Journal of Human Sport and Exercise

Lower limb muscle activation and kinematics modifications of young healthy adults while pushing a variable resistance sled

Martin G. Rosario, Monica Mathis



Introduction: The XPO Trainer used in this research is a novel device which provides low rolling resistance at low speeds with an immediate and automatic proportional increase in resistance with increased speed. Purpose: To examine the impact of using the XPO Trainer on gait and neuromuscular activation at low and high speeds in young, seemingly healthy adults. Materials and Methods: This work consisted of 35 healthy adults (age: 24.9 ± 3.2 years, weight: 149.8 ± 8 lbs, height: 66.6 ± 4.4 inches). Each participant wore accelerometers/gyroscopes sensors around each wrist and ankle, chest, and low back and surface electromyography (EMG) electrodes on their dominant leg over the quadriceps (QUAD), hamstring (HAM), anterior tibialis (TA), and gastrocnemius (GA). To initiate the tasks, participants walked then ran 40 feet with and without the XPO Trainer sled. Subjects did a total of 3 trials per tasks (total of 12) with one minute of rest between tasks to reduce fatigue factor. The data from the EMG and Mobility Lab sensors were then processed and compared through the SPSS 24 system for a repeated-measures ANOVA. Results: EMG- The QUAD muscle exhibited a substantial higher muscle activation between walk (45.39 ± 24.43) and walk push (74.40 ± 56.73) tasks. Gait Parameters- There was a significant modification (p ≤ .05) between the different gait variables and tasks, including cadence, gait speed, stride length and trunk velocity while pushing the sled. Conclusion/Clinical Relevance: With the XPO Trainer being a novel device, it is important to understand how it affects the activation and response for muscles during different activities before using it as a training tool. Understanding the effect this particular sled can provide on the different components of the (temporospatial) gait parameters and muscle activation is valuable for a clinically appropriate application to specific populations.


Variable resistance sled; Gait parameters; Muscle activation


Brill PA, Macera CA, Davis DR, Blair SN, Gordon N. (2000) Muscular strength and physical function. Med Sci Sports Exerc., 32(2):412–6.

Brooks N, Layne JE, Gordon PL, Roubenoff R, Nelson ME, Castaneda-Sceppa C. (2007) Strength training improves muscle quality and insulin sensitivity in Hispanic older adults with type 2 diabetes. Int J Med Sci., 4(1):19–27.

Cassilhas RC, Antunes HK, Tufik S, de Mello MT (2010). Mood, anxiety, and serum IGF-1 in elderly men given 24 weeks of high resistance exercise. Percept Mot Skills., 110(1):265–76.

Castaneda C, Layne JE, Munoz-Orians L, (2002) A randomized controlled trial of resistance exercise training to improve glycemic control in older adults with type 2 diabetes. Diabetes Care., 25(12):2335–41.

Collier S, Kanaley J, Carhart R Jr, (2009). Cardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre hypertension. Acta Physiol (Oxf)., 195(3):339–48.

FitzGerald SJBC, Kampert JB, Morrow JR Jr, Jackson AW, Blair SN (2004). Muscular fitness and all-cause mortality: a prospective study. J Phys Act Health., 1:7–18.

Fleck SJ, Kraemer WJ (1997). Designing resistance training programs. 2nd ed. Champaign (IL): Human Kinetics.

Fry, A.C., Smith, J.C., & Schilling, B.K. (2003). Effect of knee position on hip and knee torques during the barbell squat. Journal of Strength and Conditioning Research, 17(4), 629-633.

Gale CR, Martyn CN, Cooper C, Sayer AA (2007). Grip strength, body composition, and mortality. Int J Epidemiol., 36(1):228–35.

Guadagnin, E.C., Barbieri, F.A., Simieli, L., & Carpes, F.P. (2019). Is muscular and functional performance related to gait symmetry in older adults? A systematic review. Archives of Gerontology and Geriatrics, 84, 1-6.

Jurca , LaMonte MJ, Barlow CE, Kampert JB, Church TS, Blair SN (2005). Association of muscular strength with incidence of metabolic syndrome in men. Med Sci Sports Exerc., 37(11):1849–55.

Henderson, R.M., Leng, X.I., Chmelo, E.A., Brinkley, T.E., Lyles, M.F., Marsh, A.P., & Nicklas, B.J. (2017). Gait speed response to aerobic versus resistance exercise training in older adults. Aging Clinical & Experimental Research, 29(5), 969-976.

Hunter GR, McCarthy JP, Bamman MM (2004). Effects of resistance training on older adults. Sports Med., 34(5):329–48.

Kohrt WM, Bloomfield SA, Little KD, Nelson ME, Yingling VR (2004), American College of Sports Medicine. Position Stand: physical activity and bone health. Med Sci Sports Exerc., 36(11): 1985–96.

