Context

I’m pleased to share one of the most informative articles developed from my thesis:

“Improving Base Running in Baseball: A Linear–Curvilinear Perspective”

Base running makes a meaningful contribution to offensive performance. Previous research estimates that player speed can contribute approximately 25 runs during an MLB season, while concentrating highly skilled base runners within a lineup may increase seasonal production by as many as 70 runs.

Despite its potential value, base running is still frequently evaluated and trained using straight-line sprint measures.

Our review suggests that this may be incomplete.

Linear and curvilinear sprinting appear to be related but distinct motor qualities. MLB players who steal the most bases demonstrate high linear speeds and accelerations. However, higher linear speed and acceleration have not been similarly observed among players running two consecutive bases.

This raises an important practical question:

Does improving straight-line speed automatically produce a better base runner?

The current evidence suggests that it may not.

Curvilinear sprinting requires an inward body lean that changes how force is distributed between the legs. Rather than performing identical functions, the inside and outside limbs assume different mechanical roles.

The inside leg acts primarily as a shock absorber, decelerator, and directional controller. It manages mediolateral forces and helps redirect the athlete’s center of mass along the curved path.

The outside leg functions more as a propulsion engine. It produces greater forward force and uses a stiffer foot position to drive the athlete through the curve.

These mechanical differences extend from the hip to the foot–ankle complex. The outside-leg gluteus medius and biceps femoris demonstrate greater activation, supporting stability and forward propulsion. The inside-leg adductors and semitendinosus contribute to braking and directional control. The gastrocnemius medialis is active in both legs: it assists force absorption and momentum redirection on the inside leg, while supporting foot–ankle stability and efficient force transfer on the outside leg.

The foot also behaves differently on each side. The inside foot adopts a more mobile and absorptive position, while the outside foot becomes relatively stiffer to support an effective push-off.

What does the training evidence show?

The review identified six curvilinear sprint-training studies:

• Curvilinear sprint training produced improvements of approximately 3.36%–4.16% in one intervention, while the linear training group improved by only 0.02%–0.13%.

• Light and heavy sled training produced curved-sprint improvements of approximately 2.54%–5.90%. No significant difference was found between loading conditions.

• In female softball players, 20 weeks of powerlifting improved curvilinear home-to-second performance by 2.88%, compared with a 0.32% improvement in linear home-to-first performance.

These results are promising, but the evidence base remains limited. The six studies included only 127 athletes, approximately 92.1% of whom were male. Five studies involved soccer players, and only one involved softball players. Differences in surfaces, running directions, distances, curve radii, starting positions, and testing procedures also make direct comparisons difficult.

Most importantly, baseball-specific curvilinear training research is still largely absent.

Based on the current evidence, strength and conditioning programs should consider addressing the following areas:

Inside-leg capacity Develop eccentric strength, braking ability, and mediolateral stability through exercises such as Nordic hamstring exercises, Romanian deadlifts, Copenhagen adduction exercises, and inward-lean unilateral squats.

Outside-leg capacity Develop forward propulsion and unilateral power through outside-leg inward-lean squats, triple-extension exercises, and appropriately progressed jumping movements.

Foot–ankle function Train both the absorptive function required by the inside foot and the stiffness and propulsive strength required by the outside foot. Movement-specific progression Progress athletes from controlled full, half, and quarter-circle runs to sharper 90-degree paths and, ultimately, self-selected base-running arcs performed under game-relevant conditions.

Wearable resistance Light external loads—typically 1%–5% of body mass or approximately 200–600 grams—may provide a movement-specific training stimulus without preventing athletes from following a curved path. However, wearable resistance should be progressive, supervised, and treated as an adjunct rather than a replacement for foundational sprint, strength, and coordination training. Portable diagnostic technology Timing gates provide total sprint time but reveal little about what happens during individual steps. High-sampling foot-pod inertial sensors may help practitioners examine center-of-mass motion, step-by-step performance, speed loss, and emerging asymmetries throughout the curve.

The practical message from this article is straightforward:

Base running is not simply linear sprinting around a baseball diamond. It is a complex sequence of acceleration, inward lean, force absorption, redirection, propulsion, and re-acceleration.

Therefore, practitioners should assess and train linear and curvilinear sprinting as related—but distinct—performance qualities.

Advancing this area will require baseball-specific intervention studies comparing linear sprinting, curvilinear sprinting, resisted sprinting, strength and power development, and wearable-resistance training across different ages, positions, competitive levels, and sexes.

Better measurement can lead to better exercise prescription—and, ultimately, safer and more effective base-running development.

Context

Base running science is not just a matter of raw sprint speed.

Our recent article in Applied Sciences, “New Perspectives on Analyzing and Interpreting Base Running Efficiency: An IMU Foot Pod Methodological Case Approach,” presents a practical framework for using IMU foot-pod data to evaluate how base runners organise their mechanics across linear and curvilinear sprinting demands.

The article uses linear sprinting as a baseline and the home-to-second-base sprint as a baseball-specific task to examine how base runners express speed while entering, negotiating, and exiting the curve around first base.

