Stuart McErlain-Naylor

Lecturer in Sport and Exercise Biomechanics

University of Suffolk


Dr Stuart McErlain-Naylor is a Lecturer in Sport and Exercise Biomechanics and Course Leader for BSc (Hons) Sport and Exercise Science at the University of Suffolk, UK.

His research interests include kinetic and kinematic analysis of sporting techniques (mostly ball striking sports), analysis of post-impact accelerations, and the mechanics of flywheel resistance exercise.

Stuart organised and hosted the ISBS Sports Biomechanics Lecture Series and is Social Media Editor for the journal Sports Biomechanics.

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  • sporting technique
  • impact accelerations
  • flywheel exercise


  • PhD in Sports Biomechanics, 2018

    Loughborough University

  • Postgraduate Certificate in Academic Practice, 2020

    University of Suffolk

  • BSc in Sport and Exercise Sciences, 2013

    Loughborough University

About Me

Research Projects

Cricket Batting

The biomechanical determinants of cricket batting performance


The biomechanical determinants of badminton jump smash performance

Flywheel Exercise

Flywheel (isoinertial) eccentric overload exercise induced post-activation performance enhancement

Impact Accelerations

The effect of compliance on post-impact elastic wave accelerations

Most Recent Publications

Post flywheel squat potentiation of vertical and horizontal ground reaction force parameters during jumps and changes of direction

(1) Background: The aim of the study was to determine the post-activation performance enhancement (PAPE) of vertical and horizontal ground reaction force parameters during jumps and change of direction following flywheel squat exercise using two different flywheel inertias. (2) Methods: Eleven male athletes performed a countermovement jump (CMJ), standing broad jump (SBJ), and “modified 505” change of direction (COD) in a control condition and 6 minutes following three sets of six repetitions of flywheel half squats at one of two inertias (0.029 kg·m2 and 0.061 kg·m2). Peak directional ground reaction force, power, and rate of force development were calculated for each test. (3) Results: Higher inertia flywheel squats were able to acutely enhance CMJ peak vertical force (Bayes Factor (BF10) = 33.5, very strong; δ = 1.66; CI: 0.67, 2.70), whereas lower inertia flywheel squats were able to acutely enhance CMJ peak vertical power (BF10 = 3.65, moderate; δ = 0.93; CI: 0.11, 1.88). The vertical squat exercise induced no PAPE effect on resultant SBJ or horizontal COD ground reaction force parameters, nor were any differences observed between the inertias. (4) Conclusions: Researchers and practitioners should consider the kinetic and kinematic correspondence of a pre-load stimulus to the subsequent sport-specific activity (i.e., flywheel squat to CMJ).

Concentric and eccentric inertia-velocity and inertia-power relationships in the flywheel squat

The aim of this study was to evaluate the effects of varying flywheel inertia on velocity and power during flywheel squats. Fifteen healthy physically active males performed 6 maximal effort flywheel half-squats at each of 0.029, 0.061, 0.089, and 0.121 kg·m2, with velocity recorded via 3D motion capture and power recorded via inbuilt transducer. Peak concentric velocity (χ² = 37.9; p < 0.001), peak eccentric velocity (χ² = 24.9; p < 0.001), mean concentric velocity (F(3) = 52.7; p < 0.001), and mean eccentric velocity (χ² = 16.8; p < 0.001) all tended to decrease with increases in flywheel inertia, whereas the ratio of peak eccentric to peak concentric power (F(3) = 4.26; p = 0.010) tended to increase. Flywheel inertia had no significant effect on peak concentric or eccentric power, or the ratio of eccentric to concentric peak or mean velocities. The best fit subject-specific inertia-velocity relationships were reported for peak concentric velocity (median linear R2 = 0.95, median logarithmic R2 = 0.97). The results suggest that velocity, rather than power, should be used to prescribe and monitor flywheel squat exercise intensities, and that individualized linear relationships between inertia and peak concentric velocity can be used for this purpose.

Post flywheel squat vs. flywheel deadlift potentiation of lower limb isokinetic peak torques in male athletes

The present study investigated the post-activation performance enhancement (PAPE) of isokinetic quadriceps and hamstrings torque after flywheel (FW)-squat vs. FW-deadlift in comparison to a control condition. Fifteen male athletes were enrolled in this randomised, crossover study. Each protocol consisted of 3 sets of 6 repetitions, with an inertial load of 0.029 kg.m2. Isokinetic quadriceps (knee extension) and hamstrings (knee flexion) concentric peak torque (60º/s) and hamstring eccentric peak torque (−60º/s) were measured 5 min after experimental or control conditions. A significant condition (PAPE) effect was reported (f = 4.067, p = 0.008) for isokinetic hamstrings eccentric peak torque following FW-squat and FW-deadlift, but no significant differences were found for quadriceps and hamstrings concentric peak torques. The significant difference averaged 14 Nm between FW-squat vs. control (95% CI: 2, 28; d = 0.75, moderate; p = 0.033), and 13 Nm between FW-deadlift vs. control (95% CI: 1, 25; d = 0.68, moderate; p = 0.038). This study reported that both FW-squat and FW-deadlift exercises are equivalently capable of generating PAPE of isokinetic hamstrings eccentric torque. Practitioners may use these findings to inform strength and power development during complex training sessions consisting of flywheel-based exercises prior to a sport-specific task.

Experiences of undergraduates publishing biomechanics research

The aim of this study was to investigate student experiences of publishing undergraduate research in biomechanics. A total of twenty-nine former students with experience of publishing peer-reviewed undergraduate biomechanics research completed an online survey regarding their perceived benefits, level of involvement, and experiences in aspects of the research process. On average, students perceived their experiences to be ‘largely helpful’ or greater in all aspects. Areas were identified corresponding to: the greatest perceived benefits (e.g. understanding of the research process); the least perceived benefits (e.g. statistical analysis skills); the greatest student involvement (e.g. reading relevant literature); and the least student involvement (e.g. developing hypotheses and/or methods). A thematic analysis of open question responses identified themes relating to: future career; skills; scientific process; intra / interpersonal factors; and pedagogy. Common intended learning outcomes may be achieved through involvement in the research process independently of the level of staff involvement. Staff should be encouraged to involve students in publishable biomechanics research projects where this is possible without compromising research standards and should explore ways of recreating the publishing process internally for all students.

A practical open-source comparison of discrete and continuous biomechanical analysis techniques

Recent work has challenged the practice of extracting and analysing discrete summary metrics from continuous biomechanical data. This paper presents a practical comparison of candidate data analysis techniques including frequentist and Bayesian discrete analysis, frequentist and Bayesian statistical parametric mapping, and vector coding. Example 1 compares knee and hip flexion / extension angles during flywheel and barbell squats. Example 2 compares pelvis and thorax transverse rotations during badminton jump smashes by an international and a regional player. All example data and scripts are open-source. Statistical parametric mapping enables comparison of continuous biomechanical variables at time points other than discrete local optima. Combining this approach with vector coding provides information regarding differences in proximal-distal joint coordination throughout a movement. These continuous open-source methodologies can increase the validity and intuitive practical application of biomechanical conclusions.