Running has become a very popular sport over the past several decades with an estimate of over 35 million runners in the United States and greater than half are women. According to the Centers for Disease Control and Prevention (CDC), nearly 4 million babies are born every year in the United States (7,22,26,31,35,43). The psychological, physiological, and biomechanical differences between male and female runners are well cited (8,23,28,34,42,52); however, there is little guidance provided to health care providers, including running and strength coaches about how to transition runners back to running postpartum. This article can serve as a reference for understanding the unique challenges female runners face postpartum and give clinicians the knowledge to manage the athlete's expectations and training progression. Ultimately, the goal is to reduce potential injury and long-term consequences in this population.
Traditionally, the medical model divides the postpartum period into 3 separate but continuous phases. Phase 1 is the acute postpartum phase occurring during the first 6 to 12 hours after giving birth, phase 2 is the subacute phase typically weeks 2–6, and phase 3 is the delayed postpartum period, which lasts to approximately 6 months postdelivery. During the first 6 weeks postpartum, many medical issues such as postpartum depression, cardiomyopathy, genitourinary, and hemodynamic issues resolve. During the first 6 months, connective tissue and muscle tissue begin to heal and return to the prepregnancy state (39). However, it is acknowledged that even 6 months postdelivery, continued hormonal, ligamentous, and muscular changes occur.
In 2018, the American College of Obstetricians and Gynecologists (ACOG) released new guidelines for a “fourth trimester” in which postpartum women should receive continued care and guidance after the birth of their child. This is a significant leap forward for women in the United States; it finally recognizes that the physical and psychological changes that continue well after childbirth must be addressed. It suggests that postpartum care is ongoing rather than a single episode of care with support and services that are tailored to each woman's individual needs (33). These new guidelines open the door for women to receive the care required to return to an active lifestyle without compromising their body.
Over the course of a woman's pregnancy, the body undergoes significant physical changes, some of which are visible and others that are not. Weight gain and lower extremity edema can be the most noticeable changes; however, nearly every system of the body is affected. The changes that occur are postural, ligamentous, muscular, articular, hormonal, cardiovascular, renal, and pulmonary (1).
Barriers that may affect women when returning to running postpartum may include inadequate quality and quantity of sleep, fatigue, learning to care for a newborn, a changing schedule, physical changes, and much more (19,50).
PHYSICAL AND PHYSIOLOGICAL CHANGES
The average woman gains between 20 and 25 pounds during pregnancy, but it varies between individuals (31). This additional weight is a result of increased adipose tissue, fluid, fat, and breast tissue and growth of the placenta and fetus. Although some of the weight is lost after birth, much of the weight remains for several weeks, months, or even longer.
During pregnancy and postpartum, the pelvic floor muscles (PFMs) undergo significant change, including stretch from the increased weight gain and postural changes, increased muscular demand because of these changes, possible tearing during childbirth, and then ultimately recovery through the pregnancy and postpartum period (14). These changes may lead to decreased core stability, pelvic floor weakness, urinary incontinence, stress urinary incontinence (SUI) while running, lower back and hip pain, and other musculoskeletal injuries. The incidence of SUI in female runners ranges from 26 to 41%; this does not include the many runners who do not report SUI (28).
The PFMs are the group of muscles between the pubic bone and tailbone (14). They create a hammock-like structure that supports the urinary and genital organs, controls the bowel and bladder and sexual function, and contributes to stability and postural control. The PFMs are the inferior part of the “core (14).” The PFMs are always working at a low level; hence, they function primarily as endurance muscles. They help maintain posture and respond when we move to control intra-abdominal pressure (IAP) (Figure 1).
During running, IAP increases each time the foot hits the ground. The PFMs work in coordination with the abdominals, diaphragm, and low back muscles to control the increase in IAP (14,24,41). Hence, the activity of the PFMs is greater when running to control impact forces and to maintain alignment and posture. This muscle coordination creates a stable base for the lower extremities during running (38,49).
