Practice that preserves the information and movement of competition is argued to transfer best (Pinder and colleagues, 2011; Tier 1, theoretical).
• Review evidence. About 78% of 18 constraints-led studies reported skill gains, but most were short and rated low in quality (Clark and colleagues, 2019; Tier 1). A published commentary disputed the review’s methods (Newcombe and colleagues, 2019; Tier 1).
• Mixed practice. In 30 junior college hitters, random practice transferred better than blocked practice (Hall and colleagues, 1994; Tier 1).
• Practice versus learning. Softball pitchers who looked better under traditional practice performed the same as a constraints group once practice conditions were removed (Fava, 2025; Tier 2). In a throwing task, adding unstable-surface practice did not improve accuracy more than stable practice; both groups improved (Moreno and colleagues, 2023; Tier 1). Surface variability alone did not add a learning benefit.
• Error amplification. Exaggerating one’s own main error beat direct instruction in 13-year-olds’ standing long jump (Milanese and colleagues, 2008; Tier 1) and in weightlifters’ bar path with one-week retention (Corte and colleagues, 2013; Tier 2). In a laboratory locomotor task, the authors interpreted amplification as more helpful for initially skilled learners than for less-skilled learners, while random variation helped broadly; the overall effect of training strategy on transfer was not statistically significant, and the skill-by-strategy interaction only approached significance (Marchal-Crespo and colleagues, 2017; Tier 1). Findings are mixed.
• Attentional focus. In low-skill throwers, an external focus improved accuracy and pattern change (Southard, 2011; Tier 1). Evidence in experienced athletes and over longer training is less uniform, so outcome-focused cues are treated here as a useful option rather than a guarantee.
• Drill representativeness. Eight common pitching drills each altered trunk or shoulder kinematics differently from mound pitching, with wide individual variation (Dobos and colleagues, 2023; Tier 2).
• Timeframes. A six-week multicomponent program in 17 college/professional pitchers was followed by changes in selected measures, but no significant changes in the reported foot-contact measures or maximum pelvis/trunk angular velocities (Marsh and colleagues, 2018; Tier 1). There was no control group. The program included weighted implements, strength/mobility work, and manual therapy, so it cannot isolate one treatment or establish a board learning schedule. Source check: the seven-author list, sample, and these findings were checked in the original article, Methods and Table 5. An eight-week adolescent core program increased trunk-rotation strength/power, ball speed, and elbow varus moment, while kinematic changes did not differ between groups (Oyama, Palmer, and Laudner, 2026; Tier 1).

4.5 Angled surfaces in other sports and tasks

The following studies are contextual analogies, not tests of the board. Similar slope angles do not imply similar contact mechanics, loading, learning, or safety. These studies are not used to select a safe pitching angle or prescribe a practice dose.

• Training transfer. Six weeks of sprint training on 3-degree up and down slopes raised flat-ground top speed 3.7%, retained after 3 weeks without training (Bissas and colleagues, 2022; Tier 1).
• Acute slope comparison. Thirteen NCAA Division III athletes ran 40-yard sprints over five downhill slopes in randomized order. Approximately 5.8 degrees produced the fastest times among the tested conditions (Ebben, 2008; Tier 1). This was an acute running comparison, not a training dose, retention test, or pitching-angle recommendation. Source check: the sample, distance, slopes, and result were checked against the publisher’s abstract; the author record identifies William P. Ebben.
• Posture on slopes. Golfers on 10-degree uphill and downhill slopes adapted posture and leg angles while maintaining clubhead speed (Poolsawat and Lawsirirat, 2026; Tier 1). On 5-degree slopes, more skilled golfers were less disrupted (Nolan and colleagues, 2024; Tier 2).
• Sideways tilt. In 19 runners, a 6-degree cross-slope with lateral foot elevation raised external ankle eversion moment by 35%, while medial elevation lowered it by 16% (Willwacher and colleagues, 2013; Tier 1). The standard inside-edge-lower board setup is a lateral-elevation condition, but this does not predict all joint responses during pitching. Cross-slope walking and running also changed sideways ground-reaction forces (Damavandi and colleagues, 2012; Tier 1). In a separate 10-degree medially inclined drop-landing task, joint moments rose or fell depending on the joint and phase (Dami and colleagues, 2025; Tier 1). Dami’s full-text results report these as internal joint moments; for example, ankle inversion moment increased during the first 0–5% of landing, while knee internal-rotation moment decreased in several early intervals. None of these studies tested this pitching configuration.
• Decline loading. Five subjects performed single-leg decline squats at angles from 0 to 30 degrees. The authors reported greater patellar-tendon force above 15 degrees and changes in how joint moments were distributed (Zwerver and colleagues, 2007; Tier 1). This supports considering knee demands in decline tasks; it does not predict pitching loads or establish safe board angles.
• Landing surface. A forward-down 3.6-degree landing surface raised braking force about 10% of body weight compared with flat ground (Hagins and colleagues, 2007; Tier 1).
• Foot wedging and hip muscle activity. A medial wedge reduced gluteus medius activity in single-leg stance (Hong and colleagues, 2011; Tier 1). The board tilts the drive foot the opposite way; its effect on hip muscle activity is unmeasured.

