Medical Research

Ironwear® is supporting medical research around the world.

Ironwear® has worked with researchers from Harvard Medial School for over 15 years. See the link below.

Ironwear® donated 24 weighted vests for the following research conducted at Mississippi State University.

Effect of 3-week hypergravity training on balance, jump, and sprint performance in well-trained women.

JD Simpson, M.S., BL Miller, M.S., H Chander, Ph.D., and AC Knight, Ph.D., Mississippi State University, Neuromechanics Laboratory, Mississippi State, MS 39762


Optimizing lower extremity force in a short period of time during athletic competition is essential for success (Barr et al. 2015). Hypergravity training (HT) consists of wearing an external load (weighted vest) for extended periods of time during activities of daily living (ADL), which may improve rate of force production from the lower extremity musculature. Previous investigations have repeatedly found that a simulated hypergravity condition improves several modes of jumping and sprinting in well-trained populations when incorporated over a 3-4 week period during ADLs and/or training (Bosco et al. 1984; Bosco 1985; Khilfa et al. 2010; Rantalainen et al. 2012; Rusko and Bosco 1986; Sands et al. 1996). Barr et al. (2014) found decreased sprinting ground contact time following 8 days of HT, but did not report an improvement in overall sprint performance, suggesting exposure duration may be an important factor when implementing HT. Additionally, only a single study incorporating a HT paradigm has been conducted using well-trained female participants (Sands et al. 1996).

One of the largest gaps in the literature concerns the effect of HT on kinetic and kinematic variables of different performance measures. Clark et al. (2010) is the only study to date that has assessed changes in sprint kinematics following a longitudinal resisted sprint training protocol, which yielded minor improvements. Other studies have been limited in scope to evaluating kinetic and kinematic changes during sprinting with different external loads, with only one lone study giving consideration to changes in kinetics (Cronin et al. 2008; Cross et al. 2014). In addition, no studies to the investigators knowledge have assessed changes in kinetics and kinematics of different balance, jumping and sprinting tasks following a 3-week HT protocol. With the lack of literature concerning HT potential impact on kinetics and kinematics, the focus of this study will be to determine the effects of 3-week HT on agility, balance, jumping and sprinting tasks. Specifically, assessing changes in kinetic and kinematics in recreationally trained female participants.



Apparently healthy, well-trained females (n = 15-20) having no musculoskeletal injuries within the last 6 months will be recruited as participants. Following completion of a health screening (PAR-Q), anthropometric data (height, weight, and body composition) will be collected and participants will be asked to provide an estimated one-week training recall.

Experimental Procedures: The current study is designed to examine the potential impact of HT on kinetics and kinematics during jumping, sprinting, agility and balance measures. A within subject’s design will be incorporated. Participants will perform 1 familiarization session followed by a baseline testing session and then commence a 3-week HT period. During the HT period, all participants will wear a 10 lb. weighted vest 4 days a week for 8 hours per day during daily living activities for 3 weeks. In addition to wearing the vest during daily activities, participants will wear the vest during 3 training sessions each week. Following the 3-week HT period, participants will return to the lab for the experimental testing session. Additionally, this will also serve as a baseline for the detraining phase of the investigation, where participants will continue their normal training routines but will refrain from wearing the weighted vest during daily living activities and training (participants serve as their own control). Following the 3-week detraining phase participants will return to the lab for their final round of testing. Data collected from baseline, experimental and detraining phases will be used for analysis. Each testing session will begin with an initial warm up protocol of 10 minutes consisting of body weight squats, high-knees, jogs, gait swings and exaggerated lunges. Following warm-up, participants will complete the required performance tasks which are described in more detail below.