Kraemer WJ, Ratamess NA (2004). Fundamentals of resistance training: progression and exercise prescription. Med Sci Sport Exerc. 36:674–8.

Kraemer, William J., (2017). Understanding the science of resistance training: An evolutionary perspective. Sports Medicine. 47.12, 2415-2435.

Li, W; Li, Z; Qie, S; Yang, H; Chen, X; Liu, Y; Li, Z; Zhang, K. (2020) Analysis of the activation modalities of the lower limb muscles during walking. Technol Health Care.

Maddigan M, Button D, Behm D. (2014) Lower-Limb and Trunk Muscle Activation with Back Squats and Weighted Sled Apparatus. Journal of Strength and Conditioning Research., 28(12):3346-3353.

Medicine AcoS (2009). Position stand: progression models in resistance training for healthy adults. Med Sci Sports Exerc. 41:687–708.

Okkonen, O. & Häkkinen, K. (2013). Biomechanical comparison between sprint start, sled pulling, and selected squat-type exercises. Journal of Strength and Conditioning Research, 27(10), 2662-2673.

Osawa, Y., Shaffer, N.C., Shardell, M.D., Studenski, S.A, & Ferrucci, L. (2019). Changes in knee extension peak torque and body composition and their relationship with change in gain speed. Journal of Cachexia, Sarcopania and Muscle, 10(5), 1000-1008.

Pantoia PD, Carvalho AR, Ribas LR, Peyre-Tartaruga LA. (2018) Effect of weighted sled towing on sprinting effectiveness, power and force-velocity relationship., 13(10):0204473.

Park, B.-S., Kim, M.-Y., Lee, L.-K., Yang, S.-M., Lee, W.-D., Noh, J.-W., … Kim, J. (2015). The effects of a progressive resistance training program on walking ability in patients after stroke: a pilot study. Journal of Physical Therapy Science, 27(9), 2837–2840.

Pistacchi, M., Gioulis, M., Sanson, F., Giovannini, E.D., Filippi, G., Rossetto, F. & Marsala, S.Z. (2017). Gait analysis and clinical correlations in early Parkinson’s disease. Functional Neurology, 32(1), 28-34.

Puetz TW (2006). Physical activity and feelings of energy and fatigue: epidemiological evidence. Sports Med.36(9):767–80.

Reynaud, V., Morel, C., Givron, P., Clavelou, P., Cornut-Chauvinc, C., Pereira, B., Taithe, F., & Coudeyre, E. (2019). Walking speed is correlated with the isometric muscular strength of the knee in patients with chariot-marie-tooth type 1a. American Journal of Physical Medicine and Rehabilitation, 98(5), 422-425.

Sahil, S., Rebai, H., Elleuch, M.H., Tabka, Z., & Poumarat, G. (2008). Tibiofemoral joint kinetics during squatting with increasing external load. Journal of Sports Rehabilitation, 17(3), 300-315.

Schoenfeld, BJ; Grgic, J; Haun, C; Itagaki, T; Helms. (2019) Calculating Set-Volume for the Limb Muscles with the Performance of Multi-Joint Exercises: Implications for Resistance Training PrescriptionSports (Basel), vol. 7(7).

Shumway-Cook, A., & Woollacott, M. H. (2007). Motor control: Translating research into clinical practice. Philadelphia: Lippincott Williams & Wilkins. APA (6th ed.).

Staron RS, Karapondo DL, Kraemer WJ, Fry AC, Gordon SE, Falkel JE, et al. Skeletal muscle adaptations during early phase of heavy-resistance training in men and women. J Appl Physiol (1985). 1994;76:1247–55.

Staron RS, Leonardi MJ, Karapondo DL, Malicky ES, Falkel JE, Hagerman FC, (1985). Strength and skeletal muscle adaptations in heavy-resistance-trained women after detraining and retraining. J Appl Physiol. 1991;70:631–40.

Staron RS, Malicky ES, Leonardi MJ, Falkel JE, Hagerman FC, Dudley GA (1989). Muscle hypertrophy and fast fiber type conversions in heavy resistance-trained women. Eur J Appl Physiol. 60:71–9.

Teixeira-Samela, L.F., Olney, S.J., Nadeau, S., & Brouwer, B. (1999). Muscle strengthening and physical conditioning to reduce impairment and disability in chronic stroke survivors. Archive of Physical Medicine and Rehabilitation, 80(10), 1211-1218.

Williams MA, Haskell WL, Ades PA, (2007). Resistance exercise in individuals with and without cardiovascular disease: 2007 update: a scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism. Circulation., 116(5): 572–84.


Copyright (c) 2018 Journal of Human Sport and Exercise

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.