4.6 Footing, grip, and readiness

• Slope perception. People judge accurately and consistently whether an inclined surface can be stood on, and adjust when their center of mass changes (Regia-Corte and Wagman, 2008; Tier 1).
• Anticipatory adjustment. When people expect a slippery floor, they change foot contact in ways that reduce shear and slip distance (Cham and colleagues, 2003; Tier 2).
• Training on challenging footing. A balance-training program cut ankle sprains in 765 high school athletes (6.1% vs. 9.9%; risk ratio 0.56) (McGuine and Keene, 2006; Tier 1). Across 7 trials and 3,726 athletes, proprioceptive training reduced sprains about 35% (relative risk 0.65) (Schiftan and colleagues, 2015; Tier 1). These are background on structured balance training. They do not test a board readiness check, pitching on an incline, or full-effort grip.
• Worn mounds. The rubber area and landing spot wear into holes during games, and pitchers manage this footing routinely (Fox Sports; Tier 3).
• Readiness ratings. Zhang and colleagues (2025; Tier 1) studied 58 adults with lower-extremity injuries. The two physical therapists making inter-rater judgments had 35 and 11 years of experience and also completed a 15-minute practice session. Agreement varied by movement component, scale, and reassessment interval; some combined scores were less consistent than component scores. These findings do not show that brief practice prepares an inexperienced coach to make equivalent judgments, and they do not validate the board’s holds or step-down checks. Source check: author list, participants, rater experience, and procedures were checked in the original full text.
• Ankle screen. The weight-bearing lunge test showed intra- and inter-rater reliability of 0.97 to 0.99 (Bennell and colleagues, 1998; Tier 1).
• Fatigue. Across 25 studies, reported velocity declines ranged from 0.6% to 5.6%, with varied changes in knee flexion and arm position (Birfer, Sonne, and Holmes, 2019; Tier 1). This is a range across different studies, not a pooled effect or an inevitable response. Fatigue can cloud comparisons; the review does not establish a safe board effort or schedule.
• Video measurement. Visual analysis agreed with laboratory motion capture on 11 of 17 pitching measures in youth pitchers (Nicholls and colleagues, 1999; Tier 2). A single side view suits stride, sagittal knee motion, and trunk posture. Pelvis orientation needs a second view, and phone video cannot measure joint loading or precisely quantify three-dimensional pelvic rotation.

5. Mechanism Model

Feature 1: The drop

• What changes: the height from drive foot to landing, matched to a regulation mound by foot position.
• Evidence: mound pitching is associated with longer strides, less lead-knee flexion, and different pelvis position at foot contact compared with flat ground (Fleisig 2018; Kageyama 2016). The drop and the downhill landing change together in these studies, so the drop’s own contribution is not isolated. 6- and 10-inch mounds produced similar mechanics.
• Confidence: low to moderate that the drop contributes; untested that the board’s drop reproduces mound landing patterns.

Feature 2: The drive-foot surface

• What changes: a 15.7-degree surface under the drive foot, tilted across the foot in the standard orientation.
• Evidence: inclined platforms under the pivot leg were followed by less early pelvis or hip opening (Kageyama 2015; Itoh 2018), and, in the pitching case, higher drive-leg force toward the target on test throws after practice (Kageyama 2015). Lateral elevation of the foot raised the ankle eversion moment in running, and side-to-side ground forces rose on cross-slopes (cross-slope studies). Practitioners use the surface to load the back hip and resist forward drift (Tier 3).
• Confidence: low to moderate. The two pivot-leg studies point the same way; magnitude, transfer, and loading at 15.7 degrees under a hard push are unmeasured.