Hormonal changes create increased laxity in ligaments to accommodate for the growing fetus. Hormones, including estrogen, relaxin, and progesterone, affect all of the body's connective tissue. Recent evidence suggests that it is the interplay of all these hormones and not the presence of just one that contributes to changing joint and connective tissue laxity in pregnancy (37). These increased hormonal levels remain elevated for 6 months postpartum or longer if the woman is breastfeeding (7). Women often breastfeed 12–24 months postpartum. Physiologically, this may prolong the effects of these hormones on muscular, ligamentous, and connective tissue during the postpartum period.
This increased laxity results in postural changes including increased flaring of the rib cage, increased lumbar lordosis, increased thoracic kyphosis, anterior pelvic rotation, widening of the pelvis, and flattening of feet (1). These postural changes disrupt the pelvic floor musculature and IAP and, ultimately, the overall stability of the core. These postural changes may continue several months or years postpartum if not addressed and may contribute to running injuries later on such as sacroiliac joint dysfunction, hip or lower back pain, and leg, foot, and ankle injuries (38,49).
Bone mineral density (BMD) is also affected in the postpartum period, particularly with breastfeeding. This occurs because the calcium in the mother's bones is mobilized to meet the increased demand for calcium in the mother's milk (9,22). Hormonal changes such as high prolactin and low estrogen levels promote bone resorption (27). Estrogen levels remain low until the return of menses, which typically does not occur until the cessation of breastfeeding. Unfortunately, taking calcium supplements has not been found to increase BMD during breastfeeding (6,9,22,27).
Maternal bone loss is estimated to be 1–3% per month with 3–9% occurring at trabecular rich sites such as the hip and lumbar spine (9,21,22). In most women, BMD loss is reversed with cessation of breastfeeding and may return to baseline in 12–18 months; however, in some cases, complete recovery may not occur (27). BMD loss is associated with osteopenia and osteoporosis later in life and is a factor in bone stress injuries such as stress reactions and stress fractures among runners (27,44,47).
Muscles supporting the increased weight gain and postural changes may become increasingly tight or lengthened (1,5). The connective tissue and fascia may become overstretched at the linea alba creating a separation between the rectus abdominis in the abdominal wall, which is termed diastasis recti abdominis (DRA). Health care and strength professionals can assess for this with clinical testing. These muscles and the fascia of the lumbopelvic region play a significant role in continence, respiration, force transfer, and overall musculoskeletal stability (3,4,25,30).
Biomechanical changes may impact walking and running, resulting in decreased step length and stride length, increased base of support, and increased double support time (5,7). Not all these changes are resolved 8–16 weeks postpartum (7,11). This should not discourage women from running earlier, but it may be important to modify frequency and intensity of running. Women may benefit from education and guidance of a knowledgeable health professional when beginning or returning to run in the postpartum period.
BENEFITS OF RUNNING POSTPARTUM
Despite the challenges of increased weight gain, depression, lack of sleep, and anxiety that many women experience postpartum, numerous studies have found that exercise improves brain function, sleep, mood, body image, anxiety and depression, and overall quality of life and decreases the incidence of chronic illness (2,20,35). The addition of exercise and a running program is an excellent adjunct to traditional postpartum care. Pregnancy and excessive weight gain during pregnancy are positive predictors for obesity in postpartum women (9,13). It will be the role of the health care providers and strength professionals to help the runner understand the implications of pregnancy on her body physiologically and biomechanically.
Both exercise and being part of a community can improve the incidence of postpartum depression (35,48). The combination of the modern running stroller and social media has made running more accessible to moms in small towns and big cities alike. Social media platforms provide a space for moms to connect, ask advice about exercise and motherhood, and make plans to get out of the house to run or walk.