Performance Tasks: Balance analysis will include bi-lateral and uni-lateral stance for 3 trials of 20 seconds performed on the AMTI force plate with their eyes open and eyes closed. During these assessments the participants will be asked to stand as still as possible with both feet (bi-lateral) and one foot (uni-lateral) on the force plate. Dynamic balance will also be assessed using the Star Excursion Balance Test (SEBT) where participants will stand on one leg on top of a force plate and reach with the opposite leg in eight different directions and will be conducted on both legs. Following the balance tests, participants will perform three types of vertical jump tests. The first jumping task will include 3 separate single countermovement jumps (VJ) separated by 45-60 s rest between repetitions. Then participants will complete two sets of 4 continuous countermovement jumps (4CMJ) separated by 45-60 s of rest. The final jumping task will require participants to drop (step down) from an 18 inch (45.72 cm) box and land on a force place and subsequently jump as high as possible. All jumping tasks will be performed on an AMTI force plate. After jump performance testing a set of three 25-meter sprints with a 5-meter flying start will be conducted and timing gates will be used to determine sprint times. The final performance test will be a standardized agility test commonly used in performance assessments (i.e. the T-test). Participants will sprint 10 yards forward, shuffle 5 yards to the left, and shuffle ten yards to the right, shuffle 5 yards left and return to the starting line by running backwards. Participants will get 2 chances to perform this task.

Force plate, electromyography (EMG), and 2D video will be collected during all measures. Muscle activity from the dorsiflexors (tibials anterior), plantar flexors (medical gastrocnemius), vastus medialis (quadriceps) and medial hamstrings (biceps femoris) will be recorded during the balance and jumping tasks. The participants’ 2-D motion analysis will be used to assess changes during the 25-meter sprint and t-test using Dartfish software.

The current study will determine if wearing a weighted vest during daily living activities: Improves kinetics and kinematics of agility, jumping and sprinting tasks. Improves static and dynamic balance. Is effective as a training tool when incorporated during daily activities and training 3 days per week.


For funded/sponsored studies a complete narrative report and copy of all data will be made available to the sponsor after completion of the study. These results will be submitted for presentation at professional meetings and submitted for possible publication in a professional journal. It is anticipated that more than one paper will be submitted for publication from the proposed study.


Barr MJ, Gabbett TJ, Newton RU, Sheppard JM (2014) The effect of 8 days of a hypergravity condition on the sprinting speed and lower body power of elite rugby players. J Strength Cond Res.

Bosco C (1985) Adaptive response of human skeletal muscle to simulated hypergravity condition. Acta Physiol Scand 124 (4):507-513.

Bosco C, Rusko H, Hirvonen J (1986) The effect of extra-load conditioning on muscle performance in athletes. Med Sci Sports Exerc 18 (4):415-419.

Bosco C, Zanon S, Rusko H, Dal Monte A, Bellotti P, Latteri F, Candeloro N, Locatelli E, Azzaro E, Pozzo R, et al. (1984) The influence of extra load on the mechanical behavior of skeletal muscle. Eur J Appl Physiol Occup Physiol 53 (2):149-154.

Clark KP, Stearne DJ, Walts CT, Miller AD (2010) The longitudinal effects of resisted sprint training using weighted sleds vs. weighted vests. J Strength Cond Res 24 (12):3287-3295.

Cronin J, Hansen K, Kawamori N, McNair P (2008) Effects of weighted vests and sled towing on sprint kinematics. Sports Biomechanics / International Society of Biomechanics in Sports 7 (2):160-172.

Cronin J, Hansen KT (2006) Resisted sprint training for the acceleration phase of sprinting. Strength Cond J:42-51.

Cross MR, Brughelli ME, Cronin JB (2014) Effects of vest loading on sprint kinetics and kinematics. J Strength Cond Res 28 (7):1867-1874.

Khlifa R, Aouadi R, Hermassi S, Chelly MS, Jlid MC, Hbacha H, Castagna C (2010) Effects of a plyometric training program with and without added load on jumping ability in basketball players. J Strength Cond Res 24 (11):2955-2961.

Rantalainen, T., Ruotsalainen, I., Virmavirta, M. (2012). Effect of Weighted Vest Suit Worn During Daily Activities on Running Speed, Jumping Power, and Agility in Young Men. The Journal of Strength & Conditioning Research, 26(11), 3030-3035.

Rusko H, Bosco CC (1987) Metabolic response of endurance athletes to training with added load. Eur J Appl Physiol Occup Physiol 56 (4):412-418.

Sands WA, Poole RC, Ford HR, Cervantez RD, Irvin CI (1996) Hypergravity training: Women's Track and Field. J Strength Cond Res 10 (1):30-34.