Feature 3: The flat landing

• What changes: the stride foot lands on flat turf rather than a gentle downslope.
• Evidence: a downward-tilted landing raised braking force in a jumping task (Hagins 2007), and lead-leg braking was higher from a mound than from flat ground in pitchers who had no drop on flat ground (Chen 2014). Neither condition matches a drop from an elevated start onto flat turf.
• Confidence: unknown direction. Landing on flat turf changes the contact condition relative to a downslope. The direction and size of its effects on braking force, lead-leg action, and joint loading after board throws have not been measured.

Feature 4: Timing

• What changes: the starting height, and with it the geometry of the stride. Its effect on the timing of front-foot contact is unknown (Section 2.7).
• Evidence: between-group data link longer strides with later relative foot contact in professionals (Park 2024), and a news report states that the front foot lands earlier on flat ground than on a slope (Tier 3). Neither shows what happens when one athlete starts higher or lower.
• Confidence: low. Athletes can change stride and knee flexion, so the response must be measured.

Note on angle: the board’s 15.7-degree drive surface should not be equated with a 15.7-degree mound. At mound-matched positions the average fall across the stride matches a regulation mound’s average, about 4.2 to 4.4 degrees for 4- to 6-foot strides. The relevant angle precedent for the drive surface is the 20-degree pivot-leg platform in Itoh (2018), whose authors found 30 degrees too steep to load and 10 degrees too subtle for adolescents to feel.

6. Protocol Rationale

The ratios, session counts, and schedules below are conservative starting points, not a protocol tested on this board.

These rules support the downhill framework described in Practical Position Paper v1.6 and Training Guide v3.7. Where a rule sets a number, such as a ratio, a session count, an age, or a review window, the number is an Oates policy choice. The cited research informs the direction of the rule; it does not produce the number.

7. Safety Analysis

Precedent: decline foot angles up to 30 degrees have been studied in exercise research (Zwerver 2007); a 20-degree pivot-leg platform was used with adolescent batters (Itoh 2018). Neither study measured safety outcomes for pitching, and neither establishes the safety of this board.

8. Open Questions That Research Has Not Settled

• Whether board-and-mound blocks help more than the same number of extra mound throws.
• How long a change lasts once the board is put away.
• How the tilted drive-foot surface loads the ankle and hip during a hard push.
• How the flat landing changes the way the front leg stops the body.

9. Limitations

• No controlled study of this device exists.
• Mound-versus-flat studies do not separate the effect of the drop from the effect of the downhill landing.
• The three positive inclined-platform reports include one youth pitching case and two batting investigations, using different configurations. They lack randomized concurrent comparison groups and delayed retention tests. The pitching case has no inferential statistical analysis. A separate small thesis reported no consistent effect. The combined evidence does not establish a device-specific training benefit.
• The closest pitching study used about 10 degrees and did not report slope direction; the closest angle precedent (20 degrees) is from batting.
• The cross-slope loading studies cited here used angles up to 10 degrees and did not examine pitching. This describes the cited evidence set, not an exhaustive limit of the published literature.
• The Ryu dissertation findings are taken from the author’s abstract; the full Korean text has not been reviewed.
• The mechanism model links features to evidence by analogy in several places, identified in Section 5.

10. Manufacturer and Evidence Statement

Oates Specialties LLC manufactures and sells the TAP® Incline Board. The rationale in this paper and its companion documents draws on related research and reported practitioner experience, including the Texas Baseball Ranch’s field experience. No controlled research study has established the training effects of this exact product.

This paper provides information and an illustrative practice framework for coaches selecting tools for appropriately prepared athletes under adult supervision. The coach determines the athlete’s suitability, coaching goal, and practice exposure within the product’s stated operating conditions. Athlete feedback and subsequent mound performance guide continued use.

Published research describes the studies cited; references to researchers do not imply product endorsement. Oates makes no claim of increased velocity or reduced injury risk, and the board does not replace mound training. Clinical assessment, rehabilitation, and return-to-throwing decisions remain with qualified healthcare professionals. Readiness and footing checks are practical observations rather than validated clinical clearance tests. Grip depends on footwear, sole wear, surface condition, and movement.