Weight-bearing exercise such as running has been shown to improve BMD in the lumbar spine and femur because of the mechanical stress placed on the bone (27). When running in the postpartum period, it is important to balance the benefits of weight-bearing exercise (running) with the hormonal and physiological effects of breastfeeding on BMD. A rapid increase in training volume or intensity may ultimately lead to an imbalance of the system. A running coach with extensive knowledge of the female runner would be helpful in designing an appropriate return to running (RTR) program to decrease the incidence of training errors.
WHEN IS IT SAFE TO RETURN TO RUNNING?
There is currently no guidance available for women who want to RTR or begin to run postpartum. The American College Obstetricians and Gynecologists recommends that postpartum women return to exercise gradually when it is medically safe, when the woman can tolerate the physical stress (16). The challenge for health care providers is to balance the benefits of running postpartum with what is happening biomechanically, physiologically, and psychologically.
It is widely known that greater than 80–90% of runners are injured in the course of their running career (17,18,26,46,52,53). The most prominent risk factors for injury are history of previous injury, being a novice, and overtraining (18,42,52,55). Women who begin running for the first time postpartum are at a high risk of injury because they fall into the novice category. Risk may be made even greater by the fatigue of having a newborn, lack of sleep, and physical recovery after childbirth, along with the physical, biomechanical, and psychological compromise postpartum.
Recovery time differs slightly for women who have undergone cesarean deliveries. Their recovery time is typically longer because a cesarean is a major abdominal surgery in which the surgeon cuts through the abdominal wall and uterus. During the first 6–8 weeks postpartum, it is important to allow the tissues of the uterus, vagina, and pelvis to heal. Vaginal bleeding is normal postpartum and can be used as an indicator for overexertion (45). If the client is still bleeding, she may benefit from short and easy walking, breathing exercises, gentle pelvic floor exercises, and pelvic tilts. If bleeding increases, she is likely overexerting herself.
The timeline for biomechanical and physiological changes that occur after vaginal or cesarean delivery cannot be accelerated. In some women, changes may persist >24 months postpartum. This may be the most difficult psychological barrier for women who want to return to their prebaby body as soon as possible. Lopes et al. found that women run to manage their weight, maintain their health and wellness and for community and connection (26). Empathizing with the runner, educating her, and providing a plan to RTR will be of the utmost importance. Walking is a great way to begin safely exercising immediately postpartum. It provides many of the psychological benefits of exercise while preparing the body for running. A comprehensive RTR program will initially include a combination of walking and running.
Currently, the physician, usually the obstetrician, clears a woman for participation in running. The timeline for clearance varies between vaginal or cesarean deliveries. Recommended steps to follow when returning to run would include (a) clearance by a physician, (b) evaluation by a physical therapist specializing in pelvic health, (c) comprehensive assessment of functional movement and running gait, and (d) initiation of a running and strength training program.
By incorporating steps 2 and 3, women would have a better understanding of the changes that occurred in their body and receive individualized plans to RTR. A good RTR plan should incorporate both walking and running and adequate rest periods. As described earlier, DRA and pelvic floor dysfunction can result in a plethora of injuries immediately or several years postpartum. An examination by a pelvic health therapist will enable proper intervention for the PFMs and DRA. Most pelvic health therapists suggest an appointment 6–8 weeks postpartum. In some areas of the country, access to pelvic health therapists may not be possible. The Women's Health section of the American Physical Therapy Association has a website to help women find women's health specialists near them: https://pt.womenshealthapta.org. In addition, there are now online and telehealth options for women in rural areas of the country.
Postpartum women are already at a disadvantage when they RTR because of the biomechanical and physiological changes discussed previously. The literature shows that modifying running form can reduce the mechanical demands on much of the lower extremity and spine, which may expedite a runner's ability to RTR and decrease the risk of injury (10,15,43,51). In addition, gait analysis can serve as a means to develop a comprehensive treatment plan for injured and noninjured runners (43).