The framework focuses on step-level variables such as:

• Ground contact time • Stride length • Push-off acceleration • Impact acceleration • Inside- and outside-foot asymmetry • Linear-to-curvilinear percent differences

A key message from the paper is that asymmetry should not automatically be interpreted as dysfunction. In curvilinear running, inside- and outside-foot roles may change by segment, task demand, and individual athlete strategy.

For practitioners, this approach offers a more detailed way to investigate why speed is gained, maintained, or lost during base running. Rather than relying only on timing splits or velocity outputs, IMU foot-pod analysis can help identify whether performance changes are associated with longer ground contact times, insufficient propulsion, excessive braking, or altered foot-specific mechanics.

The article is intended as a methodological and interpretive framework, not a set of universal performance norms. Its value lies in showing how wearable sensor data can support more individualized decision-making in baseball performance environments.

Where it’s published:

Read the full article

Base running efficiency is already established in the literature, but there is still a need to better understand how that efficiency is expressed across the different phases of a sprint from home to second base.

In this paper, we build on existing base running efficiency concepts by improving how this metric is visualized and interpreted. Using GPS-derived segment-specific velocity and time data, we show how practitioners can identify where athletes accelerate, lose speed, reaccelerate, and manage the curve around first base.

Rather than focusing only on total time outcomes, this approach provides a more applied diagnostic framework for understanding individual base running strategies and performance limitations in both linear and curvilinear sprinting.

Where it’s published:

Read the full article

Context

This study examined the reliability of in-shoe inertial measurement unit (IMU) foot pod technology for quantifying kinematic variables during baseball base running.

The research evaluated whether foot pod sensors embedded in athletes’ shoes could reliably measure step-by-step mechanics during both linear sprinting (54.7 m) and curvilinear base running (home-to-second base).

Technology Used

The study used Plantiga foot pod sensors, which contain:

6-axis inertial measurement units

Triaxial accelerometers

Triaxial gyroscopes

Sampling frequency of 416 Hz

These sensors allow practitioners to measure detailed biomechanical variables at the step level, providing deeper insight into the mechanical demands of base running.

Variables Analyzed

The study quantified several key kinematic metrics relevant to baseball base running:

Maximum speed

Average speed

Ground contact time (left and right foot)

Stride length

Push-off acceleration

Impact acceleration

These metrics were analyzed across three baseball-specific running segments:

Home to first base

First to second base

Home to second base

This segmental analysis provides a deeper understanding of the mechanical differences between straight-line sprinting and curve running.

Key Findings

The results demonstrated strong reliability across most kinematic variables, indicating that IMU foot pod technology can be used to confidently monitor base-running mechanics.

Major findings included:

No statistically significant performance changes between testing sessions

94% of coefficient of variation values were below 10%

Most reliability coefficients showed good to excellent intraclass correlation values

The majority of measurements demonstrated high stability across testing days.

These results indicate that foot pod technology is a reliable tool for assessing baseball base running mechanics.

Practical Applications

Foot pod technology provides coaches and sport scientists with a deeper biomechanical understanding of base running, which can be used to improve athlete development.

Applications include:

Base Running Diagnostics

Identifying mechanical inefficiencies during curve running

Performance Optimization

Understanding stride mechanics and force application during base running

Training Prescription

Designing drills to improve stride efficiency and acceleration patterns

Injury Risk Management

Monitoring asymmetries between the inside and outside legs during curvilinear running

These insights allow practitioners to move beyond simple timing data and toward mechanically informed base-running coaching.

Context

The first peer-reviewed scientific publication emerging from the Carlos Beltran Baseball Academy—an institution inspired by the standards of a Hall of Famer—marks a decisive step forward in Sport Science by placing Base Running Science at the forefront of evidence-based baseball performance.

This peer-reviewed investigation, published in Applied Sciences (2026), evaluated the between-session reliability of 10 Hz GPS technology for quantifying linear (home-to-first) and curvilinear (home-to-second) base-running performance over 54.7 m in trained high school baseball athletes

The study applied a repeated-measures design across three sessions and examined systematic change, absolute reliability (coefficient of variation, CV), relative reliability (intraclass correlation coefficient, ICC), and practical sensitivity via smallest worthwhile change (SWC).

Key findings of direct relevance to baseball performance departments include:

1, No statistically significant systematic bias across sessions for linear or curvilinear metrics.

2. High absolute reliability, with all CVs <10% and 93% <5%, meeting accepted sport science thresholds for monitoring.

3. Strong relative reliability for most time- and speed-based metrics (ICCs frequently >0.75, many >0.90).

4. Practically sensitive metrics (TE ≤ SWC) included:

1. Linear sprint: time to 41.1 m and 54.7 m; velocity at 27.4 m and 41.1 m.

2. Curvilinear sprint: speed at 41.1 m; peak speed before first base; peak speed before second base and after first base.

