midstance

midstance

[mid′stanz]
Etymology: AS, midd + L, stare, to stand
one of the five stages in the stance phase of walking, or gait, directly associated with the period of single-leg support of body weight or the period during which the body advances over the stationary foot. During midstance the tibialis posterior and the flexor hallucis longus display their greatest activity. The midstance phase is considered in the diagnosis of many abnormal orthopedic conditions and in the analysis of the associated weaknesses of certain muscles and muscle groups. Compare initial contact stance stage, loading response stance stage, preswing stance stage, terminal stance. See also swing phase of gait.

midstance

the point of gait (walking or running) when the centre of mass of the body is above the supporting foot.

midstance

period within the gait cycle between foot flat and heel lift (see Table 1 and Table 2)
Table 1: The gait (walking) cycle
Phase of the cyclePeriodComment
Stance phase (60%)ContactFrom heel strike to foot flat
Foot unlocks to act as a shock absorber and adapt to irregularities in the ground surface
MidstanceFrom foot flat to heel lift
The total weight-bearing surface of the foot is in contact with the walking surface
PropulsionFrom heel lift to toe off
Foot is a rigid and stable lever
Swing phase (40%)From toe off limb 1 to heel strike (limb 1)
Body mass transfers from limb 1 to limb 2
Table 2: Foot events occurring during normal bipedal gait
Stance phaseEvents/movements occurring
Leg 1
Heel strike (HS)Leg 1
STJ slightly supinated, so that:
• Posterior lateral area of the 'plantar heel pad' contacts the ground surface
• Forefoot is inverted relative to the ground surface
MTJ is also supinated, so that:
• Tibialis anterior tendon is contracted and prominent
• Limb decelerates
Hallux slightly dorsiflexed due to contraction of EHL
Leg 2
Knee of supporting leg is flexed
Heel off on supporting leg
From heel strike (HS) to foot flat (FF)Leg 1
STJ begins to pronate due to:
• Internal rotations within the lower limb
• Friction between the ground surface and the heel
MTJ also begins to pronate as:
• Tibialis anterior relaxes
• Ground reaction forces act on the fifth and fourth metatarsals
The plantar heel pad becomes weight-bearing
The lateral area, then the whole forefoot, loads rapidly
The hallux ceases to dorsiflex as soon as forefoot loading occurs
Once forefoot loading in leg 1 is completed (and leg 2 has undergone toe off) the STJ should pronate no further
Leg 2
Foot moving through propulsion phase, so that leg 1 loads fully as leg 2 undergoes toe off
From foot flat (FF) to midstance (MS)Leg 1
The leg and pelvis undergo external rotation
• STJ supinates
The knee is extended
• A bisecting line through the knee exits through the middle of the second metatarsal
• Leg 2 begins its swing phase
Midstance occurs when the leg is perpendicular to the ground
• The leg is directly over the foot
• STJ is neutral
• Tibialis anterior is relaxed
• Weight is evenly distributed across the heel pad
• MTJ is fully pronated
• Toes are flat to the ground surface, with no plantarflexion of the digits
• Leg 2 is in the middle of the swing phase and passes leg 1
Midstance (MS) to toe off (TO)Leg 1
As the body weight moves anteriorly over the foot, simultaneously:
• The knee flexes rapidly
• Gastrocnemius fires to bring about heel lift (just prior to heel contact of leg 2)
• Body weight transfers to the forefoot
The foot is supinating (due to the pull of gastrocnemius)
• There is no movement of the STJ, only movement at the MTJ
• MTJ locks to convert the foot to a rigid lever
Propulsion begins
• Body weight is distributed across the metatarsal heads
• First MTPJ is dorsiflexed but both first and fifth rays are parallel to the support surface
Propulsion continues
• The body weight continues to moves further forward
• First metatarsal plantarflexes and plantar aspect of first MTPJ becomes prominent
• Remainder of the foot supinates relative to the first ray and the height of the MLA increases
• Peroneus longus fires to stabilize the first ray (peroneus longus tendon becomes prominent)
• Body weight transfers from the lateral to the medial side of the foot
• Lateral aspect of the forefoot lifts (assists transference of body weight to leg 2)
• STJ supination reduces as foot begins to unload
Swing phaseEvents/movements occurring
Leg 1
Early swingPlantar aspect of first MTPJ still prominent
Toes dorsiflexed at MTPJs to allow ground clearance during swing
MidswingPlantar aspect of first MTPJ no longer prominent
Late swingSTJ and MTJ supinated due to contraction of tibialis anterior, EHL and EDL muscles

STJ, subtalar joint; MTJ, metatarsal joint; EHL, extensor hallucis longus; MTPJ, metatarsophalangeal joint; MLA, medial longitudinal arch; EDL, extensor digitorum longus.

References in periodicals archive ?
The point of midstance (MS) was inferred from the point where the opposite ankle crossed the leg of which the foot is in contact with the floor on the sagittal plane (Mahmoudian et al.
While the piriformis has been proven to protect the femoral neck, the iliotibial band has recently been shown to create a stabilizing force along the entire thigh that lessens bending of the femur during the midstance period of the gait cycle.
Internationally-recognised basics of normal human gait, which include the ability of the Claimant to heel-strike, midstance, and toe-off with either foot can be eyeballed' within a simple clinic setting, and used as a reference-point to describe an abnormal gait pattern, if indeed an abnormal gait pattern is present.
In nondisabled subjects, sEMG has been used to show that several core muscles are active throughout the gait cycle and that several, including the rectus abdominis (RA), external oblique (EO), and internal oblique (IO), can have increased activation during specific phases, such as midstance or foot-strike [14-15].
At midstance the barefoot condition displayed significantly less dorsiflexion compared to all shoe conditions.
The relationships between foot arch volumes and dynamic plantar pressure during midstance of walking in preschool children.
In particular, the upper body is too often ignored as runners focus on footstrike, midstance, stride length and toe-off.
9,31,51) While the initial passive impact peak ground reaction forces that occur at approximately 10% to 12% stance phase are greater for shod heel-toe runners, the midstance active propulsive vertical ground reaction forces may be greater for midfoot or forefoot strikers (Figure 2).
Pairs of spring were added to the orthosis to produce different levels of muscular activity in Q during the midstance, transition period and terminal swing phase of gait.
Midstance (%): defined as the first instant all the metatarsal heads made contact with the footscan[R] plate until the heel region lost contact with the footscan[R] plate.
As concerns kinematic parameters, significant changes were evidenced at all lower limb joints (ankle, knee and hip joints): they walked with ankle in a more normal biomechanical condition, especially at toe-off when it is able to reach values of plantarflexion close to normality, knee is characterised by a better flexion during swing phase and hip revealed an improved ability in extension during midstance.
At midstance, the optimal subtalar posture for the weight bearing foot is neutral (i.