Runners often avoid weight training; however, it has been found to be helpful in reducing injury and improving performance (36,54). Postpartum athletes can begin strength training after physician clearance. Strength professionals can support the postpartum runner by facilitating them to set realistic expectations and integrating breathing, posture, and deep core stability into their strength programs. Breath holding and gripping in the buttock and abdominal wall during exercise are common compensation patterns to watch out for with postpartum athletes (25). These strategies overuse the posterior hip musculature and abdominal wall musculature creating positional changes in the pelvic girdle (25).
PRACTICAL APPLICATIONS FOR PROFESSIONALS
Despite the overwhelming changes that occur postpartum, many women begin running much sooner than their bodies are ready. Health care and strength professionals must educate the female runner and provide effective intervention (48). If a woman has a DRA or SUI, it does not mean that they cannot run, but they may have to modify their routine or add exercises to address these issues. Many women are under the misconception that leakage while running is normal, and it is not. It is our job to educate them and get them to those that can help. Regardless of professional expertise, following the steps outlined below will assist in returning women to running in the postpartum period.
FITNESS AND RUNNING HISTORY
Taking a comprehensive fitness and running history will help to better identify areas of concern for the athletes. It will be easier to identify women who may need pelvic health physical therapy before or during the RTR process and women who are at a higher risk of stress fractures and understand where the athlete may have knowledge gaps to address. This is also a great opportunity to step in and prevent unnecessary overtraining (Table 1).
SCREENING FOR DIASTASIS RECTI ABDOMINIS
To assess for DRA, the client will lay supine on a flat surface with her knees bent and feet on the floor, hands by her sides, and with her abdomen exposed. Instruct her to lift her head and neck off the floor until her shoulder blades clear the surface (7). The professional will use the umbilicus as a reference point and place their fingers vertically on the linea alba in 4 locations, 4.5 cm and 2 cm above and below the umbilicus (12,30). If the client demonstrates ≥2-finger width separation or there is a bulge at the linea alba, a DRA is present (12). Be sure to also note the depth of the DRA (Figure 2A and 2B).
Some research suggests that decreasing the separation of inter-rectus distance (IRD) will improve the function of the abdominal wall (29,40). However, other research suggests that closing the IRD may not be sufficient for improving force transfer through the abdominal wall (24). On the basis of this research, exercises to reduce IRD, such as the abdominal crunch and exercises to improve transverse abdominis activation should both be included in a well-rounded strength program. In addition, focusing on diaphragmatic breathing and pelvic floor activation is important.
If the athlete has a large separation or the professional is not comfortable treating DRA, a referral to a physical therapist with knowledge of DRA will be beneficial. The client may also be directed to online resources for postpartum women.
POSTURE AND BREATHING
As discussed earlier, postpartum women tend to have several common postural changes that remain long after birth. First, check to see whether any of these postural changes have occurred. Have the client stand with her arms beside her and feet shoulder width apart.
Start by generally noticing if the client is breathing into her diaphragm or is she a chest or belly breather. If she is not breathing into her diaphragm or rib cage, teach her how in supine, sitting, and standing. Once she can demonstrate improved breathing patterns, begin cueing her breathe with more complicated exercises such as squats, lunges, and plyometrics. Be sure to monitor the athlete's pelvic floor and abdominal wall integrity as she progresses to more difficult exercises by revisiting some of the screening questions discussed earlier.
Next, look at the position of the rib cage. Is it anteriorly flared or tucked under? Is the client gripping their abdominals or buttock? Is their pelvis tucked under?
There is no perfect posture; however, in most cases, it is ideal that the rib cage be positioned over the pelvis, the pelvis is not tucked under, and the client is not gripping in the abdominal wall and buttock. Exercises focused on retraining postural awareness while integrating breathing are crucial to build a good foundation. This foundation will impact running form and the ability to perform more complicated strength training and plyometric exercises with less complication in the future.
RUNNING WITH A RUNNING STROLLER
Running with a running stroller can affect the hip, pelvis, and trunk kinematics (32). Holding onto the stroller in front restricts arm motion, thoracic spine, and trunk motion. Research has shown that running mechanics change when running with a stroller. These changes include decreased trunk rotation, a more rigid trunk, and increased flexing forward at the hips, especially when going uphill, the pelvis tends to tip forward, and there is typically less hip extension (13,32).