Importantly, the study advanced beyond traditional timing gates by quantifying velocity-time-distance signatures across true game-specific curvilinear paths (home-to-second), including acceleration, modulation entering first base, and re-acceleration phases. For MLB organizations and performance shareholders, this provides validated, baseball-specific monitoring variables capable of informing return-to-play decisions, longitudinal talent tracking, workload management, and individualized base-running prescriptions.

Objectively, this article represents a structural advancement in base-running research for three reasons:

1. First Reliability Framework for True Baseball Curvilinear Running: Prior GPS reliability work largely examined soccer or track-based semi-circular protocols. This study uniquely validated GPS metrics using the authentic home-to-second base trajectory, directly reflecting in-game mechanics

2. Integration of Reliability with Practical Sensitivity (SWC vs. TE): By formally comparing typical error against smallest worthwhile change, the paper moves the field from descriptive measurement toward decision-making science—critical for MLB high-performance departments.

3. Establishment of Monitoring Benchmarks: The identification of specific robust metrics (e.g., speed at 41.1 m in both linear and curvilinear contexts) provides the first evidence-based recommendation set tailored specifically to baseball base running.

Within the broader sport science ecosystem, base running has historically been under-quantified relative to pitching biomechanics and hitting analytics. This publication elevates base running from observational coaching practice to a quantifiable performance domain with validated measurement parameters. As a result, it positions Base Running Science as a legitimate sub-discipline within applied baseball performance research.

For the Carlos Beltran Baseball Academy, this work does more than contribute data—it establishes institutional credibility in peer-reviewed sport science, signaling a transition from development academy to research-driven performance leader.

Where it’s published:

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Context

A new peer-reviewed publication further strengthens the scientific basis of Base Running Science by demonstrating that inside–outside foot mechanics differ meaningfully during curvilinear sprinting in baseball. A new peer-reviewed publication further strengthens the scientific basis of Base Running Science by demonstrating that inside–outside foot mechanics differ meaningfully during curvilinear sprinting in baseball.

Published in Asymmetry (2026), this study evaluated trained high school baseball players and quantified ground contact time (GCT), stride length (SL), push-off, and impact during both linear and curvilinear sprinting.

The findings were clear:

1. In linear sprinting, the outside foot demonstrated:

1. shorter stride length from L2–L4 (−0.76% to −1.34%)
2. greater push-off from L1–L4 (2.95% to 4.39%)
3. greater impact in L1 (5.63%)

2. In curvilinear sprinting, the inside foot demonstrated:

1. longer GCT in Segments 2–4 (−3.13% to −7.79%)
2. higher push-off (3.83% to 4.39%)

Most notably, the greatest inside–outside asymmetry appeared in Segment 3, indicating that the middle phase of the curve imposes the highest stabilization demands.

These results reinforce an important point:

curvilinear sprinting is not simply linear sprinting performed on a bend. It is a distinct locomotor task with foot-specific and segment-dependent demands.

That distinction matters for:

1. performance assessment
2. training design
3. return-to-play monitoring
4. long-term athlete development

Base running performance cannot be fully understood through straight-line metrics alone.

It must be evaluated in the context of the movement demands the game actually requires.

Base running is measurable. Base running is monitorable. Base running is scientific.

#BaseRunningScience #SportScience #BaseballPerformance #Biomechanics #CurvilinearSprinting

Where it’s published:

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Context

This article is important because it provides contemporary, game-derived sprint performance data from 475 Major League Baseball (MLB) players using high-resolution StatCast-Hawk-Eye tracking technology. Unlike earlier research that relied on hand timing or laboratory sprint tests, this study analyzes actual in-game performance metrics, making the findings highly ecologically valid. By examining linear and curvilinear sprint characteristics within real competition, the article bridges the gap between traditional sprint testing and baseball-specific performance demands. This represents a significant advancement in understanding how speed manifests in elite baseball contexts rather than in generalized track-based assessments.

Additionally, the study challenges the long-standing assumption that linear sprint speed alone determines base running success. It demonstrates that while early acceleration strongly predicts stolen base performance, it does not adequately explain performance in running two bases, which requires curvilinear sprint ability. This distinction is critical because it reveals that base running performance is biomechanically multidimensional. By differentiating linear and curvilinear sprint characteristics, the article reframes base running as a specific performance domain that requires targeted assessment and training strategies.

I’m excited to share our article introducing the Curvilinear Ability Test (CAT), a new field-based assessment designed to better capture the movement demands of baseball and softball base running. Unlike traditional change-of-direction tests, the CAT integrates curvilinear sprinting and change-of-direction speed to reflect the realities of how athletes actually move around the bases.

A key point from this work is that base running is not just about linear speed. The CAT was proposed to provide coaches and sport scientists with more specific information about curvilinear ability, COD performance, and segmental timing, helping identify movement strengths and weaknesses that may be missed by conventional tests.

This is an important step toward more sport-specific evaluation in baseball and softball, and I’m excited about its practical applications for talent identification, performance profiling, and training design.

#BaseRunning #Baseball #Softball #SportScience #StrengthAndConditioning #PerformanceTesting #ChangeOfDirection #CurvilinearSprinting #SportsPerformance

Where it’s published:

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