Unfortunately, many of these changes also correlate with increased lower back pain, increased pressure on the lower back facet joints, increased neural tension, lower extremity injuries, decreased gluteus muscle firing, and much more (Table 2).
Do not allow the runner to make too many changes at once to prevent an overtraining injury. Encourage the runner to try and run with and without the running stroller if possible to prevent undesirable running form in the future.
Many women RTR within the first 4 to 8 weeks postpartum with minimal to no guidance from health care or other professionals (48,50). However, lingering biomechanical and physiological changes that occur during pregnancy and remain postpartum may be a potential risk factor for injury.
Currently, there is no gold standard for the management and care of women returning to running postpartum. Health care practitioners and strength professionals can provide better guidance to their clients through education and screening for common issues these women face.
This article outlines some of these changes that occur in a woman's body that can and will affect how she walks, runs, lifts, and moves postpartum. It provides some practical applications to screen clients for common issues they may face such as DRA, SUI, dysfunctional breathing patterns, and posture dysfunction. In addition, the article provides guidance on how to address these common issues directly or through proper outside referral.
1. Albright E. Exercise during pregnancy. Curr Sports Med Rep 15: 226–227, 2016.
2. Bane SM. Postpartum exercise and lactation. Clin Obstet Gynecol 58: 885–892, 2015.
3. Behm DG, Blazevich AJ, Kay AD, McHugh M. Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: A systematic review. Appl Physiol Nutr Metab 41: 1–11, 2016.
4. Blyholder L, Chumanov E, Carr K, Heiderscheit B. Exercise behaviors and health conditions of runners after childbirth. Sports Health 9: 45–51, 2016.
5. Bø K, Artal R, Barakat R, et al. Exercise and pregnancy in recreational and elite athletes: 2016 evidence summary from the IOC expert group meeting, Lausanne. Part 1-exercise in women planning pregnancy and those who are pregnant. Br J Sports Med 50: 571–589, 2016.
6. Brembeck P, Lorentzon M, Ohlsson C, Winkvist A, Augustin H. Changes in cortical volumetric bone mineral density and thickness, and trabecular thickness in lactating women postpartum. J Clin Endocrinol Metab 100: 535–543, 2015.
7. Carpes FP, Griebeler D, Kleinpaul JF, Mann L, Mota CB. Women able-bodied gait kinematics during and post pregnancy period. Braz J Biomech 9: 34–39, 2008.
8. Charkoudian N, Joyner MJ. Physiologic considerations for exercise performance in women. Clin Chest Med 25: 247–255, 2004.
9. Colleran HL, Wideman L, Lovelady CA. Effects of energy restriction and exercise on bone mineral density during lactation. Med Sci Sports Exerc 44: 1570–1579, 2012.
10. Davis IS, Futrell E. Gait retraining: Altering the fingerprint of gait. Phys Med Rehabil Clin N Am 27: 339–355, 2016.
11. Gilleard WL. Trunk motion and gait characteristics of pregnant women when walking: Report of a longitudinal study with a control group. BMC Pregnancy Childbirth 3: 1–8, 2013.
12. Gluppe Sandra L, Hilde G, Tennfjord Merete K, Engh ME, Bø K. Effect of a postpartum training program on the prevalence of diastasis recti
abdominis in postpartum primiparous women: A randomized controlled trial. Phys Ther 98: 260–268, 2018.
13. Gregory DA, Pfeiffer KA, Vickers KE, et al. Physiologic responses to running with a jogging stroller. Int J Sports Med 33: 711–715, 2012.
14. Hartmann D, Sarton J. Chronic pelvic floor dysfunction. Best Pract Res Clin Obstet Gynaecol 28: 977–990, 2014.
15. Heiderscheit BC, Chumanov ES, Michalski MP, Wille CM, Ryan MB. Effects of step rate manipulation on joint mechanics during running. Med Sci Sports Exerc 43: 296–302, 2011.
16. Hesketh KR, Evenson KR. Prevalence of U.S. pregnant women meeting 2015 ACOG physical activity guidelines. Am J Prev Med 51: e87–e89.
17. Hespanhol Junior LC, Pena Costa LO, Lopes AD. Previous injuries and some training characteristics predict running-related injuries in recreational runners: A prospective cohort study. J Physiother 59: 263–269, 2013.
18. Hreljac A. Etiology, prevention, and early intervention of overuse injuries in runners: A biomechanical perspective. Phys Med Rehabil Clin N Am 16: 651–667: vi, 2005.
19. Hunter LP, Rychnovsky JD, Yount SM. A selective review of maternal sleep characteristics in the postpartum period. J Obstet Gynecol Neonatal Nurs 38: 60–68, 2009.
20. Kader M, Naim-Shuchana S. Physical activity and exercise during pregnancy. Eur J Physiother 16: 2–9, 2013.
21. Kalkwarf HJ. Changes in bone density during lactation and weaning. J Mammary Gland Biol Neoplasia 4: 319–329, 1999.
22. Krebs NF, Reidinger CJ, Robertson AD, Brenner M. Bone mineral density changes during lactation: Materanal, dietary, and biomechanical correlates. Am J Clin Nutr 65: 1738–1746, 1997.
23. Kuwahara T, Inoue Y, Abe M, Sato Y, Kondo N. Effects of menstrual cycle and physical training on heat loss responses during dynamic exercise at moderate intensity in a temperate environment. Am J Physiol Regul Integr Comp Physiol 288: R1347–R1353, 2005.
24. Lee D, Hodges PW. Behavior of the linea alba during a curl-up task in diastasis rectus abdominis: An observational study. J Orthop Sports Phys Ther 46: 580–589, 2016.
25. Lee DG, Lee LJ, McLaughlin L. Stability, continence and breathing: The role of fascia following pregnancy and delivery. J Bodyw Mov Ther 12: 333–348, 2008.
26. Lopes AD, Costa LOP, Saragiotto BT, et al. Musculoskeletal pain is prevalent among recreational runners who are about to compete: An observational study of 1049 runners. J Physiother 57: 179–182, 2011.
27. Lovelady CA, Bopp MJ, Colleran HL, Mackie HK, Wideman L. Effect of exercise training on loss of bone mineral density during lactation. Med Sci Sports Exerc 41: 1902–1907, 2009.
28. Lynch SL, Hoch AZ. The female runner: Gender specifics. Clin Sports Med 29: 477–498, 2010.
29. Mota P, Pascoal AG, Carita AI, Bo K. The immediate effects on inter-rectus distance of abdominal crunch and drawing-in exercises during pregnancy and the postpartum period. J Orthop Sports Phys Ther 45: 781–788, 2015.
30. Mota P, Pascoal AG, Sancho F, Carita AI, Bo K. Reliability of the inter-rectus distance measured by palpation. Comparison of palpation and ultrasound measurements. Man Ther 18: 294–298, 2013.
31. National Research Council IoM, Board on Children, Youth, and Families, Food. Weight Gain in Pregnancy: Re-examining the Guidelines. Washington, DC: National Academies Press, 2007.
32. O'Sullivan R, Kiernan D, Malone A. Run kinematics with and without a jogging stroller. Gait Posture 43: 220–224, 2016.
33. Opinion C. ACOG post natal care committee opinion. Obstetricians and Gynecologists 131: 140–150, 2018.
34. Petersen J, Sorensen H, Nielsen RO. Cumulative loads increase at the knee joint with slow-speed running compared to faster running: A biomechanical study. J Orthop Sports Phys Ther 45: 316–322, 2015.
35. Pivarnik J. Impact of physical activity during pregnancy and postpartum on chronic disease risk. Med Sci Sports Exerc 38: 989–1006, 2006.
36. Rathleff MS, Molgaard CM, Fredberg U, et al. High-load strength training improves outcome in patients with plantar fasciitis: A randomized controlled trial with 12-month follow-up. Scand J Med Sci Sports 25: e292–300, 2015.
37. Reese ME, Casey E. Hormonal influence on the neuromusculoskeletal system in pregnancy. In: Musculoskeletal Health in Pregnancy and Postpartum, Springer International Publishing Switzerland, 2015. C.M. Fitzgerald, N.A. Segal (eds.), pp. 19–39.
38. Rivera CE. Core and lumbopelvic stabilization in runners. Phys Med Rehabil Clin N Am 27: 319–337, 2016.
39. Romano M, Cacciatore A, Giordano R, La Rose B. Postpartum period: Three distinct but continuous phases. J Prenatal Med 4: 22–25, 2010.
40. Sancho MF, Pascoal AG, Mota P, Bo K. Abdominal exercises affect inter-rectus distance in postpartum women: A two-dimensional ultrasound study. Physiotherapy 101: 286–291, 2015.
41. Sapsford RR, Hodges PW. The effect of abdominal and pelvic floor muscle activation on urine flow in women. Int Urogynecol J 23: 1225–1230, 2012.
42. Saragiotto BT, Yamato TP, Hespanhol Junior LC, et al. What are the main risk factors for running-related injuries? Sports Med 44: 1153–1163, 2014.
43. Souza RB. An evidence-based videotaped running biomechanics analysis. Phys Med Rehabil Clin N Am 27: 217–236, 2016.
44. Speziali A, Tei MM, Placella G, Chillemi M, Cerulli G. Postpartum sacral stress fracture: An atypical case report. Case Rep Orthop 2015: 704393, 2015.
45. Stephenson RG, O'Connor L. Obstetric and Gynecologic Care in Physical Therapy. Thorofare, NJ: SLACK, Incorporated, 2000.
46. Taunton JE, Ryan MB, Clement DB, et al. A retrospective case-control analysis of 2002 running injuries. Br J Sports Med 36: 95–101, 2002.
47. Tenforde AS, Kraus E, Fredericson M. Bone stress injuries in runners. Phys Med Rehabil Clin N Am 27: 139–149, 2016.
48. Tenforde AS, Toth KE, Langen E, Fredericson M, Sainani KL. Running habits of competitive runners during pregnancy and breastfeeding. Sports Health 7: 172–176, 2015.
49. Terada M, Kosik KB, McCann RS, Gribble PA. Diaphragm contractility in individuals with chronic ankle instability. Med Sci Sports Exerc 48: 2040–2045, 2016.
50. Thein-Nissenbaum J. The postpartum triathlete. Phys Ther Sport 21: 95–106, 2016.
51. Thein-Nissenbaum JM, Thompson EF, Chumanov ES, Heiderscheit BC. Low back and hip pain in a postpartum runner: Applying ultrasound imaging and running analysis. J Orthop Sports Phys Ther 42: 615–624, 2012.
52. van der Worp MP, ten Haaf DS, van Cingel R, de Wijer A, Nijhuis-van der Sanden MW, Staal JB. Injuries in runners; a systematic review on risk factors and sex differences. PLoS One 10: e0114937, 2015.
53. van Gent RN, Siem D, van Middelkoop M, et al. Incidence and determinants of lower extremity running injuries in long distance runners: A systematic review. Br J Sports Med 41: 469–480, 2007; discussion 480.
54. Vikmoen O, Raastad T, Seynnes O, et al. Effects of heavy strength training on running performance and determinants of running performance in female endurance athletes. PLoS One 11: e0150799, 2016.
55. Yamato TP, Saragiotto BT, Lopes AD. A consensus definition of running-related injury in recreational runners: A modified delphi approach. J Orthop Sports Phys Ther 45: 375–380, 2015.